[SCTP] Implement Sec 2.41 of SCTP Implementers guide.

- Fixed sctp_vtag_verify_either() to comply with impguide 2.41 B) and C).
- Make sure vtag is reflected when T-bit is set in SHUTDOWN-COMPLETE sent
  due to an OOTB SHUTDOWN-ACK and in ABORT sent due to an OOTB packet.
- Do not set T-Bit in ABORT chunk in response to INIT.
- Fixed some comments to reflect the new meaning of the T-Bit.

Signed-off-by: Jerome Forissier <jerome.forissier@hp.com>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 5 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 1db12cc18cf7..33ac8bf47b0e 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -710,7 +710,9 @@ struct sctp_chunk *sctp_make_shutdown_complete(
         struct sctp_chunk *retval;
         __u8 flags = 0;
 
-        /* Maybe set the T-bit if we have no association. */
+        /* Set the T-bit if we have no association (vtag will be
+         * reflected)
+         */
         flags |= asoc ? 0 : SCTP_CHUNK_FLAG_T;
 
         retval = sctp_make_chunk(asoc, SCTP_CID_SHUTDOWN_COMPLETE, flags, 0);
@@ -732,7 +734,7 @@ struct sctp_chunk *sctp_make_shutdown_complete(
 }
 
 /* Create an ABORT.  Note that we set the T bit if we have no
- * association.
+ * association, except when responding to an INIT (sctpimpguide 2.41).
  */
 struct sctp_chunk *sctp_make_abort(const struct sctp_association *asoc,
                               const struct sctp_chunk *chunk,
@@ -741,8 +743,16 @@ struct sctp_chunk *sctp_make_abort(const struct sctp_association *asoc,
         struct sctp_chunk *retval;
         __u8 flags = 0;
 
-        /* Maybe set the T-bit if we have no association.  */
-        flags |= asoc ? 0 : SCTP_CHUNK_FLAG_T;
+        /* Set the T-bit if we have no association and 'chunk' is not
+         * an INIT (vtag will be reflected).
+         */
+        if (!asoc) {
+                if (chunk && chunk->chunk_hdr &&
+                    chunk->chunk_hdr->type == SCTP_CID_INIT)
+                        flags = 0;
+                else
+                        flags = SCTP_CHUNK_FLAG_T;
+        }
 
         retval = sctp_make_chunk(asoc, SCTP_CID_ABORT, flags, hint);
 
@@ -2744,7 +2754,6 @@ struct sctp_chunk *sctp_make_fwdtsn(const struct sctp_association *asoc,
 
         hint = (nstreams + 1) * sizeof(__u32);
 
-        /* Maybe set the T-bit if we have no association.  */
         retval = sctp_make_chunk(asoc, SCTP_CID_FWD_TSN, 0, hint);
 
         if (!retval)