tcp: record most recent RTT in RACK loss detection
authorYuchung Cheng <ycheng@google.com>
Fri, 13 Jan 2017 06:11:32 +0000 (22:11 -0800)
committerDavid S. Miller <davem@davemloft.net>
Sat, 14 Jan 2017 03:37:16 +0000 (22:37 -0500)
commitdeed7be78f512d003c6290da0a781479b31b3d74
treeac478434d723eb690fa62943f262c251d92a538c
parente636f8b0104d6622aaaed6aa5ef17dfbf165bc51
tcp: record most recent RTT in RACK loss detection

Record the most recent RTT in RACK. It is often identical to the
"ca_rtt_us" values in tcp_clean_rtx_queue. But when the packet has
been retransmitted, RACK choses to believe the ACK is for the
(latest) retransmitted packet if the RTT is over minimum RTT.

This requires passing the arrival time of the most recent ACK to
RACK routines. The timestamp is now recorded in the "ack_time"
in tcp_sacktag_state during the ACK processing.

This patch does not change the RACK algorithm itself. It only adds
the RTT variable to prepare the next main patch.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/linux/tcp.h
include/net/tcp.h
net/ipv4/tcp_input.c
net/ipv4/tcp_recovery.c