The sender should create a SACK only if the size of the final SCTP
packet does not exceed the current MTU. Base on RFC 4960:
6.1. Transmission of DATA Chunks
Before an endpoint transmits a DATA chunk, if any received DATA
chunks have not been acknowledged (e.g., due to delayed ack), the
sender should create a SACK and bundle it with the outbound DATA
chunk, as long as the size of the final SCTP packet does not exceed
the current MTU.
Signed-off-by: Wei Yongjun <yjwei@xxxxxxxxxxxxxx>
---
net/sctp/output.c | 28 ++++++++++++++++------------
1 files changed, 16 insertions(+), 12 deletions(-)
diff --git a/net/sctp/output.c b/net/sctp/output.c
index 94c110d..21b9efd 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -222,6 +222,16 @@ static sctp_xmit_t sctp_packet_bundle_auth(struct sctp_packet *pkt,
return retval;
}
+static int can_append_chunk(struct sctp_packet *pkt, size_t size)
+{
+ size_t psize = pkt->size;
+ size_t pmtu = ((pkt->transport->asoc) ?
+ (pkt->transport->asoc->pathmtu) :
+ (pkt->transport->pathmtu));
+
+ return (psize + size <= pmtu);
+}
+
/* Try to bundle a SACK with the packet. */
static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
struct sctp_chunk *chunk)
@@ -235,11 +245,15 @@ static sctp_xmit_t sctp_packet_bundle_sack(struct sctp_packet *pkt,
!pkt->has_cookie_echo) {
struct sctp_association *asoc;
struct timer_list *timer;
+ __u16 chunk_len;
+
asoc = pkt->transport->asoc;
timer = &asoc->timers[SCTP_EVENT_TIMEOUT_SACK];
+ chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length)) +
+ sizeof(struct sctp_sack_chunk);
/* If the SACK timer is running, we have a pending SACK */
- if (timer_pending(timer)) {
+ if (timer_pending(timer) && can_append_chunk(pkt, chunk_len)) {
struct sctp_chunk *sack;
asoc->a_rwnd = asoc->rwnd;
sack = sctp_make_sack(asoc);
@@ -262,9 +276,6 @@ sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
{
sctp_xmit_t retval = SCTP_XMIT_OK;
__u16 chunk_len = WORD_ROUND(ntohs(chunk->chunk_hdr->length));
- size_t psize;
- size_t pmtu;
- int too_big;
SCTP_DEBUG_PRINTK("%s: packet:%p chunk:%p\n", __func__, packet,
chunk);
@@ -279,15 +290,8 @@ sctp_xmit_t sctp_packet_append_chunk(struct sctp_packet *packet,
if (retval != SCTP_XMIT_OK)
goto finish;
- psize = packet->size;
- pmtu = ((packet->transport->asoc) ?
- (packet->transport->asoc->pathmtu) :
- (packet->transport->pathmtu));
-
- too_big = (psize + chunk_len > pmtu);
-
/* Decide if we need to fragment or resubmit later. */
- if (too_big) {
+ if (!can_append_chunk(packet, chunk_len)) {
/* It's OK to fragmet at IP level if any one of the following
* is true:
* 1. The packet is empty (meaning this chunk is greater
--
1.6.2.2
--
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