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authorYuchung Cheng <ycheng@google.com>2016-09-19 23:39:21 -0400
committerDavid S. Miller <davem@davemloft.net>2016-09-21 00:23:01 -0400
commitc0402760f565ae066621ebf8720a32fba074d538 (patch)
treeda6a5945e2985312febcf7e2a2493b5544d52742 /net/ipv4/tcp_cong.c
parent77bfc174c38e558a3425d3b069aa2762b2fedfdd (diff)
downloadlinux-c0402760f565ae066621ebf8720a32fba074d538.tar.bz2
tcp: new CC hook to set sending rate with rate_sample in any CA state
This commit introduces an optional new "omnipotent" hook, cong_control(), for congestion control modules. The cong_control() function is called at the end of processing an ACK (i.e., after updating sequence numbers, the SACK scoreboard, and loss detection). At that moment we have precise delivery rate information the congestion control module can use to control the sending behavior (using cwnd, TSO skb size, and pacing rate) in any CA state. This function can also be used by a congestion control that prefers not to use the default cwnd reduction approach (i.e., the PRR algorithm) during CA_Recovery to control the cwnd and sending rate during loss recovery. We take advantage of the fact that recent changes defer the retransmission or transmission of new data (e.g. by F-RTO) in recovery until the new tcp_cong_control() function is run. With this commit, we only run tcp_update_pacing_rate() if the congestion control is not using this new API. New congestion controls which use the new API do not want the TCP stack to run the default pacing rate calculation and overwrite whatever pacing rate they have chosen at initialization time. Signed-off-by: Van Jacobson <vanj@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_cong.c')
-rw-r--r--net/ipv4/tcp_cong.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 882caa4e72bc..1294af4e0127 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -69,7 +69,7 @@ int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
int ret = 0;
/* all algorithms must implement ssthresh and cong_avoid ops */
- if (!ca->ssthresh || !ca->cong_avoid) {
+ if (!ca->ssthresh || !(ca->cong_avoid || ca->cong_control)) {
pr_err("%s does not implement required ops\n", ca->name);
return -EINVAL;
}