diff mbox series

[net,3/4] sctp: subtract sctphdr len in sctp_transport_pl_hlen

Message ID 5f9e29853938b5ad1cdb5e1a1de14ebcd04b58d8.1635413715.git.lucien.xin@gmail.com (mailing list archive)
State Accepted
Commit cc4665ca646c96181a7c00198aa72c59e0c576e8
Delegated to: Netdev Maintainers
Headers show
Series sctp: a couple of fixes for PLPMTUD | expand

Checks

Context Check Description
netdev/cover_letter success Series has a cover letter
netdev/fixes_present success Fixes tag present in non-next series
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for net
netdev/subject_prefix success Link
netdev/cc_maintainers warning 2 maintainers not CCed: nhorman@tuxdriver.com vyasevich@gmail.com
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 14 this patch: 14
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Fixes tag looks correct
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 9 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 14 this patch: 14
netdev/header_inline success No static functions without inline keyword in header files

Commit Message

Xin Long Oct. 28, 2021, 9:36 a.m. UTC
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>
---
 include/net/sctp/sctp.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

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)