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: libipt_TTL.c 3507 2004-12-28 13:11:59Z /C=DE/ST=Berlin/L=Berlin/O=Netfilter Project/OU=Development/CN=rusty/emailAddress=rusty@netfilter.org $
   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 <iptables.h>
  13
  14 #include <linux/netfilter_ipv4/ip_tables.h>
  15 #include <linux/netfilter_ipv4/ipt_TTL.h>
  16
  17 #define IPT_TTL_USED    1
  18
  19 static void init(struct ipt_entry_target *t, unsigned int *nfcache)
  20 {
  21 }
  22
  23 static void help(void)
  24 {
  25         printf(
  26 "TTL target v%s options\n"
  27 "  --ttl-set value              Set TTL to <value 0-255>\n"
  28 "  --ttl-dec value              Decrement TTL by <value 1-255>\n"
  29 "  --ttl-inc value              Increment TTL by <value 1-255>\n"
  30 , IPTABLES_VERSION);
  31 }
  32
  33 static int parse(int c, char **argv, int invert, unsigned int *flags,
  34                 const struct ipt_entry *entry,
  35                 struct ipt_entry_target **target)
  36 {
  37         struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data;
  38         unsigned int value;
  39
  40         if (*flags & IPT_TTL_USED) {
  41                 exit_error(PARAMETER_PROBLEM,
  42                                 "Can't specify TTL option twice");
  43         }
  44
  45         if (!optarg)
  46                 exit_error(PARAMETER_PROBLEM,
  47                                 "TTL: You must specify a value");
  48
  49         if (check_inverse(optarg, &invert, NULL, 0))
  50                 exit_error(PARAMETER_PROBLEM,
  51                                 "TTL: unexpected `!'");
  52
  53         if (string_to_number(optarg, 0, 255, &value) == -1)
  54                 exit_error(PARAMETER_PROBLEM,
  55                            "TTL: Expected value between 0 and 255");
  56
  57         switch (c) {
  58
  59                 case '1':
  60                         info->mode = IPT_TTL_SET;
  61                         break;
  62
  63                 case '2':
  64                         if (value == 0) {
  65                                 exit_error(PARAMETER_PROBLEM,
  66                                         "TTL: decreasing by 0?");
  67                         }
  68
  69                         info->mode = IPT_TTL_DEC;
  70                         break;
  71
  72                 case '3':
  73                         if (value == 0) {
  74                                 exit_error(PARAMETER_PROBLEM,
  75                                         "TTL: increasing by 0?");
  76                         }
  77
  78                         info->mode = IPT_TTL_INC;
  79                         break;
  80
  81                 default:
  82                         return 0;
  83
  84         }
  85
  86         info->ttl = value;
  87         *flags |= IPT_TTL_USED;
  88
  89         return 1;
  90 }
  91
  92 static void final_check(unsigned int flags)
  93 {
  94         if (!(flags & IPT_TTL_USED))
  95                 exit_error(PARAMETER_PROBLEM,
  96                                 "TTL: You must specify an action");
  97 }
  98
  99 static void save(const struct ipt_ip *ip,
 100                 const struct ipt_entry_target *target)
 101 {
 102         const struct ipt_TTL_info *info =
 103                 (struct ipt_TTL_info *) target->data;
 104
 105         switch (info->mode) {
 106                 case IPT_TTL_SET:
 107                         printf("--ttl-set ");
 108                         break;
 109                 case IPT_TTL_DEC:
 110                         printf("--ttl-dec ");
 111                         break;
 112
 113                 case IPT_TTL_INC:
 114                         printf("--ttl-inc ");
 115                         break;
 116         }
 117         printf("%u ", info->ttl);
 118 }
 119
 120 static void print(const struct ipt_ip *ip,
 121                 const struct ipt_entry_target *target, int numeric)
 122 {
 123         const struct ipt_TTL_info *info =
 124                 (struct ipt_TTL_info *) target->data;
 125
 126         printf("TTL ");
 127         switch (info->mode) {
 128                 case IPT_TTL_SET:
 129                         printf("set to ");
 130                         break;
 131                 case IPT_TTL_DEC:
 132                         printf("decrement by ");
 133                         break;
 134                 case IPT_TTL_INC:
 135                         printf("increment by ");
 136                         break;
 137         }
 138         printf("%u ", info->ttl);
 139 }
 140
 141 static struct option opts[] = {
 142         { "ttl-set", 1, 0, '1' },
 143         { "ttl-dec", 1, 0, '2' },
 144         { "ttl-inc", 1, 0, '3' },
 145         { 0 }
 146 };
 147
 148 static struct iptables_target TTL = {
 149         .next           = NULL,
 150         .name           = "TTL",
 151         .version        = IPTABLES_VERSION,
 152         .size           = IPT_ALIGN(sizeof(struct ipt_TTL_info)),
 153         .userspacesize  = IPT_ALIGN(sizeof(struct ipt_TTL_info)),
 154         .help           = &help,
 155         .init           = &init,
 156         .parse          = &parse,
 157         .final_check    = &final_check,
 158         .print          = &print,
 159         .save           = &save,
 160         .extra_opts     = opts
 161 };
 162
 163 void _init(void)
 164 {
 165         register_target(&TTL);
 166 }