extensions/libip6t_hl.c

   1 /*
   2  * IPv6 Hop Limit matching module
   3  * Maciej Soltysiak <solt@dns.toxicfilms.tv>
   4  * Based on HW's ttl match
   5  * This program is released under the terms of GNU GPL
   6  * Cleanups by Stephane Ouellette <ouellettes@videotron.ca>
   7  */
   8
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <getopt.h>
  13 #include <ip6tables.h>
  14
  15 #include <linux/netfilter_ipv6/ip6_tables.h>
  16 #include <linux/netfilter_ipv6/ip6t_hl.h>
  17
  18 static void hl_help(void)
  19 {
  20         printf(
  21 "hl match options:\n"
  22 "  --hl-eq [!] value    Match hop limit value\n"
  23 "  --hl-lt value        Match HL < value\n"
  24 "  --hl-gt value        Match HL > value\n");
  25 }
  26
  27 static int hl_parse(int c, char **argv, int invert, unsigned int *flags,
  28                     const void *entry, struct xt_entry_match **match)
  29 {
  30         struct ip6t_hl_info *info = (struct ip6t_hl_info *) (*match)->data;
  31         u_int8_t value;
  32
  33         check_inverse(optarg, &invert, &optind, 0);
  34         value = atoi(argv[optind-1]);
  35
  36         if (*flags)
  37                 exit_error(PARAMETER_PROBLEM,
  38                                 "Can't specify HL option twice");
  39
  40         if (!optarg)
  41                 exit_error(PARAMETER_PROBLEM,
  42                                 "hl: You must specify a value");
  43         switch (c) {
  44                 case '2':
  45                         if (invert)
  46                                 info->mode = IP6T_HL_NE;
  47                         else
  48                                 info->mode = IP6T_HL_EQ;
  49
  50                         /* is 0 allowed? */
  51                         info->hop_limit = value;
  52                         *flags = 1;
  53
  54                         break;
  55                 case '3':
  56                         if (invert)
  57                                 exit_error(PARAMETER_PROBLEM,
  58                                                 "hl: unexpected `!'");
  59
  60                         info->mode = IP6T_HL_LT;
  61                         info->hop_limit = value;
  62                         *flags = 1;
  63
  64                         break;
  65                 case '4':
  66                         if (invert)
  67                                 exit_error(PARAMETER_PROBLEM,
  68                                                 "hl: unexpected `!'");
  69
  70                         info->mode = IP6T_HL_GT;
  71                         info->hop_limit = value;
  72                         *flags = 1;
  73
  74                         break;
  75                 default:
  76                         return 0;
  77         }
  78
  79         return 1;
  80 }
  81
  82 static void hl_check(unsigned int flags)
  83 {
  84         if (!flags)
  85                 exit_error(PARAMETER_PROBLEM,
  86                         "HL match: You must specify one of "
  87                         "`--hl-eq', `--hl-lt', `--hl-gt'");
  88 }
  89
  90 static void hl_print(const void *ip, const struct xt_entry_match *match,
  91                      int numeric)
  92 {
  93         static const char *op[] = {
  94                 [IP6T_HL_EQ] = "==",
  95                 [IP6T_HL_NE] = "!=",
  96                 [IP6T_HL_LT] = "<",
  97                 [IP6T_HL_GT] = ">" };
  98
  99         const struct ip6t_hl_info *info =
 100                 (struct ip6t_hl_info *) match->data;
 101
 102         printf("HL match HL %s %u ", op[info->mode], info->hop_limit);
 103 }
 104
 105 static void hl_save(const void *ip, const struct xt_entry_match *match)
 106 {
 107         static const char *op[] = {
 108                 [IP6T_HL_EQ] = "eq",
 109                 [IP6T_HL_NE] = "eq !",
 110                 [IP6T_HL_LT] = "lt",
 111                 [IP6T_HL_GT] = "gt" };
 112
 113         const struct ip6t_hl_info *info =
 114                 (struct ip6t_hl_info *) match->data;
 115
 116         printf("--hl-%s %u ", op[info->mode], info->hop_limit);
 117 }
 118
 119 static const struct option hl_opts[] = {
 120         { .name = "hl",    .has_arg = 1, .val = '2' },
 121         { .name = "hl-eq", .has_arg = 1, .val = '2' },
 122         { .name = "hl-lt", .has_arg = 1, .val = '3' },
 123         { .name = "hl-gt", .has_arg = 1, .val = '4' },
 124         { .name = NULL }
 125 };
 126
 127 static struct xtables_match hl_mt6_reg = {
 128         .name          = "hl",
 129         .version       = XTABLES_VERSION,
 130         .family        = PF_INET6,
 131         .size          = XT_ALIGN(sizeof(struct ip6t_hl_info)),
 132         .userspacesize = XT_ALIGN(sizeof(struct ip6t_hl_info)),
 133         .help          = hl_help,
 134         .parse         = hl_parse,
 135         .final_check   = hl_check,
 136         .print         = hl_print,
 137         .save          = hl_save,
 138         .extra_opts    = hl_opts,
 139 };
 140
 141
 142 void _init(void)
 143 {
 144         xtables_register_match(&hl_mt6_reg);
 145 }