Subject: [PATCH 15/36] Revert "sctp: remove sctp_transport_pmtu_check"

From: Xin Long <[email-masked]>
Date: Sun, 18 Nov 2018 16:14:47 +0800

[ Upstream commit 69fec325a64383667b8a35df5d48d6ce52fb2782 ]

This reverts commit 22d7be267eaa8114dcc28d66c1c347f667d7878a.

The dst's mtu in transport can be updated by a non sctp place like
in xfrm where the MTU information didn't get synced between asoc,
transport and dst, so it is still needed to do the pmtu check
in sctp_packet_config.

Acked-by: Neil Horman <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 include/net/sctp/sctp.h | 12 ++++++++++++
 net/sctp/output.c       |  3 +++
 2 files changed, 15 insertions(+)

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index 8c2caa370e0f..ab9242e51d9e 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -608,4 +608,16 @@ static inline __u32 sctp_dst_mtu(const struct dst_entry *dst)
 				 SCTP_DEFAULT_MINSEGMENT));
 }
 
+static inline bool sctp_transport_pmtu_check(struct sctp_transport *t)
+{
+	__u32 pmtu = sctp_dst_mtu(t->dst);
+
+	if (t->pathmtu == pmtu)
+		return true;
+
+	t->pathmtu = pmtu;
+
+	return false;
+}
+
 #endif /* __net_sctp_h__ */
diff --git a/net/sctp/output.c b/net/sctp/output.c
index 7f849b01ec8e..2b258e57384f 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -118,6 +118,9 @@ void sctp_packet_config(struct sctp_packet *packet, __u32 vtag,
 		sctp_transport_route(tp, NULL, sp);
 		if (asoc->param_flags & SPP_PMTUD_ENABLE)
 			sctp_assoc_sync_pmtu(asoc);
+	} else if (!sctp_transport_pmtu_check(tp)) {
+		if (asoc->param_flags & SPP_PMTUD_ENABLE)
+			sctp_assoc_sync_pmtu(asoc);
 	}
 
 	/* If there a is a prepend chunk stick it on the list before
-- 
2.19.1