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diff --git a/src/openvpn/gremlin.c b/src/openvpn/gremlin.c
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+/*
+ * 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