diff options
Diffstat (limited to 'extensions/libxt_udp.c')
| -rw-r--r-- | extensions/libxt_udp.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/extensions/libxt_udp.c b/extensions/libxt_udp.c new file mode 100644 index 0000000..c379536 --- /dev/null +++ b/extensions/libxt_udp.c @@ -0,0 +1,249 @@ +/* Shared library add-on to iptables to add UDP support. */ +#include <stdio.h> +#include <netdb.h> +#include <string.h> +#include <stdlib.h> +#include <getopt.h> +#include <xtables.h> +#include <linux/netfilter/xt_tcpudp.h> + +/* Function which prints out usage message. */ +static void +help(void) +{ + printf( +"UDP v%s options:\n" +" --source-port [!] port[:port]\n" +" --sport ...\n" +" match source port(s)\n" +" --destination-port [!] port[:port]\n" +" --dport ...\n" +" match destination port(s)\n", +IPTABLES_VERSION); +} + +static struct option opts[] = { + { "source-port", 1, 0, '1' }, + { "sport", 1, 0, '1' }, /* synonym */ + { "destination-port", 1, 0, '2' }, + { "dport", 1, 0, '2' }, /* synonym */ + {0} +}; + +static void +parse_udp_ports(const char *portstring, u_int16_t *ports) +{ + char *buffer; + char *cp; + + buffer = strdup(portstring); + if ((cp = strchr(buffer, ':')) == NULL) + ports[0] = ports[1] = parse_port(buffer, "udp"); + else { + *cp = '\0'; + cp++; + + ports[0] = buffer[0] ? parse_port(buffer, "udp") : 0; + ports[1] = cp[0] ? parse_port(cp, "udp") : 0xFFFF; + + if (ports[0] > ports[1]) + exit_error(PARAMETER_PROBLEM, + "invalid portrange (min > max)"); + } + free(buffer); +} + +/* Initialize the match. */ +static void +init(struct xt_entry_match *m, unsigned int *nfcache) +{ + struct xt_udp *udpinfo = (struct xt_udp *)m->data; + + udpinfo->spts[1] = udpinfo->dpts[1] = 0xFFFF; +} + +#define UDP_SRC_PORTS 0x01 +#define UDP_DST_PORTS 0x02 + +/* Function which parses command options; returns true if it + ate an option */ +static int +parse(int c, char **argv, int invert, unsigned int *flags, + const void *entry, + unsigned int *nfcache, + struct xt_entry_match **match) +{ + struct xt_udp *udpinfo = (struct xt_udp *)(*match)->data; + + switch (c) { + case '1': + if (*flags & UDP_SRC_PORTS) + exit_error(PARAMETER_PROBLEM, + "Only one `--source-port' allowed"); + check_inverse(optarg, &invert, &optind, 0); + parse_udp_ports(argv[optind-1], udpinfo->spts); + if (invert) + udpinfo->invflags |= XT_UDP_INV_SRCPT; + *flags |= UDP_SRC_PORTS; + break; + + case '2': + if (*flags & UDP_DST_PORTS) + exit_error(PARAMETER_PROBLEM, + "Only one `--destination-port' allowed"); + check_inverse(optarg, &invert, &optind, 0); + parse_udp_ports(argv[optind-1], udpinfo->dpts); + if (invert) + udpinfo->invflags |= XT_UDP_INV_DSTPT; + *flags |= UDP_DST_PORTS; + break; + + default: + return 0; + } + + return 1; +} + +/* Final check; we don't care. */ +static void +final_check(unsigned int flags) +{ +} + +static char * +port_to_service(int port) +{ + struct servent *service; + + if ((service = getservbyport(htons(port), "udp"))) + return service->s_name; + + return NULL; +} + +static void +print_port(u_int16_t port, int numeric) +{ + char *service; + + if (numeric || (service = port_to_service(port)) == NULL) + printf("%u", port); + else + printf("%s", service); +} + +static void +print_ports(const char *name, u_int16_t min, u_int16_t max, + int invert, int numeric) +{ + const char *inv = invert ? "!" : ""; + + if (min != 0 || max != 0xFFFF || invert) { + printf("%s", name); + if (min == max) { + printf(":%s", inv); + print_port(min, numeric); + } else { + printf("s:%s", inv); + print_port(min, numeric); + printf(":"); + print_port(max, numeric); + } + printf(" "); + } +} + +/* Prints out the union ipt_matchinfo. */ +static void +print(const void *ip, + const struct xt_entry_match *match, int numeric) +{ + const struct xt_udp *udp = (struct xt_udp *)match->data; + + printf("udp "); + print_ports("spt", udp->spts[0], udp->spts[1], + udp->invflags & XT_UDP_INV_SRCPT, + numeric); + print_ports("dpt", udp->dpts[0], udp->dpts[1], + udp->invflags & XT_UDP_INV_DSTPT, + numeric); + if (udp->invflags & ~XT_UDP_INV_MASK) + printf("Unknown invflags: 0x%X ", + udp->invflags & ~XT_UDP_INV_MASK); +} + +/* Saves the union ipt_matchinfo in parsable form to stdout. */ +static void save(const void *ip, const struct xt_entry_match *match) +{ + const struct xt_udp *udpinfo = (struct xt_udp *)match->data; + + if (udpinfo->spts[0] != 0 + || udpinfo->spts[1] != 0xFFFF) { + if (udpinfo->invflags & XT_UDP_INV_SRCPT) + printf("! "); + if (udpinfo->spts[0] + != udpinfo->spts[1]) + printf("--sport %u:%u ", + udpinfo->spts[0], + udpinfo->spts[1]); + else + printf("--sport %u ", + udpinfo->spts[0]); + } + + if (udpinfo->dpts[0] != 0 + || udpinfo->dpts[1] != 0xFFFF) { + if (udpinfo->invflags & XT_UDP_INV_DSTPT) + printf("! "); + if (udpinfo->dpts[0] + != udpinfo->dpts[1]) + printf("--dport %u:%u ", + udpinfo->dpts[0], + udpinfo->dpts[1]); + else + printf("--dport %u ", + udpinfo->dpts[0]); + } +} + +static +struct xtables_match udp = { + .next = NULL, + .family = AF_INET, + .name = "udp", + .version = IPTABLES_VERSION, + .size = XT_ALIGN(sizeof(struct xt_udp)), + .userspacesize = XT_ALIGN(sizeof(struct xt_udp)), + .help = &help, + .init = &init, + .parse = &parse, + .final_check = &final_check, + .print = &print, + .save = &save, + .extra_opts = opts +}; + +static +struct xtables_match udp6 = { + .next = NULL, + .family = AF_INET6, + .name = "udp", + .version = IPTABLES_VERSION, + .size = XT_ALIGN(sizeof(struct xt_udp)), + .userspacesize = XT_ALIGN(sizeof(struct xt_udp)), + .help = &help, + .init = &init, + .parse = &parse, + .final_check = &final_check, + .print = &print, + .save = &save, + .extra_opts = opts +}; + +void +_init(void) +{ + xtables_register_match(&udp); + xtables_register_match(&udp6); +} |