From 876c27314ce51fe7e7e2aeb24a6448da1a26c78f Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Tue, 3 Apr 2018 12:10:09 +0200 Subject: [PATCH] netfilter: nf_conntrack_sip: allow duplicate SDP expectations Callum Sinclair reported SIP IP Phone errors that he tracked down to such phones sending session descriptions for different media types but with same port numbers. The expect core will only 'refresh' existing expectation if it is from same master AND same expectation class (media type). As expectation class is different, we get an error. The SIP connection tracking code will then 1). drop the SDP packet 2). if an rtp expectation was already installed successfully, error on rtcp expectation will cancel the rtp one. Make the expect core report back to caller when the conflict is due to different expectation class and have SIP tracker ignore soft-error. Reported-by: Callum Sinclair Tested-by: Callum Sinclair Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_conntrack_expect.c | 5 ++++- net/netfilter/nf_conntrack_sip.c | 16 ++++++++++++---- 2 files changed, 16 insertions(+), 5 deletions(-) diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c index 8ef21d9..4b2b3d5 100644 --- a/net/netfilter/nf_conntrack_expect.c +++ b/net/netfilter/nf_conntrack_expect.c @@ -252,7 +252,7 @@ static inline int expect_clash(const struct nf_conntrack_expect *a, static inline int expect_matches(const struct nf_conntrack_expect *a, const struct nf_conntrack_expect *b) { - return a->master == b->master && a->class == b->class && + return a->master == b->master && nf_ct_tuple_equal(&a->tuple, &b->tuple) && nf_ct_tuple_mask_equal(&a->mask, &b->mask) && net_eq(nf_ct_net(a->master), nf_ct_net(b->master)) && @@ -421,6 +421,9 @@ static inline int __nf_ct_expect_check(struct nf_conntrack_expect *expect) h = nf_ct_expect_dst_hash(net, &expect->tuple); hlist_for_each_entry_safe(i, next, &nf_ct_expect_hash[h], hnode) { if (expect_matches(i, expect)) { + if (i->class != expect->class) + return -EALREADY; + if (nf_ct_remove_expect(i)) break; } else if (expect_clash(i, expect)) { diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c index 4dbb5ba..908e51e 100644 --- a/net/netfilter/nf_conntrack_sip.c +++ b/net/netfilter/nf_conntrack_sip.c @@ -938,11 +938,19 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff, datalen, rtp_exp, rtcp_exp, mediaoff, medialen, daddr); else { - if (nf_ct_expect_related(rtp_exp) == 0) { - if (nf_ct_expect_related(rtcp_exp) != 0) - nf_ct_unexpect_related(rtp_exp); - else + /* -EALREADY handling works around end-points that send + * SDP messages with identical port but different media type, + * we pretend expectation was set up. + */ + int errp = nf_ct_expect_related(rtp_exp); + + if (errp == 0 || errp == -EALREADY) { + int errcp = nf_ct_expect_related(rtcp_exp); + + if (errcp == 0 || errcp == -EALREADY) ret = NF_ACCEPT; + else if (errp == 0) + nf_ct_unexpect_related(rtp_exp); } } nf_ct_expect_put(rtcp_exp); -- 2.7.4