lwn.git/net/sctp/outqueue.c, branch v3.0.22

sctp: Do not account for sizeof(struct sk_buff) in estimated rwnd

2012-01-06T22:14:09+00:00

[ Upstream commit a76c0adf60f6ca5ff3481992e4ea0383776b24d2 ] When checking whether a DATA chunk fits into the estimated rwnd a full sizeof(struct sk_buff) is added to the needed chunk size. This quickly exhausts the available rwnd space and leads to packets being sent which are much below the PMTU limit. This can lead to much worse performance. The reason for this behaviour was to avoid putting too much memory pressure on the receiver. The concept is not completely irational because a Linux receiver does in fact clone an skb for each DATA chunk delivered. However, Linux also reserves half the available socket buffer space for data structures therefore usage of it is already accounted for. When proposing to change this the last time it was noted that this behaviour was introduced to solve a performance issue caused by rwnd overusage in combination with small DATA chunks. Trying to reproduce this I found that with the sk_buff overhead removed, the performance would improve significantly unless socket buffer limits are increased. The following numbers have been gathered using a patched iperf supporting SCTP over a live 1 Gbit ethernet network. The -l option was used to limit DATA chunk sizes. The numbers listed are based on the average of 3 test runs each. Default values have been used for sk_(r|w)mem. Chunk Size Unpatched No Overhead ------------------------------------- 4 15.2 Kbit [!] 12.2 Mbit [!] 8 35.8 Kbit [!] 26.0 Mbit [!] 16 95.5 Kbit [!] 54.4 Mbit [!] 32 106.7 Mbit 102.3 Mbit 64 189.2 Mbit 188.3 Mbit 128 331.2 Mbit 334.8 Mbit 256 537.7 Mbit 536.0 Mbit 512 766.9 Mbit 766.6 Mbit 1024 810.1 Mbit 808.6 Mbit Signed-off-by: Thomas Graf Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

sctp: Enforce retransmission limit during shutdown

2011-07-07T21:08:44+00:00

When initiating a graceful shutdown while having data chunks on the retransmission queue with a peer which is in zero window mode the shutdown is never completed because the retransmission error count is reset periodically by the following two rules: - Do not timeout association while doing zero window probe. - Reset overall error count when a heartbeat request has been acknowledged. The graceful shutdown will wait for all outstanding TSN to be acknowledged before sending the SHUTDOWN request. This never happens due to the peer's zero window not acknowledging the continuously retransmitted data chunks. Although the error counter is incremented for each failed retransmission, the receiving of the SACK announcing the zero window clears the error count again immediately. Also heartbeat requests continue to be sent periodically. The peer acknowledges these requests causing the error counter to be reset as well. This patch changes behaviour to only reset the overall error counter for the above rules while not in shutdown. After reaching the maximum number of retransmission attempts, the T5 shutdown guard timer is scheduled to give the receiver some additional time to recover. The timer is stopped as soon as the receiver acknowledges any data. The issue can be easily reproduced by establishing a sctp association over the loopback device, constantly queueing data at the sender while not reading any at the receiver. Wait for the window to reach zero, then initiate a shutdown by killing both processes simultaneously. The association will never be freed and the chunks on the retransmission queue will be retransmitted indefinitely. Signed-off-by: Thomas Graf Acked-by: Vlad Yasevich Signed-off-by: David S. Miller

sctp: move chunk from retransmit queue to abandoned list

2011-04-20T08:51:06+00:00

If there is still data waiting to retransmit and remain in retransmit queue, while doing the next retransmit, if the chunk is abandoned, we should move it to abandoned list. Signed-off-by: Wei Yongjun Signed-off-by: Vlad Yasevich Signed-off-by: David S. Miller

sctp: remove completely unsed EMPTY state

2011-04-20T08:51:03+00:00

SCTP does not SCTP_STATE_EMPTY and we can never be in that state. Remove useless code. Signed-off-by: Vlad Yasevich Signed-off-by: Wei Yongjun Signed-off-by: David S. Miller

sctp: teach CACC algorithm about removed transports

2011-04-20T04:45:21+00:00

When we have have to remove a transport due to ASCONF, we move the data to a new active path. This can trigger CACC algorithm to not mark that data as missing when SACKs arrive. This is because the transport passed to the CACC algorithm is the one this data is sitting on, not the one it was sent on (that one may be gone). So, by sending the original transport (even if it's NULL), we may start marking data as missing. Signed-off-by: Vlad Yasevich Signed-off-by: Wei Yongjun Signed-off-by: David S. Miller

Fix common misspellings

2011-03-31T14:26:23+00:00

Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi

sctp: several declared/set but unused fixes

2011-03-07T23:51:14+00:00

Signed-off-by: Hagen Paul Pfeifer Signed-off-by: David S. Miller

net/sctp: Use pr_fmt and pr_

2010-08-26T21:11:48+00:00

Change SCTP_DEBUG_PRINTK and SCTP_DEBUG_PRINTK_IPADDR to use do { print } while (0) guards. Add SCTP_DEBUG_PRINTK_CONT to fix errors in log when lines were continued. Add #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt Add a missing newline in "Failed bind hash alloc" Signed-off-by: Joe Perches Signed-off-by: David S. Miller

net: Remove unnecessary returns from void function()s

2010-05-18T06:23:14+00:00

This patch removes from net/ (but not any netfilter files) all the unnecessary return; statements that precede the last closing brace of void functions. It does not remove the returns that are immediately preceded by a label as gcc doesn't like that. Done via: $ grep -rP --include=*.[ch] -l "return;\n}" net/ | \ xargs perl -i -e 'local $/ ; while (<>) { s/\n[ \t\n]+return;\n}/\n}/g; print; }' Signed-off-by: Joe Perches Signed-off-by: David S. Miller

sctp: Optimize computation of highest new tsn in SACK.

2010-05-01T02:41:10+00:00

Right now, if the highest tsn in the SACK doesn't change, we'll end up scanning the transmitted lists on the transports twice: once for locating the highest _new_ tsn, and once for actually tagging chunks as acked. This is a waste, since we can record the highest _new_ tsn at the same time as tagging chunks. Long ago this was not possible because we would try to mark chunks as missing at the same time as tagging them acked and this approach didn't work. Now that the two steps are separate, we can re-use the old approach. Signed-off-by: Vlad Yasevich