From 554153b1cd01203fc462f814749b37fe081121a8 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Thu, 28 Oct 2021 05:36:03 -0400 Subject: [PATCH] sctp: subtract sctphdr len in sctp_transport_pl_hlen [ 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 Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- 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 bc00410223b03..189fdb9db1622 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)