Commit 7c3ceb4f authored by Neil Horman's avatar Neil Horman Committed by David S. Miller
Browse files

[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: default avatarNeil Horman <nhorman@tuxdriver.com>
Acked-by: default avatarMark Butler <butlerm@middle.net>
Acked-by: default avatarVlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: default avatarSridhar Samudrala <sri@us.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 91ef5d2d

include/net/sctp/structs.h

+1 −0
Original line number Diff line number Diff line
@@ -712,6 +712,7 @@ struct sctp_chunk { 
	__u8 tsn_gap_acked;	/* Is this chunk acked by a GAP ACK? */

	__s8 fast_retransmit;	 /* Is this chunk fast retransmitted? */

	__u8 tsn_missing_report; /* Data chunk missing counter. */

	__u8 data_accepted; 	/* At least 1 chunk in this packet accepted */

};



void sctp_chunk_hold(struct sctp_chunk *);

net/sctp/inqueue.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

net/sctp/sm_statefuns.c

+36 −10
Original line number Diff line number Diff line
@@ -5151,7 +5151,9 @@ static int sctp_eat_data(const struct sctp_association *asoc, 
	int tmp;

	__u32 tsn;

	int account_value;

	struct sctp_tsnmap *map = (struct sctp_tsnmap *)&asoc->peer.tsn_map;

	struct sock *sk = asoc->base.sk;

	int rcvbuf_over = 0;



	data_hdr = chunk->subh.data_hdr = (sctp_datahdr_t *)chunk->skb->data;

	skb_pull(chunk->skb, sizeof(sctp_datahdr_t));
@@ -5162,10 +5164,16 @@ static int sctp_eat_data(const struct sctp_association *asoc, 
	/* ASSERT:  Now skb->data is really the user data.  */



	/*

	 * if we are established, and we have used up our receive

	 * buffer memory, drop the frame

	 */

	if (asoc->state == SCTP_STATE_ESTABLISHED) {

	 * If we are established, and we have used up our receive buffer

	 * memory, think about droping the frame.

	 * Note that we have an opportunity to improve performance here.

	 * If we accept one chunk from an skbuff, we have to keep all the

	 * memory of that skbuff around until the chunk is read into user

	 * space. Therefore, once we accept 1 chunk we may as well accept all

	 * remaining chunks in the skbuff. The data_accepted flag helps us do

	 * that.

	 */

	if ((asoc->state == SCTP_STATE_ESTABLISHED) && (!chunk->data_accepted)) {

		/*

		 * If the receive buffer policy is 1, then each

		 * association can allocate up to sk_rcvbuf bytes
@@ -5176,9 +5184,25 @@ static int sctp_eat_data(const struct sctp_association *asoc, 
			account_value = atomic_read(&asoc->rmem_alloc);

		else

			account_value = atomic_read(&sk->sk_rmem_alloc);



		if (account_value > sk->sk_rcvbuf)

		if (account_value > sk->sk_rcvbuf) {

			/*

			 * We need to make forward progress, even when we are

			 * under memory pressure, so we always allow the

			 * next tsn after the ctsn ack point to be accepted.

			 * This lets us avoid deadlocks in which we have to

			 * drop frames that would otherwise let us drain the

			 * receive queue.

			 */

			if ((sctp_tsnmap_get_ctsn(map) + 1) != tsn)

				return SCTP_IERROR_IGNORE_TSN;



			/*

			 * We're going to accept the frame but we should renege

			 * to make space for it. This will send us down that

			 * path later in this function.

			 */

			rcvbuf_over = 1;

		}

	}



	/* Process ECN based congestion.
@@ -5226,6 +5250,7 @@ static int sctp_eat_data(const struct sctp_association *asoc, 
	datalen -= sizeof(sctp_data_chunk_t);



	deliver = SCTP_CMD_CHUNK_ULP;

	chunk->data_accepted = 1;



	/* Think about partial delivery. */

	if ((datalen >= asoc->rwnd) && (!asoc->ulpq.pd_mode)) {
@@ -5242,7 +5267,8 @@ static int sctp_eat_data(const struct sctp_association *asoc, 
	 * large spill over.

	 */

	if (!asoc->rwnd || asoc->rwnd_over ||

	    (datalen > asoc->rwnd + asoc->frag_point)) {

	    (datalen > asoc->rwnd + asoc->frag_point) ||

	    rcvbuf_over) {



		/* If this is the next TSN, consider reneging to make

		 * room.   Note: Playing nice with a confused sender.  A
@@ -5250,8 +5276,8 @@ static int sctp_eat_data(const struct sctp_association *asoc, 
		 * space and in the future we may want to detect and

		 * do more drastic reneging.

		 */

		if (sctp_tsnmap_has_gap(&asoc->peer.tsn_map) &&

		    (sctp_tsnmap_get_ctsn(&asoc->peer.tsn_map) + 1) == tsn) {

		if (sctp_tsnmap_has_gap(map) &&

		    (sctp_tsnmap_get_ctsn(map) + 1) == tsn) {

			SCTP_DEBUG_PRINTK("Reneging for tsn:%u\n", tsn);

			deliver = SCTP_CMD_RENEGE;

		} else {

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