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net: sctp: Open out the check for Nagle 

The check for Nagle contains 6 separate checks all of which must be true
before a data packet is delayed.
Separate out each into its own 'if (test) return SCTP_XMIT_OK' so that
the reasons can be individually described.

Also return directly with SCTP_XMIT_RWND_FULL.
Delete the now-unused 'retval' variable and 'finish' label from
sctp_packet_can_append_data().

Signed-off-by: David Laight <david.laight@aculab.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Laight 2014-07-22 08:59:08 +00:00 committed by David S. Miller
parent 8fd90bb889
commit 723189faca
1 changed files with 35 additions and 32 deletions
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67
net/sctp/output.c
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@ -633,7 +633,6 @@ nomem:
static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
struct sctp_chunk *chunk)
{
sctp_xmit_t retval = SCTP_XMIT_OK;
size_t datasize, rwnd, inflight, flight_size;
struct sctp_transport *transport = packet->transport;
struct sctp_association *asoc = transport->asoc;
@ -658,15 +657,11 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
datasize = sctp_data_size(chunk);
if (datasize > rwnd) {
if (inflight > 0) {
/* We have (at least) one data chunk in flight,
* so we can't fall back to rule 6.1 B).
*/
retval = SCTP_XMIT_RWND_FULL;
goto finish;
}
}
if (datasize > rwnd && inflight > 0)
/* We have (at least) one data chunk in flight,
* so we can't fall back to rule 6.1 B).
*/
return SCTP_XMIT_RWND_FULL;
/* RFC 2960 6.1 Transmission of DATA Chunks
*
@ -680,36 +675,44 @@ static sctp_xmit_t sctp_packet_can_append_data(struct sctp_packet *packet,
* When a Fast Retransmit is being performed the sender SHOULD
* ignore the value of cwnd and SHOULD NOT delay retransmission.
*/
if (chunk->fast_retransmit != SCTP_NEED_FRTX)
if (flight_size >= transport->cwnd) {
retval = SCTP_XMIT_RWND_FULL;
goto finish;
}
if (chunk->fast_retransmit != SCTP_NEED_FRTX &&
flight_size >= transport->cwnd)
return SCTP_XMIT_RWND_FULL;
/* Nagle's algorithm to solve small-packet problem:
* Inhibit the sending of new chunks when new outgoing data arrives
* if any previously transmitted data on the connection remains
* unacknowledged.
*/
if (!sctp_sk(asoc->base.sk)->nodelay && sctp_packet_empty(packet) &&
inflight && sctp_state(asoc, ESTABLISHED)) {
unsigned int max = transport->pathmtu - packet->overhead;
unsigned int len = chunk->skb->len + q->out_qlen;
/* Check whether this chunk and all the rest of pending
* data will fit or delay in hopes of bundling a full
* sized packet.
* Don't delay large message writes that may have been
* fragmeneted into small peices.
*/
if ((len < max) && chunk->msg->can_delay) {
retval = SCTP_XMIT_NAGLE_DELAY;
goto finish;
}
}
if (sctp_sk(asoc->base.sk)->nodelay)
/* Nagle disabled */
return SCTP_XMIT_OK;
finish:
return retval;
if (!sctp_packet_empty(packet))
/* Append to packet */
return SCTP_XMIT_OK;
if (inflight == 0)
/* Nothing unacked */
return SCTP_XMIT_OK;
if (!sctp_state(asoc, ESTABLISHED))
return SCTP_XMIT_OK;
/* Check whether this chunk and all the rest of pending data will fit
* or delay in hopes of bundling a full sized packet.
*/
if (chunk->skb->len + q->out_qlen >= transport->pathmtu - packet->overhead)
/* Enough data queued to fill a packet */
return SCTP_XMIT_OK;
/* Don't delay large message writes that may have been fragmented */
if (!chunk->msg->can_delay)
return SCTP_XMIT_OK;
/* Defer until all data acked or packet full */
return SCTP_XMIT_NAGLE_DELAY;
}
/* This private function does management things when adding DATA chunk */