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/* Shared library add-on to iptables to add UDP support. */
#include <stdbool.h>
#include <stdio.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <netinet/in.h>
#include <xtables.h>
#include <linux/netfilter/xt_tcpudp.h>
static void udp_help(void)
{
printf(
"udp match 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");
}
static const struct option udp_opts[] = {
{.name = "source-port", .has_arg = true, .val = '1'},
{.name = "sport", .has_arg = true, .val = '1'}, /* synonym */
{.name = "destination-port", .has_arg = true, .val = '2'},
{.name = "dport", .has_arg = true, .val = '2'}, /* synonym */
XT_GETOPT_TABLEEND,
};
static void
parse_udp_ports(const char *portstring, uint16_t *ports)
{
char *buffer;
char *cp;
buffer = strdup(portstring);
if ((cp = strchr(buffer, ':')) == NULL)
ports[0] = ports[1] = xtables_parse_port(buffer, "udp");
else {
*cp = '\0';
cp++;
ports[0] = buffer[0] ? xtables_parse_port(buffer, "udp") : 0;
ports[1] = cp[0] ? xtables_parse_port(cp, "udp") : 0xFFFF;
if (ports[0] > ports[1])
xtables_error(PARAMETER_PROBLEM,
"invalid portrange (min > max)");
}
free(buffer);
}
static void udp_init(struct xt_entry_match *m)
{
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
static int
udp_parse(int c, char **argv, int invert, unsigned int *flags,
const void *entry, struct xt_entry_match **match)
{
struct xt_udp *udpinfo = (struct xt_udp *)(*match)->data;
switch (c) {
case '1':
if (*flags & UDP_SRC_PORTS)
xtables_error(PARAMETER_PROBLEM,
"Only one `--source-port' allowed");
xtables_check_inverse(optarg, &invert, &optind, 0, argv);
parse_udp_ports(optarg, udpinfo->spts);
if (invert)
udpinfo->invflags |= XT_UDP_INV_SRCPT;
*flags |= UDP_SRC_PORTS;
break;
case '2':
if (*flags & UDP_DST_PORTS)
xtables_error(PARAMETER_PROBLEM,
"Only one `--destination-port' allowed");
xtables_check_inverse(optarg, &invert, &optind, 0, argv);
parse_udp_ports(optarg, udpinfo->dpts);
if (invert)
udpinfo->invflags |= XT_UDP_INV_DSTPT;
*flags |= UDP_DST_PORTS;
break;
default:
return 0;
}
return 1;
}
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(uint16_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, uint16_t min, uint16_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(" ");
}
}
static void
udp_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);
}
static void udp_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_match = {
.family = NFPROTO_UNSPEC,
.name = "udp",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_udp)),
.userspacesize = XT_ALIGN(sizeof(struct xt_udp)),
.help = udp_help,
.init = udp_init,
.parse = udp_parse,
.print = udp_print,
.save = udp_save,
.extra_opts = udp_opts,
};
void
_init(void)
{
xtables_register_match(&udp_match);
}
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