[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: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netfilter/nf_conntrack_sip.h b/include/linux/netfilter/nf_conntrack_sip.h
index 71fa3eb5f4856c8d91a2c2c425644e1a41993e2d..5da04e586a3fb399fcda285cb23f6046bc8e447b 100644 (file)
--- a/include/linux/netfilter/nf_conntrack_sip.h
+++ b/include/linux/netfilter/nf_conntrack_sip.h
@@ -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,

diff --git a/net/ipv4/netfilter/nf_nat_sip.c b/net/ipv4/netfilter/nf_nat_sip.c
index 4429069d9b4215aa1136b0b4b8ff3f464322d018..bcddccddf76887e6deca2ae05610b7e58de254a8 100644 (file)
--- a/net/ipv4/netfilter/nf_nat_sip.c
+++ b/net/ipv4/netfilter/nf_nat_sip.c
@@ -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;

diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index f40a525732d138ed58508d38338adcaca2e64061..57de22c770a3bbf50d3b48c129b16c7c47e6c610 100644 (file)
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -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();
-       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;
-       rcu_read_unlock();
+       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)
+                       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();
 
        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 {