[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>
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index eba99f3..7f4fea1 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -712,6 +712,7 @@
__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 *);
diff --git a/net/sctp/inqueue.c b/net/sctp/inqueue.c
index 297b895..cf0c767 100644
--- a/net/sctp/inqueue.c
+++ b/net/sctp/inqueue.c
@@ -149,6 +149,7 @@
/* 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;
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 2b9a832..f5d131f 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -5151,7 +5151,9 @@
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 @@
/* 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 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) {
+ 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 @@
account_value = atomic_read(&asoc->rmem_alloc);
else
account_value = atomic_read(&sk->sk_rmem_alloc);
+ 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;
- if (account_value > sk->sk_rcvbuf)
- 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 @@
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 @@
* 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 @@
* 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 {