[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, 24 insertions, 18 deletions

diff --git a/include/net/sctp/sm.h b/include/net/sctp/sm.h
index 5576db56324d..f4fcee104707 100644
--- a/include/net/sctp/sm.h
+++ b/include/net/sctp/sm.h
@@ -407,32 +407,38 @@ sctp_vtag_verify(const struct sctp_chunk *chunk,
         return 0;
 }
 
-/* Check VTAG of the packet matches the sender's own tag OR its peer's
- * tag and the T bit is set in the Chunk Flags.
+/* Check VTAG of the packet matches the sender's own tag and the T bit is
+ * not set, OR its peer's tag and the T bit is set in the Chunk Flags.
  */
 static inline int
 sctp_vtag_verify_either(const struct sctp_chunk *chunk,
                         const struct sctp_association *asoc)
 {
-        /* RFC 2960 Section 8.5.1, sctpimpguide-06 Section 2.13.2
+        /* RFC 2960 Section 8.5.1, sctpimpguide Section 2.41
          *
-         * B) The receiver of a ABORT shall accept the packet if the
-         * Verification Tag field of the packet matches its own tag OR it
-         * is set to its peer's tag and the T bit is set in the Chunk
-         * Flags. Otherwise, the receiver MUST silently discard the packet
-         * and take no further action.
-         *
-         * (C) The receiver of a SHUTDOWN COMPLETE shall accept the
-         * packet if the Verification Tag field of the packet
-         * matches its own tag OR it is set to its peer's tag and
-         * the T bit is set in the Chunk Flags.  Otherwise, the
-         * receiver MUST silently discard the packet and take no
-         * further action....
+         * B) The receiver of a ABORT MUST accept the packet
+         *    if the Verification Tag field of the packet matches its own tag
+         *    and the T bit is not set
+         *    OR
+         *    it is set to its peer's tag and the T bit is set in the Chunk
+         *    Flags.
+         *    Otherwise, the receiver MUST silently discard the packet
+         *    and take no further action.
          *
+         * C) The receiver of a SHUTDOWN COMPLETE shall accept the packet
+         *    if the Verification Tag field of the packet matches its own tag
+         *    and the T bit is not set
+         *    OR
+         *    it is set to its peer's tag and the T bit is set in the Chunk
+         *    Flags.
+         *    Otherwise, the receiver MUST silently discard the packet
+         *    and take no further action.  An endpoint MUST ignore the
+         *    SHUTDOWN COMPLETE if it is not in the SHUTDOWN-ACK-SENT state.
          */
-        if ((ntohl(chunk->sctp_hdr->vtag) == asoc->c.my_vtag) ||
-            (sctp_test_T_bit(chunk) && (ntohl(chunk->sctp_hdr->vtag)
-            == asoc->c.peer_vtag))) {
+        if ((!sctp_test_T_bit(chunk) &&
+             (ntohl(chunk->sctp_hdr->vtag) == asoc->c.my_vtag)) ||
+            (sctp_test_T_bit(chunk) &&
+             (ntohl(chunk->sctp_hdr->vtag) == asoc->c.peer_vtag))) {
                 return 1;
         }