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/*
* SSDP connection tracking helper
* (SSDP = Simple Service Discovery Protocol)
* For documentation about SSDP see
* http://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol
*
* Copyright (C) 2014 Ashley Hughes <ashley.hughes@blueyonder.co.uk>
* Based on the SSDP conntrack helper (nf_conntrack_ssdp.c),
* :http://marc.info/?t=132945775100001&r=1&w=2
* (C) 2012 Ian Pilcher <arequipeno@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include "conntrackd.h"
#include "helper.h"
#include "myct.h"
#include "log.h"
#include <errno.h>
#include <arpa/inet.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <libmnl/libmnl.h>
#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
#include <libnetfilter_queue/libnetfilter_queue.h>
#include <libnetfilter_queue/libnetfilter_queue_tcp.h>
#include <libnetfilter_queue/pktbuff.h>
#include <linux/netfilter.h>
#define SSDP_MCAST_ADDR "239.255.255.250"
#define UPNP_MCAST_LL_ADDR "FF02::C" /* link-local */
#define UPNP_MCAST_SL_ADDR "FF05::C" /* site-local */
#define SSDP_M_SEARCH "M-SEARCH"
#define SSDP_M_SEARCH_SIZE (sizeof SSDP_M_SEARCH - 1)
static int ssdp_helper_cb(struct pkt_buff *pkt, uint32_t protoff,
struct myct *myct, uint32_t ctinfo)
{
int ret = NF_ACCEPT;
union nfct_attr_grp_addr daddr, saddr, taddr;
struct iphdr *net_hdr = (struct iphdr *)pktb_network_header(pkt);
int good_packet = 0;
struct nf_expect *exp;
u_int16_t port;
unsigned int dataoff;
void *sb_ptr;
cthelper_get_addr_dst(myct->ct, MYCT_DIR_ORIG, &daddr);
switch (nfct_get_attr_u8(myct->ct, ATTR_L3PROTO)) {
case AF_INET:
inet_pton(AF_INET, SSDP_MCAST_ADDR, &(taddr.ip));
if (daddr.ip == taddr.ip)
good_packet = 1;
break;
case AF_INET6:
inet_pton(AF_INET6, UPNP_MCAST_LL_ADDR, &(taddr.ip6));
if (daddr.ip6[0] == taddr.ip6[0] &&
daddr.ip6[1] == taddr.ip6[1] &&
daddr.ip6[2] == taddr.ip6[2] &&
daddr.ip6[3] == taddr.ip6[3]) {
good_packet = 1;
break;
}
inet_pton(AF_INET6, UPNP_MCAST_SL_ADDR, &(taddr.ip6));
if (daddr.ip6[0] == taddr.ip6[0] &&
daddr.ip6[1] == taddr.ip6[1] &&
daddr.ip6[2] == taddr.ip6[2] &&
daddr.ip6[3] == taddr.ip6[3]) {
good_packet = 1;
break;
}
break;
default:
break;
}
if (!good_packet) {
pr_debug("ssdp_help: destination address not multicast; ignoring\n");
return NF_ACCEPT;
}
/* No data? Ignore */
dataoff = net_hdr->ihl*4 + sizeof(struct udphdr);
if (dataoff >= pktb_len(pkt)) {
pr_debug("ssdp_help: UDP payload too small for M-SEARCH; ignoring\n");
return NF_ACCEPT;
}
sb_ptr = pktb_network_header(pkt) + dataoff;
if (memcmp(sb_ptr, SSDP_M_SEARCH, SSDP_M_SEARCH_SIZE) != 0) {
pr_debug("ssdp_help: UDP payload does not begin with 'M-SEARCH'; ignoring\n");
return NF_ACCEPT;
}
cthelper_get_addr_src(myct->ct, MYCT_DIR_ORIG, &saddr);
cthelper_get_port_src(myct->ct, MYCT_DIR_ORIG, &port);
exp = nfexp_new();
if (exp == NULL)
return NF_DROP;
if (cthelper_expect_init(exp, myct->ct, 0, NULL, &saddr,
IPPROTO_UDP, NULL, &port,
NF_CT_EXPECT_PERMANENT)) {
nfexp_destroy(exp);
return NF_DROP;
}
myct->exp = exp;
return ret;
}
static struct ctd_helper ssdp_helper = {
.name = "ssdp",
.l4proto = IPPROTO_UDP,
.priv_data_len = 0,
.cb = ssdp_helper_cb,
.policy = {
[0] = {
.name = "ssdp",
.expect_max = 1,
.expect_timeout = 5 * 60,
},
},
};
static void __attribute__ ((constructor)) ssdp_init(void)
{
helper_register(&ssdp_helper);
}
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