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 <>
Signed-off-by: default avatarDavid S. Miller <>
parent 0d0ab037
......@@ -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,
......@@ -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);
......@@ -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;
......@@ -70,6 +70,14 @@ unsigned int (*nf_nat_sdp_addr_hook)(struct sk_buff *skb,
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;
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;
exp = __nf_ct_expect_find(&tuple);
if (exp && exp->master != ct &&
nfct_help(exp->master)->helper == nfct_help(ct)->helper &&
exp->class == class)
skip_expect = 1;
do {
exp = __nf_ct_expect_find(&tuple);
if (skip_expect)
return NF_ACCEPT;
if (!exp || exp->master == ct ||
nfct_help(exp->master)->helper != nfct_help(ct)->helper ||
exp->class != class)
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);
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 {
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