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/* 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);
}
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