1 files changed, 176 insertions, 0 deletions
diff --git a/vendor/github.com/pion/transport/vnet/udpproxy.go b/vendor/github.com/pion/transport/vnet/udpproxy.go
new file mode 100644
index 0000000..c774955
--- /dev/null
+++ b/vendor/github.com/pion/transport/vnet/udpproxy.go
@@ -0,0 +1,176 @@
+package vnet
+
+import (
+	"net"
+	"sync"
+	"time"
+)
+
+// UDPProxy is a proxy between real server(net.UDPConn) and vnet.UDPConn.
+//
+// High level design:
+//                           ..............................................
+//                           :         Virtual Network (vnet)             :
+//                           :                                            :
+//   +-------+ *         1 +----+         +--------+                      :
+//   | :App  |------------>|:Net|--o<-----|:Router |          .............................
+//   +-------+             +----+         |        |          :        UDPProxy           :
+//                           :            |        |       +----+     +---------+     +---------+     +--------+
+//                           :            |        |--->o--|:Net|-->o-| vnet.   |-->o-|  net.   |--->-| :Real  |
+//                           :            |        |       +----+     | UDPConn |     | UDPConn |     | Server |
+//                           :            |        |          :       +---------+     +---------+     +--------+
+//                           :            |        |          ............................:
+//                           :            +--------+                       :
+//                           ...............................................
+type UDPProxy struct {
+	// The router bind to.
+	router *Router
+
+	// Each vnet source, bind to a real socket to server.
+	// key is real server addr, which is net.Addr
+	// value is *aUDPProxyWorker
+	workers sync.Map
+
+	// For each endpoint, we never know when to start and stop proxy,
+	// so we stop the endpoint when timeout.
+	timeout time.Duration
+
+	// For utest, to mock the target real server.
+	// Optional, use the address of received client packet.
+	mockRealServerAddr *net.UDPAddr
+}
+
+// NewProxy create a proxy, the router for this proxy belongs/bind to. If need to proxy for
+// please create a new proxy for each router. For all addresses we proxy, we will create a
+// vnet.Net in this router and proxy all packets.
+func NewProxy(router *Router) (*UDPProxy, error) {
+	v := &UDPProxy{router: router, timeout: 2 * time.Minute}
+	return v, nil
+}
+
+// Close the proxy, stop all workers.
+func (v *UDPProxy) Close() error {
+	// nolint:godox // TODO: FIXME: Do cleanup.
+	return nil
+}
+
+// Proxy starts a worker for server, ignore if already started.
+func (v *UDPProxy) Proxy(client *Net, server *net.UDPAddr) error {
+	// Note that even if the worker exists, it's also ok to create a same worker,
+	// because the router will use the last one, and the real server will see a address
+	// change event after we switch to the next worker.
+	if _, ok := v.workers.Load(server.String()); ok {
+		// nolint:godox // TODO: Need to restart the stopped worker?
+		return nil
+	}
+
+	// Not exists, create a new one.
+	worker := &aUDPProxyWorker{
+		router: v.router, mockRealServerAddr: v.mockRealServerAddr,
+	}
+	v.workers.Store(server.String(), worker)
+
+	return worker.Proxy(client, server)
+}
+
+// A proxy worker for a specified proxy server.
+type aUDPProxyWorker struct {
+	router             *Router
+	mockRealServerAddr *net.UDPAddr
+
+	// Each vnet source, bind to a real socket to server.
+	// key is vnet client addr, which is net.Addr
+	// value is *net.UDPConn
+	endpoints sync.Map
+}
+
+func (v *aUDPProxyWorker) Proxy(client *Net, serverAddr *net.UDPAddr) error { // nolint:gocognit
+	// Create vnet for real server by serverAddr.
+	nw := NewNet(&NetConfig{
+		StaticIP: serverAddr.IP.String(),
+	})
+	if err := v.router.AddNet(nw); err != nil {
+		return err
+	}
+
+	// We must create a "same" vnet.UDPConn as the net.UDPConn,
+	// which has the same ip:port, to copy packets between them.
+	vnetSocket, err := nw.ListenUDP("udp4", serverAddr)
+	if err != nil {
+		return err
+	}
+
+	// Got new vnet client, start a new endpoint.
+	findEndpointBy := func(addr net.Addr) (*net.UDPConn, error) {
+		// Exists binding.
+		if value, ok := v.endpoints.Load(addr.String()); ok {
+			// Exists endpoint, reuse it.
+			return value.(*net.UDPConn), nil
+		}
+
+		// The real server we proxy to, for utest to mock it.
+		realAddr := serverAddr
+		if v.mockRealServerAddr != nil {
+			realAddr = v.mockRealServerAddr
+		}
+
+		// Got new vnet client, create new endpoint.
+		realSocket, err := net.DialUDP("udp4", nil, realAddr)
+		if err != nil {
+			return nil, err
+		}
+
+		// Bind address.
+		v.endpoints.Store(addr.String(), realSocket)
+
+		// Got packet from real serverAddr, we should proxy it to vnet.
+		// nolint:godox // TODO: FIXME: Do cleanup.
+		go func(vnetClientAddr net.Addr) {
+			buf := make([]byte, 1500)
+			for {
+				n, _, err := realSocket.ReadFrom(buf)
+				if err != nil {
+					return
+				}
+
+				if n <= 0 {
+					continue // Drop packet
+				}
+
+				if _, err := vnetSocket.WriteTo(buf[:n], vnetClientAddr); err != nil {
+					return
+				}
+			}
+		}(addr)
+
+		return realSocket, nil
+	}
+
+	// Start a proxy goroutine.
+	// nolint:godox // TODO: FIXME: Do cleanup.
+	go func() {
+		buf := make([]byte, 1500)
+
+		for {
+			n, addr, err := vnetSocket.ReadFrom(buf)
+			if err != nil {
+				return
+			}
+
+			if n <= 0 || addr == nil {
+				continue // Drop packet
+			}
+
+			realSocket, err := findEndpointBy(addr)
+			if err != nil {
+				continue // Drop packet.
+			}
+
+			if _, err := realSocket.Write(buf[:n]); err != nil {
+				return
+			}
+		}
+	}()
+
+	return nil
+}