[PATCH 4.14 022/109] sctp: update dst pmtu with the correct daddr

Greg Kroah-Hartman
2018-10-16T17:17:51Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit d7ab5cdce54da631f0c8c11e506c974536a3581e ]

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: 4895c771c7f0 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/transport.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -254,6 +254,7 @@ void sctp_transport_pmtu(struct sctp_tra
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)) {
@@ -265,12 +266,19 @@ bool sctp_transport_update_pmtu(struct s
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;
}