extensions/libipt_udp.c

/* 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 <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.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",
NETFILTER_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 int
service_to_port(const char *name)
{
	struct servent *service;

	if ((service = getservbyname(name, "udp")) != NULL)
		return ntohs((unsigned short) service->s_port);

		return -1;
}

static u_int16_t
parse_udp_port(const char *port)
{
	int portnum;

	if ((portnum = string_to_number(port, 0, 65535)) != -1 ||
	    (portnum = service_to_port(port)) != -1)
		return (u_int16_t)portnum;

		exit_error(PARAMETER_PROBLEM,
			   "invalid UDP port/service `%s' specified", port);
	}

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_udp_port(buffer);
	else {
		*cp = '\0';
		cp++;

		ports[0] = buffer[0] ? parse_udp_port(buffer) : 0;
		ports[1] = cp[0] ? parse_udp_port(cp) : 0xFFFF;
	}
	free(buffer);
}

/* Initialize the match. */
static void
init(struct ipt_entry_match *m, unsigned int *nfcache)
{
	struct ipt_udp *udpinfo = (struct ipt_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 struct ipt_entry *entry,
      unsigned int *nfcache,
      struct ipt_entry_match **match)
{
	struct ipt_udp *udpinfo = (struct ipt_udp *)(*match)->data;

	switch (c) {
	case '1':
		if (*flags & UDP_SRC_PORTS)
			exit_error(PARAMETER_PROBLEM,
				   "Only one `--source-port' allowed");
		if (check_inverse(optarg, &invert))
			optind++;
		parse_udp_ports(argv[optind-1], udpinfo->spts);
		if (invert)
			udpinfo->invflags |= IPT_UDP_INV_SRCPT;
		*flags |= UDP_SRC_PORTS;
		*nfcache |= NFC_IP_SRC_PT;
		break;

	case '2':
		if (*flags & UDP_DST_PORTS)
			exit_error(PARAMETER_PROBLEM,
				   "Only one `--destination-port' allowed");
		if (check_inverse(optarg, &invert))
			optind++;
		parse_udp_ports(argv[optind-1], udpinfo->dpts);
		if (invert)
			udpinfo->invflags |= IPT_UDP_INV_DSTPT;
		*flags |= UDP_DST_PORTS;
		*nfcache |= NFC_IP_DST_PT;
		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 struct ipt_ip *ip,
      const struct ipt_entry_match *match, int numeric)
{
	const struct ipt_udp *udp = (struct ipt_udp *)match->data;

	printf("udp ");
	print_ports("spt", udp->spts[0], udp->spts[1],
		    udp->invflags & IPT_UDP_INV_SRCPT,
		    numeric);
	print_ports("dpt", udp->dpts[0], udp->dpts[1],
		    udp->invflags & IPT_UDP_INV_DSTPT,
		    numeric);
	if (udp->invflags & ~IPT_UDP_INV_MASK)
		printf("Unknown invflags: 0x%X ",
		       udp->invflags & ~IPT_UDP_INV_MASK);
}

/* Saves the union ipt_matchinfo in parsable form to stdout. */
static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
{
	const struct ipt_udp *udpinfo = (struct ipt_udp *)match->data;

	if (udpinfo->spts[0] != 0
	    || udpinfo->spts[1] != 0xFFFF) {
		if (udpinfo->invflags & IPT_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 & IPT_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]);
	}
}

struct iptables_match udp
= { NULL,
    "udp",
    NETFILTER_VERSION,
    IPT_ALIGN(sizeof(struct ipt_udp)),
    IPT_ALIGN(sizeof(struct ipt_udp)),
    &help,
    &init,
    &parse,
    &final_check,
    &print,
    &save,
    opts
};

void
_init(void)
{
	register_match(&udp);
}