From 8880eccbc789e2f59e954197693567fe7a640b33 Mon Sep 17 00:00:00 2001
From: Xin Long <lucien.xin@gmail.com>
Date: Thu, 28 Oct 2021 05:36:03 -0400
Subject: [PATCH] sctp: subtract sctphdr len in sctp_transport_pl_hlen
Git-commit: cc4665ca646c96181a7c00198aa72c59e0c576e8
Patch-mainline: v5.16-rc1
References: stable-5.14.19
[ Upstream commit cc4665ca646c96181a7c00198aa72c59e0c576e8 ]
sctp_transport_pl_hlen() is called to calculate the outer header length
for PL. However, as the Figure in rfc8899#section-4.4:
Any additional
headers .--- MPS -----.
| | |
v v v
+------------------------------+
| IP | ** | PL | protocol data |
+------------------------------+
<----- PLPMTU ----->
<---------- PMTU -------------->
Outer header are IP + Any additional headers, which doesn't include
Packetization Layer itself header, namely sctphdr, whereas sctphdr
is counted by __sctp_mtu_payload().
The incorrect calculation caused the link pathmtu to be set larger
than expected by t->pl.pmtu + sctp_transport_pl_hlen(). This patch
is to fix it by subtracting sctphdr len in sctp_transport_pl_hlen().
Fixes: d9e2e410ae30 ("sctp: add the constants/variables and states and some APIs for transport")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
include/net/sctp/sctp.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index bc00410223b0..189fdb9db162 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -626,7 +626,8 @@ static inline __u32 sctp_min_frag_point(struct sctp_sock *sp, __u16 datasize)
static inline int sctp_transport_pl_hlen(struct sctp_transport *t)
{
- return __sctp_mtu_payload(sctp_sk(t->asoc->base.sk), t, 0, 0);
+ return __sctp_mtu_payload(sctp_sk(t->asoc->base.sk), t, 0, 0) -
+ sizeof(struct sctphdr);
}
static inline void sctp_transport_pl_reset(struct sctp_transport *t)
--
2.26.2