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 <xtables.h>
  14
  15 #include <linux/netfilter_ipv6/ip6t_hl.h>
  16
  17 static void hl_help(void)
  18 {
  19         printf(
  20 "hl match options:\n"
  21 "[!] --hl-eq value      Match hop limit value\n"
  22 "  --hl-lt value        Match HL < value\n"
  23 "  --hl-gt value        Match HL > value\n");
  24 }
  25
  26 static int hl_parse(int c, char **argv, int invert, unsigned int *flags,
  27                     const void *entry, struct xt_entry_match **match)
  28 {
  29         struct ip6t_hl_info *info = (struct ip6t_hl_info *) (*match)->data;
  30         u_int8_t value;
  31
  32         xtables_check_inverse(optarg, &invert, &optind, 0);
  33         value = atoi(argv[optind-1]);
  34
  35         if (*flags)
  36                 xtables_error(PARAMETER_PROBLEM,
  37                                 "Can't specify HL option twice");
  38
  39         if (!optarg)
  40                 xtables_error(PARAMETER_PROBLEM,
  41                                 "hl: You must specify a value");
  42         switch (c) {
  43                 case '2':
  44                         if (invert)
  45                                 info->mode = IP6T_HL_NE;
  46                         else
  47                                 info->mode = IP6T_HL_EQ;
  48
  49                         /* is 0 allowed? */
  50                         info->hop_limit = value;
  51                         *flags = 1;
  52
  53                         break;
  54                 case '3':
  55                         if (invert)
  56                                 xtables_error(PARAMETER_PROBLEM,
  57                                                 "hl: unexpected `!'");
  58
  59                         info->mode = IP6T_HL_LT;
  60                         info->hop_limit = value;
  61                         *flags = 1;
  62
  63                         break;
  64                 case '4':
  65                         if (invert)
  66                                 xtables_error(PARAMETER_PROBLEM,
  67                                                 "hl: unexpected `!'");
  68
  69                         info->mode = IP6T_HL_GT;
  70                         info->hop_limit = value;
  71                         *flags = 1;
  72
  73                         break;
  74                 default:
  75                         return 0;
  76         }
  77
  78         return 1;
  79 }
  80
  81 static void hl_check(unsigned int flags)
  82 {
  83         if (!flags)
  84                 xtables_error(PARAMETER_PROBLEM,
  85                         "HL match: You must specify one of "
  86                         "`--hl-eq', `--hl-lt', `--hl-gt'");
  87 }
  88
  89 static void hl_print(const void *ip, const struct xt_entry_match *match,
  90                      int numeric)
  91 {
  92         static const char *const op[] = {
  93                 [IP6T_HL_EQ] = "==",
  94                 [IP6T_HL_NE] = "!=",
  95                 [IP6T_HL_LT] = "<",
  96                 [IP6T_HL_GT] = ">" };
  97
  98         const struct ip6t_hl_info *info =
  99                 (struct ip6t_hl_info *) match->data;
 100
 101         printf("HL match HL %s %u ", op[info->mode], info->hop_limit);
 102 }
 103
 104 static void hl_save(const void *ip, const struct xt_entry_match *match)
 105 {
 106         static const char *const op[] = {
 107                 [IP6T_HL_EQ] = "--hl-eq",
 108                 [IP6T_HL_NE] = "! --hl-eq",
 109                 [IP6T_HL_LT] = "--hl-lt",
 110                 [IP6T_HL_GT] = "--hl-gt" };
 111
 112         const struct ip6t_hl_info *info =
 113                 (struct ip6t_hl_info *) match->data;
 114
 115         printf("%s %u ", op[info->mode], info->hop_limit);
 116 }
 117
 118 static const struct option hl_opts[] = {
 119         { .name = "hl",    .has_arg = 1, .val = '2' },
 120         { .name = "hl-eq", .has_arg = 1, .val = '2' },
 121         { .name = "hl-lt", .has_arg = 1, .val = '3' },
 122         { .name = "hl-gt", .has_arg = 1, .val = '4' },
 123         { .name = NULL }
 124 };
 125
 126 static struct xtables_match hl_mt6_reg = {
 127         .name          = "hl",
 128         .version       = XTABLES_VERSION,
 129         .family        = NFPROTO_IPV6,
 130         .size          = XT_ALIGN(sizeof(struct ip6t_hl_info)),
 131         .userspacesize = XT_ALIGN(sizeof(struct ip6t_hl_info)),
 132         .help          = hl_help,
 133         .parse         = hl_parse,
 134         .final_check   = hl_check,
 135         .print         = hl_print,
 136         .save          = hl_save,
 137         .extra_opts    = hl_opts,
 138 };
 139
 140
 141 void _init(void)
 142 {
 143         xtables_register_match(&hl_mt6_reg);
 144 }