tcp: use TS opt on RTTs for congestion control
authorYuchung Cheng <ycheng@google.com>
Wed, 31 May 2017 18:30:53 +0000 (11:30 -0700)
committerDavid S. Miller <davem@davemloft.net>
Fri, 2 Jun 2017 18:19:23 +0000 (14:19 -0400)
commit775e68a93fe4d33ec93949c8022ed84b97a97096
tree70959496b390c3b4854b736bc00b383c2a608538
parent9ae122c62a26ed3022d0affb5b7fffe0292bae16
tcp: use TS opt on RTTs for congestion control

Currently when a data packet is retransmitted, we do not compute an
RTT sample for congestion control due to Kern's check. Therefore the
congestion control that uses RTT signals may not receive any update
during loss recovery which could last many round trips. For example,
BBR and Vegas may not be able to update its min RTT estimation if the
network path has shortened until it recovers from losses. This patch
mitigates that by using TCP timestamp options for RTT measurement
for congestion control. Note that we already use timestamps for
RTT estimation.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/tcp_input.c