added n'th packet match to patch-o-matic

diff --git a/extensions/.nth-test b/extensions/.nth-test
new file mode 100755 (executable)
index 0000000..536da95
--- /dev/null
+++ b/extensions/.nth-test
@@ -0,0 +1,3 @@
+#!/bin/sh
+# True if nth is applied.
+[ -f $KERNEL_DIR/include/linux/netfilter_ipv4/ipt_nth.h ] && echo nth

diff --git a/extensions/libipt_nth.c b/extensions/libipt_nth.c
new file mode 100644 (file)
index 0000000..5fdd362
--- /dev/null
+++ b/extensions/libipt_nth.c
@@ -0,0 +1,179 @@
+/* 
+   Shared library add-on to iptables to add match support for every Nth packet
+   
+   This file is distributed under the terms of the GNU General Public
+   License (GPL). Copies of the GPL can be obtained from:
+   ftp://prep.ai.mit.edu/pub/gnu/GPL
+
+   2001-07-17 Fabrice MARIE <fabrice@celestix.com> : initial development.
+*/
+
+#include <stdio.h>
+#include <netdb.h>
+#include <string.h>
+#include <stdlib.h>
+#include <syslog.h>
+#include <getopt.h>
+#include <iptables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_nth.h>
+
+
+/* Function which prints out usage message. */
+static void
+help(void)
+{
+       printf(
+"nth v%s options:\n"
+"  --every     Nth            Match every Nth packet.\n\n",
+" [--start]    counter        Initialize the counter at the number 'counter'\n"
+"                             instead of 0. Must be of the form :\n"
+"                             0 <= counter <= (nth-1)"
+"                             Example if nth=2 : 0 <= counter <= 1\n\n"
+NETFILTER_VERSION);
+}
+
+static struct option opts[] = {
+       { "every", 1, 0, '1' },
+       { "start", 1, 0, '2' },
+       { 0 }
+};
+
+/* Initialize the target. */
+static void
+init(struct ipt_entry_match *m, unsigned int *nfcache)
+{
+       *nfcache |= NFC_UNKNOWN;
+}
+
+#define IPT_NTH_OPT_EVERY      0x01
+#define IPT_NTH_OPT_NOT_EVERY  0x02
+#define IPT_NTH_OPT_START      0x04
+
+/* Function which parses command options; returns true if it
+   ate an option */
+static int
+parse(int c, char **argv, int invert, unsigned int *flags,
+      const struct ipt_entry *entry,
+      unsigned int *nfcache,
+      struct ipt_entry_match **match)
+{
+       struct ipt_nth_info *nthinfo = (struct ipt_nth_info *)(*match)->data;
+       int num;
+
+       switch (c) {
+       case '1':
+               /* check for common mistakes... */
+               if ((!invert) && (*flags & IPT_NTH_OPT_EVERY))
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify --every twice");
+               if (invert && (*flags & IPT_NTH_OPT_NOT_EVERY))
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify ! --every twice");
+               if ((!invert) && (*flags & IPT_NTH_OPT_NOT_EVERY))
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify --every with ! --every");
+               if (invert && (*flags & IPT_NTH_OPT_EVERY))
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify ! --every with --every");
+
+               /* Remember, this function will interpret a leading 0 to be 
+                  Octal, a leading 0x to be hexdecimal... */
+                num = string_to_number(optarg, 2, 100);
+                if (num < 2)
+                        exit_error(PARAMETER_PROBLEM,
+                                   "bad --every `%s', must be between 2 and 100", optarg);
+
+               /* assign the values */
+               nthinfo->every = num-1;
+               nthinfo->startat = 0;
+               if (invert)
+               {
+                       *flags |= IPT_NTH_OPT_NOT_EVERY;
+                       nthinfo->not = 1;
+               }
+               else
+               {
+                       *flags |= IPT_NTH_OPT_EVERY;
+                       nthinfo->not = 0;
+               }
+               break;
+       case '2':
+               /* check for common mistakes... */
+               if (!((*flags & IPT_NTH_OPT_EVERY) ||
+                     (*flags & IPT_NTH_OPT_NOT_EVERY)))
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify --start before --every");
+               if (invert)
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify with ! --start");
+               if (*flags & IPT_NTH_OPT_START)
+                       exit_error(PARAMETER_PROBLEM,
+                                  "Can't specify --start twice");
+               num = string_to_number(optarg, 0, nthinfo->every);
+                if (num < 0)
+                        exit_error(PARAMETER_PROBLEM,
+                                   "bad --start `%s', must between 0 and %u", optarg, nthinfo->every);
+               *flags |= IPT_NTH_OPT_START;
+               nthinfo->startat = num;
+               break;
+       default:
+               return 0;
+       }
+       return 1;
+}
+
+/* Final check; nothing. */
+static void final_check(unsigned int flags)
+{
+}
+
+/* Prints out the targinfo. */
+static void
+print(const struct ipt_ip *ip,
+      const struct ipt_entry_match *match,
+      int numeric)
+{
+       const struct ipt_nth_info *nthinfo
+               = (const struct ipt_nth_info *)match->data;
+
+       if (nthinfo->not == 1)
+               printf(" !");
+       printf("every %uth ", (nthinfo->every +1));
+       if (nthinfo->startat != 0)
+               printf(" start at %u ", nthinfo->startat);
+}
+
+/* Saves the union ipt_targinfo in parsable form to stdout. */
+static void
+save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
+{
+       const struct ipt_nth_info *nthinfo
+               = (const struct ipt_nth_info *)match->data;
+
+       if (nthinfo->not == 1)
+               printf("! ");
+       printf("--every %u ", (nthinfo->every +1));
+       if (nthinfo->startat != 0)
+               printf(" --start %u", nthinfo->startat );
+}
+
+struct iptables_match nth
+= { NULL,
+    "nth",
+    NETFILTER_VERSION,
+    IPT_ALIGN(sizeof(struct ipt_nth_info)),
+    IPT_ALIGN(sizeof(struct ipt_nth_info)),
+    &help,
+    &init,
+    &parse,
+    &final_check,
+    &print,
+    &save,
+    opts
+};
+
+void _init(void)
+{
+       register_match(&nth);
+}