[SCTP]: Allow spillover of receive buffer to avoid deadlock.

This patch fixes a deadlock situation in the receive path by allowing
temporary spillover of the receive buffer.

- If the chunk we receive has a tsn that immediately follows the ctsn,
  accept it even if we run out of receive buffer space and renege data with
  higher TSNs.
- Once we accept one chunk in a packet, accept all the remaining chunks
  even if we run out of receive buffer space.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Mark Butler <butlerm@middle.net>
Acked-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/inqueue.c

@@ -149,6 +149,7 @@ struct sctp_chunk *sctp_inq_pop(struct sctp_inq *queue)
 		/* This is the first chunk in the packet.  */
 		chunk->singleton = 1;
 		ch = (sctp_chunkhdr_t *) chunk->skb->data;
+		chunk->data_accepted = 0;
 	}
 
         chunk->chunk_hdr = ch;