SCTP: Send ABORT chunk with correct tag in response to INIT ACK

When SCTP client received an INIT ACK chunk with missing mandatory
parameter such as "cookie parameter", it will send back a ABORT
with T-bit not set and verification tag is set to 0.
This is because before we accept this INIT ACK chunk, we do not know
the peer's tag.  This patch change to reflect vtag when responding to
INIT ACK with missing mandatory parameter.
Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/sm_statefuns.c

@@ -5176,7 +5176,22 @@ static struct sctp_packet *sctp_ootb_pkt_new(const struct sctp_association *asoc
 	 * association exists, otherwise, use the peer's vtag.
 	 */
 	if (asoc) {
-		vtag = asoc->peer.i.init_tag;
+		/* Special case the INIT-ACK as there is no peer's vtag
+		 * yet.
+		 */
+		switch(chunk->chunk_hdr->type) {
+		case SCTP_CID_INIT_ACK:
+		{
+			sctp_initack_chunk_t *initack;
+
+			initack = (sctp_initack_chunk_t *)chunk->chunk_hdr;
+			vtag = ntohl(initack->init_hdr.init_tag);
+			break;
+		}
+		default:
+			vtag = asoc->peer.i.init_tag;
+			break;
+		}
 	} else {
 		/* Special case the INIT and stale COOKIE_ECHO as there is no
 		 * vtag yet.