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Commit c7f485ab authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

[NETFILTER]: nf_conntrack_sip: RTP routing optimization 



Optimize call routing between NATed endpoints: when an external
registrar sends a media description that contains an existing RTP
expectation from a different SNATed connection, the gatekeeper
is trying to route the call directly between the two endpoints.

We assume both endpoints can reach each other directly and
"un-NAT" the addresses, which makes the media stream go between
the two endpoints directly.

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0d0ab037

include/linux/netfilter/nf_conntrack_sip.h

+6 −0
Original line number Diff line number Diff line
@@ -114,6 +114,12 @@ extern unsigned int (*nf_nat_sdp_addr_hook)(struct sk_buff *skb, 
					    enum sdp_header_types type,

					    enum sdp_header_types term,

					    const union nf_inet_addr *addr);

extern unsigned int (*nf_nat_sdp_port_hook)(struct sk_buff *skb,

					    const char **dptr,

					    unsigned int *datalen,

					    unsigned int matchoff,

					    unsigned int matchlen,

					    u_int16_t port);

extern unsigned int (*nf_nat_sdp_session_hook)(struct sk_buff *skb,

					       const char **dptr,

					       unsigned int dataoff,

net/ipv4/netfilter/nf_nat_sip.c

+3 −0
Original line number Diff line number Diff line
@@ -461,6 +461,7 @@ static void __exit nf_nat_sip_fini(void) 
	rcu_assign_pointer(nf_nat_sip_hook, NULL);

	rcu_assign_pointer(nf_nat_sip_expect_hook, NULL);

	rcu_assign_pointer(nf_nat_sdp_addr_hook, NULL);

	rcu_assign_pointer(nf_nat_sdp_port_hook, NULL);

	rcu_assign_pointer(nf_nat_sdp_session_hook, NULL);

	rcu_assign_pointer(nf_nat_sdp_media_hook, NULL);

	synchronize_rcu();
@@ -471,11 +472,13 @@ static int __init nf_nat_sip_init(void) 
	BUG_ON(nf_nat_sip_hook != NULL);

	BUG_ON(nf_nat_sip_expect_hook != NULL);

	BUG_ON(nf_nat_sdp_addr_hook != NULL);

	BUG_ON(nf_nat_sdp_port_hook != NULL);

	BUG_ON(nf_nat_sdp_session_hook != NULL);

	BUG_ON(nf_nat_sdp_media_hook != NULL);

	rcu_assign_pointer(nf_nat_sip_hook, ip_nat_sip);

	rcu_assign_pointer(nf_nat_sip_expect_hook, ip_nat_sip_expect);

	rcu_assign_pointer(nf_nat_sdp_addr_hook, ip_nat_sdp_addr);

	rcu_assign_pointer(nf_nat_sdp_port_hook, ip_nat_sdp_port);

	rcu_assign_pointer(nf_nat_sdp_session_hook, ip_nat_sdp_session);

	rcu_assign_pointer(nf_nat_sdp_media_hook, ip_nat_sdp_media);

	return 0;

net/netfilter/nf_conntrack_sip.c

+49 −10
Original line number Diff line number Diff line
@@ -70,6 +70,14 @@ unsigned int (*nf_nat_sdp_addr_hook)(struct sk_buff *skb, 
				     __read_mostly;

EXPORT_SYMBOL_GPL(nf_nat_sdp_addr_hook);



unsigned int (*nf_nat_sdp_port_hook)(struct sk_buff *skb,

				     const char **dptr,

				     unsigned int *datalen,

				     unsigned int matchoff,

				     unsigned int matchlen,

				     u_int16_t port) __read_mostly;

EXPORT_SYMBOL_GPL(nf_nat_sdp_port_hook);



unsigned int (*nf_nat_sdp_session_hook)(struct sk_buff *skb,

					const char **dptr,

					unsigned int dataoff,
@@ -730,9 +738,10 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, 
	union nf_inet_addr *saddr;

	struct nf_conntrack_tuple tuple;

	int family = ct->tuplehash[!dir].tuple.src.l3num;

	int skip_expect = 0, ret = NF_DROP;

	int direct_rtp = 0, skip_expect = 0, ret = NF_DROP;

	u_int16_t base_port;

	__be16 rtp_port, rtcp_port;

	typeof(nf_nat_sdp_port_hook) nf_nat_sdp_port;

	typeof(nf_nat_sdp_media_hook) nf_nat_sdp_media;



	saddr = NULL;
@@ -746,6 +755,14 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, 
	 * to register it since we can see the same media description multiple

	 * times on different connections in case multiple endpoints receive

	 * the same call.

	 *

	 * RTP optimization: if we find a matching media channel expectation

	 * and both the expectation and this connection are SNATed, we assume

	 * both sides can reach each other directly and use the final

	 * destination address from the expectation. We still need to keep

	 * the NATed expectations for media that might arrive from the

	 * outside, and additionally need to expect the direct RTP stream

	 * in case it passes through us even without NAT.

	 */

	memset(&tuple, 0, sizeof(tuple));

	if (saddr)
@@ -756,20 +773,42 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, 
	tuple.dst.u.udp.port	= port;



	rcu_read_lock();

	do {

		exp = __nf_ct_expect_find(&tuple);

	if (exp && exp->master != ct &&

	    nfct_help(exp->master)->helper == nfct_help(ct)->helper &&

	    exp->class == class)



		if (!exp || exp->master == ct ||

		    nfct_help(exp->master)->helper != nfct_help(ct)->helper ||

		    exp->class != class)

			break;



		if (exp->tuple.src.l3num == AF_INET && !direct_rtp &&

		    (exp->saved_ip != exp->tuple.dst.u3.ip ||

		     exp->saved_proto.udp.port != exp->tuple.dst.u.udp.port) &&

		    ct->status & IPS_NAT_MASK) {

			daddr->ip		= exp->saved_ip;

			tuple.dst.u3.ip		= exp->saved_ip;

			tuple.dst.u.udp.port	= exp->saved_proto.udp.port;

			direct_rtp = 1;

		} else

			skip_expect = 1;

	} while (!skip_expect);

	rcu_read_unlock();



	if (skip_expect)

		return NF_ACCEPT;



	base_port = ntohs(tuple.dst.u.udp.port) & ~1;

	rtp_port = htons(base_port);

	rtcp_port = htons(base_port + 1);



	if (direct_rtp) {

		nf_nat_sdp_port = rcu_dereference(nf_nat_sdp_port_hook);

		if (nf_nat_sdp_port &&

		    !nf_nat_sdp_port(skb, dptr, datalen,

				     mediaoff, medialen, ntohs(rtp_port)))

			goto err1;

	}



	if (skip_expect)

		return NF_ACCEPT;



	rtp_exp = nf_ct_expect_alloc(ct);

	if (rtp_exp == NULL)

		goto err1;
@@ -783,7 +822,7 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, 
			  IPPROTO_UDP, NULL, &rtcp_port);



	nf_nat_sdp_media = rcu_dereference(nf_nat_sdp_media_hook);

	if (nf_nat_sdp_media && ct->status & IPS_NAT_MASK)

	if (nf_nat_sdp_media && ct->status & IPS_NAT_MASK && !direct_rtp)

		ret = nf_nat_sdp_media(skb, dptr, datalen, rtp_exp, rtcp_exp,

				       mediaoff, medialen, daddr);

	else {