extensions/libxt_udp.c

   1 /* Shared library add-on to iptables to add UDP support. */
   2 #include <stdio.h>
   3 #include <netdb.h>
   4 #include <string.h>
   5 #include <stdlib.h>
   6 #include <getopt.h>
   7 #include <xtables.h>
   8 #include <linux/netfilter/xt_tcpudp.h>
   9
  10 /* Function which prints out usage message. */
  11 static void udp_help(void)
  12 {
  13         printf(
  14 "udp match options:\n"
  15 " --source-port [!] port[:port]\n"
  16 " --sport ...\n"
  17 "                               match source port(s)\n"
  18 " --destination-port [!] port[:port]\n"
  19 " --dport ...\n"
  20 "                               match destination port(s)\n");
  21 }
  22
  23 static const struct option udp_opts[] = {
  24         { "source-port", 1, NULL, '1' },
  25         { "sport", 1, NULL, '1' }, /* synonym */
  26         { "destination-port", 1, NULL, '2' },
  27         { "dport", 1, NULL, '2' }, /* synonym */
  28         { .name = NULL }
  29 };
  30
  31 static void
  32 parse_udp_ports(const char *portstring, u_int16_t *ports)
  33 {
  34         char *buffer;
  35         char *cp;
  36
  37         buffer = strdup(portstring);
  38         if ((cp = strchr(buffer, ':')) == NULL)
  39                 ports[0] = ports[1] = parse_port(buffer, "udp");
  40         else {
  41                 *cp = '\0';
  42                 cp++;
  43
  44                 ports[0] = buffer[0] ? parse_port(buffer, "udp") : 0;
  45                 ports[1] = cp[0] ? parse_port(cp, "udp") : 0xFFFF;
  46
  47                 if (ports[0] > ports[1])
  48                         exit_error(PARAMETER_PROBLEM,
  49                                    "invalid portrange (min > max)");
  50         }
  51         free(buffer);
  52 }
  53
  54 /* Initialize the match. */
  55 static void udp_init(struct xt_entry_match *m)
  56 {
  57         struct xt_udp *udpinfo = (struct xt_udp *)m->data;
  58
  59         udpinfo->spts[1] = udpinfo->dpts[1] = 0xFFFF;
  60 }
  61
  62 #define UDP_SRC_PORTS 0x01
  63 #define UDP_DST_PORTS 0x02
  64
  65 /* Function which parses command options; returns true if it
  66    ate an option */
  67 static int
  68 udp_parse(int c, char **argv, int invert, unsigned int *flags,
  69           const void *entry, struct xt_entry_match **match)
  70 {
  71         struct xt_udp *udpinfo = (struct xt_udp *)(*match)->data;
  72
  73         switch (c) {
  74         case '1':
  75                 if (*flags & UDP_SRC_PORTS)
  76                         exit_error(PARAMETER_PROBLEM,
  77                                    "Only one `--source-port' allowed");
  78                 check_inverse(optarg, &invert, &optind, 0);
  79                 parse_udp_ports(argv[optind-1], udpinfo->spts);
  80                 if (invert)
  81                         udpinfo->invflags |= XT_UDP_INV_SRCPT;
  82                 *flags |= UDP_SRC_PORTS;
  83                 break;
  84
  85         case '2':
  86                 if (*flags & UDP_DST_PORTS)
  87                         exit_error(PARAMETER_PROBLEM,
  88                                    "Only one `--destination-port' allowed");
  89                 check_inverse(optarg, &invert, &optind, 0);
  90                 parse_udp_ports(argv[optind-1], udpinfo->dpts);
  91                 if (invert)
  92                         udpinfo->invflags |= XT_UDP_INV_DSTPT;
  93                 *flags |= UDP_DST_PORTS;
  94                 break;
  95
  96         default:
  97                 return 0;
  98         }
  99
 100         return 1;
 101 }
 102
 103 static char *
 104 port_to_service(int port)
 105 {
 106         struct servent *service;
 107
 108         if ((service = getservbyport(htons(port), "udp")))
 109                 return service->s_name;
 110
 111         return NULL;
 112 }
 113
 114 static void
 115 print_port(u_int16_t port, int numeric)
 116 {
 117         char *service;
 118
 119         if (numeric || (service = port_to_service(port)) == NULL)
 120                 printf("%u", port);
 121         else
 122                 printf("%s", service);
 123 }
 124
 125 static void
 126 print_ports(const char *name, u_int16_t min, u_int16_t max,
 127             int invert, int numeric)
 128 {
 129         const char *inv = invert ? "!" : "";
 130
 131         if (min != 0 || max != 0xFFFF || invert) {
 132                 printf("%s", name);
 133                 if (min == max) {
 134                         printf(":%s", inv);
 135                         print_port(min, numeric);
 136                 } else {
 137                         printf("s:%s", inv);
 138                         print_port(min, numeric);
 139                         printf(":");
 140                         print_port(max, numeric);
 141                 }
 142                 printf(" ");
 143         }
 144 }
 145
 146 /* Prints out the union ipt_matchinfo. */
 147 static void
 148 udp_print(const void *ip, const struct xt_entry_match *match, int numeric)
 149 {
 150         const struct xt_udp *udp = (struct xt_udp *)match->data;
 151
 152         printf("udp ");
 153         print_ports("spt", udp->spts[0], udp->spts[1],
 154                     udp->invflags & XT_UDP_INV_SRCPT,
 155                     numeric);
 156         print_ports("dpt", udp->dpts[0], udp->dpts[1],
 157                     udp->invflags & XT_UDP_INV_DSTPT,
 158                     numeric);
 159         if (udp->invflags & ~XT_UDP_INV_MASK)
 160                 printf("Unknown invflags: 0x%X ",
 161                        udp->invflags & ~XT_UDP_INV_MASK);
 162 }
 163
 164 /* Saves the union ipt_matchinfo in parsable form to stdout. */
 165 static void udp_save(const void *ip, const struct xt_entry_match *match)
 166 {
 167         const struct xt_udp *udpinfo = (struct xt_udp *)match->data;
 168
 169         if (udpinfo->spts[0] != 0
 170             || udpinfo->spts[1] != 0xFFFF) {
 171                 if (udpinfo->invflags & XT_UDP_INV_SRCPT)
 172                         printf("! ");
 173                 if (udpinfo->spts[0]
 174                     != udpinfo->spts[1])
 175                         printf("--sport %u:%u ",
 176                                udpinfo->spts[0],
 177                                udpinfo->spts[1]);
 178                 else
 179                         printf("--sport %u ",
 180                                udpinfo->spts[0]);
 181         }
 182
 183         if (udpinfo->dpts[0] != 0
 184             || udpinfo->dpts[1] != 0xFFFF) {
 185                 if (udpinfo->invflags & XT_UDP_INV_DSTPT)
 186                         printf("! ");
 187                 if (udpinfo->dpts[0]
 188                     != udpinfo->dpts[1])
 189                         printf("--dport %u:%u ",
 190                                udpinfo->dpts[0],
 191                                udpinfo->dpts[1]);
 192                 else
 193                         printf("--dport %u ",
 194                                udpinfo->dpts[0]);
 195         }
 196 }
 197
 198 static struct xtables_match udp_match = {
 199         .family         = AF_INET,
 200         .name           = "udp",
 201         .version        = XTABLES_VERSION,
 202         .size           = XT_ALIGN(sizeof(struct xt_udp)),
 203         .userspacesize  = XT_ALIGN(sizeof(struct xt_udp)),
 204         .help           = udp_help,
 205         .init           = udp_init,
 206         .parse          = udp_parse,
 207         .print          = udp_print,
 208         .save           = udp_save,
 209         .extra_opts     = udp_opts,
 210 };
 211
 212 static struct xtables_match udp_match6 = {
 213         .family         = AF_INET6,
 214         .name           = "udp",
 215         .version        = XTABLES_VERSION,
 216         .size           = XT_ALIGN(sizeof(struct xt_udp)),
 217         .userspacesize  = XT_ALIGN(sizeof(struct xt_udp)),
 218         .help           = udp_help,
 219         .init           = udp_init,
 220         .parse          = udp_parse,
 221         .print          = udp_print,
 222         .save           = udp_save,
 223         .extra_opts     = udp_opts,
 224 };
 225
 226 void
 227 _init(void)
 228 {
 229         xtables_register_match(&udp_match);
 230         xtables_register_match(&udp_match6);
 231 }