summaryrefslogtreecommitdiff
path: root/bitmask_android/openvpn/src/openvpn/gremlin.c
blob: f0aa7f619c2005447114a7abe87198dc3d771e17 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 * Test protocol robustness by simulating dropped packets and
 * network outages when the --gremlin option is used.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif

#include "syshead.h"

#ifdef ENABLE_DEBUG

#include "error.h"
#include "common.h"
#include "misc.h"
#include "otime.h"
#include "gremlin.h"

#include "memdbg.h"

/*
 * Parameters for packet corruption and droppage.
 * Each parameter has 4 possible levels, 0 = disabled,
 * while 1, 2, and 3 are enumerated in the below arrays.
 * The parameter is a 2-bit field within the --gremlin
 * parameter.
 */

/*
 * Probability that we will drop a packet is 1 / n
 */
static const int drop_freq[] = { 500, 100, 50 };

/*
 * Probability that we will corrupt a packet is 1 / n
 */
static const int corrupt_freq[] = { 500, 100, 50 };

/*
 * When network goes up, it will be up for between
 * UP_LOW and UP_HIGH seconds.
 */
static const int up_low[] =  {  60, 10,  5 };
static const int up_high[] = { 600, 60, 10 };

/*
 * When network goes down, it will be down for between
 * DOWN_LOW and DOWN_HIGH seconds.
 */
static const int down_low[] =  {  5, 10,  10 };
static const int down_high[] = { 10, 60, 120 };

/*
 * Packet flood levels:
 *  { number of packets, packet size }
 */
static const struct packet_flood_parms packet_flood_data[] =
  {{10, 100}, {10, 1500}, {100, 1500}};

struct packet_flood_parms
get_packet_flood_parms (int level)
{
  ASSERT (level > 0 && level < 4);
  return packet_flood_data [level - 1];
}

/*
 * Return true with probability 1/n
 */
static bool flip(int n) {
  return (get_random() % n) == 0;
}

/*
 * Return uniformly distributed random number between
 * low and high.
 */
static int roll(int low, int high) {
  int ret;
  ASSERT (low <= high);
  ret = low + (get_random() % (high - low + 1));
  ASSERT (ret >= low && ret <= high);
  return ret;
}

static bool initialized; /* GLOBAL */
static bool up;          /* GLOBAL */
static time_t next;      /* GLOBAL */

/*
 * Return false if we should drop a packet.
 */
bool
ask_gremlin (int flags)
{
  const int up_down_level = GREMLIN_UP_DOWN_LEVEL (flags);
  const int drop_level = GREMLIN_DROP_LEVEL (flags);

  if (!initialized)
    {
      initialized = true;

      if (up_down_level)
	up = false;
      else
	up = true;

      next = now;
    }

  if (up_down_level) /* change up/down state? */
    {
      if (now >= next)
	{
	  int delta;
	  if (up)
	    {
	      delta = roll (down_low[up_down_level-1], down_high[up_down_level-1]);
	      up = false;
	    }
	  else
	    {
	      delta = roll (up_low[up_down_level-1], up_high[up_down_level-1]);
	      up = true;
	    }
      
	  msg (D_GREMLIN,
	       "GREMLIN: CONNECTION GOING %s FOR %d SECONDS",
	       (up ? "UP" : "DOWN"),
	       delta);
	  next = now + delta;
	}
    }

  if (drop_level)
    {
      if (up && flip (drop_freq[drop_level-1]))
	{
	  dmsg (D_GREMLIN_VERBOSE, "GREMLIN: Random packet drop");
	  return false;
	}
    }

  return up;
}

/*
 * Possibly corrupt a packet.
 */
void corrupt_gremlin (struct buffer *buf, int flags) {
  const int corrupt_level = GREMLIN_CORRUPT_LEVEL (flags);
  if (corrupt_level)
    {
      if (flip (corrupt_freq[corrupt_level-1]))
	{
	  do
	    {
	      if (buf->len > 0)
		{
		  uint8_t r = roll (0, 255);
		  int method = roll (0, 5);

		  switch (method) {
		  case 0: /* corrupt the first byte */
		    *BPTR (buf) = r;
		    break;
		  case 1: /* corrupt the last byte */
		    *(BPTR (buf) + buf->len - 1) = r;
		    break;
		  case 2: /* corrupt a random byte */
		    *(BPTR(buf) + roll (0, buf->len - 1)) = r;
		    break;
		  case 3: /* append a random byte */
		    buf_write (buf, &r, 1);
		    break;
		  case 4: /* reduce length by 1 */
		    --buf->len;
		    break;
		  case 5: /* reduce length by a random amount */
		    buf->len -= roll (0, buf->len - 1);
		    break;
		  }
		  dmsg (D_GREMLIN_VERBOSE, "GREMLIN: Packet Corruption, method=%d", method);
		}
	      else
		break;
	    } while (flip (2)); /* a 50% chance we will corrupt again */
	}
    }
}

#else
static void dummy(void) {}
#endif