[pkg] update vendor

26 files changed, 4280 insertions, 0 deletions

diff --git a/vendor/github.com/xtaci/kcp-go/v5/.gitignore b/vendor/github.com/xtaci/kcp-go/v5/.gitignore
new file mode 100644
index 0000000..2f4178c
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/.gitignore
@@ -0,0 +1,25 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+/vendor/
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
+*.test
+*.prof
diff --git a/vendor/github.com/xtaci/kcp-go/v5/.travis.yml b/vendor/github.com/xtaci/kcp-go/v5/.travis.yml
new file mode 100644
index 0000000..0e7c4ac
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/.travis.yml
@@ -0,0 +1,20 @@
+language: go
+go:
+    - 1.11.x
+    - 1.12.x
+    - 1.13.x
+
+env:
+    - GO111MODULE=on 
+
+before_install:
+    - go get -t -v ./...
+
+install:
+    - go get github.com/xtaci/kcp-go
+
+script:
+    - go test -coverprofile=coverage.txt -covermode=atomic -bench . -timeout 10m
+
+after_success:
+    - bash <(curl -s https://codecov.io/bash)
diff --git a/vendor/github.com/xtaci/kcp-go/v5/LICENSE b/vendor/github.com/xtaci/kcp-go/v5/LICENSE
new file mode 100644
index 0000000..8294d13
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/LICENSE
@@ -0,0 +1,22 @@
+The MIT License (MIT)
+
+Copyright (c) 2015 Daniel Fu
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
diff --git a/vendor/github.com/xtaci/kcp-go/v5/README.md b/vendor/github.com/xtaci/kcp-go/v5/README.md
new file mode 100644
index 0000000..d2273f8
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/README.md
@@ -0,0 +1,285 @@
+<img src="kcp-go.png" alt="kcp-go" height="50px" />
+
+
+[![GoDoc][1]][2] [![Powered][9]][10] [![MIT licensed][11]][12] [![Build Status][3]][4] [![Go Report Card][5]][6] [![Coverage Statusd][7]][8] [![Sourcegraph][13]][14]
+
+[1]: https://godoc.org/github.com/xtaci/kcp-go?status.svg
+[2]: https://pkg.go.dev/github.com/xtaci/kcp-go
+[3]: https://travis-ci.org/xtaci/kcp-go.svg?branch=master
+[4]: https://travis-ci.org/xtaci/kcp-go
+[5]: https://goreportcard.com/badge/github.com/xtaci/kcp-go
+[6]: https://goreportcard.com/report/github.com/xtaci/kcp-go
+[7]: https://codecov.io/gh/xtaci/kcp-go/branch/master/graph/badge.svg
+[8]: https://codecov.io/gh/xtaci/kcp-go
+[9]: https://img.shields.io/badge/KCP-Powered-blue.svg
+[10]: https://github.com/skywind3000/kcp
+[11]: https://img.shields.io/badge/license-MIT-blue.svg
+[12]: LICENSE
+[13]: https://sourcegraph.com/github.com/xtaci/kcp-go/-/badge.svg
+[14]: https://sourcegraph.com/github.com/xtaci/kcp-go?badge
+
+## Introduction
+
+**kcp-go** is a **Production-Grade Reliable-UDP** library for [golang](https://golang.org/). 
+
+This library intents to provide a **smooth, resilient, ordered, error-checked and anonymous** delivery of streams over **UDP** packets, it has been battle-tested with opensource project [kcptun](https://github.com/xtaci/kcptun). Millions of devices(from low-end MIPS routers to high-end servers) have deployed **kcp-go** powered program in a variety of forms like **online games, live broadcasting, file synchronization and network acceleration**.
+
+[Lastest Release](https://github.com/xtaci/kcp-go/releases)
+
+## Features
+
+1. Designed for **Latency-sensitive** scenarios.
+1. **Cache friendly** and **Memory optimized** design, offers extremely **High Performance** core.
+1. Handles **>5K concurrent connections** on a single commodity server.
+1. Compatible with [net.Conn](https://golang.org/pkg/net/#Conn) and [net.Listener](https://golang.org/pkg/net/#Listener), a drop-in replacement for [net.TCPConn](https://golang.org/pkg/net/#TCPConn).
+1. [FEC(Forward Error Correction)](https://en.wikipedia.org/wiki/Forward_error_correction) Support with [Reed-Solomon Codes](https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction)
+1. Packet level encryption support with [AES](https://en.wikipedia.org/wiki/Advanced_Encryption_Standard), [TEA](https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm), [3DES](https://en.wikipedia.org/wiki/Triple_DES), [Blowfish](https://en.wikipedia.org/wiki/Blowfish_(cipher)), [Cast5](https://en.wikipedia.org/wiki/CAST-128), [Salsa20]( https://en.wikipedia.org/wiki/Salsa20), etc. in [CFB](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Feedback_.28CFB.29) mode, which generates completely anonymous packet.
+1. Only **A fixed number of goroutines** will be created for the entire server application, costs in **context switch** between goroutines have been taken into consideration.
+1. Compatible with [skywind3000's](https://github.com/skywind3000) C version with various improvements.
+1. Platform-dependent optimizations: [sendmmsg](http://man7.org/linux/man-pages/man2/sendmmsg.2.html) and [recvmmsg](http://man7.org/linux/man-pages/man2/recvmmsg.2.html) were expoloited for linux.
+
+## Documentation
+
+For complete documentation, see the associated [Godoc](https://godoc.org/github.com/xtaci/kcp-go).
+
+## Specification
+
+<img src="frame.png" alt="Frame Format" height="109px" />
+
+```
+NONCE:
+  16bytes cryptographically secure random number, nonce changes for every packet.
+  
+CRC32:
+  CRC-32 checksum of data using the IEEE polynomial
+ 
+FEC TYPE:
+  typeData = 0xF1
+  typeParity = 0xF2
+  
+FEC SEQID:
+  monotonically increasing in range: [0, (0xffffffff/shardSize) * shardSize - 1]
+  
+SIZE:
+  The size of KCP frame plus 2
+```
+
+```
++-----------------+
+| SESSION         |
++-----------------+
+| KCP(ARQ)        |
++-----------------+
+| FEC(OPTIONAL)   |
++-----------------+
+| CRYPTO(OPTIONAL)|
++-----------------+
+| UDP(PACKET)     |
++-----------------+
+| IP              |
++-----------------+
+| LINK            |
++-----------------+
+| PHY             |
++-----------------+
+(LAYER MODEL OF KCP-GO)
+```
+
+
+## Examples
+
+1. [simple examples](https://github.com/xtaci/kcp-go/tree/master/examples)
+2. [kcptun client](https://github.com/xtaci/kcptun/blob/master/client/main.go)
+3. [kcptun server](https://github.com/xtaci/kcptun/blob/master/server/main.go)
+
+## Benchmark
+```
+===
+Model Name:	MacBook Pro
+Model Identifier:	MacBookPro14,1
+Processor Name:	Intel Core i5
+Processor Speed:	3.1 GHz
+Number of Processors:	1
+Total Number of Cores:	2
+L2 Cache (per Core):	256 KB
+L3 Cache:	4 MB
+Memory:	8 GB
+===
+
+$ go test -v -run=^$ -bench .
+beginning tests, encryption:salsa20, fec:10/3
+goos: darwin
+goarch: amd64
+pkg: github.com/xtaci/kcp-go
+BenchmarkSM4-4                 	   50000	     32180 ns/op	  93.23 MB/s	       0 B/op	       0 allocs/op
+BenchmarkAES128-4              	  500000	      3285 ns/op	 913.21 MB/s	       0 B/op	       0 allocs/op
+BenchmarkAES192-4              	  300000	      3623 ns/op	 827.85 MB/s	       0 B/op	       0 allocs/op
+BenchmarkAES256-4              	  300000	      3874 ns/op	 774.20 MB/s	       0 B/op	       0 allocs/op
+BenchmarkTEA-4                 	  100000	     15384 ns/op	 195.00 MB/s	       0 B/op	       0 allocs/op
+BenchmarkXOR-4                 	20000000	        89.9 ns/op	33372.00 MB/s	       0 B/op	       0 allocs/op
+BenchmarkBlowfish-4            	   50000	     26927 ns/op	 111.41 MB/s	       0 B/op	       0 allocs/op
+BenchmarkNone-4                	30000000	        45.7 ns/op	65597.94 MB/s	       0 B/op	       0 allocs/op
+BenchmarkCast5-4               	   50000	     34258 ns/op	  87.57 MB/s	       0 B/op	       0 allocs/op
+Benchmark3DES-4                	   10000	    117149 ns/op	  25.61 MB/s	       0 B/op	       0 allocs/op
+BenchmarkTwofish-4             	   50000	     33538 ns/op	  89.45 MB/s	       0 B/op	       0 allocs/op
+BenchmarkXTEA-4                	   30000	     45666 ns/op	  65.69 MB/s	       0 B/op	       0 allocs/op
+BenchmarkSalsa20-4             	  500000	      3308 ns/op	 906.76 MB/s	       0 B/op	       0 allocs/op
+BenchmarkCRC32-4               	20000000	        65.2 ns/op	15712.43 MB/s
+BenchmarkCsprngSystem-4        	 1000000	      1150 ns/op	  13.91 MB/s
+BenchmarkCsprngMD5-4           	10000000	       145 ns/op	 110.26 MB/s
+BenchmarkCsprngSHA1-4          	10000000	       158 ns/op	 126.54 MB/s
+BenchmarkCsprngNonceMD5-4      	10000000	       153 ns/op	 104.22 MB/s
+BenchmarkCsprngNonceAES128-4   	100000000	        19.1 ns/op	 837.81 MB/s
+BenchmarkFECDecode-4           	 1000000	      1119 ns/op	1339.61 MB/s	    1606 B/op	       2 allocs/op
+BenchmarkFECEncode-4           	 2000000	       832 ns/op	1801.83 MB/s	      17 B/op	       0 allocs/op
+BenchmarkFlush-4               	 5000000	       272 ns/op	       0 B/op	       0 allocs/op
+BenchmarkEchoSpeed4K-4         	    5000	    259617 ns/op	  15.78 MB/s	    5451 B/op	     149 allocs/op
+BenchmarkEchoSpeed64K-4        	    1000	   1706084 ns/op	  38.41 MB/s	   56002 B/op	    1604 allocs/op
+BenchmarkEchoSpeed512K-4       	     100	  14345505 ns/op	  36.55 MB/s	  482597 B/op	   13045 allocs/op
+BenchmarkEchoSpeed1M-4         	      30	  34859104 ns/op	  30.08 MB/s	 1143773 B/op	   27186 allocs/op
+BenchmarkSinkSpeed4K-4         	   50000	     31369 ns/op	 130.57 MB/s	    1566 B/op	      30 allocs/op
+BenchmarkSinkSpeed64K-4        	    5000	    329065 ns/op	 199.16 MB/s	   21529 B/op	     453 allocs/op
+BenchmarkSinkSpeed256K-4       	     500	   2373354 ns/op	 220.91 MB/s	  166332 B/op	    3554 allocs/op
+BenchmarkSinkSpeed1M-4         	     300	   5117927 ns/op	 204.88 MB/s	  310378 B/op	    6988 allocs/op
+PASS
+ok  	github.com/xtaci/kcp-go	50.349s
+```
+
+```
+=== Raspberry Pi 4 ===
+
+➜  kcp-go git:(master) cat /proc/cpuinfo
+processor	: 0
+model name	: ARMv7 Processor rev 3 (v7l)
+BogoMIPS	: 108.00
+Features	: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
+CPU implementer	: 0x41
+CPU architecture: 7
+CPU variant	: 0x0
+CPU part	: 0xd08
+CPU revision	: 3
+
+➜  kcp-go git:(master)  go test -run=^$ -bench .
+2020/01/05 19:25:13 beginning tests, encryption:salsa20, fec:10/3
+goos: linux
+goarch: arm
+pkg: github.com/xtaci/kcp-go/v5
+BenchmarkSM4-4                     20000             86475 ns/op          34.69 MB/s           0 B/op          0 allocs/op
+BenchmarkAES128-4                  20000             62254 ns/op          48.19 MB/s           0 B/op          0 allocs/op
+BenchmarkAES192-4                  20000             71802 ns/op          41.78 MB/s           0 B/op          0 allocs/op
+BenchmarkAES256-4                  20000             80570 ns/op          37.23 MB/s           0 B/op          0 allocs/op
+BenchmarkTEA-4                     50000             37343 ns/op          80.34 MB/s           0 B/op          0 allocs/op
+BenchmarkXOR-4                    100000             22266 ns/op         134.73 MB/s           0 B/op          0 allocs/op
+BenchmarkBlowfish-4                20000             66123 ns/op          45.37 MB/s           0 B/op          0 allocs/op
+BenchmarkNone-4                  3000000               518 ns/op        5786.77 MB/s           0 B/op          0 allocs/op
+BenchmarkCast5-4                   20000             76705 ns/op          39.11 MB/s           0 B/op          0 allocs/op
+Benchmark3DES-4                     5000            418868 ns/op           7.16 MB/s           0 B/op          0 allocs/op
+BenchmarkTwofish-4                  5000            326896 ns/op           9.18 MB/s           0 B/op          0 allocs/op
+BenchmarkXTEA-4                    10000            114418 ns/op          26.22 MB/s           0 B/op          0 allocs/op
+BenchmarkSalsa20-4                 50000             36736 ns/op          81.66 MB/s           0 B/op          0 allocs/op
+BenchmarkCRC32-4                 1000000              1735 ns/op         589.98 MB/s
+BenchmarkCsprngSystem-4          1000000              2179 ns/op           7.34 MB/s
+BenchmarkCsprngMD5-4             2000000               811 ns/op          19.71 MB/s
+BenchmarkCsprngSHA1-4            2000000               862 ns/op          23.19 MB/s
+BenchmarkCsprngNonceMD5-4        2000000               878 ns/op          18.22 MB/s
+BenchmarkCsprngNonceAES128-4     5000000               326 ns/op          48.97 MB/s
+BenchmarkFECDecode-4              200000              9081 ns/op         165.16 MB/s         140 B/op          1 allocs/op
+BenchmarkFECEncode-4              100000             12039 ns/op         124.59 MB/s          11 B/op          0 allocs/op
+BenchmarkFlush-4                  100000             21704 ns/op               0 B/op          0 allocs/op
+BenchmarkEchoSpeed4K-4              2000            981182 ns/op           4.17 MB/s       12384 B/op        424 allocs/op
+BenchmarkEchoSpeed64K-4              100          10503324 ns/op           6.24 MB/s      123616 B/op       3779 allocs/op
+BenchmarkEchoSpeed512K-4              20         138633802 ns/op           3.78 MB/s     1606584 B/op      29233 allocs/op
+BenchmarkEchoSpeed1M-4                 5         372903568 ns/op           2.81 MB/s     4080504 B/op      63600 allocs/op
+BenchmarkSinkSpeed4K-4             10000            121239 ns/op          33.78 MB/s        4647 B/op        104 allocs/op
+BenchmarkSinkSpeed64K-4             1000           1587906 ns/op          41.27 MB/s       50914 B/op       1115 allocs/op
+BenchmarkSinkSpeed256K-4             100          16277830 ns/op          32.21 MB/s      453027 B/op       9296 allocs/op
+BenchmarkSinkSpeed1M-4               100          31040703 ns/op          33.78 MB/s      898097 B/op      18932 allocs/op
+PASS
+ok      github.com/xtaci/kcp-go/v5      64.151s
+```
+
+
+## Typical Flame Graph
+![Flame Graph in kcptun](flame.png)
+
+## Key Design Considerations
+
+1. slice vs. container/list
+
+`kcp.flush()` loops through the send queue for retransmission checking for every 20ms(interval).
+
+I've wrote a benchmark for comparing sequential loop through *slice* and *container/list* here:
+
+https://github.com/xtaci/notes/blob/master/golang/benchmark2/cachemiss_test.go
+
+```
+BenchmarkLoopSlice-4   	2000000000	         0.39 ns/op
+BenchmarkLoopList-4    	100000000	        54.6 ns/op
+```
+
+List structure introduces **heavy cache misses** compared to slice which owns better **locality**, 5000 connections with 32 window size and 20ms interval will cost 6us/0.03%(cpu) using slice, and 8.7ms/43.5%(cpu) for list for each `kcp.flush()`.
+
+2. Timing accuracy vs. syscall clock_gettime
+
+Timing is **critical** to **RTT estimator**, inaccurate timing leads to false retransmissions in KCP, but calling `time.Now()` costs 42 cycles(10.5ns on 4GHz CPU, 15.6ns on my MacBook Pro 2.7GHz). 
+
+The benchmark for time.Now() lies here:
+
+https://github.com/xtaci/notes/blob/master/golang/benchmark2/syscall_test.go
+
+```
+BenchmarkNow-4         	100000000	        15.6 ns/op
+```
+
+In kcp-go, after each `kcp.output()` function call, current clock time will be updated upon return, and for a single `kcp.flush()` operation, current time will be queried from system once. For most of the time, 5000 connections costs 5000 * 15.6ns = 78us(a fixed cost while no packet needs to be sent), as for 10MB/s data transfering with 1400 MTU, `kcp.output()` will be called around 7500 times and costs 117us for `time.Now()` in **every second**.
+
+3. Memory management
+
+Primary memory allocation are done from a global buffer pool xmit.Buf, in kcp-go, when we need to allocate some bytes, we can get from that pool, and a fixed-capacity 1500 bytes(mtuLimit) will be returned, the rx queue, tx queue and fec queue all receive bytes from there, and they will return the bytes to the pool after using to prevent unnecessary zer0ing of bytes. The pool mechanism maintained a high watermark for slice objects, these in-flight objects from the pool will survive from the perodical garbage collection, meanwhile the pool kept the ability to return the memory to runtime if in idle.
+
+4. Information security
+
+kcp-go is shipped with builtin packet encryption powered by various block encryption algorithms and works in [Cipher Feedback Mode](https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Feedback_(CFB)), for each packet to be sent, the encryption process will start from encrypting a [nonce](https://en.wikipedia.org/wiki/Cryptographic_nonce) from the [system entropy](https://en.wikipedia.org/wiki//dev/random), so encryption to same plaintexts never leads to a same ciphertexts thereafter.
+
+The contents of the packets are completely anonymous with encryption, including the headers(FEC,KCP), checksums and contents. Note that, no matter which encryption method you choose on you upper layer, if you disable encryption, the transmit will be insecure somehow, since the header is ***PLAINTEXT*** to everyone it would be susceptible to header tampering, such as jamming the *sliding window size*, *round-trip time*, *FEC property* and *checksums*. ```AES-128``` is suggested for minimal encryption since modern CPUs are shipped with [AES-NI](https://en.wikipedia.org/wiki/AES_instruction_set) instructions and performs even better than `salsa20`(check the table above).
+
+Other possible attacks to kcp-go includes: a) [traffic analysis](https://en.wikipedia.org/wiki/Traffic_analysis), dataflow on specific websites may have pattern while interchanging data, but this type of eavesdropping has been mitigated by adapting [smux](https://github.com/xtaci/smux) to mix data streams so as to introduce noises, perfect solution to this has not appeared yet, theroretically by shuffling/mixing messages on larger scale network may mitigate this problem.  b) [replay attack](https://en.wikipedia.org/wiki/Replay_attack), since the asymmetrical encryption has not been introduced into kcp-go for some reason, capturing the packets and replay them on a different machine is possible, (notice: hijacking the session and decrypting the contents is still *impossible*), so upper layers should contain a asymmetrical encryption system to guarantee the authenticity of each message(to process message exactly once), such as HTTPS/OpenSSL/LibreSSL, only by signing the requests with private keys can eliminate this type of attack. 
+
+## Connection Termination
+
+Control messages like **SYN/FIN/RST** in TCP **are not defined** in KCP, you need some **keepalive/heartbeat mechanism** in the application-level. A real world example is to use some **multiplexing** protocol over session, such as [smux](https://github.com/xtaci/smux)(with embedded keepalive mechanism), see [kcptun](https://github.com/xtaci/kcptun) for example.
+
+## FAQ
+
+Q: I'm handling >5K connections on my server, the CPU utilization is so high.
+
+A: A standalone `agent` or `gate` server for running kcp-go is suggested, not only for CPU utilization, but also important to the **precision** of RTT measurements(timing) which indirectly affects retransmission. By increasing update `interval` with `SetNoDelay` like `conn.SetNoDelay(1, 40, 1, 1)` will dramatically reduce system load, but lower the performance.
+
+Q: When should I enable FEC?
+
+A: Forward error correction is critical to long-distance transmission, because a packet loss will lead to a huge penalty in time. And for the complicated packet routing network in modern world, round-trip time based loss check will not always be efficient, the big deviation of RTT samples in the long way usually leads to a larger RTO value in typical rtt estimator, which in other words, slows down the transmission.
+  
+Q: Should I enable encryption?
+
+A: Yes, for the safety of protocol, even if the upper layer has encrypted.
+
+## Who is using this?
+
+1. https://github.com/xtaci/kcptun -- A Secure Tunnel Based On KCP over UDP.
+2. https://github.com/getlantern/lantern -- Lantern delivers fast access to the open Internet. 
+3. https://github.com/smallnest/rpcx -- A RPC service framework based on net/rpc like alibaba Dubbo and weibo Motan.
+4. https://github.com/gonet2/agent -- A gateway for games with stream multiplexing.
+5. https://github.com/syncthing/syncthing -- Open Source Continuous File Synchronization.
+
+## Links
+
+1. https://github.com/xtaci/smux/ -- A Stream Multiplexing Library for golang with least memory
+1. https://github.com/xtaci/libkcp -- FEC enhanced KCP session library for iOS/Android in C++
+1. https://github.com/skywind3000/kcp -- A Fast and Reliable ARQ Protocol
+1. https://github.com/klauspost/reedsolomon -- Reed-Solomon Erasure Coding in Go
+
+## Consulting 
+
+WeChat(付费技术咨询)
+
+<img src="wechat_donate.jpg" alt="kcptun" height="120px" /> 
diff --git a/vendor/github.com/xtaci/kcp-go/v5/autotune.go b/vendor/github.com/xtaci/kcp-go/v5/autotune.go
new file mode 100644
index 0000000..1f85be3
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/autotune.go
@@ -0,0 +1,64 @@
+package kcp
+
+const maxAutoTuneSamples = 258
+
+// pulse represents a 0/1 signal with time sequence
+type pulse struct {
+	bit bool   // 0 or 1
+	seq uint32 // sequence of the signal
+}
+
+// autoTune object
+type autoTune struct {
+	pulses [maxAutoTuneSamples]pulse
+}
+
+// Sample adds a signal sample to the pulse buffer
+func (tune *autoTune) Sample(bit bool, seq uint32) {
+	tune.pulses[seq%maxAutoTuneSamples] = pulse{bit, seq}
+}
+
+// Find a period for a given signal
+// returns -1 if not found
+//
+//    ---              ------
+//      |              |
+//      |______________|
+//          Period
+//  Falling Edge    Rising Edge
+func (tune *autoTune) FindPeriod(bit bool) int {
+	// last pulse and initial index setup
+	lastPulse := tune.pulses[0]
+	idx := 1
+
+	// left edge
+	var leftEdge int
+	for ; idx < len(tune.pulses); idx++ {
+		if lastPulse.bit != bit && tune.pulses[idx].bit == bit { // edge found
+			if lastPulse.seq+1 == tune.pulses[idx].seq { // ensure edge continuity
+				leftEdge = idx
+				break
+			}
+		}
+		lastPulse = tune.pulses[idx]
+	}
+
+	// right edge
+	var rightEdge int
+	lastPulse = tune.pulses[leftEdge]
+	idx = leftEdge + 1
+
+	for ; idx < len(tune.pulses); idx++ {
+		if lastPulse.seq+1 == tune.pulses[idx].seq { // ensure pulses in this level monotonic
+			if lastPulse.bit == bit && tune.pulses[idx].bit != bit { // edge found
+				rightEdge = idx
+				break
+			}
+		} else {
+			return -1
+		}
+		lastPulse = tune.pulses[idx]
+	}
+
+	return rightEdge - leftEdge
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/batchconn.go b/vendor/github.com/xtaci/kcp-go/v5/batchconn.go
new file mode 100644
index 0000000..6c30701
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/batchconn.go
@@ -0,0 +1,12 @@
+package kcp
+
+import "golang.org/x/net/ipv4"
+
+const (
+	batchSize = 16
+)
+
+type batchConn interface {
+	WriteBatch(ms []ipv4.Message, flags int) (int, error)
+	ReadBatch(ms []ipv4.Message, flags int) (int, error)
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/crypt.go b/vendor/github.com/xtaci/kcp-go/v5/crypt.go
new file mode 100644
index 0000000..d882852
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/crypt.go
@@ -0,0 +1,618 @@
+package kcp
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/des"
+	"crypto/sha1"
+	"unsafe"
+
+	xor "github.com/templexxx/xorsimd"
+	"github.com/tjfoc/gmsm/sm4"
+
+	"golang.org/x/crypto/blowfish"
+	"golang.org/x/crypto/cast5"
+	"golang.org/x/crypto/pbkdf2"
+	"golang.org/x/crypto/salsa20"
+	"golang.org/x/crypto/tea"
+	"golang.org/x/crypto/twofish"
+	"golang.org/x/crypto/xtea"
+)
+
+var (
+	initialVector = []byte{167, 115, 79, 156, 18, 172, 27, 1, 164, 21, 242, 193, 252, 120, 230, 107}
+	saltxor       = `sH3CIVoF#rWLtJo6`
+)
+
+// BlockCrypt defines encryption/decryption methods for a given byte slice.
+// Notes on implementing: the data to be encrypted contains a builtin
+// nonce at the first 16 bytes
+type BlockCrypt interface {
+	// Encrypt encrypts the whole block in src into dst.
+	// Dst and src may point at the same memory.
+	Encrypt(dst, src []byte)
+
+	// Decrypt decrypts the whole block in src into dst.
+	// Dst and src may point at the same memory.
+	Decrypt(dst, src []byte)
+}
+
+type salsa20BlockCrypt struct {
+	key [32]byte
+}
+
+// NewSalsa20BlockCrypt https://en.wikipedia.org/wiki/Salsa20
+func NewSalsa20BlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(salsa20BlockCrypt)
+	copy(c.key[:], key)
+	return c, nil
+}
+
+func (c *salsa20BlockCrypt) Encrypt(dst, src []byte) {
+	salsa20.XORKeyStream(dst[8:], src[8:], src[:8], &c.key)
+	copy(dst[:8], src[:8])
+}
+func (c *salsa20BlockCrypt) Decrypt(dst, src []byte) {
+	salsa20.XORKeyStream(dst[8:], src[8:], src[:8], &c.key)
+	copy(dst[:8], src[:8])
+}
+
+type sm4BlockCrypt struct {
+	encbuf [sm4.BlockSize]byte // 64bit alignment enc/dec buffer
+	decbuf [2 * sm4.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewSM4BlockCrypt https://github.com/tjfoc/gmsm/tree/master/sm4
+func NewSM4BlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(sm4BlockCrypt)
+	block, err := sm4.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *sm4BlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *sm4BlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type twofishBlockCrypt struct {
+	encbuf [twofish.BlockSize]byte
+	decbuf [2 * twofish.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewTwofishBlockCrypt https://en.wikipedia.org/wiki/Twofish
+func NewTwofishBlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(twofishBlockCrypt)
+	block, err := twofish.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *twofishBlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *twofishBlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type tripleDESBlockCrypt struct {
+	encbuf [des.BlockSize]byte
+	decbuf [2 * des.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewTripleDESBlockCrypt https://en.wikipedia.org/wiki/Triple_DES
+func NewTripleDESBlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(tripleDESBlockCrypt)
+	block, err := des.NewTripleDESCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *tripleDESBlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *tripleDESBlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type cast5BlockCrypt struct {
+	encbuf [cast5.BlockSize]byte
+	decbuf [2 * cast5.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewCast5BlockCrypt https://en.wikipedia.org/wiki/CAST-128
+func NewCast5BlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(cast5BlockCrypt)
+	block, err := cast5.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *cast5BlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *cast5BlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type blowfishBlockCrypt struct {
+	encbuf [blowfish.BlockSize]byte
+	decbuf [2 * blowfish.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewBlowfishBlockCrypt https://en.wikipedia.org/wiki/Blowfish_(cipher)
+func NewBlowfishBlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(blowfishBlockCrypt)
+	block, err := blowfish.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *blowfishBlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *blowfishBlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type aesBlockCrypt struct {
+	encbuf [aes.BlockSize]byte
+	decbuf [2 * aes.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewAESBlockCrypt https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
+func NewAESBlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(aesBlockCrypt)
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *aesBlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *aesBlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type teaBlockCrypt struct {
+	encbuf [tea.BlockSize]byte
+	decbuf [2 * tea.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewTEABlockCrypt https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm
+func NewTEABlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(teaBlockCrypt)
+	block, err := tea.NewCipherWithRounds(key, 16)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *teaBlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *teaBlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type xteaBlockCrypt struct {
+	encbuf [xtea.BlockSize]byte
+	decbuf [2 * xtea.BlockSize]byte
+	block  cipher.Block
+}
+
+// NewXTEABlockCrypt https://en.wikipedia.org/wiki/XTEA
+func NewXTEABlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(xteaBlockCrypt)
+	block, err := xtea.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	c.block = block
+	return c, nil
+}
+
+func (c *xteaBlockCrypt) Encrypt(dst, src []byte) { encrypt(c.block, dst, src, c.encbuf[:]) }
+func (c *xteaBlockCrypt) Decrypt(dst, src []byte) { decrypt(c.block, dst, src, c.decbuf[:]) }
+
+type simpleXORBlockCrypt struct {
+	xortbl []byte
+}
+
+// NewSimpleXORBlockCrypt simple xor with key expanding
+func NewSimpleXORBlockCrypt(key []byte) (BlockCrypt, error) {
+	c := new(simpleXORBlockCrypt)
+	c.xortbl = pbkdf2.Key(key, []byte(saltxor), 32, mtuLimit, sha1.New)
+	return c, nil
+}
+
+func (c *simpleXORBlockCrypt) Encrypt(dst, src []byte) { xor.Bytes(dst, src, c.xortbl) }
+func (c *simpleXORBlockCrypt) Decrypt(dst, src []byte) { xor.Bytes(dst, src, c.xortbl) }
+
+type noneBlockCrypt struct{}
+
+// NewNoneBlockCrypt does nothing but copying
+func NewNoneBlockCrypt(key []byte) (BlockCrypt, error) {
+	return new(noneBlockCrypt), nil
+}
+
+func (c *noneBlockCrypt) Encrypt(dst, src []byte) { copy(dst, src) }
+func (c *noneBlockCrypt) Decrypt(dst, src []byte) { copy(dst, src) }
+
+// packet encryption with local CFB mode
+func encrypt(block cipher.Block, dst, src, buf []byte) {
+	switch block.BlockSize() {
+	case 8:
+		encrypt8(block, dst, src, buf)
+	case 16:
+		encrypt16(block, dst, src, buf)
+	default:
+		panic("unsupported cipher block size")
+	}
+}
+
+// optimized encryption for the ciphers which works in 8-bytes
+func encrypt8(block cipher.Block, dst, src, buf []byte) {
+	tbl := buf[:8]
+	block.Encrypt(tbl, initialVector)
+	n := len(src) / 8
+	base := 0
+	repeat := n / 8
+	left := n % 8
+	ptr_tbl := (*uint64)(unsafe.Pointer(&tbl[0]))
+
+	for i := 0; i < repeat; i++ {
+		s := src[base:][0:64]
+		d := dst[base:][0:64]
+		// 1
+		*(*uint64)(unsafe.Pointer(&d[0])) = *(*uint64)(unsafe.Pointer(&s[0])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[0:8])
+		// 2
+		*(*uint64)(unsafe.Pointer(&d[8])) = *(*uint64)(unsafe.Pointer(&s[8])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[8:16])
+		// 3
+		*(*uint64)(unsafe.Pointer(&d[16])) = *(*uint64)(unsafe.Pointer(&s[16])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[16:24])
+		// 4
+		*(*uint64)(unsafe.Pointer(&d[24])) = *(*uint64)(unsafe.Pointer(&s[24])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[24:32])
+		// 5
+		*(*uint64)(unsafe.Pointer(&d[32])) = *(*uint64)(unsafe.Pointer(&s[32])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[32:40])
+		// 6
+		*(*uint64)(unsafe.Pointer(&d[40])) = *(*uint64)(unsafe.Pointer(&s[40])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[40:48])
+		// 7
+		*(*uint64)(unsafe.Pointer(&d[48])) = *(*uint64)(unsafe.Pointer(&s[48])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[48:56])
+		// 8
+		*(*uint64)(unsafe.Pointer(&d[56])) = *(*uint64)(unsafe.Pointer(&s[56])) ^ *ptr_tbl
+		block.Encrypt(tbl, d[56:64])
+		base += 64
+	}
+
+	switch left {
+	case 7:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 6:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 5:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 4:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 3:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 2:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 1:
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *ptr_tbl
+		block.Encrypt(tbl, dst[base:])
+		base += 8
+		fallthrough
+	case 0:
+		xorBytes(dst[base:], src[base:], tbl)
+	}
+}
+
+// optimized encryption for the ciphers which works in 16-bytes
+func encrypt16(block cipher.Block, dst, src, buf []byte) {
+	tbl := buf[:16]
+	block.Encrypt(tbl, initialVector)
+	n := len(src) / 16
+	base := 0
+	repeat := n / 8
+	left := n % 8
+	for i := 0; i < repeat; i++ {
+		s := src[base:][0:128]
+		d := dst[base:][0:128]
+		// 1
+		xor.Bytes16Align(d[0:16], s[0:16], tbl)
+		block.Encrypt(tbl, d[0:16])
+		// 2
+		xor.Bytes16Align(d[16:32], s[16:32], tbl)
+		block.Encrypt(tbl, d[16:32])
+		// 3
+		xor.Bytes16Align(d[32:48], s[32:48], tbl)
+		block.Encrypt(tbl, d[32:48])
+		// 4
+		xor.Bytes16Align(d[48:64], s[48:64], tbl)
+		block.Encrypt(tbl, d[48:64])
+		// 5
+		xor.Bytes16Align(d[64:80], s[64:80], tbl)
+		block.Encrypt(tbl, d[64:80])
+		// 6
+		xor.Bytes16Align(d[80:96], s[80:96], tbl)
+		block.Encrypt(tbl, d[80:96])
+		// 7
+		xor.Bytes16Align(d[96:112], s[96:112], tbl)
+		block.Encrypt(tbl, d[96:112])
+		// 8
+		xor.Bytes16Align(d[112:128], s[112:128], tbl)
+		block.Encrypt(tbl, d[112:128])
+		base += 128
+	}
+
+	switch left {
+	case 7:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 6:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 5:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 4:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 3:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 2:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 1:
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		block.Encrypt(tbl, dst[base:])
+		base += 16
+		fallthrough
+	case 0:
+		xorBytes(dst[base:], src[base:], tbl)
+	}
+}
+
+// decryption
+func decrypt(block cipher.Block, dst, src, buf []byte) {
+	switch block.BlockSize() {
+	case 8:
+		decrypt8(block, dst, src, buf)
+	case 16:
+		decrypt16(block, dst, src, buf)
+	default:
+		panic("unsupported cipher block size")
+	}
+}
+
+// decrypt 8 bytes block, all byte slices are supposed to be 64bit aligned
+func decrypt8(block cipher.Block, dst, src, buf []byte) {
+	tbl := buf[0:8]
+	next := buf[8:16]
+	block.Encrypt(tbl, initialVector)
+	n := len(src) / 8
+	base := 0
+	repeat := n / 8
+	left := n % 8
+	ptr_tbl := (*uint64)(unsafe.Pointer(&tbl[0]))
+	ptr_next := (*uint64)(unsafe.Pointer(&next[0]))
+
+	for i := 0; i < repeat; i++ {
+		s := src[base:][0:64]
+		d := dst[base:][0:64]
+		// 1
+		block.Encrypt(next, s[0:8])
+		*(*uint64)(unsafe.Pointer(&d[0])) = *(*uint64)(unsafe.Pointer(&s[0])) ^ *ptr_tbl
+		// 2
+		block.Encrypt(tbl, s[8:16])
+		*(*uint64)(unsafe.Pointer(&d[8])) = *(*uint64)(unsafe.Pointer(&s[8])) ^ *ptr_next
+		// 3
+		block.Encrypt(next, s[16:24])
+		*(*uint64)(unsafe.Pointer(&d[16])) = *(*uint64)(unsafe.Pointer(&s[16])) ^ *ptr_tbl
+		// 4
+		block.Encrypt(tbl, s[24:32])
+		*(*uint64)(unsafe.Pointer(&d[24])) = *(*uint64)(unsafe.Pointer(&s[24])) ^ *ptr_next
+		// 5
+		block.Encrypt(next, s[32:40])
+		*(*uint64)(unsafe.Pointer(&d[32])) = *(*uint64)(unsafe.Pointer(&s[32])) ^ *ptr_tbl
+		// 6
+		block.Encrypt(tbl, s[40:48])
+		*(*uint64)(unsafe.Pointer(&d[40])) = *(*uint64)(unsafe.Pointer(&s[40])) ^ *ptr_next
+		// 7
+		block.Encrypt(next, s[48:56])
+		*(*uint64)(unsafe.Pointer(&d[48])) = *(*uint64)(unsafe.Pointer(&s[48])) ^ *ptr_tbl
+		// 8
+		block.Encrypt(tbl, s[56:64])
+		*(*uint64)(unsafe.Pointer(&d[56])) = *(*uint64)(unsafe.Pointer(&s[56])) ^ *ptr_next
+		base += 64
+	}
+
+	switch left {
+	case 7:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 6:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 5:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 4:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 3:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 2:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 1:
+		block.Encrypt(next, src[base:])
+		*(*uint64)(unsafe.Pointer(&dst[base])) = *(*uint64)(unsafe.Pointer(&src[base])) ^ *(*uint64)(unsafe.Pointer(&tbl[0]))
+		tbl, next = next, tbl
+		base += 8
+		fallthrough
+	case 0:
+		xorBytes(dst[base:], src[base:], tbl)
+	}
+}
+
+func decrypt16(block cipher.Block, dst, src, buf []byte) {
+	tbl := buf[0:16]
+	next := buf[16:32]
+	block.Encrypt(tbl, initialVector)
+	n := len(src) / 16
+	base := 0
+	repeat := n / 8
+	left := n % 8
+	for i := 0; i < repeat; i++ {
+		s := src[base:][0:128]
+		d := dst[base:][0:128]
+		// 1
+		block.Encrypt(next, s[0:16])
+		xor.Bytes16Align(d[0:16], s[0:16], tbl)
+		// 2
+		block.Encrypt(tbl, s[16:32])
+		xor.Bytes16Align(d[16:32], s[16:32], next)
+		// 3
+		block.Encrypt(next, s[32:48])
+		xor.Bytes16Align(d[32:48], s[32:48], tbl)
+		// 4
+		block.Encrypt(tbl, s[48:64])
+		xor.Bytes16Align(d[48:64], s[48:64], next)
+		// 5
+		block.Encrypt(next, s[64:80])
+		xor.Bytes16Align(d[64:80], s[64:80], tbl)
+		// 6
+		block.Encrypt(tbl, s[80:96])
+		xor.Bytes16Align(d[80:96], s[80:96], next)
+		// 7
+		block.Encrypt(next, s[96:112])
+		xor.Bytes16Align(d[96:112], s[96:112], tbl)
+		// 8
+		block.Encrypt(tbl, s[112:128])
+		xor.Bytes16Align(d[112:128], s[112:128], next)
+		base += 128
+	}
+
+	switch left {
+	case 7:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 6:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 5:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 4:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 3:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 2:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 1:
+		block.Encrypt(next, src[base:])
+		xor.Bytes16Align(dst[base:], src[base:], tbl)
+		tbl, next = next, tbl
+		base += 16
+		fallthrough
+	case 0:
+		xorBytes(dst[base:], src[base:], tbl)
+	}
+}
+
+// per bytes xors
+func xorBytes(dst, a, b []byte) int {
+	n := len(a)
+	if len(b) < n {
+		n = len(b)
+	}
+	if n == 0 {
+		return 0
+	}
+
+	for i := 0; i < n; i++ {
+		dst[i] = a[i] ^ b[i]
+	}
+	return n
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/donate.png b/vendor/github.com/xtaci/kcp-go/v5/donate.png
new file mode 100644
index 0000000..0f353d9
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/donate.png
diff --git a/vendor/github.com/xtaci/kcp-go/v5/entropy.go b/vendor/github.com/xtaci/kcp-go/v5/entropy.go
new file mode 100644
index 0000000..156c1cd
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/entropy.go
@@ -0,0 +1,52 @@
+package kcp
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/md5"
+	"crypto/rand"
+	"io"
+)
+
+// Entropy defines a entropy source
+type Entropy interface {
+	Init()
+	Fill(nonce []byte)
+}
+
+// nonceMD5 nonce generator for packet header
+type nonceMD5 struct {
+	seed [md5.Size]byte
+}
+
+func (n *nonceMD5) Init() { /*nothing required*/ }
+
+func (n *nonceMD5) Fill(nonce []byte) {
+	if n.seed[0] == 0 { // entropy update
+		io.ReadFull(rand.Reader, n.seed[:])
+	}
+	n.seed = md5.Sum(n.seed[:])
+	copy(nonce, n.seed[:])
+}
+
+// nonceAES128 nonce generator for packet headers
+type nonceAES128 struct {
+	seed  [aes.BlockSize]byte
+	block cipher.Block
+}
+
+func (n *nonceAES128) Init() {
+	var key [16]byte //aes-128
+	io.ReadFull(rand.Reader, key[:])
+	io.ReadFull(rand.Reader, n.seed[:])
+	block, _ := aes.NewCipher(key[:])
+	n.block = block
+}
+
+func (n *nonceAES128) Fill(nonce []byte) {
+	if n.seed[0] == 0 { // entropy update
+		io.ReadFull(rand.Reader, n.seed[:])
+	}
+	n.block.Encrypt(n.seed[:], n.seed[:])
+	copy(nonce, n.seed[:])
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/fec.go b/vendor/github.com/xtaci/kcp-go/v5/fec.go
new file mode 100644
index 0000000..0a203ee
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/fec.go
@@ -0,0 +1,381 @@
+package kcp
+
+import (
+	"encoding/binary"
+	"sync/atomic"
+
+	"github.com/klauspost/reedsolomon"
+)
+
+const (
+	fecHeaderSize      = 6
+	fecHeaderSizePlus2 = fecHeaderSize + 2 // plus 2B data size
+	typeData           = 0xf1
+	typeParity         = 0xf2
+	fecExpire          = 60000
+	rxFECMulti         = 3 // FEC keeps rxFECMulti* (dataShard+parityShard) ordered packets in memory
+)
+
+// fecPacket is a decoded FEC packet
+type fecPacket []byte
+
+func (bts fecPacket) seqid() uint32 { return binary.LittleEndian.Uint32(bts) }
+func (bts fecPacket) flag() uint16  { return binary.LittleEndian.Uint16(bts[4:]) }
+func (bts fecPacket) data() []byte  { return bts[6:] }
+
+// fecElement has auxcilliary time field
+type fecElement struct {
+	fecPacket
+	ts uint32
+}
+
+// fecDecoder for decoding incoming packets
+type fecDecoder struct {
+	rxlimit      int // queue size limit
+	dataShards   int
+	parityShards int
+	shardSize    int
+	rx           []fecElement // ordered receive queue
+
+	// caches
+	decodeCache [][]byte
+	flagCache   []bool
+
+	// zeros
+	zeros []byte
+
+	// RS decoder
+	codec reedsolomon.Encoder
+
+	// auto tune fec parameter
+	autoTune autoTune
+}
+
+func newFECDecoder(dataShards, parityShards int) *fecDecoder {
+	if dataShards <= 0 || parityShards <= 0 {
+		return nil
+	}
+
+	dec := new(fecDecoder)
+	dec.dataShards = dataShards
+	dec.parityShards = parityShards
+	dec.shardSize = dataShards + parityShards
+	dec.rxlimit = rxFECMulti * dec.shardSize
+	codec, err := reedsolomon.New(dataShards, parityShards)
+	if err != nil {
+		return nil
+	}
+	dec.codec = codec
+	dec.decodeCache = make([][]byte, dec.shardSize)
+	dec.flagCache = make([]bool, dec.shardSize)
+	dec.zeros = make([]byte, mtuLimit)
+	return dec
+}
+
+// decode a fec packet
+func (dec *fecDecoder) decode(in fecPacket) (recovered [][]byte) {
+	// sample to auto FEC tuner
+	if in.flag() == typeData {
+		dec.autoTune.Sample(true, in.seqid())
+	} else {
+		dec.autoTune.Sample(false, in.seqid())
+	}
+
+	// check if FEC parameters is out of sync
+	var shouldTune bool
+	if int(in.seqid())%dec.shardSize < dec.dataShards {
+		if in.flag() != typeData { // expect typeData
+			shouldTune = true
+		}
+	} else {
+		if in.flag() != typeParity {
+			shouldTune = true
+		}
+	}
+
+	if shouldTune {
+		autoDS := dec.autoTune.FindPeriod(true)
+		autoPS := dec.autoTune.FindPeriod(false)
+
+		// edges found, we can tune parameters now
+		if autoDS > 0 && autoPS > 0 && autoDS < 256 && autoPS < 256 {
+			// and make sure it's different
+			if autoDS != dec.dataShards || autoPS != dec.parityShards {
+				dec.dataShards = autoDS
+				dec.parityShards = autoPS
+				dec.shardSize = autoDS + autoPS
+				dec.rxlimit = rxFECMulti * dec.shardSize
+				codec, err := reedsolomon.New(autoDS, autoPS)
+				if err != nil {
+					return nil
+				}
+				dec.codec = codec
+				dec.decodeCache = make([][]byte, dec.shardSize)
+				dec.flagCache = make([]bool, dec.shardSize)
+				//log.Println("autotune to :", dec.dataShards, dec.parityShards)
+			}
+		}
+	}
+
+	// insertion
+	n := len(dec.rx) - 1
+	insertIdx := 0
+	for i := n; i >= 0; i-- {
+		if in.seqid() == dec.rx[i].seqid() { // de-duplicate
+			return nil
+		} else if _itimediff(in.seqid(), dec.rx[i].seqid()) > 0 { // insertion
+			insertIdx = i + 1
+			break
+		}
+	}
+
+	// make a copy
+	pkt := fecPacket(xmitBuf.Get().([]byte)[:len(in)])
+	copy(pkt, in)
+	elem := fecElement{pkt, currentMs()}
+
+	// insert into ordered rx queue
+	if insertIdx == n+1 {
+		dec.rx = append(dec.rx, elem)
+	} else {
+		dec.rx = append(dec.rx, fecElement{})
+		copy(dec.rx[insertIdx+1:], dec.rx[insertIdx:]) // shift right
+		dec.rx[insertIdx] = elem
+	}
+
+	// shard range for current packet
+	shardBegin := pkt.seqid() - pkt.seqid()%uint32(dec.shardSize)
+	shardEnd := shardBegin + uint32(dec.shardSize) - 1
+
+	// max search range in ordered queue for current shard
+	searchBegin := insertIdx - int(pkt.seqid()%uint32(dec.shardSize))
+	if searchBegin < 0 {
+		searchBegin = 0
+	}
+	searchEnd := searchBegin + dec.shardSize - 1
+	if searchEnd >= len(dec.rx) {
+		searchEnd = len(dec.rx) - 1
+	}
+
+	// re-construct datashards
+	if searchEnd-searchBegin+1 >= dec.dataShards {
+		var numshard, numDataShard, first, maxlen int
+
+		// zero caches
+		shards := dec.decodeCache
+		shardsflag := dec.flagCache
+		for k := range dec.decodeCache {
+			shards[k] = nil
+			shardsflag[k] = false
+		}
+
+		// shard assembly
+		for i := searchBegin; i <= searchEnd; i++ {
+			seqid := dec.rx[i].seqid()
+			if _itimediff(seqid, shardEnd) > 0 {
+				break
+			} else if _itimediff(seqid, shardBegin) >= 0 {
+				shards[seqid%uint32(dec.shardSize)] = dec.rx[i].data()
+				shardsflag[seqid%uint32(dec.shardSize)] = true
+				numshard++
+				if dec.rx[i].flag() == typeData {
+					numDataShard++
+				}
+				if numshard == 1 {
+					first = i
+				}
+				if len(dec.rx[i].data()) > maxlen {
+					maxlen = len(dec.rx[i].data())
+				}
+			}
+		}
+
+		if numDataShard == dec.dataShards {
+			// case 1: no loss on data shards
+			dec.rx = dec.freeRange(first, numshard, dec.rx)
+		} else if numshard >= dec.dataShards {
+			// case 2: loss on data shards, but it's recoverable from parity shards
+			for k := range shards {
+				if shards[k] != nil {
+					dlen := len(shards[k])
+					shards[k] = shards[k][:maxlen]
+					copy(shards[k][dlen:], dec.zeros)
+				} else if k < dec.dataShards {
+					shards[k] = xmitBuf.Get().([]byte)[:0]
+				}
+			}
+			if err := dec.codec.ReconstructData(shards); err == nil {
+				for k := range shards[:dec.dataShards] {
+					if !shardsflag[k] {
+						// recovered data should be recycled
+						recovered = append(recovered, shards[k])
+					}
+				}
+			}
+			dec.rx = dec.freeRange(first, numshard, dec.rx)
+		}
+	}
+
+	// keep rxlimit
+	if len(dec.rx) > dec.rxlimit {
+		if dec.rx[0].flag() == typeData { // track the unrecoverable data
+			atomic.AddUint64(&DefaultSnmp.FECShortShards, 1)
+		}
+		dec.rx = dec.freeRange(0, 1, dec.rx)
+	}
+
+	// timeout policy
+	current := currentMs()
+	numExpired := 0
+	for k := range dec.rx {
+		if _itimediff(current, dec.rx[k].ts) > fecExpire {
+			numExpired++
+			continue
+		}
+		break
+	}
+	if numExpired > 0 {
+		dec.rx = dec.freeRange(0, numExpired, dec.rx)
+	}
+	return
+}
+
+// free a range of fecPacket
+func (dec *fecDecoder) freeRange(first, n int, q []fecElement) []fecElement {
+	for i := first; i < first+n; i++ { // recycle buffer
+		xmitBuf.Put([]byte(q[i].fecPacket))
+	}
+
+	if first == 0 && n < cap(q)/2 {
+		return q[n:]
+	}
+	copy(q[first:], q[first+n:])
+	return q[:len(q)-n]
+}
+
+// release all segments back to xmitBuf
+func (dec *fecDecoder) release() {
+	if n := len(dec.rx); n > 0 {
+		dec.rx = dec.freeRange(0, n, dec.rx)
+	}
+}
+
+type (
+	// fecEncoder for encoding outgoing packets
+	fecEncoder struct {
+		dataShards   int
+		parityShards int
+		shardSize    int
+		paws         uint32 // Protect Against Wrapped Sequence numbers
+		next         uint32 // next seqid
+
+		shardCount int // count the number of datashards collected
+		maxSize    int // track maximum data length in datashard
+
+		headerOffset  int // FEC header offset
+		payloadOffset int // FEC payload offset
+
+		// caches
+		shardCache  [][]byte
+		encodeCache [][]byte
+
+		// zeros
+		zeros []byte
+
+		// RS encoder
+		codec reedsolomon.Encoder
+	}
+)
+
+func newFECEncoder(dataShards, parityShards, offset int) *fecEncoder {
+	if dataShards <= 0 || parityShards <= 0 {
+		return nil
+	}
+	enc := new(fecEncoder)
+	enc.dataShards = dataShards
+	enc.parityShards = parityShards
+	enc.shardSize = dataShards + parityShards
+	enc.paws = 0xffffffff / uint32(enc.shardSize) * uint32(enc.shardSize)
+	enc.headerOffset = offset
+	enc.payloadOffset = enc.headerOffset + fecHeaderSize
+
+	codec, err := reedsolomon.New(dataShards, parityShards)
+	if err != nil {
+		return nil
+	}
+	enc.codec = codec
+
+	// caches
+	enc.encodeCache = make([][]byte, enc.shardSize)
+	enc.shardCache = make([][]byte, enc.shardSize)
+	for k := range enc.shardCache {
+		enc.shardCache[k] = make([]byte, mtuLimit)
+	}
+	enc.zeros = make([]byte, mtuLimit)
+	return enc
+}
+
+// encodes the packet, outputs parity shards if we have collected quorum datashards
+// notice: the contents of 'ps' will be re-written in successive calling
+func (enc *fecEncoder) encode(b []byte) (ps [][]byte) {
+	// The header format:
+	// | FEC SEQID(4B) | FEC TYPE(2B) | SIZE (2B) | PAYLOAD(SIZE-2) |
+	// |<-headerOffset                |<-payloadOffset
+	enc.markData(b[enc.headerOffset:])
+	binary.LittleEndian.PutUint16(b[enc.payloadOffset:], uint16(len(b[enc.payloadOffset:])))
+
+	// copy data from payloadOffset to fec shard cache
+	sz := len(b)
+	enc.shardCache[enc.shardCount] = enc.shardCache[enc.shardCount][:sz]
+	copy(enc.shardCache[enc.shardCount][enc.payloadOffset:], b[enc.payloadOffset:])
+	enc.shardCount++
+
+	// track max datashard length
+	if sz > enc.maxSize {
+		enc.maxSize = sz
+	}
+
+	//  Generation of Reed-Solomon Erasure Code
+	if enc.shardCount == enc.dataShards {
+		// fill '0' into the tail of each datashard
+		for i := 0; i < enc.dataShards; i++ {
+			shard := enc.shardCache[i]
+			slen := len(shard)
+			copy(shard[slen:enc.maxSize], enc.zeros)
+		}
+
+		// construct equal-sized slice with stripped header
+		cache := enc.encodeCache
+		for k := range cache {
+			cache[k] = enc.shardCache[k][enc.payloadOffset:enc.maxSize]
+		}
+
+		// encoding
+		if err := enc.codec.Encode(cache); err == nil {
+			ps = enc.shardCache[enc.dataShards:]
+			for k := range ps {
+				enc.markParity(ps[k][enc.headerOffset:])
+				ps[k] = ps[k][:enc.maxSize]
+			}
+		}
+
+		// counters resetting
+		enc.shardCount = 0
+		enc.maxSize = 0
+	}
+
+	return
+}
+
+func (enc *fecEncoder) markData(data []byte) {
+	binary.LittleEndian.PutUint32(data, enc.next)
+	binary.LittleEndian.PutUint16(data[4:], typeData)
+	enc.next++
+}
+
+func (enc *fecEncoder) markParity(data []byte) {
+	binary.LittleEndian.PutUint32(data, enc.next)
+	binary.LittleEndian.PutUint16(data[4:], typeParity)
+	// sequence wrap will only happen at parity shard
+	enc.next = (enc.next + 1) % enc.paws
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/flame.png b/vendor/github.com/xtaci/kcp-go/v5/flame.png
new file mode 100644
index 0000000..672f649
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/flame.png
diff --git a/vendor/github.com/xtaci/kcp-go/v5/frame.png b/vendor/github.com/xtaci/kcp-go/v5/frame.png
new file mode 100644
index 0000000..0b0aefd
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/frame.png
diff --git a/vendor/github.com/xtaci/kcp-go/v5/go.mod b/vendor/github.com/xtaci/kcp-go/v5/go.mod
new file mode 100644
index 0000000..ff51020
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/go.mod
@@ -0,0 +1,20 @@
+module github.com/xtaci/kcp-go/v5
+
+require (
+	github.com/klauspost/cpuid v1.3.1 // indirect
+	github.com/klauspost/reedsolomon v1.9.9
+	github.com/mmcloughlin/avo v0.0.0-20200803215136-443f81d77104 // indirect
+	github.com/pkg/errors v0.9.1
+	github.com/stretchr/testify v1.6.1
+	github.com/templexxx/cpu v0.0.7 // indirect
+	github.com/templexxx/xorsimd v0.4.1
+	github.com/tjfoc/gmsm v1.3.2
+	github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae
+	golang.org/x/crypto v0.0.0-20200728195943-123391ffb6de
+	golang.org/x/net v0.0.0-20200707034311-ab3426394381
+	golang.org/x/sys v0.0.0-20200808120158-1030fc2bf1d9 // indirect
+	golang.org/x/tools v0.0.0-20200808161706-5bf02b21f123 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+)
+
+go 1.13
diff --git a/vendor/github.com/xtaci/kcp-go/v5/go.sum b/vendor/github.com/xtaci/kcp-go/v5/go.sum
new file mode 100644
index 0000000..db81c71
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/go.sum
@@ -0,0 +1,69 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/klauspost/cpuid v1.2.4/go.mod h1:Pj4uuM528wm8OyEC2QMXAi2YiTZ96dNQPGgoMS4s3ek=
+github.com/klauspost/cpuid v1.3.1 h1:5JNjFYYQrZeKRJ0734q51WCEEn2huer72Dc7K+R/b6s=
+github.com/klauspost/cpuid v1.3.1/go.mod h1:bYW4mA6ZgKPob1/Dlai2LviZJO7KGI3uoWLd42rAQw4=
+github.com/klauspost/reedsolomon v1.9.9 h1:qCL7LZlv17xMixl55nq2/Oa1Y86nfO8EqDfv2GHND54=
+github.com/klauspost/reedsolomon v1.9.9/go.mod h1:O7yFFHiQwDR6b2t63KPUpccPtNdp5ADgh1gg4fd12wo=
+github.com/mmcloughlin/avo v0.0.0-20200803215136-443f81d77104 h1:ULR/QWMgcgRiZLUjSSJMU+fW+RDMstRdmnDWj9Q+AsA=
+github.com/mmcloughlin/avo v0.0.0-20200803215136-443f81d77104/go.mod h1:wqKykBG2QzQDJEzvRkcS8x6MiSJkF52hXZsXcjaB3ls=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd0=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/templexxx/cpu v0.0.1 h1:hY4WdLOgKdc8y13EYklu9OUTXik80BkxHoWvTO6MQQY=
+github.com/templexxx/cpu v0.0.1/go.mod h1:w7Tb+7qgcAlIyX4NhLuDKt78AHA5SzPmq0Wj6HiEnnk=
+github.com/templexxx/cpu v0.0.7 h1:pUEZn8JBy/w5yzdYWgx+0m0xL9uk6j4K91C5kOViAzo=
+github.com/templexxx/cpu v0.0.7/go.mod h1:w7Tb+7qgcAlIyX4NhLuDKt78AHA5SzPmq0Wj6HiEnnk=
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diff --git a/vendor/github.com/xtaci/kcp-go/v5/kcp-go.png b/vendor/github.com/xtaci/kcp-go/v5/kcp-go.png
new file mode 100644
index 0000000..151b7c4
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/kcp-go.png
diff --git a/vendor/github.com/xtaci/kcp-go/v5/kcp.go b/vendor/github.com/xtaci/kcp-go/v5/kcp.go
new file mode 100644
index 0000000..0c6c304
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/kcp.go
@@ -0,0 +1,1080 @@
+package kcp
+
+import (
+	"encoding/binary"
+	"sync/atomic"
+	"time"
+)
+
+const (
+	IKCP_RTO_NDL     = 30  // no delay min rto
+	IKCP_RTO_MIN     = 100 // normal min rto
+	IKCP_RTO_DEF     = 200
+	IKCP_RTO_MAX     = 60000
+	IKCP_CMD_PUSH    = 81 // cmd: push data
+	IKCP_CMD_ACK     = 82 // cmd: ack
+	IKCP_CMD_WASK    = 83 // cmd: window probe (ask)
+	IKCP_CMD_WINS    = 84 // cmd: window size (tell)
+	IKCP_ASK_SEND    = 1  // need to send IKCP_CMD_WASK
+	IKCP_ASK_TELL    = 2  // need to send IKCP_CMD_WINS
+	IKCP_WND_SND     = 32
+	IKCP_WND_RCV     = 32
+	IKCP_MTU_DEF     = 1400
+	IKCP_ACK_FAST    = 3
+	IKCP_INTERVAL    = 100
+	IKCP_OVERHEAD    = 24
+	IKCP_DEADLINK    = 20
+	IKCP_THRESH_INIT = 2
+	IKCP_THRESH_MIN  = 2
+	IKCP_PROBE_INIT  = 7000   // 7 secs to probe window size
+	IKCP_PROBE_LIMIT = 120000 // up to 120 secs to probe window
+	IKCP_SN_OFFSET   = 12
+)
+
+// monotonic reference time point
+var refTime time.Time = time.Now()
+
+// currentMs returns current elapsed monotonic milliseconds since program startup
+func currentMs() uint32 { return uint32(time.Since(refTime) / time.Millisecond) }
+
+// output_callback is a prototype which ought capture conn and call conn.Write
+type output_callback func(buf []byte, size int)
+
+/* encode 8 bits unsigned int */
+func ikcp_encode8u(p []byte, c byte) []byte {
+	p[0] = c
+	return p[1:]
+}
+
+/* decode 8 bits unsigned int */
+func ikcp_decode8u(p []byte, c *byte) []byte {
+	*c = p[0]
+	return p[1:]
+}
+
+/* encode 16 bits unsigned int (lsb) */
+func ikcp_encode16u(p []byte, w uint16) []byte {
+	binary.LittleEndian.PutUint16(p, w)
+	return p[2:]
+}
+
+/* decode 16 bits unsigned int (lsb) */
+func ikcp_decode16u(p []byte, w *uint16) []byte {
+	*w = binary.LittleEndian.Uint16(p)
+	return p[2:]
+}
+
+/* encode 32 bits unsigned int (lsb) */
+func ikcp_encode32u(p []byte, l uint32) []byte {
+	binary.LittleEndian.PutUint32(p, l)
+	return p[4:]
+}
+
+/* decode 32 bits unsigned int (lsb) */
+func ikcp_decode32u(p []byte, l *uint32) []byte {
+	*l = binary.LittleEndian.Uint32(p)
+	return p[4:]
+}
+
+func _imin_(a, b uint32) uint32 {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+func _imax_(a, b uint32) uint32 {
+	if a >= b {
+		return a
+	}
+	return b
+}
+
+func _ibound_(lower, middle, upper uint32) uint32 {
+	return _imin_(_imax_(lower, middle), upper)
+}
+
+func _itimediff(later, earlier uint32) int32 {
+	return (int32)(later - earlier)
+}
+
+// segment defines a KCP segment
+type segment struct {
+	conv     uint32
+	cmd      uint8
+	frg      uint8
+	wnd      uint16
+	ts       uint32
+	sn       uint32
+	una      uint32
+	rto      uint32
+	xmit     uint32
+	resendts uint32
+	fastack  uint32
+	acked    uint32 // mark if the seg has acked
+	data     []byte
+}
+
+// encode a segment into buffer
+func (seg *segment) encode(ptr []byte) []byte {
+	ptr = ikcp_encode32u(ptr, seg.conv)
+	ptr = ikcp_encode8u(ptr, seg.cmd)
+	ptr = ikcp_encode8u(ptr, seg.frg)
+	ptr = ikcp_encode16u(ptr, seg.wnd)
+	ptr = ikcp_encode32u(ptr, seg.ts)
+	ptr = ikcp_encode32u(ptr, seg.sn)
+	ptr = ikcp_encode32u(ptr, seg.una)
+	ptr = ikcp_encode32u(ptr, uint32(len(seg.data)))
+	atomic.AddUint64(&DefaultSnmp.OutSegs, 1)
+	return ptr
+}
+
+// KCP defines a single KCP connection
+type KCP struct {
+	conv, mtu, mss, state                  uint32
+	snd_una, snd_nxt, rcv_nxt              uint32
+	ssthresh                               uint32
+	rx_rttvar, rx_srtt                     int32
+	rx_rto, rx_minrto                      uint32
+	snd_wnd, rcv_wnd, rmt_wnd, cwnd, probe uint32
+	interval, ts_flush                     uint32
+	nodelay, updated                       uint32
+	ts_probe, probe_wait                   uint32
+	dead_link, incr                        uint32
+
+	fastresend     int32
+	nocwnd, stream int32
+
+	snd_queue []segment
+	rcv_queue []segment
+	snd_buf   []segment
+	rcv_buf   []segment
+
+	acklist []ackItem
+
+	buffer   []byte
+	reserved int
+	output   output_callback
+}
+
+type ackItem struct {
+	sn uint32
+	ts uint32
+}
+
+// NewKCP create a new kcp state machine
+//
+// 'conv' must be equal in the connection peers, or else data will be silently rejected.
+//
+// 'output' function will be called whenever these is data to be sent on wire.
+func NewKCP(conv uint32, output output_callback) *KCP {
+	kcp := new(KCP)
+	kcp.conv = conv
+	kcp.snd_wnd = IKCP_WND_SND
+	kcp.rcv_wnd = IKCP_WND_RCV
+	kcp.rmt_wnd = IKCP_WND_RCV
+	kcp.mtu = IKCP_MTU_DEF
+	kcp.mss = kcp.mtu - IKCP_OVERHEAD
+	kcp.buffer = make([]byte, kcp.mtu)
+	kcp.rx_rto = IKCP_RTO_DEF
+	kcp.rx_minrto = IKCP_RTO_MIN
+	kcp.interval = IKCP_INTERVAL
+	kcp.ts_flush = IKCP_INTERVAL
+	kcp.ssthresh = IKCP_THRESH_INIT
+	kcp.dead_link = IKCP_DEADLINK
+	kcp.output = output
+	return kcp
+}
+
+// newSegment creates a KCP segment
+func (kcp *KCP) newSegment(size int) (seg segment) {
+	seg.data = xmitBuf.Get().([]byte)[:size]
+	return
+}
+
+// delSegment recycles a KCP segment
+func (kcp *KCP) delSegment(seg *segment) {
+	if seg.data != nil {
+		xmitBuf.Put(seg.data)
+		seg.data = nil
+	}
+}
+
+// ReserveBytes keeps n bytes untouched from the beginning of the buffer,
+// the output_callback function should be aware of this.
+//
+// Return false if n >= mss
+func (kcp *KCP) ReserveBytes(n int) bool {
+	if n >= int(kcp.mtu-IKCP_OVERHEAD) || n < 0 {
+		return false
+	}
+	kcp.reserved = n
+	kcp.mss = kcp.mtu - IKCP_OVERHEAD - uint32(n)
+	return true
+}
+
+// PeekSize checks the size of next message in the recv queue
+func (kcp *KCP) PeekSize() (length int) {
+	if len(kcp.rcv_queue) == 0 {
+		return -1
+	}
+
+	seg := &kcp.rcv_queue[0]
+	if seg.frg == 0 {
+		return len(seg.data)
+	}
+
+	if len(kcp.rcv_queue) < int(seg.frg+1) {
+		return -1
+	}
+
+	for k := range kcp.rcv_queue {
+		seg := &kcp.rcv_queue[k]
+		length += len(seg.data)
+		if seg.frg == 0 {
+			break
+		}
+	}
+	return
+}
+
+// Receive data from kcp state machine
+//
+// Return number of bytes read.
+//
+// Return -1 when there is no readable data.
+//
+// Return -2 if len(buffer) is smaller than kcp.PeekSize().
+func (kcp *KCP) Recv(buffer []byte) (n int) {
+	peeksize := kcp.PeekSize()
+	if peeksize < 0 {
+		return -1
+	}
+
+	if peeksize > len(buffer) {
+		return -2
+	}
+
+	var fast_recover bool
+	if len(kcp.rcv_queue) >= int(kcp.rcv_wnd) {
+		fast_recover = true
+	}
+
+	// merge fragment
+	count := 0
+	for k := range kcp.rcv_queue {
+		seg := &kcp.rcv_queue[k]
+		copy(buffer, seg.data)
+		buffer = buffer[len(seg.data):]
+		n += len(seg.data)
+		count++
+		kcp.delSegment(seg)
+		if seg.frg == 0 {
+			break
+		}
+	}
+	if count > 0 {
+		kcp.rcv_queue = kcp.remove_front(kcp.rcv_queue, count)
+	}
+
+	// move available data from rcv_buf -> rcv_queue
+	count = 0
+	for k := range kcp.rcv_buf {
+		seg := &kcp.rcv_buf[k]
+		if seg.sn == kcp.rcv_nxt && len(kcp.rcv_queue)+count < int(kcp.rcv_wnd) {
+			kcp.rcv_nxt++
+			count++
+		} else {
+			break
+		}
+	}
+
+	if count > 0 {
+		kcp.rcv_queue = append(kcp.rcv_queue, kcp.rcv_buf[:count]...)
+		kcp.rcv_buf = kcp.remove_front(kcp.rcv_buf, count)
+	}
+
+	// fast recover
+	if len(kcp.rcv_queue) < int(kcp.rcv_wnd) && fast_recover {
+		// ready to send back IKCP_CMD_WINS in ikcp_flush
+		// tell remote my window size
+		kcp.probe |= IKCP_ASK_TELL
+	}
+	return
+}
+
+// Send is user/upper level send, returns below zero for error
+func (kcp *KCP) Send(buffer []byte) int {
+	var count int
+	if len(buffer) == 0 {
+		return -1
+	}
+
+	// append to previous segment in streaming mode (if possible)
+	if kcp.stream != 0 {
+		n := len(kcp.snd_queue)
+		if n > 0 {
+			seg := &kcp.snd_queue[n-1]
+			if len(seg.data) < int(kcp.mss) {
+				capacity := int(kcp.mss) - len(seg.data)
+				extend := capacity
+				if len(buffer) < capacity {
+					extend = len(buffer)
+				}
+
+				// grow slice, the underlying cap is guaranteed to
+				// be larger than kcp.mss
+				oldlen := len(seg.data)
+				seg.data = seg.data[:oldlen+extend]
+				copy(seg.data[oldlen:], buffer)
+				buffer = buffer[extend:]
+			}
+		}
+
+		if len(buffer) == 0 {
+			return 0
+		}
+	}
+
+	if len(buffer) <= int(kcp.mss) {
+		count = 1
+	} else {
+		count = (len(buffer) + int(kcp.mss) - 1) / int(kcp.mss)
+	}
+
+	if count > 255 {
+		return -2
+	}
+
+	if count == 0 {
+		count = 1
+	}
+
+	for i := 0; i < count; i++ {
+		var size int
+		if len(buffer) > int(kcp.mss) {
+			size = int(kcp.mss)
+		} else {
+			size = len(buffer)
+		}
+		seg := kcp.newSegment(size)
+		copy(seg.data, buffer[:size])
+		if kcp.stream == 0 { // message mode
+			seg.frg = uint8(count - i - 1)
+		} else { // stream mode
+			seg.frg = 0
+		}
+		kcp.snd_queue = append(kcp.snd_queue, seg)
+		buffer = buffer[size:]
+	}
+	return 0
+}
+
+func (kcp *KCP) update_ack(rtt int32) {
+	// https://tools.ietf.org/html/rfc6298
+	var rto uint32
+	if kcp.rx_srtt == 0 {
+		kcp.rx_srtt = rtt
+		kcp.rx_rttvar = rtt >> 1
+	} else {
+		delta := rtt - kcp.rx_srtt
+		kcp.rx_srtt += delta >> 3
+		if delta < 0 {
+			delta = -delta
+		}
+		if rtt < kcp.rx_srtt-kcp.rx_rttvar {
+			// if the new RTT sample is below the bottom of the range of
+			// what an RTT measurement is expected to be.
+			// give an 8x reduced weight versus its normal weighting
+			kcp.rx_rttvar += (delta - kcp.rx_rttvar) >> 5
+		} else {
+			kcp.rx_rttvar += (delta - kcp.rx_rttvar) >> 2
+		}
+	}
+	rto = uint32(kcp.rx_srtt) + _imax_(kcp.interval, uint32(kcp.rx_rttvar)<<2)
+	kcp.rx_rto = _ibound_(kcp.rx_minrto, rto, IKCP_RTO_MAX)
+}
+
+func (kcp *KCP) shrink_buf() {
+	if len(kcp.snd_buf) > 0 {
+		seg := &kcp.snd_buf[0]
+		kcp.snd_una = seg.sn
+	} else {
+		kcp.snd_una = kcp.snd_nxt
+	}
+}
+
+func (kcp *KCP) parse_ack(sn uint32) {
+	if _itimediff(sn, kcp.snd_una) < 0 || _itimediff(sn, kcp.snd_nxt) >= 0 {
+		return
+	}
+
+	for k := range kcp.snd_buf {
+		seg := &kcp.snd_buf[k]
+		if sn == seg.sn {
+			// mark and free space, but leave the segment here,
+			// and wait until `una` to delete this, then we don't
+			// have to shift the segments behind forward,
+			// which is an expensive operation for large window
+			seg.acked = 1
+			kcp.delSegment(seg)
+			break
+		}
+		if _itimediff(sn, seg.sn) < 0 {
+			break
+		}
+	}
+}
+
+func (kcp *KCP) parse_fastack(sn, ts uint32) {
+	if _itimediff(sn, kcp.snd_una) < 0 || _itimediff(sn, kcp.snd_nxt) >= 0 {
+		return
+	}
+
+	for k := range kcp.snd_buf {
+		seg := &kcp.snd_buf[k]
+		if _itimediff(sn, seg.sn) < 0 {
+			break
+		} else if sn != seg.sn && _itimediff(seg.ts, ts) <= 0 {
+			seg.fastack++
+		}
+	}
+}
+
+func (kcp *KCP) parse_una(una uint32) int {
+	count := 0
+	for k := range kcp.snd_buf {
+		seg := &kcp.snd_buf[k]
+		if _itimediff(una, seg.sn) > 0 {
+			kcp.delSegment(seg)
+			count++
+		} else {
+			break
+		}
+	}
+	if count > 0 {
+		kcp.snd_buf = kcp.remove_front(kcp.snd_buf, count)
+	}
+	return count
+}
+
+// ack append
+func (kcp *KCP) ack_push(sn, ts uint32) {
+	kcp.acklist = append(kcp.acklist, ackItem{sn, ts})
+}
+
+// returns true if data has repeated
+func (kcp *KCP) parse_data(newseg segment) bool {
+	sn := newseg.sn
+	if _itimediff(sn, kcp.rcv_nxt+kcp.rcv_wnd) >= 0 ||
+		_itimediff(sn, kcp.rcv_nxt) < 0 {
+		return true
+	}
+
+	n := len(kcp.rcv_buf) - 1
+	insert_idx := 0
+	repeat := false
+	for i := n; i >= 0; i-- {
+		seg := &kcp.rcv_buf[i]
+		if seg.sn == sn {
+			repeat = true
+			break
+		}
+		if _itimediff(sn, seg.sn) > 0 {
+			insert_idx = i + 1
+			break
+		}
+	}
+
+	if !repeat {
+		// replicate the content if it's new
+		dataCopy := xmitBuf.Get().([]byte)[:len(newseg.data)]
+		copy(dataCopy, newseg.data)
+		newseg.data = dataCopy
+
+		if insert_idx == n+1 {
+			kcp.rcv_buf = append(kcp.rcv_buf, newseg)
+		} else {
+			kcp.rcv_buf = append(kcp.rcv_buf, segment{})
+			copy(kcp.rcv_buf[insert_idx+1:], kcp.rcv_buf[insert_idx:])
+			kcp.rcv_buf[insert_idx] = newseg
+		}
+	}
+
+	// move available data from rcv_buf -> rcv_queue
+	count := 0
+	for k := range kcp.rcv_buf {
+		seg := &kcp.rcv_buf[k]
+		if seg.sn == kcp.rcv_nxt && len(kcp.rcv_queue)+count < int(kcp.rcv_wnd) {
+			kcp.rcv_nxt++
+			count++
+		} else {
+			break
+		}
+	}
+	if count > 0 {
+		kcp.rcv_queue = append(kcp.rcv_queue, kcp.rcv_buf[:count]...)
+		kcp.rcv_buf = kcp.remove_front(kcp.rcv_buf, count)
+	}
+
+	return repeat
+}
+
+// Input a packet into kcp state machine.
+//
+// 'regular' indicates it's a real data packet from remote, and it means it's not generated from ReedSolomon
+// codecs.
+//
+// 'ackNoDelay' will trigger immediate ACK, but surely it will not be efficient in bandwidth
+func (kcp *KCP) Input(data []byte, regular, ackNoDelay bool) int {
+	snd_una := kcp.snd_una
+	if len(data) < IKCP_OVERHEAD {
+		return -1
+	}
+
+	var latest uint32 // the latest ack packet
+	var flag int
+	var inSegs uint64
+	var windowSlides bool
+
+	for {
+		var ts, sn, length, una, conv uint32
+		var wnd uint16
+		var cmd, frg uint8
+
+		if len(data) < int(IKCP_OVERHEAD) {
+			break
+		}
+
+		data = ikcp_decode32u(data, &conv)
+		if conv != kcp.conv {
+			return -1
+		}
+
+		data = ikcp_decode8u(data, &cmd)
+		data = ikcp_decode8u(data, &frg)
+		data = ikcp_decode16u(data, &wnd)
+		data = ikcp_decode32u(data, &ts)
+		data = ikcp_decode32u(data, &sn)
+		data = ikcp_decode32u(data, &una)
+		data = ikcp_decode32u(data, &length)
+		if len(data) < int(length) {
+			return -2
+		}
+
+		if cmd != IKCP_CMD_PUSH && cmd != IKCP_CMD_ACK &&
+			cmd != IKCP_CMD_WASK && cmd != IKCP_CMD_WINS {
+			return -3
+		}
+
+		// only trust window updates from regular packets. i.e: latest update
+		if regular {
+			kcp.rmt_wnd = uint32(wnd)
+		}
+		if kcp.parse_una(una) > 0 {
+			windowSlides = true
+		}
+		kcp.shrink_buf()
+
+		if cmd == IKCP_CMD_ACK {
+			kcp.parse_ack(sn)
+			kcp.parse_fastack(sn, ts)
+			flag |= 1
+			latest = ts
+		} else if cmd == IKCP_CMD_PUSH {
+			repeat := true
+			if _itimediff(sn, kcp.rcv_nxt+kcp.rcv_wnd) < 0 {
+				kcp.ack_push(sn, ts)
+				if _itimediff(sn, kcp.rcv_nxt) >= 0 {
+					var seg segment
+					seg.conv = conv
+					seg.cmd = cmd
+					seg.frg = frg
+					seg.wnd = wnd
+					seg.ts = ts
+					seg.sn = sn
+					seg.una = una
+					seg.data = data[:length] // delayed data copying
+					repeat = kcp.parse_data(seg)
+				}
+			}
+			if regular && repeat {
+				atomic.AddUint64(&DefaultSnmp.RepeatSegs, 1)
+			}
+		} else if cmd == IKCP_CMD_WASK {
+			// ready to send back IKCP_CMD_WINS in Ikcp_flush
+			// tell remote my window size
+			kcp.probe |= IKCP_ASK_TELL
+		} else if cmd == IKCP_CMD_WINS {
+			// do nothing
+		} else {
+			return -3
+		}
+
+		inSegs++
+		data = data[length:]
+	}
+	atomic.AddUint64(&DefaultSnmp.InSegs, inSegs)
+
+	// update rtt with the latest ts
+	// ignore the FEC packet
+	if flag != 0 && regular {
+		current := currentMs()
+		if _itimediff(current, latest) >= 0 {
+			kcp.update_ack(_itimediff(current, latest))
+		}
+	}
+
+	// cwnd update when packet arrived
+	if kcp.nocwnd == 0 {
+		if _itimediff(kcp.snd_una, snd_una) > 0 {
+			if kcp.cwnd < kcp.rmt_wnd {
+				mss := kcp.mss
+				if kcp.cwnd < kcp.ssthresh {
+					kcp.cwnd++
+					kcp.incr += mss
+				} else {
+					if kcp.incr < mss {
+						kcp.incr = mss
+					}
+					kcp.incr += (mss*mss)/kcp.incr + (mss / 16)
+					if (kcp.cwnd+1)*mss <= kcp.incr {
+						if mss > 0 {
+							kcp.cwnd = (kcp.incr + mss - 1) / mss
+						} else {
+							kcp.cwnd = kcp.incr + mss - 1
+						}
+					}
+				}
+				if kcp.cwnd > kcp.rmt_wnd {
+					kcp.cwnd = kcp.rmt_wnd
+					kcp.incr = kcp.rmt_wnd * mss
+				}
+			}
+		}
+	}
+
+	if windowSlides { // if window has slided, flush
+		kcp.flush(false)
+	} else if ackNoDelay && len(kcp.acklist) > 0 { // ack immediately
+		kcp.flush(true)
+	}
+	return 0
+}
+
+func (kcp *KCP) wnd_unused() uint16 {
+	if len(kcp.rcv_queue) < int(kcp.rcv_wnd) {
+		return uint16(int(kcp.rcv_wnd) - len(kcp.rcv_queue))
+	}
+	return 0
+}
+
+// flush pending data
+func (kcp *KCP) flush(ackOnly bool) uint32 {
+	var seg segment
+	seg.conv = kcp.conv
+	seg.cmd = IKCP_CMD_ACK
+	seg.wnd = kcp.wnd_unused()
+	seg.una = kcp.rcv_nxt
+
+	buffer := kcp.buffer
+	ptr := buffer[kcp.reserved:] // keep n bytes untouched
+
+	// makeSpace makes room for writing
+	makeSpace := func(space int) {
+		size := len(buffer) - len(ptr)
+		if size+space > int(kcp.mtu) {
+			kcp.output(buffer, size)
+			ptr = buffer[kcp.reserved:]
+		}
+	}
+
+	// flush bytes in buffer if there is any
+	flushBuffer := func() {
+		size := len(buffer) - len(ptr)
+		if size > kcp.reserved {
+			kcp.output(buffer, size)
+		}
+	}
+
+	// flush acknowledges
+	for i, ack := range kcp.acklist {
+		makeSpace(IKCP_OVERHEAD)
+		// filter jitters caused by bufferbloat
+		if _itimediff(ack.sn, kcp.rcv_nxt) >= 0 || len(kcp.acklist)-1 == i {
+			seg.sn, seg.ts = ack.sn, ack.ts
+			ptr = seg.encode(ptr)
+		}
+	}
+	kcp.acklist = kcp.acklist[0:0]
+
+	if ackOnly { // flash remain ack segments
+		flushBuffer()
+		return kcp.interval
+	}
+
+	// probe window size (if remote window size equals zero)
+	if kcp.rmt_wnd == 0 {
+		current := currentMs()
+		if kcp.probe_wait == 0 {
+			kcp.probe_wait = IKCP_PROBE_INIT
+			kcp.ts_probe = current + kcp.probe_wait
+		} else {
+			if _itimediff(current, kcp.ts_probe) >= 0 {
+				if kcp.probe_wait < IKCP_PROBE_INIT {
+					kcp.probe_wait = IKCP_PROBE_INIT
+				}
+				kcp.probe_wait += kcp.probe_wait / 2
+				if kcp.probe_wait > IKCP_PROBE_LIMIT {
+					kcp.probe_wait = IKCP_PROBE_LIMIT
+				}
+				kcp.ts_probe = current + kcp.probe_wait
+				kcp.probe |= IKCP_ASK_SEND
+			}
+		}
+	} else {
+		kcp.ts_probe = 0
+		kcp.probe_wait = 0
+	}
+
+	// flush window probing commands
+	if (kcp.probe & IKCP_ASK_SEND) != 0 {
+		seg.cmd = IKCP_CMD_WASK
+		makeSpace(IKCP_OVERHEAD)
+		ptr = seg.encode(ptr)
+	}
+
+	// flush window probing commands
+	if (kcp.probe & IKCP_ASK_TELL) != 0 {
+		seg.cmd = IKCP_CMD_WINS
+		makeSpace(IKCP_OVERHEAD)
+		ptr = seg.encode(ptr)
+	}
+
+	kcp.probe = 0
+
+	// calculate window size
+	cwnd := _imin_(kcp.snd_wnd, kcp.rmt_wnd)
+	if kcp.nocwnd == 0 {
+		cwnd = _imin_(kcp.cwnd, cwnd)
+	}
+
+	// sliding window, controlled by snd_nxt && sna_una+cwnd
+	newSegsCount := 0
+	for k := range kcp.snd_queue {
+		if _itimediff(kcp.snd_nxt, kcp.snd_una+cwnd) >= 0 {
+			break
+		}
+		newseg := kcp.snd_queue[k]
+		newseg.conv = kcp.conv
+		newseg.cmd = IKCP_CMD_PUSH
+		newseg.sn = kcp.snd_nxt
+		kcp.snd_buf = append(kcp.snd_buf, newseg)
+		kcp.snd_nxt++
+		newSegsCount++
+	}
+	if newSegsCount > 0 {
+		kcp.snd_queue = kcp.remove_front(kcp.snd_queue, newSegsCount)
+	}
+
+	// calculate resent
+	resent := uint32(kcp.fastresend)
+	if kcp.fastresend <= 0 {
+		resent = 0xffffffff
+	}
+
+	// check for retransmissions
+	current := currentMs()
+	var change, lostSegs, fastRetransSegs, earlyRetransSegs uint64
+	minrto := int32(kcp.interval)
+
+	ref := kcp.snd_buf[:len(kcp.snd_buf)] // for bounds check elimination
+	for k := range ref {
+		segment := &ref[k]
+		needsend := false
+		if segment.acked == 1 {
+			continue
+		}
+		if segment.xmit == 0 { // initial transmit
+			needsend = true
+			segment.rto = kcp.rx_rto
+			segment.resendts = current + segment.rto
+		} else if segment.fastack >= resent { // fast retransmit
+			needsend = true
+			segment.fastack = 0
+			segment.rto = kcp.rx_rto
+			segment.resendts = current + segment.rto
+			change++
+			fastRetransSegs++
+		} else if segment.fastack > 0 && newSegsCount == 0 { // early retransmit
+			needsend = true
+			segment.fastack = 0
+			segment.rto = kcp.rx_rto
+			segment.resendts = current + segment.rto
+			change++
+			earlyRetransSegs++
+		} else if _itimediff(current, segment.resendts) >= 0 { // RTO
+			needsend = true
+			if kcp.nodelay == 0 {
+				segment.rto += kcp.rx_rto
+			} else {
+				segment.rto += kcp.rx_rto / 2
+			}
+			segment.fastack = 0
+			segment.resendts = current + segment.rto
+			lostSegs++
+		}
+
+		if needsend {
+			current = currentMs()
+			segment.xmit++
+			segment.ts = current
+			segment.wnd = seg.wnd
+			segment.una = seg.una
+
+			need := IKCP_OVERHEAD + len(segment.data)
+			makeSpace(need)
+			ptr = segment.encode(ptr)
+			copy(ptr, segment.data)
+			ptr = ptr[len(segment.data):]
+
+			if segment.xmit >= kcp.dead_link {
+				kcp.state = 0xFFFFFFFF
+			}
+		}
+
+		// get the nearest rto
+		if rto := _itimediff(segment.resendts, current); rto > 0 && rto < minrto {
+			minrto = rto
+		}
+	}
+
+	// flash remain segments
+	flushBuffer()
+
+	// counter updates
+	sum := lostSegs
+	if lostSegs > 0 {
+		atomic.AddUint64(&DefaultSnmp.LostSegs, lostSegs)
+	}
+	if fastRetransSegs > 0 {
+		atomic.AddUint64(&DefaultSnmp.FastRetransSegs, fastRetransSegs)
+		sum += fastRetransSegs
+	}
+	if earlyRetransSegs > 0 {
+		atomic.AddUint64(&DefaultSnmp.EarlyRetransSegs, earlyRetransSegs)
+		sum += earlyRetransSegs
+	}
+	if sum > 0 {
+		atomic.AddUint64(&DefaultSnmp.RetransSegs, sum)
+	}
+
+	// cwnd update
+	if kcp.nocwnd == 0 {
+		// update ssthresh
+		// rate halving, https://tools.ietf.org/html/rfc6937
+		if change > 0 {
+			inflight := kcp.snd_nxt - kcp.snd_una
+			kcp.ssthresh = inflight / 2
+			if kcp.ssthresh < IKCP_THRESH_MIN {
+				kcp.ssthresh = IKCP_THRESH_MIN
+			}
+			kcp.cwnd = kcp.ssthresh + resent
+			kcp.incr = kcp.cwnd * kcp.mss
+		}
+
+		// congestion control, https://tools.ietf.org/html/rfc5681
+		if lostSegs > 0 {
+			kcp.ssthresh = cwnd / 2
+			if kcp.ssthresh < IKCP_THRESH_MIN {
+				kcp.ssthresh = IKCP_THRESH_MIN
+			}
+			kcp.cwnd = 1
+			kcp.incr = kcp.mss
+		}
+
+		if kcp.cwnd < 1 {
+			kcp.cwnd = 1
+			kcp.incr = kcp.mss
+		}
+	}
+
+	return uint32(minrto)
+}
+
+// (deprecated)
+//
+// Update updates state (call it repeatedly, every 10ms-100ms), or you can ask
+// ikcp_check when to call it again (without ikcp_input/_send calling).
+// 'current' - current timestamp in millisec.
+func (kcp *KCP) Update() {
+	var slap int32
+
+	current := currentMs()
+	if kcp.updated == 0 {
+		kcp.updated = 1
+		kcp.ts_flush = current
+	}
+
+	slap = _itimediff(current, kcp.ts_flush)
+
+	if slap >= 10000 || slap < -10000 {
+		kcp.ts_flush = current
+		slap = 0
+	}
+
+	if slap >= 0 {
+		kcp.ts_flush += kcp.interval
+		if _itimediff(current, kcp.ts_flush) >= 0 {
+			kcp.ts_flush = current + kcp.interval
+		}
+		kcp.flush(false)
+	}
+}
+
+// (deprecated)
+//
+// Check determines when should you invoke ikcp_update:
+// returns when you should invoke ikcp_update in millisec, if there
+// is no ikcp_input/_send calling. you can call ikcp_update in that
+// time, instead of call update repeatly.
+// Important to reduce unnacessary ikcp_update invoking. use it to
+// schedule ikcp_update (eg. implementing an epoll-like mechanism,
+// or optimize ikcp_update when handling massive kcp connections)
+func (kcp *KCP) Check() uint32 {
+	current := currentMs()
+	ts_flush := kcp.ts_flush
+	tm_flush := int32(0x7fffffff)
+	tm_packet := int32(0x7fffffff)
+	minimal := uint32(0)
+	if kcp.updated == 0 {
+		return current
+	}
+
+	if _itimediff(current, ts_flush) >= 10000 ||
+		_itimediff(current, ts_flush) < -10000 {
+		ts_flush = current
+	}
+
+	if _itimediff(current, ts_flush) >= 0 {
+		return current
+	}
+
+	tm_flush = _itimediff(ts_flush, current)
+
+	for k := range kcp.snd_buf {
+		seg := &kcp.snd_buf[k]
+		diff := _itimediff(seg.resendts, current)
+		if diff <= 0 {
+			return current
+		}
+		if diff < tm_packet {
+			tm_packet = diff
+		}
+	}
+
+	minimal = uint32(tm_packet)
+	if tm_packet >= tm_flush {
+		minimal = uint32(tm_flush)
+	}
+	if minimal >= kcp.interval {
+		minimal = kcp.interval
+	}
+
+	return current + minimal
+}
+
+// SetMtu changes MTU size, default is 1400
+func (kcp *KCP) SetMtu(mtu int) int {
+	if mtu < 50 || mtu < IKCP_OVERHEAD {
+		return -1
+	}
+	if kcp.reserved >= int(kcp.mtu-IKCP_OVERHEAD) || kcp.reserved < 0 {
+		return -1
+	}
+
+	buffer := make([]byte, mtu)
+	if buffer == nil {
+		return -2
+	}
+	kcp.mtu = uint32(mtu)
+	kcp.mss = kcp.mtu - IKCP_OVERHEAD - uint32(kcp.reserved)
+	kcp.buffer = buffer
+	return 0
+}
+
+// NoDelay options
+// fastest: ikcp_nodelay(kcp, 1, 20, 2, 1)
+// nodelay: 0:disable(default), 1:enable
+// interval: internal update timer interval in millisec, default is 100ms
+// resend: 0:disable fast resend(default), 1:enable fast resend
+// nc: 0:normal congestion control(default), 1:disable congestion control
+func (kcp *KCP) NoDelay(nodelay, interval, resend, nc int) int {
+	if nodelay >= 0 {
+		kcp.nodelay = uint32(nodelay)
+		if nodelay != 0 {
+			kcp.rx_minrto = IKCP_RTO_NDL
+		} else {
+			kcp.rx_minrto = IKCP_RTO_MIN
+		}
+	}
+	if interval >= 0 {
+		if interval > 5000 {
+			interval = 5000
+		} else if interval < 10 {
+			interval = 10
+		}
+		kcp.interval = uint32(interval)
+	}
+	if resend >= 0 {
+		kcp.fastresend = int32(resend)
+	}
+	if nc >= 0 {
+		kcp.nocwnd = int32(nc)
+	}
+	return 0
+}
+
+// WndSize sets maximum window size: sndwnd=32, rcvwnd=32 by default
+func (kcp *KCP) WndSize(sndwnd, rcvwnd int) int {
+	if sndwnd > 0 {
+		kcp.snd_wnd = uint32(sndwnd)
+	}
+	if rcvwnd > 0 {
+		kcp.rcv_wnd = uint32(rcvwnd)
+	}
+	return 0
+}
+
+// WaitSnd gets how many packet is waiting to be sent
+func (kcp *KCP) WaitSnd() int {
+	return len(kcp.snd_buf) + len(kcp.snd_queue)
+}
+
+// remove front n elements from queue
+// if the number of elements to remove is more than half of the size.
+// just shift the rear elements to front, otherwise just reslice q to q[n:]
+// then the cost of runtime.growslice can always be less than n/2
+func (kcp *KCP) remove_front(q []segment, n int) []segment {
+	if n > cap(q)/2 {
+		newn := copy(q, q[n:])
+		return q[:newn]
+	}
+	return q[n:]
+}
+
+// Release all cached outgoing segments
+func (kcp *KCP) ReleaseTX() {
+	for k := range kcp.snd_queue {
+		if kcp.snd_queue[k].data != nil {
+			xmitBuf.Put(kcp.snd_queue[k].data)
+		}
+	}
+	for k := range kcp.snd_buf {
+		if kcp.snd_buf[k].data != nil {
+			xmitBuf.Put(kcp.snd_buf[k].data)
+		}
+	}
+	kcp.snd_queue = nil
+	kcp.snd_buf = nil
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/readloop.go b/vendor/github.com/xtaci/kcp-go/v5/readloop.go
new file mode 100644
index 0000000..697395a
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/readloop.go
@@ -0,0 +1,39 @@
+package kcp
+
+import (
+	"sync/atomic"
+
+	"github.com/pkg/errors"
+)
+
+func (s *UDPSession) defaultReadLoop() {
+	buf := make([]byte, mtuLimit)
+	var src string
+	for {
+		if n, addr, err := s.conn.ReadFrom(buf); err == nil {
+			// make sure the packet is from the same source
+			if src == "" { // set source address
+				src = addr.String()
+			} else if addr.String() != src {
+				atomic.AddUint64(&DefaultSnmp.InErrs, 1)
+				continue
+			}
+			s.packetInput(buf[:n])
+		} else {
+			s.notifyReadError(errors.WithStack(err))
+			return
+		}
+	}
+}
+
+func (l *Listener) defaultMonitor() {
+	buf := make([]byte, mtuLimit)
+	for {
+		if n, from, err := l.conn.ReadFrom(buf); err == nil {
+			l.packetInput(buf[:n], from)
+		} else {
+			l.notifyReadError(errors.WithStack(err))
+			return
+		}
+	}
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/readloop_generic.go b/vendor/github.com/xtaci/kcp-go/v5/readloop_generic.go
new file mode 100644
index 0000000..5dbe4f4
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/readloop_generic.go
@@ -0,0 +1,11 @@
+// +build !linux
+
+package kcp
+
+func (s *UDPSession) readLoop() {
+	s.defaultReadLoop()
+}
+
+func (l *Listener) monitor() {
+	l.defaultMonitor()
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/readloop_linux.go b/vendor/github.com/xtaci/kcp-go/v5/readloop_linux.go
new file mode 100644
index 0000000..be194af
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/readloop_linux.go
@@ -0,0 +1,111 @@
+// +build linux
+
+package kcp
+
+import (
+	"net"
+	"os"
+	"sync/atomic"
+
+	"github.com/pkg/errors"
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+)
+
+// the read loop for a client session
+func (s *UDPSession) readLoop() {
+	// default version
+	if s.xconn == nil {
+		s.defaultReadLoop()
+		return
+	}
+
+	// x/net version
+	var src string
+	msgs := make([]ipv4.Message, batchSize)
+	for k := range msgs {
+		msgs[k].Buffers = [][]byte{make([]byte, mtuLimit)}
+	}
+
+	for {
+		if count, err := s.xconn.ReadBatch(msgs, 0); err == nil {
+			for i := 0; i < count; i++ {
+				msg := &msgs[i]
+				// make sure the packet is from the same source
+				if src == "" { // set source address if nil
+					src = msg.Addr.String()
+				} else if msg.Addr.String() != src {
+					atomic.AddUint64(&DefaultSnmp.InErrs, 1)
+					continue
+				}
+
+				// source and size has validated
+				s.packetInput(msg.Buffers[0][:msg.N])
+			}
+		} else {
+			// compatibility issue:
+			// for linux kernel<=2.6.32, support for sendmmsg is not available
+			// an error of type os.SyscallError will be returned
+			if operr, ok := err.(*net.OpError); ok {
+				if se, ok := operr.Err.(*os.SyscallError); ok {
+					if se.Syscall == "recvmmsg" {
+						s.defaultReadLoop()
+						return
+					}
+				}
+			}
+			s.notifyReadError(errors.WithStack(err))
+			return
+		}
+	}
+}
+
+// monitor incoming data for all connections of server
+func (l *Listener) monitor() {
+	var xconn batchConn
+	if _, ok := l.conn.(*net.UDPConn); ok {
+		addr, err := net.ResolveUDPAddr("udp", l.conn.LocalAddr().String())
+		if err == nil {
+			if addr.IP.To4() != nil {
+				xconn = ipv4.NewPacketConn(l.conn)
+			} else {
+				xconn = ipv6.NewPacketConn(l.conn)
+			}
+		}
+	}
+
+	// default version
+	if xconn == nil {
+		l.defaultMonitor()
+		return
+	}
+
+	// x/net version
+	msgs := make([]ipv4.Message, batchSize)
+	for k := range msgs {
+		msgs[k].Buffers = [][]byte{make([]byte, mtuLimit)}
+	}
+
+	for {
+		if count, err := xconn.ReadBatch(msgs, 0); err == nil {
+			for i := 0; i < count; i++ {
+				msg := &msgs[i]
+				l.packetInput(msg.Buffers[0][:msg.N], msg.Addr)
+			}
+		} else {
+			// compatibility issue:
+			// for linux kernel<=2.6.32, support for sendmmsg is not available
+			// an error of type os.SyscallError will be returned
+			if operr, ok := err.(*net.OpError); ok {
+				if se, ok := operr.Err.(*os.SyscallError); ok {
+					if se.Syscall == "recvmmsg" {
+						l.defaultMonitor()
+						return
+					}
+				}
+			}
+			l.notifyReadError(errors.WithStack(err))
+			return
+		}
+	}
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/sess.go b/vendor/github.com/xtaci/kcp-go/v5/sess.go
new file mode 100644
index 0000000..2dedd74
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/sess.go
@@ -0,0 +1,1075 @@
+// Package kcp-go is a Reliable-UDP library for golang.
+//
+// This library intents to provide a smooth, resilient, ordered,
+// error-checked and anonymous delivery of streams over UDP packets.
+//
+// The interfaces of this package aims to be compatible with
+// net.Conn in standard library, but offers powerful features for advanced users.
+package kcp
+
+import (
+	"crypto/rand"
+	"encoding/binary"
+	"hash/crc32"
+	"io"
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/pkg/errors"
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+)
+
+const (
+	// 16-bytes nonce for each packet
+	nonceSize = 16
+
+	// 4-bytes packet checksum
+	crcSize = 4
+
+	// overall crypto header size
+	cryptHeaderSize = nonceSize + crcSize
+
+	// maximum packet size
+	mtuLimit = 1500
+
+	// accept backlog
+	acceptBacklog = 128
+)
+
+var (
+	errInvalidOperation = errors.New("invalid operation")
+	errTimeout          = errors.New("timeout")
+)
+
+var (
+	// a system-wide packet buffer shared among sending, receiving and FEC
+	// to mitigate high-frequency memory allocation for packets, bytes from xmitBuf
+	// is aligned to 64bit
+	xmitBuf sync.Pool
+)
+
+func init() {
+	xmitBuf.New = func() interface{} {
+		return make([]byte, mtuLimit)
+	}
+}
+
+type (
+	// UDPSession defines a KCP session implemented by UDP
+	UDPSession struct {
+		conn    net.PacketConn // the underlying packet connection
+		ownConn bool           // true if we created conn internally, false if provided by caller
+		kcp     *KCP           // KCP ARQ protocol
+		l       *Listener      // pointing to the Listener object if it's been accepted by a Listener
+		block   BlockCrypt     // block encryption object
+
+		// kcp receiving is based on packets
+		// recvbuf turns packets into stream
+		recvbuf []byte
+		bufptr  []byte
+
+		// FEC codec
+		fecDecoder *fecDecoder
+		fecEncoder *fecEncoder
+
+		// settings
+		remote     net.Addr  // remote peer address
+		rd         time.Time // read deadline
+		wd         time.Time // write deadline
+		headerSize int       // the header size additional to a KCP frame
+		ackNoDelay bool      // send ack immediately for each incoming packet(testing purpose)
+		writeDelay bool      // delay kcp.flush() for Write() for bulk transfer
+		dup        int       // duplicate udp packets(testing purpose)
+
+		// notifications
+		die          chan struct{} // notify current session has Closed
+		dieOnce      sync.Once
+		chReadEvent  chan struct{} // notify Read() can be called without blocking
+		chWriteEvent chan struct{} // notify Write() can be called without blocking
+
+		// socket error handling
+		socketReadError      atomic.Value
+		socketWriteError     atomic.Value
+		chSocketReadError    chan struct{}
+		chSocketWriteError   chan struct{}
+		socketReadErrorOnce  sync.Once
+		socketWriteErrorOnce sync.Once
+
+		// nonce generator
+		nonce Entropy
+
+		// packets waiting to be sent on wire
+		txqueue         []ipv4.Message
+		xconn           batchConn // for x/net
+		xconnWriteError error
+
+		mu sync.Mutex
+	}
+
+	setReadBuffer interface {
+		SetReadBuffer(bytes int) error
+	}
+
+	setWriteBuffer interface {
+		SetWriteBuffer(bytes int) error
+	}
+
+	setDSCP interface {
+		SetDSCP(int) error
+	}
+)
+
+// newUDPSession create a new udp session for client or server
+func newUDPSession(conv uint32, dataShards, parityShards int, l *Listener, conn net.PacketConn, ownConn bool, remote net.Addr, block BlockCrypt) *UDPSession {
+	sess := new(UDPSession)
+	sess.die = make(chan struct{})
+	sess.nonce = new(nonceAES128)
+	sess.nonce.Init()
+	sess.chReadEvent = make(chan struct{}, 1)
+	sess.chWriteEvent = make(chan struct{}, 1)
+	sess.chSocketReadError = make(chan struct{})
+	sess.chSocketWriteError = make(chan struct{})
+	sess.remote = remote
+	sess.conn = conn
+	sess.ownConn = ownConn
+	sess.l = l
+	sess.block = block
+	sess.recvbuf = make([]byte, mtuLimit)
+
+	// cast to writebatch conn
+	if _, ok := conn.(*net.UDPConn); ok {
+		addr, err := net.ResolveUDPAddr("udp", conn.LocalAddr().String())
+		if err == nil {
+			if addr.IP.To4() != nil {
+				sess.xconn = ipv4.NewPacketConn(conn)
+			} else {
+				sess.xconn = ipv6.NewPacketConn(conn)
+			}
+		}
+	}
+
+	// FEC codec initialization
+	sess.fecDecoder = newFECDecoder(dataShards, parityShards)
+	if sess.block != nil {
+		sess.fecEncoder = newFECEncoder(dataShards, parityShards, cryptHeaderSize)
+	} else {
+		sess.fecEncoder = newFECEncoder(dataShards, parityShards, 0)
+	}
+
+	// calculate additional header size introduced by FEC and encryption
+	if sess.block != nil {
+		sess.headerSize += cryptHeaderSize
+	}
+	if sess.fecEncoder != nil {
+		sess.headerSize += fecHeaderSizePlus2
+	}
+
+	sess.kcp = NewKCP(conv, func(buf []byte, size int) {
+		if size >= IKCP_OVERHEAD+sess.headerSize {
+			sess.output(buf[:size])
+		}
+	})
+	sess.kcp.ReserveBytes(sess.headerSize)
+
+	if sess.l == nil { // it's a client connection
+		go sess.readLoop()
+		atomic.AddUint64(&DefaultSnmp.ActiveOpens, 1)
+	} else {
+		atomic.AddUint64(&DefaultSnmp.PassiveOpens, 1)
+	}
+
+	// start per-session updater
+	SystemTimedSched.Put(sess.update, time.Now())
+
+	currestab := atomic.AddUint64(&DefaultSnmp.CurrEstab, 1)
+	maxconn := atomic.LoadUint64(&DefaultSnmp.MaxConn)
+	if currestab > maxconn {
+		atomic.CompareAndSwapUint64(&DefaultSnmp.MaxConn, maxconn, currestab)
+	}
+
+	return sess
+}
+
+// Read implements net.Conn
+func (s *UDPSession) Read(b []byte) (n int, err error) {
+	for {
+		s.mu.Lock()
+		if len(s.bufptr) > 0 { // copy from buffer into b
+			n = copy(b, s.bufptr)
+			s.bufptr = s.bufptr[n:]
+			s.mu.Unlock()
+			atomic.AddUint64(&DefaultSnmp.BytesReceived, uint64(n))
+			return n, nil
+		}
+
+		if size := s.kcp.PeekSize(); size > 0 { // peek data size from kcp
+			if len(b) >= size { // receive data into 'b' directly
+				s.kcp.Recv(b)
+				s.mu.Unlock()
+				atomic.AddUint64(&DefaultSnmp.BytesReceived, uint64(size))
+				return size, nil
+			}
+
+			// if necessary resize the stream buffer to guarantee a sufficient buffer space
+			if cap(s.recvbuf) < size {
+				s.recvbuf = make([]byte, size)
+			}
+
+			// resize the length of recvbuf to correspond to data size
+			s.recvbuf = s.recvbuf[:size]
+			s.kcp.Recv(s.recvbuf)
+			n = copy(b, s.recvbuf)   // copy to 'b'
+			s.bufptr = s.recvbuf[n:] // pointer update
+			s.mu.Unlock()
+			atomic.AddUint64(&DefaultSnmp.BytesReceived, uint64(n))
+			return n, nil
+		}
+
+		// deadline for current reading operation
+		var timeout *time.Timer
+		var c <-chan time.Time
+		if !s.rd.IsZero() {
+			if time.Now().After(s.rd) {
+				s.mu.Unlock()
+				return 0, errors.WithStack(errTimeout)
+			}
+
+			delay := time.Until(s.rd)
+			timeout = time.NewTimer(delay)
+			c = timeout.C
+		}
+		s.mu.Unlock()
+
+		// wait for read event or timeout or error
+		select {
+		case <-s.chReadEvent:
+			if timeout != nil {
+				timeout.Stop()
+			}
+		case <-c:
+			return 0, errors.WithStack(errTimeout)
+		case <-s.chSocketReadError:
+			return 0, s.socketReadError.Load().(error)
+		case <-s.die:
+			return 0, errors.WithStack(io.ErrClosedPipe)
+		}
+	}
+}
+
+// Write implements net.Conn
+func (s *UDPSession) Write(b []byte) (n int, err error) { return s.WriteBuffers([][]byte{b}) }
+
+// WriteBuffers write a vector of byte slices to the underlying connection
+func (s *UDPSession) WriteBuffers(v [][]byte) (n int, err error) {
+	for {
+		select {
+		case <-s.chSocketWriteError:
+			return 0, s.socketWriteError.Load().(error)
+		case <-s.die:
+			return 0, errors.WithStack(io.ErrClosedPipe)
+		default:
+		}
+
+		s.mu.Lock()
+
+		// make sure write do not overflow the max sliding window on both side
+		waitsnd := s.kcp.WaitSnd()
+		if waitsnd < int(s.kcp.snd_wnd) && waitsnd < int(s.kcp.rmt_wnd) {
+			for _, b := range v {
+				n += len(b)
+				for {
+					if len(b) <= int(s.kcp.mss) {
+						s.kcp.Send(b)
+						break
+					} else {
+						s.kcp.Send(b[:s.kcp.mss])
+						b = b[s.kcp.mss:]
+					}
+				}
+			}
+
+			waitsnd = s.kcp.WaitSnd()
+			if waitsnd >= int(s.kcp.snd_wnd) || waitsnd >= int(s.kcp.rmt_wnd) || !s.writeDelay {
+				s.kcp.flush(false)
+				s.uncork()
+			}
+			s.mu.Unlock()
+			atomic.AddUint64(&DefaultSnmp.BytesSent, uint64(n))
+			return n, nil
+		}
+
+		var timeout *time.Timer
+		var c <-chan time.Time
+		if !s.wd.IsZero() {
+			if time.Now().After(s.wd) {
+				s.mu.Unlock()
+				return 0, errors.WithStack(errTimeout)
+			}
+			delay := time.Until(s.wd)
+			timeout = time.NewTimer(delay)
+			c = timeout.C
+		}
+		s.mu.Unlock()
+
+		select {
+		case <-s.chWriteEvent:
+			if timeout != nil {
+				timeout.Stop()
+			}
+		case <-c:
+			return 0, errors.WithStack(errTimeout)
+		case <-s.chSocketWriteError:
+			return 0, s.socketWriteError.Load().(error)
+		case <-s.die:
+			return 0, errors.WithStack(io.ErrClosedPipe)
+		}
+	}
+}
+
+// uncork sends data in txqueue if there is any
+func (s *UDPSession) uncork() {
+	if len(s.txqueue) > 0 {
+		s.tx(s.txqueue)
+		// recycle
+		for k := range s.txqueue {
+			xmitBuf.Put(s.txqueue[k].Buffers[0])
+			s.txqueue[k].Buffers = nil
+		}
+		s.txqueue = s.txqueue[:0]
+	}
+}
+
+// Close closes the connection.
+func (s *UDPSession) Close() error {
+	var once bool
+	s.dieOnce.Do(func() {
+		close(s.die)
+		once = true
+	})
+
+	if once {
+		atomic.AddUint64(&DefaultSnmp.CurrEstab, ^uint64(0))
+
+		// try best to send all queued messages
+		s.mu.Lock()
+		s.kcp.flush(false)
+		s.uncork()
+		// release pending segments
+		s.kcp.ReleaseTX()
+		if s.fecDecoder != nil {
+			s.fecDecoder.release()
+		}
+		s.mu.Unlock()
+
+		if s.l != nil { // belongs to listener
+			s.l.closeSession(s.remote)
+			return nil
+		} else if s.ownConn { // client socket close
+			return s.conn.Close()
+		} else {
+			return nil
+		}
+	} else {
+		return errors.WithStack(io.ErrClosedPipe)
+	}
+}
+
+// LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.
+func (s *UDPSession) LocalAddr() net.Addr { return s.conn.LocalAddr() }
+
+// RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.
+func (s *UDPSession) RemoteAddr() net.Addr { return s.remote }
+
+// SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.
+func (s *UDPSession) SetDeadline(t time.Time) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.rd = t
+	s.wd = t
+	s.notifyReadEvent()
+	s.notifyWriteEvent()
+	return nil
+}
+
+// SetReadDeadline implements the Conn SetReadDeadline method.
+func (s *UDPSession) SetReadDeadline(t time.Time) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.rd = t
+	s.notifyReadEvent()
+	return nil
+}
+
+// SetWriteDeadline implements the Conn SetWriteDeadline method.
+func (s *UDPSession) SetWriteDeadline(t time.Time) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.wd = t
+	s.notifyWriteEvent()
+	return nil
+}
+
+// SetWriteDelay delays write for bulk transfer until the next update interval
+func (s *UDPSession) SetWriteDelay(delay bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.writeDelay = delay
+}
+
+// SetWindowSize set maximum window size
+func (s *UDPSession) SetWindowSize(sndwnd, rcvwnd int) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.kcp.WndSize(sndwnd, rcvwnd)
+}
+
+// SetMtu sets the maximum transmission unit(not including UDP header)
+func (s *UDPSession) SetMtu(mtu int) bool {
+	if mtu > mtuLimit {
+		return false
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.kcp.SetMtu(mtu)
+	return true
+}
+
+// SetStreamMode toggles the stream mode on/off
+func (s *UDPSession) SetStreamMode(enable bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if enable {
+		s.kcp.stream = 1
+	} else {
+		s.kcp.stream = 0
+	}
+}
+
+// SetACKNoDelay changes ack flush option, set true to flush ack immediately,
+func (s *UDPSession) SetACKNoDelay(nodelay bool) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.ackNoDelay = nodelay
+}
+
+// (deprecated)
+//
+// SetDUP duplicates udp packets for kcp output.
+func (s *UDPSession) SetDUP(dup int) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.dup = dup
+}
+
+// SetNoDelay calls nodelay() of kcp
+// https://github.com/skywind3000/kcp/blob/master/README.en.md#protocol-configuration
+func (s *UDPSession) SetNoDelay(nodelay, interval, resend, nc int) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.kcp.NoDelay(nodelay, interval, resend, nc)
+}
+
+// SetDSCP sets the 6bit DSCP field in IPv4 header, or 8bit Traffic Class in IPv6 header.
+//
+// if the underlying connection has implemented `func SetDSCP(int) error`, SetDSCP() will invoke
+// this function instead.
+//
+// It has no effect if it's accepted from Listener.
+func (s *UDPSession) SetDSCP(dscp int) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.l != nil {
+		return errInvalidOperation
+	}
+
+	// interface enabled
+	if ts, ok := s.conn.(setDSCP); ok {
+		return ts.SetDSCP(dscp)
+	}
+
+	if nc, ok := s.conn.(net.Conn); ok {
+		var succeed bool
+		if err := ipv4.NewConn(nc).SetTOS(dscp << 2); err == nil {
+			succeed = true
+		}
+		if err := ipv6.NewConn(nc).SetTrafficClass(dscp); err == nil {
+			succeed = true
+		}
+
+		if succeed {
+			return nil
+		}
+	}
+	return errInvalidOperation
+}
+
+// SetReadBuffer sets the socket read buffer, no effect if it's accepted from Listener
+func (s *UDPSession) SetReadBuffer(bytes int) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.l == nil {
+		if nc, ok := s.conn.(setReadBuffer); ok {
+			return nc.SetReadBuffer(bytes)
+		}
+	}
+	return errInvalidOperation
+}
+
+// SetWriteBuffer sets the socket write buffer, no effect if it's accepted from Listener
+func (s *UDPSession) SetWriteBuffer(bytes int) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.l == nil {
+		if nc, ok := s.conn.(setWriteBuffer); ok {
+			return nc.SetWriteBuffer(bytes)
+		}
+	}
+	return errInvalidOperation
+}
+
+// post-processing for sending a packet from kcp core
+// steps:
+// 1. FEC packet generation
+// 2. CRC32 integrity
+// 3. Encryption
+// 4. TxQueue
+func (s *UDPSession) output(buf []byte) {
+	var ecc [][]byte
+
+	// 1. FEC encoding
+	if s.fecEncoder != nil {
+		ecc = s.fecEncoder.encode(buf)
+	}
+
+	// 2&3. crc32 & encryption
+	if s.block != nil {
+		s.nonce.Fill(buf[:nonceSize])
+		checksum := crc32.ChecksumIEEE(buf[cryptHeaderSize:])
+		binary.LittleEndian.PutUint32(buf[nonceSize:], checksum)
+		s.block.Encrypt(buf, buf)
+
+		for k := range ecc {
+			s.nonce.Fill(ecc[k][:nonceSize])
+			checksum := crc32.ChecksumIEEE(ecc[k][cryptHeaderSize:])
+			binary.LittleEndian.PutUint32(ecc[k][nonceSize:], checksum)
+			s.block.Encrypt(ecc[k], ecc[k])
+		}
+	}
+
+	// 4. TxQueue
+	var msg ipv4.Message
+	for i := 0; i < s.dup+1; i++ {
+		bts := xmitBuf.Get().([]byte)[:len(buf)]
+		copy(bts, buf)
+		msg.Buffers = [][]byte{bts}
+		msg.Addr = s.remote
+		s.txqueue = append(s.txqueue, msg)
+	}
+
+	for k := range ecc {
+		bts := xmitBuf.Get().([]byte)[:len(ecc[k])]
+		copy(bts, ecc[k])
+		msg.Buffers = [][]byte{bts}
+		msg.Addr = s.remote
+		s.txqueue = append(s.txqueue, msg)
+	}
+}
+
+// sess update to trigger protocol
+func (s *UDPSession) update() {
+	select {
+	case <-s.die:
+	default:
+		s.mu.Lock()
+		interval := s.kcp.flush(false)
+		waitsnd := s.kcp.WaitSnd()
+		if waitsnd < int(s.kcp.snd_wnd) && waitsnd < int(s.kcp.rmt_wnd) {
+			s.notifyWriteEvent()
+		}
+		s.uncork()
+		s.mu.Unlock()
+		// self-synchronized timed scheduling
+		SystemTimedSched.Put(s.update, time.Now().Add(time.Duration(interval)*time.Millisecond))
+	}
+}
+
+// GetConv gets conversation id of a session
+func (s *UDPSession) GetConv() uint32 { return s.kcp.conv }
+
+// GetRTO gets current rto of the session
+func (s *UDPSession) GetRTO() uint32 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.kcp.rx_rto
+}
+
+// GetSRTT gets current srtt of the session
+func (s *UDPSession) GetSRTT() int32 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.kcp.rx_srtt
+}
+
+// GetRTTVar gets current rtt variance of the session
+func (s *UDPSession) GetSRTTVar() int32 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.kcp.rx_rttvar
+}
+
+func (s *UDPSession) notifyReadEvent() {
+	select {
+	case s.chReadEvent <- struct{}{}:
+	default:
+	}
+}
+
+func (s *UDPSession) notifyWriteEvent() {
+	select {
+	case s.chWriteEvent <- struct{}{}:
+	default:
+	}
+}
+
+func (s *UDPSession) notifyReadError(err error) {
+	s.socketReadErrorOnce.Do(func() {
+		s.socketReadError.Store(err)
+		close(s.chSocketReadError)
+	})
+}
+
+func (s *UDPSession) notifyWriteError(err error) {
+	s.socketWriteErrorOnce.Do(func() {
+		s.socketWriteError.Store(err)
+		close(s.chSocketWriteError)
+	})
+}
+
+// packet input stage
+func (s *UDPSession) packetInput(data []byte) {
+	decrypted := false
+	if s.block != nil && len(data) >= cryptHeaderSize {
+		s.block.Decrypt(data, data)
+		data = data[nonceSize:]
+		checksum := crc32.ChecksumIEEE(data[crcSize:])
+		if checksum == binary.LittleEndian.Uint32(data) {
+			data = data[crcSize:]
+			decrypted = true
+		} else {
+			atomic.AddUint64(&DefaultSnmp.InCsumErrors, 1)
+		}
+	} else if s.block == nil {
+		decrypted = true
+	}
+
+	if decrypted && len(data) >= IKCP_OVERHEAD {
+		s.kcpInput(data)
+	}
+}
+
+func (s *UDPSession) kcpInput(data []byte) {
+	var kcpInErrors, fecErrs, fecRecovered, fecParityShards uint64
+
+	fecFlag := binary.LittleEndian.Uint16(data[4:])
+	if fecFlag == typeData || fecFlag == typeParity { // 16bit kcp cmd [81-84] and frg [0-255] will not overlap with FEC type 0x00f1 0x00f2
+		if len(data) >= fecHeaderSizePlus2 {
+			f := fecPacket(data)
+			if f.flag() == typeParity {
+				fecParityShards++
+			}
+
+			// lock
+			s.mu.Lock()
+			// if fecDecoder is not initialized, create one with default parameter
+			if s.fecDecoder == nil {
+				s.fecDecoder = newFECDecoder(1, 1)
+			}
+			recovers := s.fecDecoder.decode(f)
+			if f.flag() == typeData {
+				if ret := s.kcp.Input(data[fecHeaderSizePlus2:], true, s.ackNoDelay); ret != 0 {
+					kcpInErrors++
+				}
+			}
+
+			for _, r := range recovers {
+				if len(r) >= 2 { // must be larger than 2bytes
+					sz := binary.LittleEndian.Uint16(r)
+					if int(sz) <= len(r) && sz >= 2 {
+						if ret := s.kcp.Input(r[2:sz], false, s.ackNoDelay); ret == 0 {
+							fecRecovered++
+						} else {
+							kcpInErrors++
+						}
+					} else {
+						fecErrs++
+					}
+				} else {
+					fecErrs++
+				}
+				// recycle the recovers
+				xmitBuf.Put(r)
+			}
+
+			// to notify the readers to receive the data
+			if n := s.kcp.PeekSize(); n > 0 {
+				s.notifyReadEvent()
+			}
+			// to notify the writers
+			waitsnd := s.kcp.WaitSnd()
+			if waitsnd < int(s.kcp.snd_wnd) && waitsnd < int(s.kcp.rmt_wnd) {
+				s.notifyWriteEvent()
+			}
+
+			s.uncork()
+			s.mu.Unlock()
+		} else {
+			atomic.AddUint64(&DefaultSnmp.InErrs, 1)
+		}
+	} else {
+		s.mu.Lock()
+		if ret := s.kcp.Input(data, true, s.ackNoDelay); ret != 0 {
+			kcpInErrors++
+		}
+		if n := s.kcp.PeekSize(); n > 0 {
+			s.notifyReadEvent()
+		}
+		waitsnd := s.kcp.WaitSnd()
+		if waitsnd < int(s.kcp.snd_wnd) && waitsnd < int(s.kcp.rmt_wnd) {
+			s.notifyWriteEvent()
+		}
+		s.uncork()
+		s.mu.Unlock()
+	}
+
+	atomic.AddUint64(&DefaultSnmp.InPkts, 1)
+	atomic.AddUint64(&DefaultSnmp.InBytes, uint64(len(data)))
+	if fecParityShards > 0 {
+		atomic.AddUint64(&DefaultSnmp.FECParityShards, fecParityShards)
+	}
+	if kcpInErrors > 0 {
+		atomic.AddUint64(&DefaultSnmp.KCPInErrors, kcpInErrors)
+	}
+	if fecErrs > 0 {
+		atomic.AddUint64(&DefaultSnmp.FECErrs, fecErrs)
+	}
+	if fecRecovered > 0 {
+		atomic.AddUint64(&DefaultSnmp.FECRecovered, fecRecovered)
+	}
+
+}
+
+type (
+	// Listener defines a server which will be waiting to accept incoming connections
+	Listener struct {
+		block        BlockCrypt     // block encryption
+		dataShards   int            // FEC data shard
+		parityShards int            // FEC parity shard
+		conn         net.PacketConn // the underlying packet connection
+		ownConn      bool           // true if we created conn internally, false if provided by caller
+
+		sessions        map[string]*UDPSession // all sessions accepted by this Listener
+		sessionLock     sync.RWMutex
+		chAccepts       chan *UDPSession // Listen() backlog
+		chSessionClosed chan net.Addr    // session close queue
+
+		die     chan struct{} // notify the listener has closed
+		dieOnce sync.Once
+
+		// socket error handling
+		socketReadError     atomic.Value
+		chSocketReadError   chan struct{}
+		socketReadErrorOnce sync.Once
+
+		rd atomic.Value // read deadline for Accept()
+	}
+)
+
+// packet input stage
+func (l *Listener) packetInput(data []byte, addr net.Addr) {
+	decrypted := false
+	if l.block != nil && len(data) >= cryptHeaderSize {
+		l.block.Decrypt(data, data)
+		data = data[nonceSize:]
+		checksum := crc32.ChecksumIEEE(data[crcSize:])
+		if checksum == binary.LittleEndian.Uint32(data) {
+			data = data[crcSize:]
+			decrypted = true
+		} else {
+			atomic.AddUint64(&DefaultSnmp.InCsumErrors, 1)
+		}
+	} else if l.block == nil {
+		decrypted = true
+	}
+
+	if decrypted && len(data) >= IKCP_OVERHEAD {
+		l.sessionLock.RLock()
+		s, ok := l.sessions[addr.String()]
+		l.sessionLock.RUnlock()
+
+		var conv, sn uint32
+		convRecovered := false
+		fecFlag := binary.LittleEndian.Uint16(data[4:])
+		if fecFlag == typeData || fecFlag == typeParity { // 16bit kcp cmd [81-84] and frg [0-255] will not overlap with FEC type 0x00f1 0x00f2
+			// packet with FEC
+			if fecFlag == typeData && len(data) >= fecHeaderSizePlus2+IKCP_OVERHEAD {
+				conv = binary.LittleEndian.Uint32(data[fecHeaderSizePlus2:])
+				sn = binary.LittleEndian.Uint32(data[fecHeaderSizePlus2+IKCP_SN_OFFSET:])
+				convRecovered = true
+			}
+		} else {
+			// packet without FEC
+			conv = binary.LittleEndian.Uint32(data)
+			sn = binary.LittleEndian.Uint32(data[IKCP_SN_OFFSET:])
+			convRecovered = true
+		}
+
+		if ok { // existing connection
+			if !convRecovered || conv == s.kcp.conv { // parity data or valid conversation
+				s.kcpInput(data)
+			} else if sn == 0 { // should replace current connection
+				s.Close()
+				s = nil
+			}
+		}
+
+		if s == nil && convRecovered { // new session
+			if len(l.chAccepts) < cap(l.chAccepts) { // do not let the new sessions overwhelm accept queue
+				s := newUDPSession(conv, l.dataShards, l.parityShards, l, l.conn, false, addr, l.block)
+				s.kcpInput(data)
+				l.sessionLock.Lock()
+				l.sessions[addr.String()] = s
+				l.sessionLock.Unlock()
+				l.chAccepts <- s
+			}
+		}
+	}
+}
+
+func (l *Listener) notifyReadError(err error) {
+	l.socketReadErrorOnce.Do(func() {
+		l.socketReadError.Store(err)
+		close(l.chSocketReadError)
+
+		// propagate read error to all sessions
+		l.sessionLock.RLock()
+		for _, s := range l.sessions {
+			s.notifyReadError(err)
+		}
+		l.sessionLock.RUnlock()
+	})
+}
+
+// SetReadBuffer sets the socket read buffer for the Listener
+func (l *Listener) SetReadBuffer(bytes int) error {
+	if nc, ok := l.conn.(setReadBuffer); ok {
+		return nc.SetReadBuffer(bytes)
+	}
+	return errInvalidOperation
+}
+
+// SetWriteBuffer sets the socket write buffer for the Listener
+func (l *Listener) SetWriteBuffer(bytes int) error {
+	if nc, ok := l.conn.(setWriteBuffer); ok {
+		return nc.SetWriteBuffer(bytes)
+	}
+	return errInvalidOperation
+}
+
+// SetDSCP sets the 6bit DSCP field in IPv4 header, or 8bit Traffic Class in IPv6 header.
+//
+// if the underlying connection has implemented `func SetDSCP(int) error`, SetDSCP() will invoke
+// this function instead.
+func (l *Listener) SetDSCP(dscp int) error {
+	// interface enabled
+	if ts, ok := l.conn.(setDSCP); ok {
+		return ts.SetDSCP(dscp)
+	}
+
+	if nc, ok := l.conn.(net.Conn); ok {
+		var succeed bool
+		if err := ipv4.NewConn(nc).SetTOS(dscp << 2); err == nil {
+			succeed = true
+		}
+		if err := ipv6.NewConn(nc).SetTrafficClass(dscp); err == nil {
+			succeed = true
+		}
+
+		if succeed {
+			return nil
+		}
+	}
+	return errInvalidOperation
+}
+
+// Accept implements the Accept method in the Listener interface; it waits for the next call and returns a generic Conn.
+func (l *Listener) Accept() (net.Conn, error) {
+	return l.AcceptKCP()
+}
+
+// AcceptKCP accepts a KCP connection
+func (l *Listener) AcceptKCP() (*UDPSession, error) {
+	var timeout <-chan time.Time
+	if tdeadline, ok := l.rd.Load().(time.Time); ok && !tdeadline.IsZero() {
+		timeout = time.After(time.Until(tdeadline))
+	}
+
+	select {
+	case <-timeout:
+		return nil, errors.WithStack(errTimeout)
+	case c := <-l.chAccepts:
+		return c, nil
+	case <-l.chSocketReadError:
+		return nil, l.socketReadError.Load().(error)
+	case <-l.die:
+		return nil, errors.WithStack(io.ErrClosedPipe)
+	}
+}
+
+// SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.
+func (l *Listener) SetDeadline(t time.Time) error {
+	l.SetReadDeadline(t)
+	l.SetWriteDeadline(t)
+	return nil
+}
+
+// SetReadDeadline implements the Conn SetReadDeadline method.
+func (l *Listener) SetReadDeadline(t time.Time) error {
+	l.rd.Store(t)
+	return nil
+}
+
+// SetWriteDeadline implements the Conn SetWriteDeadline method.
+func (l *Listener) SetWriteDeadline(t time.Time) error { return errInvalidOperation }
+
+// Close stops listening on the UDP address, and closes the socket
+func (l *Listener) Close() error {
+	var once bool
+	l.dieOnce.Do(func() {
+		close(l.die)
+		once = true
+	})
+
+	var err error
+	if once {
+		if l.ownConn {
+			err = l.conn.Close()
+		}
+	} else {
+		err = errors.WithStack(io.ErrClosedPipe)
+	}
+	return err
+}
+
+// closeSession notify the listener that a session has closed
+func (l *Listener) closeSession(remote net.Addr) (ret bool) {
+	l.sessionLock.Lock()
+	defer l.sessionLock.Unlock()
+	if _, ok := l.sessions[remote.String()]; ok {
+		delete(l.sessions, remote.String())
+		return true
+	}
+	return false
+}
+
+// Addr returns the listener's network address, The Addr returned is shared by all invocations of Addr, so do not modify it.
+func (l *Listener) Addr() net.Addr { return l.conn.LocalAddr() }
+
+// Listen listens for incoming KCP packets addressed to the local address laddr on the network "udp",
+func Listen(laddr string) (net.Listener, error) { return ListenWithOptions(laddr, nil, 0, 0) }
+
+// ListenWithOptions listens for incoming KCP packets addressed to the local address laddr on the network "udp" with packet encryption.
+//
+// 'block' is the block encryption algorithm to encrypt packets.
+//
+// 'dataShards', 'parityShards' specify how many parity packets will be generated following the data packets.
+//
+// Check https://github.com/klauspost/reedsolomon for details
+func ListenWithOptions(laddr string, block BlockCrypt, dataShards, parityShards int) (*Listener, error) {
+	udpaddr, err := net.ResolveUDPAddr("udp", laddr)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+	conn, err := net.ListenUDP("udp", udpaddr)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	return serveConn(block, dataShards, parityShards, conn, true)
+}
+
+// ServeConn serves KCP protocol for a single packet connection.
+func ServeConn(block BlockCrypt, dataShards, parityShards int, conn net.PacketConn) (*Listener, error) {
+	return serveConn(block, dataShards, parityShards, conn, false)
+}
+
+func serveConn(block BlockCrypt, dataShards, parityShards int, conn net.PacketConn, ownConn bool) (*Listener, error) {
+	l := new(Listener)
+	l.conn = conn
+	l.ownConn = ownConn
+	l.sessions = make(map[string]*UDPSession)
+	l.chAccepts = make(chan *UDPSession, acceptBacklog)
+	l.chSessionClosed = make(chan net.Addr)
+	l.die = make(chan struct{})
+	l.dataShards = dataShards
+	l.parityShards = parityShards
+	l.block = block
+	l.chSocketReadError = make(chan struct{})
+	go l.monitor()
+	return l, nil
+}
+
+// Dial connects to the remote address "raddr" on the network "udp" without encryption and FEC
+func Dial(raddr string) (net.Conn, error) { return DialWithOptions(raddr, nil, 0, 0) }
+
+// DialWithOptions connects to the remote address "raddr" on the network "udp" with packet encryption
+//
+// 'block' is the block encryption algorithm to encrypt packets.
+//
+// 'dataShards', 'parityShards' specify how many parity packets will be generated following the data packets.
+//
+// Check https://github.com/klauspost/reedsolomon for details
+func DialWithOptions(raddr string, block BlockCrypt, dataShards, parityShards int) (*UDPSession, error) {
+	// network type detection
+	udpaddr, err := net.ResolveUDPAddr("udp", raddr)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+	network := "udp4"
+	if udpaddr.IP.To4() == nil {
+		network = "udp"
+	}
+
+	conn, err := net.ListenUDP(network, nil)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	var convid uint32
+	binary.Read(rand.Reader, binary.LittleEndian, &convid)
+	return newUDPSession(convid, dataShards, parityShards, nil, conn, true, udpaddr, block), nil
+}
+
+// NewConn3 establishes a session and talks KCP protocol over a packet connection.
+func NewConn3(convid uint32, raddr net.Addr, block BlockCrypt, dataShards, parityShards int, conn net.PacketConn) (*UDPSession, error) {
+	return newUDPSession(convid, dataShards, parityShards, nil, conn, false, raddr, block), nil
+}
+
+// NewConn2 establishes a session and talks KCP protocol over a packet connection.
+func NewConn2(raddr net.Addr, block BlockCrypt, dataShards, parityShards int, conn net.PacketConn) (*UDPSession, error) {
+	var convid uint32
+	binary.Read(rand.Reader, binary.LittleEndian, &convid)
+	return NewConn3(convid, raddr, block, dataShards, parityShards, conn)
+}
+
+// NewConn establishes a session and talks KCP protocol over a packet connection.
+func NewConn(raddr string, block BlockCrypt, dataShards, parityShards int, conn net.PacketConn) (*UDPSession, error) {
+	udpaddr, err := net.ResolveUDPAddr("udp", raddr)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+	return NewConn2(udpaddr, block, dataShards, parityShards, conn)
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/snmp.go b/vendor/github.com/xtaci/kcp-go/v5/snmp.go
new file mode 100644
index 0000000..f961810
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/snmp.go
@@ -0,0 +1,164 @@
+package kcp
+
+import (
+	"fmt"
+	"sync/atomic"
+)
+
+// Snmp defines network statistics indicator
+type Snmp struct {
+	BytesSent        uint64 // bytes sent from upper level
+	BytesReceived    uint64 // bytes received to upper level
+	MaxConn          uint64 // max number of connections ever reached
+	ActiveOpens      uint64 // accumulated active open connections
+	PassiveOpens     uint64 // accumulated passive open connections
+	CurrEstab        uint64 // current number of established connections
+	InErrs           uint64 // UDP read errors reported from net.PacketConn
+	InCsumErrors     uint64 // checksum errors from CRC32
+	KCPInErrors      uint64 // packet iput errors reported from KCP
+	InPkts           uint64 // incoming packets count
+	OutPkts          uint64 // outgoing packets count
+	InSegs           uint64 // incoming KCP segments
+	OutSegs          uint64 // outgoing KCP segments
+	InBytes          uint64 // UDP bytes received
+	OutBytes         uint64 // UDP bytes sent
+	RetransSegs      uint64 // accmulated retransmited segments
+	FastRetransSegs  uint64 // accmulated fast retransmitted segments
+	EarlyRetransSegs uint64 // accmulated early retransmitted segments
+	LostSegs         uint64 // number of segs inferred as lost
+	RepeatSegs       uint64 // number of segs duplicated
+	FECRecovered     uint64 // correct packets recovered from FEC
+	FECErrs          uint64 // incorrect packets recovered from FEC
+	FECParityShards  uint64 // FEC segments received
+	FECShortShards   uint64 // number of data shards that's not enough for recovery
+}
+
+func newSnmp() *Snmp {
+	return new(Snmp)
+}
+
+// Header returns all field names
+func (s *Snmp) Header() []string {
+	return []string{
+		"BytesSent",
+		"BytesReceived",
+		"MaxConn",
+		"ActiveOpens",
+		"PassiveOpens",
+		"CurrEstab",
+		"InErrs",
+		"InCsumErrors",
+		"KCPInErrors",
+		"InPkts",
+		"OutPkts",
+		"InSegs",
+		"OutSegs",
+		"InBytes",
+		"OutBytes",
+		"RetransSegs",
+		"FastRetransSegs",
+		"EarlyRetransSegs",
+		"LostSegs",
+		"RepeatSegs",
+		"FECParityShards",
+		"FECErrs",
+		"FECRecovered",
+		"FECShortShards",
+	}
+}
+
+// ToSlice returns current snmp info as slice
+func (s *Snmp) ToSlice() []string {
+	snmp := s.Copy()
+	return []string{
+		fmt.Sprint(snmp.BytesSent),
+		fmt.Sprint(snmp.BytesReceived),
+		fmt.Sprint(snmp.MaxConn),
+		fmt.Sprint(snmp.ActiveOpens),
+		fmt.Sprint(snmp.PassiveOpens),
+		fmt.Sprint(snmp.CurrEstab),
+		fmt.Sprint(snmp.InErrs),
+		fmt.Sprint(snmp.InCsumErrors),
+		fmt.Sprint(snmp.KCPInErrors),
+		fmt.Sprint(snmp.InPkts),
+		fmt.Sprint(snmp.OutPkts),
+		fmt.Sprint(snmp.InSegs),
+		fmt.Sprint(snmp.OutSegs),
+		fmt.Sprint(snmp.InBytes),
+		fmt.Sprint(snmp.OutBytes),
+		fmt.Sprint(snmp.RetransSegs),
+		fmt.Sprint(snmp.FastRetransSegs),
+		fmt.Sprint(snmp.EarlyRetransSegs),
+		fmt.Sprint(snmp.LostSegs),
+		fmt.Sprint(snmp.RepeatSegs),
+		fmt.Sprint(snmp.FECParityShards),
+		fmt.Sprint(snmp.FECErrs),
+		fmt.Sprint(snmp.FECRecovered),
+		fmt.Sprint(snmp.FECShortShards),
+	}
+}
+
+// Copy make a copy of current snmp snapshot
+func (s *Snmp) Copy() *Snmp {
+	d := newSnmp()
+	d.BytesSent = atomic.LoadUint64(&s.BytesSent)
+	d.BytesReceived = atomic.LoadUint64(&s.BytesReceived)
+	d.MaxConn = atomic.LoadUint64(&s.MaxConn)
+	d.ActiveOpens = atomic.LoadUint64(&s.ActiveOpens)
+	d.PassiveOpens = atomic.LoadUint64(&s.PassiveOpens)
+	d.CurrEstab = atomic.LoadUint64(&s.CurrEstab)
+	d.InErrs = atomic.LoadUint64(&s.InErrs)
+	d.InCsumErrors = atomic.LoadUint64(&s.InCsumErrors)
+	d.KCPInErrors = atomic.LoadUint64(&s.KCPInErrors)
+	d.InPkts = atomic.LoadUint64(&s.InPkts)
+	d.OutPkts = atomic.LoadUint64(&s.OutPkts)
+	d.InSegs = atomic.LoadUint64(&s.InSegs)
+	d.OutSegs = atomic.LoadUint64(&s.OutSegs)
+	d.InBytes = atomic.LoadUint64(&s.InBytes)
+	d.OutBytes = atomic.LoadUint64(&s.OutBytes)
+	d.RetransSegs = atomic.LoadUint64(&s.RetransSegs)
+	d.FastRetransSegs = atomic.LoadUint64(&s.FastRetransSegs)
+	d.EarlyRetransSegs = atomic.LoadUint64(&s.EarlyRetransSegs)
+	d.LostSegs = atomic.LoadUint64(&s.LostSegs)
+	d.RepeatSegs = atomic.LoadUint64(&s.RepeatSegs)
+	d.FECParityShards = atomic.LoadUint64(&s.FECParityShards)
+	d.FECErrs = atomic.LoadUint64(&s.FECErrs)
+	d.FECRecovered = atomic.LoadUint64(&s.FECRecovered)
+	d.FECShortShards = atomic.LoadUint64(&s.FECShortShards)
+	return d
+}
+
+// Reset values to zero
+func (s *Snmp) Reset() {
+	atomic.StoreUint64(&s.BytesSent, 0)
+	atomic.StoreUint64(&s.BytesReceived, 0)
+	atomic.StoreUint64(&s.MaxConn, 0)
+	atomic.StoreUint64(&s.ActiveOpens, 0)
+	atomic.StoreUint64(&s.PassiveOpens, 0)
+	atomic.StoreUint64(&s.CurrEstab, 0)
+	atomic.StoreUint64(&s.InErrs, 0)
+	atomic.StoreUint64(&s.InCsumErrors, 0)
+	atomic.StoreUint64(&s.KCPInErrors, 0)
+	atomic.StoreUint64(&s.InPkts, 0)
+	atomic.StoreUint64(&s.OutPkts, 0)
+	atomic.StoreUint64(&s.InSegs, 0)
+	atomic.StoreUint64(&s.OutSegs, 0)
+	atomic.StoreUint64(&s.InBytes, 0)
+	atomic.StoreUint64(&s.OutBytes, 0)
+	atomic.StoreUint64(&s.RetransSegs, 0)
+	atomic.StoreUint64(&s.FastRetransSegs, 0)
+	atomic.StoreUint64(&s.EarlyRetransSegs, 0)
+	atomic.StoreUint64(&s.LostSegs, 0)
+	atomic.StoreUint64(&s.RepeatSegs, 0)
+	atomic.StoreUint64(&s.FECParityShards, 0)
+	atomic.StoreUint64(&s.FECErrs, 0)
+	atomic.StoreUint64(&s.FECRecovered, 0)
+	atomic.StoreUint64(&s.FECShortShards, 0)
+}
+
+// DefaultSnmp is the global KCP connection statistics collector
+var DefaultSnmp *Snmp
+
+func init() {
+	DefaultSnmp = newSnmp()
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/timedsched.go b/vendor/github.com/xtaci/kcp-go/v5/timedsched.go
new file mode 100644
index 0000000..2db7c20
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/timedsched.go
@@ -0,0 +1,146 @@
+package kcp
+
+import (
+	"container/heap"
+	"runtime"
+	"sync"
+	"time"
+)
+
+// SystemTimedSched is the library level timed-scheduler
+var SystemTimedSched *TimedSched = NewTimedSched(runtime.NumCPU())
+
+type timedFunc struct {
+	execute func()
+	ts      time.Time
+}
+
+// a heap for sorted timed function
+type timedFuncHeap []timedFunc
+
+func (h timedFuncHeap) Len() int            { return len(h) }
+func (h timedFuncHeap) Less(i, j int) bool  { return h[i].ts.Before(h[j].ts) }
+func (h timedFuncHeap) Swap(i, j int)       { h[i], h[j] = h[j], h[i] }
+func (h *timedFuncHeap) Push(x interface{}) { *h = append(*h, x.(timedFunc)) }
+func (h *timedFuncHeap) Pop() interface{} {
+	old := *h
+	n := len(old)
+	x := old[n-1]
+	old[n-1].execute = nil // avoid memory leak
+	*h = old[0 : n-1]
+	return x
+}
+
+// TimedSched represents the control struct for timed parallel scheduler
+type TimedSched struct {
+	// prepending tasks
+	prependTasks    []timedFunc
+	prependLock     sync.Mutex
+	chPrependNotify chan struct{}
+
+	// tasks will be distributed through chTask
+	chTask chan timedFunc
+
+	dieOnce sync.Once
+	die     chan struct{}
+}
+
+// NewTimedSched creates a parallel-scheduler with given parallelization
+func NewTimedSched(parallel int) *TimedSched {
+	ts := new(TimedSched)
+	ts.chTask = make(chan timedFunc)
+	ts.die = make(chan struct{})
+	ts.chPrependNotify = make(chan struct{}, 1)
+
+	for i := 0; i < parallel; i++ {
+		go ts.sched()
+	}
+	go ts.prepend()
+	return ts
+}
+
+func (ts *TimedSched) sched() {
+	var tasks timedFuncHeap
+	timer := time.NewTimer(0)
+	drained := false
+	for {
+		select {
+		case task := <-ts.chTask:
+			now := time.Now()
+			if now.After(task.ts) {
+				// already delayed! execute immediately
+				task.execute()
+			} else {
+				heap.Push(&tasks, task)
+				// properly reset timer to trigger based on the top element
+				stopped := timer.Stop()
+				if !stopped && !drained {
+					<-timer.C
+				}
+				timer.Reset(tasks[0].ts.Sub(now))
+				drained = false
+			}
+		case now := <-timer.C:
+			drained = true
+			for tasks.Len() > 0 {
+				if now.After(tasks[0].ts) {
+					heap.Pop(&tasks).(timedFunc).execute()
+				} else {
+					timer.Reset(tasks[0].ts.Sub(now))
+					drained = false
+					break
+				}
+			}
+		case <-ts.die:
+			return
+		}
+	}
+}
+
+func (ts *TimedSched) prepend() {
+	var tasks []timedFunc
+	for {
+		select {
+		case <-ts.chPrependNotify:
+			ts.prependLock.Lock()
+			// keep cap to reuse slice
+			if cap(tasks) < cap(ts.prependTasks) {
+				tasks = make([]timedFunc, 0, cap(ts.prependTasks))
+			}
+			tasks = tasks[:len(ts.prependTasks)]
+			copy(tasks, ts.prependTasks)
+			for k := range ts.prependTasks {
+				ts.prependTasks[k].execute = nil // avoid memory leak
+			}
+			ts.prependTasks = ts.prependTasks[:0]
+			ts.prependLock.Unlock()
+
+			for k := range tasks {
+				select {
+				case ts.chTask <- tasks[k]:
+					tasks[k].execute = nil // avoid memory leak
+				case <-ts.die:
+					return
+				}
+			}
+			tasks = tasks[:0]
+		case <-ts.die:
+			return
+		}
+	}
+}
+
+// Put a function 'f' awaiting to be executed at 'deadline'
+func (ts *TimedSched) Put(f func(), deadline time.Time) {
+	ts.prependLock.Lock()
+	ts.prependTasks = append(ts.prependTasks, timedFunc{f, deadline})
+	ts.prependLock.Unlock()
+
+	select {
+	case ts.chPrependNotify <- struct{}{}:
+	default:
+	}
+}
+
+// Close terminates this scheduler
+func (ts *TimedSched) Close() { ts.dieOnce.Do(func() { close(ts.die) }) }
diff --git a/vendor/github.com/xtaci/kcp-go/v5/tx.go b/vendor/github.com/xtaci/kcp-go/v5/tx.go
new file mode 100644
index 0000000..3397b82
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/tx.go
@@ -0,0 +1,24 @@
+package kcp
+
+import (
+	"sync/atomic"
+
+	"github.com/pkg/errors"
+	"golang.org/x/net/ipv4"
+)
+
+func (s *UDPSession) defaultTx(txqueue []ipv4.Message) {
+	nbytes := 0
+	npkts := 0
+	for k := range txqueue {
+		if n, err := s.conn.WriteTo(txqueue[k].Buffers[0], txqueue[k].Addr); err == nil {
+			nbytes += n
+			npkts++
+		} else {
+			s.notifyWriteError(errors.WithStack(err))
+			break
+		}
+	}
+	atomic.AddUint64(&DefaultSnmp.OutPkts, uint64(npkts))
+	atomic.AddUint64(&DefaultSnmp.OutBytes, uint64(nbytes))
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/tx_generic.go b/vendor/github.com/xtaci/kcp-go/v5/tx_generic.go
new file mode 100644
index 0000000..0b4f349
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/tx_generic.go
@@ -0,0 +1,11 @@
+// +build !linux
+
+package kcp
+
+import (
+	"golang.org/x/net/ipv4"
+)
+
+func (s *UDPSession) tx(txqueue []ipv4.Message) {
+	s.defaultTx(txqueue)
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/tx_linux.go b/vendor/github.com/xtaci/kcp-go/v5/tx_linux.go
new file mode 100644
index 0000000..4f19df5
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/tx_linux.go
@@ -0,0 +1,51 @@
+// +build linux
+
+package kcp
+
+import (
+	"net"
+	"os"
+	"sync/atomic"
+
+	"github.com/pkg/errors"
+	"golang.org/x/net/ipv4"
+)
+
+func (s *UDPSession) tx(txqueue []ipv4.Message) {
+	// default version
+	if s.xconn == nil || s.xconnWriteError != nil {
+		s.defaultTx(txqueue)
+		return
+	}
+
+	// x/net version
+	nbytes := 0
+	npkts := 0
+	for len(txqueue) > 0 {
+		if n, err := s.xconn.WriteBatch(txqueue, 0); err == nil {
+			for k := range txqueue[:n] {
+				nbytes += len(txqueue[k].Buffers[0])
+			}
+			npkts += n
+			txqueue = txqueue[n:]
+		} else {
+			// compatibility issue:
+			// for linux kernel<=2.6.32, support for sendmmsg is not available
+			// an error of type os.SyscallError will be returned
+			if operr, ok := err.(*net.OpError); ok {
+				if se, ok := operr.Err.(*os.SyscallError); ok {
+					if se.Syscall == "sendmmsg" {
+						s.xconnWriteError = se
+						s.defaultTx(txqueue)
+						return
+					}
+				}
+			}
+			s.notifyWriteError(errors.WithStack(err))
+			break
+		}
+	}
+
+	atomic.AddUint64(&DefaultSnmp.OutPkts, uint64(npkts))
+	atomic.AddUint64(&DefaultSnmp.OutBytes, uint64(nbytes))
+}
diff --git a/vendor/github.com/xtaci/kcp-go/v5/wechat_donate.jpg b/vendor/github.com/xtaci/kcp-go/v5/wechat_donate.jpg
new file mode 100644
index 0000000..ad72505
--- /dev/null
+++ b/vendor/github.com/xtaci/kcp-go/v5/wechat_donate.jpg