extensions/libipt_ttl.c

   1 /* Shared library add-on to iptables to add TTL matching support
   2  * (C) 2000 by Harald Welte <laforge@gnumonks.org>
   3  *
   4  * $Id$
   5  *
   6  * This program is released under the terms of GNU GPL */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <getopt.h>
  12 #include <iptables.h>
  13
  14 #include <linux/netfilter_ipv4/ip_tables.h>
  15 #include <linux/netfilter_ipv4/ipt_ttl.h>
  16
  17 static void ttl_help(void)
  18 {
  19         printf(
  20 "ttl match options:\n"
  21 "  --ttl-eq value       Match time to live value\n"
  22 "  --ttl-lt value       Match TTL < value\n"
  23 "  --ttl-gt value       Match TTL > value\n");
  24 }
  25
  26 static int ttl_parse(int c, char **argv, int invert, unsigned int *flags,
  27                      const void *entry, struct xt_entry_match **match)
  28 {
  29         struct ipt_ttl_info *info = (struct ipt_ttl_info *) (*match)->data;
  30         unsigned int value;
  31
  32         check_inverse(optarg, &invert, &optind, 0);
  33
  34         switch (c) {
  35                 case '2':
  36                         if (string_to_number(optarg, 0, 255, &value) == -1)
  37                                 exit_error(PARAMETER_PROBLEM,
  38                                            "ttl: Expected value between 0 and 255");
  39
  40                         if (invert)
  41                                 info->mode = IPT_TTL_NE;
  42                         else
  43                                 info->mode = IPT_TTL_EQ;
  44
  45                         /* is 0 allowed? */
  46                         info->ttl = value;
  47                         break;
  48                 case '3':
  49                         if (string_to_number(optarg, 0, 255, &value) == -1)
  50                                 exit_error(PARAMETER_PROBLEM,
  51                                            "ttl: Expected value between 0 and 255");
  52
  53                         if (invert)
  54                                 exit_error(PARAMETER_PROBLEM,
  55                                                 "ttl: unexpected `!'");
  56
  57                         info->mode = IPT_TTL_LT;
  58                         info->ttl = value;
  59                         break;
  60                 case '4':
  61                         if (string_to_number(optarg, 0, 255, &value) == -1)
  62                                 exit_error(PARAMETER_PROBLEM,
  63                                            "ttl: Expected value between 0 and 255");
  64
  65                         if (invert)
  66                                 exit_error(PARAMETER_PROBLEM,
  67                                                 "ttl: unexpected `!'");
  68
  69                         info->mode = IPT_TTL_GT;
  70                         info->ttl = value;
  71                         break;
  72                 default:
  73                         return 0;
  74
  75         }
  76
  77         if (*flags)
  78                 exit_error(PARAMETER_PROBLEM,
  79                                 "Can't specify TTL option twice");
  80         *flags = 1;
  81
  82         return 1;
  83 }
  84
  85 static void ttl_check(unsigned int flags)
  86 {
  87         if (!flags)
  88                 exit_error(PARAMETER_PROBLEM,
  89                         "TTL match: You must specify one of "
  90                         "`--ttl-eq', `--ttl-lt', `--ttl-gt");
  91 }
  92
  93 static void ttl_print(const void *ip, const struct xt_entry_match *match,
  94                       int numeric)
  95 {
  96         const struct ipt_ttl_info *info =
  97                 (struct ipt_ttl_info *) match->data;
  98
  99         printf("TTL match ");
 100         switch (info->mode) {
 101                 case IPT_TTL_EQ:
 102                         printf("TTL == ");
 103                         break;
 104                 case IPT_TTL_NE:
 105                         printf("TTL != ");
 106                         break;
 107                 case IPT_TTL_LT:
 108                         printf("TTL < ");
 109                         break;
 110                 case IPT_TTL_GT:
 111                         printf("TTL > ");
 112                         break;
 113         }
 114         printf("%u ", info->ttl);
 115 }
 116
 117 static void ttl_save(const void *ip, const struct xt_entry_match *match)
 118 {
 119         const struct ipt_ttl_info *info =
 120                 (struct ipt_ttl_info *) match->data;
 121
 122         switch (info->mode) {
 123                 case IPT_TTL_EQ:
 124                         printf("--ttl-eq ");
 125                         break;
 126                 case IPT_TTL_NE:
 127                         printf("! --ttl-eq ");
 128                         break;
 129                 case IPT_TTL_LT:
 130                         printf("--ttl-lt ");
 131                         break;
 132                 case IPT_TTL_GT:
 133                         printf("--ttl-gt ");
 134                         break;
 135                 default:
 136                         /* error */
 137                         break;
 138         }
 139         printf("%u ", info->ttl);
 140 }
 141
 142 static const struct option ttl_opts[] = {
 143         { "ttl", 1, NULL, '2' },
 144         { "ttl-eq", 1, NULL, '2'},
 145         { "ttl-lt", 1, NULL, '3'},
 146         { "ttl-gt", 1, NULL, '4'},
 147         { .name = NULL }
 148 };
 149
 150 static struct xtables_match ttl_mt_reg = {
 151         .name           = "ttl",
 152         .version        = XTABLES_VERSION,
 153         .family         = PF_INET,
 154         .size           = XT_ALIGN(sizeof(struct ipt_ttl_info)),
 155         .userspacesize  = XT_ALIGN(sizeof(struct ipt_ttl_info)),
 156         .help           = ttl_help,
 157         .parse          = ttl_parse,
 158         .final_check    = ttl_check,
 159         .print          = ttl_print,
 160         .save           = ttl_save,
 161         .extra_opts     = ttl_opts,
 162 };
 163
 164
 165 void _init(void)
 166 {
 167         xtables_register_match(&ttl_mt_reg);
 168 }