Commit d7ab5cdc authored Sep 20, 2018 by Xin Long Committed by David S. Miller Sep 20, 2018

sctp: update dst pmtu with the correct daddr



When processing pmtu update from an icmp packet, it calls .update_pmtu
with sk instead of skb in sctp_transport_update_pmtu.

However for sctp, the daddr in the transport might be different from
inet_sock->inet_daddr or sk->sk_v6_daddr, which is used to update or
create the route cache. The incorrect daddr will cause a different
route cache created for the path.

So before calling .update_pmtu, inet_sock->inet_daddr/sk->sk_v6_daddr
should be updated with the daddr in the transport, and update it back
after it's done.

The issue has existed since route exceptions introduction.

Fixes: 4895c771 ("ipv4: Add FIB nexthop exceptions.")
Reported-by:  <ian.periam@dialogic.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8c6ec361

net/sctp/transport.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -260,6 +260,7 @@ void sctp_transport_pmtu(struct sctp_transport transport, struct sock sk)
		bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
		{
		struct dst_entry *dst = sctp_transport_dst_check(t);
		struct sock *sk = t->asoc->base.sk;
		bool change = true;

		if (unlikely(pmtu < SCTP_DEFAULT_MINSEGMENT)) {
		@@ -271,12 +272,19 @@ bool sctp_transport_update_pmtu(struct sctp_transport *t, u32 pmtu)
		pmtu = SCTP_TRUNC4(pmtu);

		if (dst) {
		dst->ops->update_pmtu(dst, t->asoc->base.sk, NULL, pmtu);
		struct sctp_pf *pf = sctp_get_pf_specific(dst->ops->family);
		union sctp_addr addr;

		pf->af->from_sk(&addr, sk);
		pf->to_sk_daddr(&t->ipaddr, sk);
		dst->ops->update_pmtu(dst, sk, NULL, pmtu);
		pf->to_sk_daddr(&addr, sk);

		dst = sctp_transport_dst_check(t);
		}

		if (!dst) {
		t->af_specific->get_dst(t, &t->saddr, &t->fl, t->asoc->base.sk);
		t->af_specific->get_dst(t, &t->saddr, &t->fl, sk);
		dst = t->dst;
		}

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