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#include <stdint.h>
#include <stdio.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <xtables.h>
#include <linux/netfilter/xt_tcpudp.h>
enum {
O_SOURCE_PORT = 0,
O_DEST_PORT,
};
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");
}
#define s struct xt_udp
static const struct xt_option_entry udp_opts[] = {
{.name = "source-port", .id = O_SOURCE_PORT, .type = XTTYPE_PORTRC,
.flags = XTOPT_INVERT | XTOPT_PUT, XTOPT_POINTER(s, spts)},
{.name = "sport", .id = O_SOURCE_PORT, .type = XTTYPE_PORTRC,
.flags = XTOPT_INVERT | XTOPT_PUT, XTOPT_POINTER(s, spts)},
{.name = "destination-port", .id = O_DEST_PORT, .type = XTTYPE_PORTRC,
.flags = XTOPT_INVERT | XTOPT_PUT, XTOPT_POINTER(s, dpts)},
{.name = "dport", .id = O_DEST_PORT, .type = XTTYPE_PORTRC,
.flags = XTOPT_INVERT | XTOPT_PUT, XTOPT_POINTER(s, dpts)},
XTOPT_TABLEEND,
};
#undef s
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;
}
static void udp_parse(struct xt_option_call *cb)
{
struct xt_udp *udpinfo = cb->data;
xtables_option_parse(cb);
switch (cb->entry->id) {
case O_SOURCE_PORT:
if (cb->invert)
udpinfo->invflags |= XT_UDP_INV_SRCPT;
break;
case O_DEST_PORT:
if (cb->invert)
udpinfo->invflags |= XT_UDP_INV_DSTPT;
break;
}
}
static const char *
port_to_service(int port)
{
const struct servent *service;
if ((service = getservbyport(htons(port), "udp")))
return service->s_name;
return NULL;
}
static void
print_port(uint16_t port, int numeric)
{
const char *service;
if (numeric || (service = port_to_service(port)) == NULL)
printf("%u", port);
else
printf("%s", service);
}
static bool skip_ports_match(uint16_t min, uint16_t max, bool inv)
{
return min == 0 && max == UINT16_MAX && !inv;
}
static void
print_ports(const char *name, uint16_t min, uint16_t max,
int invert, int numeric)
{
const char *inv = invert ? "!" : "";
if (!skip_ports_match(min, max, 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);
}
}
}
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;
bool inv_srcpt = udpinfo->invflags & XT_UDP_INV_SRCPT;
bool inv_dstpt = udpinfo->invflags & XT_UDP_INV_DSTPT;
if (!skip_ports_match(udpinfo->spts[0], udpinfo->spts[1], inv_srcpt)) {
if (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 (!skip_ports_match(udpinfo->dpts[0], udpinfo->dpts[1], inv_dstpt)) {
if (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 int udp_xlate(struct xt_xlate *xl,
const struct xt_xlate_mt_params *params)
{
const struct xt_udp *udpinfo = (struct xt_udp *)params->match->data;
bool inv_srcpt = udpinfo->invflags & XT_UDP_INV_SRCPT;
bool inv_dstpt = udpinfo->invflags & XT_UDP_INV_DSTPT;
bool xlated = false;
if (!skip_ports_match(udpinfo->spts[0], udpinfo->spts[1], inv_srcpt)) {
if (udpinfo->spts[0] != udpinfo->spts[1]) {
xt_xlate_add(xl,"udp sport %s%u-%u",
inv_srcpt ? "!= ": "",
udpinfo->spts[0], udpinfo->spts[1]);
} else {
xt_xlate_add(xl, "udp sport %s%u",
inv_srcpt ? "!= ": "",
udpinfo->spts[0]);
}
xlated = true;
}
if (!skip_ports_match(udpinfo->dpts[0], udpinfo->dpts[1], inv_dstpt)) {
if (udpinfo->dpts[0] != udpinfo->dpts[1]) {
xt_xlate_add(xl,"udp dport %s%u-%u",
inv_dstpt ? "!= ": "",
udpinfo->dpts[0], udpinfo->dpts[1]);
} else {
xt_xlate_add(xl,"udp dport %s%u",
inv_dstpt ? "!= ": "",
udpinfo->dpts[0]);
}
xlated = true;
}
if (!xlated)
xt_xlate_add(xl, "meta l4proto udp");
return 1;
}
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,
.print = udp_print,
.save = udp_save,
.x6_parse = udp_parse,
.x6_options = udp_opts,
.xlate = udp_xlate,
};
void
_init(void)
{
xtables_register_match(&udp_match);
}
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