Commit cc4665ca authored by Xin Long's avatar Xin Long Committed by David S. Miller
Browse files

sctp: subtract sctphdr len in sctp_transport_pl_hlen 



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: d9e2e410 ("sctp: add the constants/variables and states and some APIs for transport")
Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c6ea04ea

include/net/sctp/sctp.h

+2 −1
Original line number Diff line number Diff line
@@ -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)