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Diffstat (limited to 'src/openvpn/gremlin.c')
| -rw-r--r-- | src/openvpn/gremlin.c | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/src/openvpn/gremlin.c b/src/openvpn/gremlin.c new file mode 100644 index 0000000..0a3cf19 --- /dev/null +++ b/src/openvpn/gremlin.c @@ -0,0 +1,221 @@ +/* + * 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) 2002-2005 OpenVPN Solutions LLC <info@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 WIN32 +#include "config-win32.h" +#else +#include "config.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 |