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-reset",
  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()
  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
  71 help(void)
  72 {
  73         printf(
  74 "REJECT options:\n"
  75 "--reject-with type              drop input packet and send back\n"
  76 "                                a reply packet according to type:\n");
  77
  78         print_reject_types();
  79
  80         printf("(*) See man page or read the INCOMPATIBILITES file for compatibility issues.\n");
  81 }
  82
  83 static struct option opts[] = {
  84         { "reject-with", 1, 0, '1' },
  85         { 0 }
  86 };
  87
  88 /* Allocate and initialize the target. */
  89 static void
  90 init(struct ipt_entry_target *t, unsigned int *nfcache)
  91 {
  92         struct ipt_reject_info *reject = (struct ipt_reject_info *)t->data;
  93
  94         /* default */
  95         reject->with = IPT_ICMP_PORT_UNREACHABLE;
  96
  97         /* Can't cache this */
  98         *nfcache |= NFC_UNKNOWN;
  99 }
 100
 101 /* Function which parses command options; returns true if it
 102    ate an option */
 103 static int
 104 parse(int c, char **argv, int invert, unsigned int *flags,
 105       const struct ipt_entry *entry,
 106       struct ipt_entry_target **target)
 107 {
 108         struct ipt_reject_info *reject = (struct ipt_reject_info *)(*target)->data;
 109         unsigned int limit = sizeof(reject_table)/sizeof(struct reject_names);
 110         unsigned int i;
 111
 112         switch(c) {
 113         case '1':
 114                 if (check_inverse(optarg, &invert, NULL, 0))
 115                         exit_error(PARAMETER_PROBLEM,
 116                                    "Unexpected `!' after --reject-with");
 117                 for (i = 0; i < limit; i++) {
 118                         if ((strncasecmp(reject_table[i].name, optarg, strlen(optarg)) == 0)
 119                             || (strncasecmp(reject_table[i].alias, optarg, strlen(optarg)) == 0)) {
 120                                 reject->with = reject_table[i].with;
 121                                 return 1;
 122                         }
 123                 }
 124                 /* This due to be dropped late in 2.4 pre-release cycle --RR */
 125                 if (strncasecmp("echo-reply", optarg, strlen(optarg)) == 0
 126                     || strncasecmp("echoreply", optarg, strlen(optarg)) == 0)
 127                         fprintf(stderr, "--reject-with echo-reply no longer"
 128                                 " supported\n");
 129                 exit_error(PARAMETER_PROBLEM, "unknown reject type `%s'",optarg);
 130         default:
 131                 /* Fall through */
 132                 break;
 133         }
 134         return 0;
 135 }
 136
 137 /* Final check; nothing. */
 138 static void final_check(unsigned int flags)
 139 {
 140 }
 141
 142 /* Prints out ipt_reject_info. */
 143 static void
 144 print(const struct ipt_ip *ip,
 145       const struct ipt_entry_target *target,
 146       int numeric)
 147 {
 148         const struct ipt_reject_info *reject
 149                 = (const struct ipt_reject_info *)target->data;
 150         unsigned int i;
 151
 152         for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++) {
 153                 if (reject_table[i].with == reject->with)
 154                         break;
 155         }
 156         printf("reject-with %s ", reject_table[i].name);
 157 }
 158
 159 /* Saves ipt_reject in parsable form to stdout. */
 160 static void save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
 161 {
 162         const struct ipt_reject_info *reject
 163                 = (const struct ipt_reject_info *)target->data;
 164         unsigned int i;
 165
 166         for (i = 0; i < sizeof(reject_table)/sizeof(struct reject_names); i++)
 167                 if (reject_table[i].with == reject->with)
 168                         break;
 169
 170         printf("--reject-with %s ", reject_table[i].name);
 171 }
 172
 173 static
 174 struct iptables_target reject
 175 = { NULL,
 176     "REJECT",
 177     IPTABLES_VERSION,
 178     IPT_ALIGN(sizeof(struct ipt_reject_info)),
 179     IPT_ALIGN(sizeof(struct ipt_reject_info)),
 180     &help,
 181     &init,
 182     &parse,
 183     &final_check,
 184     &print,
 185     &save,
 186     opts
 187 };
 188
 189 void _init(void)
 190 {
 191         register_target(&reject);
 192 }