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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 /include
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 'include')
-rw-r--r--include/net/tcp.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1aa9628ae608..f83b7f220a65 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -919,6 +919,10 @@ struct tcp_congestion_ops {
u32 (*tso_segs_goal)(struct sock *sk);
/* returns the multiplier used in tcp_sndbuf_expand (optional) */
u32 (*sndbuf_expand)(struct sock *sk);
+ /* call when packets are delivered to update cwnd and pacing rate,
+ * after all the ca_state processing. (optional)
+ */
+ void (*cong_control)(struct sock *sk, const struct rate_sample *rs);
/* get info for inet_diag (optional) */
size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
union tcp_cc_info *info);