user/iptables/extensions/libipt_TTL.c

   1 /* Shared library add-on to iptables for the TTL target
   2  * (C) 2000 by Harald Welte <laforge@gnumonks.org>
   3  *
   4  * $Id$
   5  *
   6  * This program is distributed under the terms of GNU GPL
   7  */
   8 #include <stdio.h>
   9 #include <string.h>
  10 #include <stdlib.h>
  11 #include <getopt.h>
  12 #include <xtables.h>
  13
  14 #include <linux/netfilter_ipv4/ipt_TTL.h>
  15
  16 #define IPT_TTL_USED    1
  17
  18 static void TTL_help(void)
  19 {
  20         printf(
  21 "TTL target options\n"
  22 "  --ttl-set value              Set TTL to <value 0-255>\n"
  23 "  --ttl-dec value              Decrement TTL by <value 1-255>\n"
  24 "  --ttl-inc value              Increment TTL by <value 1-255>\n");
  25 }
  26
  27 static int TTL_parse(int c, char **argv, int invert, unsigned int *flags,
  28                      const void *entry, struct xt_entry_target **target)
  29 {
  30         struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data;
  31         unsigned int value;
  32
  33         if (*flags & IPT_TTL_USED) {
  34                 xtables_error(PARAMETER_PROBLEM,
  35                                 "Can't specify TTL option twice");
  36         }
  37
  38         if (!optarg)
  39                 xtables_error(PARAMETER_PROBLEM,
  40                                 "TTL: You must specify a value");
  41
  42         if (xtables_check_inverse(optarg, &invert, NULL, 0))
  43                 xtables_error(PARAMETER_PROBLEM,
  44                                 "TTL: unexpected `!'");
  45
  46         if (!xtables_strtoui(optarg, NULL, &value, 0, UINT8_MAX))
  47                 xtables_error(PARAMETER_PROBLEM,
  48                            "TTL: Expected value between 0 and 255");
  49
  50         switch (c) {
  51
  52                 case '1':
  53                         info->mode = IPT_TTL_SET;
  54                         break;
  55
  56                 case '2':
  57                         if (value == 0) {
  58                                 xtables_error(PARAMETER_PROBLEM,
  59                                         "TTL: decreasing by 0?");
  60                         }
  61
  62                         info->mode = IPT_TTL_DEC;
  63                         break;
  64
  65                 case '3':
  66                         if (value == 0) {
  67                                 xtables_error(PARAMETER_PROBLEM,
  68                                         "TTL: increasing by 0?");
  69                         }
  70
  71                         info->mode = IPT_TTL_INC;
  72                         break;
  73
  74                 default:
  75                         return 0;
  76
  77         }
  78
  79         info->ttl = value;
  80         *flags |= IPT_TTL_USED;
  81
  82         return 1;
  83 }
  84
  85 static void TTL_check(unsigned int flags)
  86 {
  87         if (!(flags & IPT_TTL_USED))
  88                 xtables_error(PARAMETER_PROBLEM,
  89                                 "TTL: You must specify an action");
  90 }
  91
  92 static void TTL_save(const void *ip, const struct xt_entry_target *target)
  93 {
  94         const struct ipt_TTL_info *info =
  95                 (struct ipt_TTL_info *) target->data;
  96
  97         switch (info->mode) {
  98                 case IPT_TTL_SET:
  99                         printf("--ttl-set ");
 100                         break;
 101                 case IPT_TTL_DEC:
 102                         printf("--ttl-dec ");
 103                         break;
 104
 105                 case IPT_TTL_INC:
 106                         printf("--ttl-inc ");
 107                         break;
 108         }
 109         printf("%u ", info->ttl);
 110 }
 111
 112 static void TTL_print(const void *ip, const struct xt_entry_target *target,
 113                       int numeric)
 114 {
 115         const struct ipt_TTL_info *info =
 116                 (struct ipt_TTL_info *) target->data;
 117
 118         printf("TTL ");
 119         switch (info->mode) {
 120                 case IPT_TTL_SET:
 121                         printf("set to ");
 122                         break;
 123                 case IPT_TTL_DEC:
 124                         printf("decrement by ");
 125                         break;
 126                 case IPT_TTL_INC:
 127                         printf("increment by ");
 128                         break;
 129         }
 130         printf("%u ", info->ttl);
 131 }
 132
 133 static const struct option TTL_opts[] = {
 134         { "ttl-set", 1, NULL, '1' },
 135         { "ttl-dec", 1, NULL, '2' },
 136         { "ttl-inc", 1, NULL, '3' },
 137         { .name = NULL }
 138 };
 139
 140 static struct xtables_target ttl_tg_reg = {
 141         .name           = "TTL",
 142         .version        = XTABLES_VERSION,
 143         .family         = NFPROTO_IPV4,
 144         .size           = XT_ALIGN(sizeof(struct ipt_TTL_info)),
 145         .userspacesize  = XT_ALIGN(sizeof(struct ipt_TTL_info)),
 146         .help           = TTL_help,
 147         .parse          = TTL_parse,
 148         .final_check    = TTL_check,
 149         .print          = TTL_print,
 150         .save           = TTL_save,
 151         .extra_opts     = TTL_opts,
 152 };
 153
 154 void _init(void)
 155 {
 156         xtables_register_target(&ttl_tg_reg);
 157 }