extensions/libipt_REJECT.c

   1 /* Shared library add-on to iptables to add customized REJECT support.
   2  *
   3  * (C) 2000 Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>
   4  */
   5 #include <stdio.h>
   6 #include <string.h>
   7 #include <stdlib.h>
   8 #include <getopt.h>
   9 #include <iptables.h>
  10 #include <linux/netfilter_ipv4/ip_tables.h>
  11 #include <linux/netfilter_ipv4/ipt_REJECT.h>
  12 #include <linux/version.h>
  13
  14 /* If we are compiling against a kernel that does not support
  15  * IPT_ICMP_ADMIN_PROHIBITED, we are emulating it.
  16  * The result will be a plain DROP of the packet instead of
  17  * reject. -- Maciej Soltysiak <solt@dns.toxicfilms.tv>
  18  */
  19 #ifndef IPT_ICMP_ADMIN_PROHIBITED
  20 #define IPT_ICMP_ADMIN_PROHIBITED       IPT_TCP_RESET + 1
  21 #endif
  22
  23 struct reject_names {
  24         const char *name;
  25         const char *alias;
  26         enum ipt_reject_with with;
  27         const char *desc;
  28 };
  29
  30 static const struct reject_names reject_table[] = {
  31         {"icmp-net-unreachable", "net-unreach",
  32                 IPT_ICMP_NET_UNREACHABLE, "ICMP network unreachable"},
  33         {"icmp-host-unreachable", "host-unreach",
  34                 IPT_ICMP_HOST_UNREACHABLE, "ICMP host unreachable"},
  35         {"icmp-proto-unreachable", "proto-unreach",
  36                 IPT_ICMP_PROT_UNREACHABLE, "ICMP protocol unreachable"},
  37         {"icmp-port-unreachable", "port-unreach",
  38                 IPT_ICMP_PORT_UNREACHABLE, "ICMP port unreachable (default)"},
  39 #if 0
  40         {"echo-reply", "echoreply",
  41          IPT_ICMP_ECHOREPLY, "for ICMP echo only: faked ICMP echo reply"},
  42 #endif
  43         {"icmp-net-prohibited", "net-prohib",
  44          IPT_ICMP_NET_PROHIBITED, "ICMP network prohibited"},
  45         {"icmp-host-prohibited", "host-prohib",
  46          IPT_ICMP_HOST_PROHIBITED, "ICMP host prohibited"},
  47         {"tcp-reset", "tcp-rst",
  48          IPT_TCP_RESET, "TCP RST packet"},
  49         {"icmp-admin-prohibited", "admin-prohib",
  50          IPT_ICMP_ADMIN_PROHIBITED, "ICMP administratively prohibited (*)"}
  51 };
  52
  53 static void
  54 print_reject_types(void)
  55 {
  56         unsigned int i;
  57
  58         printf("Valid reject types:\n");
  59
  60         for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
  61                 printf("    %-25s\t%s\n", reject_table[i].name, reject_table[i].desc);
  62                 printf("    %-25s\talias\n", reject_table[i].alias);
  63         }
  64         printf("\n");
  65 }
  66
  67 /* Saves the union ipt_targinfo in parsable form to stdout. */
  68
  69 /* Function which prints out usage message. */
  70 static void REJECT_help(void)
  71 {
  72         printf(
  73 "REJECT target options:\n"
  74 "--reject-with type              drop input packet and send back\n"
  75 "                                a reply packet according to type:\n");
  76
  77         print_reject_types();
  78
  79         printf("(*) See man page or read the INCOMPATIBILITES file for compatibility issues.\n");
  80 }
  81
  82 static const struct option REJECT_opts[] = {
  83         { "reject-with", 1, NULL, '1' },
  84         { .name = NULL }
  85 };
  86
  87 /* Allocate and initialize the target. */
  88 static void REJECT_init(struct xt_entry_target *t)
  89 {
  90         struct ipt_reject_info *reject = (struct ipt_reject_info *)t->data;
  91
  92         /* default */
  93         reject->with = IPT_ICMP_PORT_UNREACHABLE;
  94
  95 }
  96
  97 /* Function which parses command options; returns true if it
  98    ate an option */
  99 static int REJECT_parse(int c, char **argv, int invert, unsigned int *flags,
 100                         const void *entry, struct xt_entry_target **target)
 101 {
 102         struct ipt_reject_info *reject = (struct ipt_reject_info *)(*target)->data;
 103         unsigned int limit = sizeof(reject_table)/sizeof(struct reject_names);
 104         unsigned int i;
 105
 106         switch(c) {
 107         case '1':
 108                 if (check_inverse(optarg, &invert, NULL, 0))
 109                         exit_error(PARAMETER_PROBLEM,
 110                                    "Unexpected `!' after --reject-with");
 111                 for (i = 0; i < limit; i++) {
 112                         if ((strncasecmp(reject_table[i].name, optarg, strlen(optarg)) == 0)
 113                             || (strncasecmp(reject_table[i].alias, optarg, strlen(optarg)) == 0)) {
 114                                 reject->with = reject_table[i].with;
 115                                 return 1;
 116                         }
 117                 }
 118                 /* This due to be dropped late in 2.4 pre-release cycle --RR */
 119                 if (strncasecmp("echo-reply", optarg, strlen(optarg)) == 0
 120                     || strncasecmp("echoreply", optarg, strlen(optarg)) == 0)
 121                         fprintf(stderr, "--reject-with echo-reply no longer"
 122                                 " supported\n");
 123                 exit_error(PARAMETER_PROBLEM, "unknown reject type `%s'",optarg);
 124         default:
 125                 /* Fall through */
 126                 break;
 127         }
 128         return 0;
 129 }
 130
 131 /* Prints out ipt_reject_info. */
 132 static void REJECT_print(const void *ip, const struct xt_entry_target *target,
 133                          int numeric)
 134 {
 135         const struct ipt_reject_info *reject
 136                 = (const struct ipt_reject_info *)target->data;
 137         unsigned int i;
 138
 139         for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
 140                 if (reject_table[i].with == reject->with)
 141                         break;
 142         }
 143         printf("reject-with %s ", reject_table[i].name);
 144 }
 145
 146 /* Saves ipt_reject in parsable form to stdout. */
 147 static void REJECT_save(const void *ip, const struct xt_entry_target *target)
 148 {
 149         const struct ipt_reject_info *reject
 150                 = (const struct ipt_reject_info *)target->data;
 151         unsigned int i;
 152
 153         for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++)
 154                 if (reject_table[i].with == reject->with)
 155                         break;
 156
 157         printf("--reject-with %s ", reject_table[i].name);
 158 }
 159
 160 static struct xtables_target reject_tg_reg = {
 161         .name           = "REJECT",
 162         .version        = XTABLES_VERSION,
 163         .family         = PF_INET,
 164         .size           = XT_ALIGN(sizeof(struct ipt_reject_info)),
 165         .userspacesize  = XT_ALIGN(sizeof(struct ipt_reject_info)),
 166         .help           = REJECT_help,
 167         .init           = REJECT_init,
 168         .parse          = REJECT_parse,
 169         .print          = REJECT_print,
 170         .save           = REJECT_save,
 171         .extra_opts     = REJECT_opts,
 172 };
 173
 174 void _init(void)
 175 {
 176         xtables_register_target(&reject_tg_reg);
 177 }