Commit ecf938fe authored Jan 22, 2019 by Xin Long Committed by David S. Miller Jan 24, 2019

sctp: set flow sport from saddr only when it's 0



Now sctp_transport_pmtu() passes transport->saddr into .get_dst() to set
flow sport from 'saddr'. However, transport->saddr is set only when
transport->dst exists in sctp_transport_route().

If sctp_transport_pmtu() is called without transport->saddr set, like
when transport->dst doesn't exists, the flow sport will be set to 0
from transport->saddr, which will cause a wrong route to be got.

Commit 6e91b578 ("sctp: re-use sctp_transport_pmtu in
sctp_transport_route") made the issue be triggered more easily
since sctp_transport_pmtu() would be called in sctp_transport_route()
after that.

In gerneral, fl4->fl4_sport should always be set to
htons(asoc->base.bind_addr.port), unless transport->asoc doesn't exist
in sctp_v4/6_get_dst(), which is the case:

  sctp_ootb_pkt_new() ->
    sctp_transport_route()

For that, we can simply handle it by setting flow sport from saddr only
when it's 0 in sctp_v4/6_get_dst().

Fixes: 6e91b578 ("sctp: re-use sctp_transport_pmtu in sctp_transport_route")
Reported-by: Ying Xu <yinxu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 4ff40b86

net/sctp/ipv6.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -280,6 +280,7 @@ static void sctp_v6_get_dst(struct sctp_transport t, union sctp_addr saddr,

		if (saddr) {
		fl6->saddr = saddr->v6.sin6_addr;
		if (!fl6->fl6_sport)
		fl6->fl6_sport = saddr->v6.sin6_port;

		pr_debug("src=%pI6 - ", &fl6->saddr);

net/sctp/protocol.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -440,6 +440,7 @@ static void sctp_v4_get_dst(struct sctp_transport t, union sctp_addr saddr,
		}
		if (saddr) {
		fl4->saddr = saddr->v4.sin_addr.s_addr;
		if (!fl4->fl4_sport)
		fl4->fl4_sport = saddr->v4.sin_port;
		}

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