release/src/router/openvpn/gremlin.c

   1 /*
   2  *  OpenVPN -- An application to securely tunnel IP networks
   3  *             over a single UDP port, with support for SSL/TLS-based
   4  *             session authentication and key exchange,
   5  *             packet encryption, packet authentication, and
   6  *             packet compression.
   7  *
   8  *  Copyright (C) 2002-2009 OpenVPN Technologies, Inc. <sales@openvpn.net>
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License version 2
  12  *  as published by the Free Software Foundation.
  13  *
  14  *  This program is distributed in the hope that it will be useful,
  15  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  *  GNU General Public License for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License
  20  *  along with this program (see the file COPYING included with this
  21  *  distribution); if not, write to the Free Software Foundation, Inc.,
  22  *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  23  */
  24
  25 /*
  26  * Test protocol robustness by simulating dropped packets and
  27  * network outages when the --gremlin option is used.
  28  */
  29
  30 #include "syshead.h"
  31
  32 #ifdef ENABLE_DEBUG
  33
  34 #include "error.h"
  35 #include "common.h"
  36 #include "misc.h"
  37 #include "otime.h"
  38 #include "gremlin.h"
  39
  40 #include "memdbg.h"
  41
  42 /*
  43  * Parameters for packet corruption and droppage.
  44  * Each parameter has 4 possible levels, 0 = disabled,
  45  * while 1, 2, and 3 are enumerated in the below arrays.
  46  * The parameter is a 2-bit field within the --gremlin
  47  * parameter.
  48  */
  49
  50 /*
  51  * Probability that we will drop a packet is 1 / n
  52  */
  53 static const int drop_freq[] = { 500, 100, 50 };
  54
  55 /*
  56  * Probability that we will corrupt a packet is 1 / n
  57  */
  58 static const int corrupt_freq[] = { 500, 100, 50 };
  59
  60 /*
  61  * When network goes up, it will be up for between
  62  * UP_LOW and UP_HIGH seconds.
  63  */
  64 static const int up_low[] =  {  60, 10,  5 };
  65 static const int up_high[] = { 600, 60, 10 };
  66
  67 /*
  68  * When network goes down, it will be down for between
  69  * DOWN_LOW and DOWN_HIGH seconds.
  70  */
  71 static const int down_low[] =  {  5, 10,  10 };
  72 static const int down_high[] = { 10, 60, 120 };
  73
  74 /*
  75  * Packet flood levels:
  76  *  { number of packets, packet size }
  77  */
  78 static const struct packet_flood_parms packet_flood_data[] =
  79   {{10, 100}, {10, 1500}, {100, 1500}};
  80
  81 struct packet_flood_parms
  82 get_packet_flood_parms (int level)
  83 {
  84   ASSERT (level > 0 && level < 4);
  85   return packet_flood_data [level - 1];
  86 }
  87
  88 /*
  89  * Return true with probability 1/n
  90  */
  91 static bool flip(int n) {
  92   return (get_random() % n) == 0;
  93 }
  94
  95 /*
  96  * Return uniformly distributed random number between
  97  * low and high.
  98  */
  99 static int roll(int low, int high) {
 100   int ret;
 101   ASSERT (low <= high);
 102   ret = low + (get_random() % (high - low + 1));
 103   ASSERT (ret >= low && ret <= high);
 104   return ret;
 105 }
 106
 107 static bool initialized; /* GLOBAL */
 108 static bool up;          /* GLOBAL */
 109 static time_t next;      /* GLOBAL */
 110
 111 /*
 112  * Return false if we should drop a packet.
 113  */
 114 bool
 115 ask_gremlin (int flags)
 116 {
 117   const int up_down_level = GREMLIN_UP_DOWN_LEVEL (flags);
 118   const int drop_level = GREMLIN_DROP_LEVEL (flags);
 119
 120   if (!initialized)
 121     {
 122       initialized = true;
 123
 124       if (up_down_level)
 125         up = false;
 126       else
 127         up = true;
 128
 129       next = now;
 130     }
 131
 132   if (up_down_level) /* change up/down state? */
 133     {
 134       if (now >= next)
 135         {
 136           int delta;
 137           if (up)
 138             {
 139               delta = roll (down_low[up_down_level-1], down_high[up_down_level-1]);
 140               up = false;
 141             }
 142           else
 143             {
 144               delta = roll (up_low[up_down_level-1], up_high[up_down_level-1]);
 145               up = true;
 146             }
 147
 148           msg (D_GREMLIN,
 149                "GREMLIN: CONNECTION GOING %s FOR %d SECONDS",
 150                (up ? "UP" : "DOWN"),
 151                delta);
 152           next = now + delta;
 153         }
 154     }
 155
 156   if (drop_level)
 157     {
 158       if (up && flip (drop_freq[drop_level-1]))
 159         {
 160           dmsg (D_GREMLIN_VERBOSE, "GREMLIN: Random packet drop");
 161           return false;
 162         }
 163     }
 164
 165   return up;
 166 }
 167
 168 /*
 169  * Possibly corrupt a packet.
 170  */
 171 void corrupt_gremlin (struct buffer *buf, int flags) {
 172   const int corrupt_level = GREMLIN_CORRUPT_LEVEL (flags);
 173   if (corrupt_level)
 174     {
 175       if (flip (corrupt_freq[corrupt_level-1]))
 176         {
 177           do
 178             {
 179               if (buf->len > 0)
 180                 {
 181                   uint8_t r = roll (0, 255);
 182                   int method = roll (0, 5);
 183
 184                   switch (method) {
 185                   case 0: /* corrupt the first byte */
 186                     *BPTR (buf) = r;
 187                     break;
 188                   case 1: /* corrupt the last byte */
 189                     *(BPTR (buf) + buf->len - 1) = r;
 190                     break;
 191                   case 2: /* corrupt a random byte */
 192                     *(BPTR(buf) + roll (0, buf->len - 1)) = r;
 193                     break;
 194                   case 3: /* append a random byte */
 195                     buf_write (buf, &r, 1);
 196                     break;
 197                   case 4: /* reduce length by 1 */
 198                     --buf->len;
 199                     break;
 200                   case 5: /* reduce length by a random amount */
 201                     buf->len -= roll (0, buf->len - 1);
 202                     break;
 203                   }
 204                   dmsg (D_GREMLIN_VERBOSE, "GREMLIN: Packet Corruption, method=%d", method);
 205                 }
 206               else
 207                 break;
 208             } while (flip (2)); /* a 50% chance we will corrupt again */
 209         }
 210     }
 211 }
 212
 213 #else
 214 static void dummy(void) {}
 215 #endif