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authorYuchung Cheng <ycheng@google.com>2017-12-07 11:33:33 -0800
committerDavid S. Miller <davem@davemloft.net>2017-12-08 14:14:11 -0500
commit6065fd0d179b96ddc488c76542349bcb148a95fd (patch)
tree39472b7c1cc30a0ce316278fc8854101245b97b7
parent428aec5e69fa17d223e1495f395833c50770f7ae (diff)
downloadlinux-stericsson-6065fd0d179b96ddc488c76542349bcb148a95fd.tar.gz
tcp: evaluate packet losses upon RTT change
RACK skips an ACK unless it advances the most recently delivered TX timestamp (rack.mstamp). Since RACK also uses the most recent RTT to decide if a packet is lost, RACK should still run the loss detection whenever the most recent RTT changes. For example, an ACK that does not advance the timestamp but triggers the cwnd undo due to reordering, would then use the most recent (higher) RTT measurement to detect further losses. Signed-off-by: Yuchung Cheng <ycheng@google.com> Reviewed-by: Neal Cardwell <ncardwell@google.com> Reviewed-by: Priyaranjan Jha <priyarjha@google.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/tcp_recovery.c19
1 files changed, 8 insertions, 11 deletions
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index 0c182303e62e..3a81720ac0c4 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -117,13 +117,8 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
{
u32 rtt_us;
- if (tp->rack.mstamp &&
- !tcp_rack_sent_after(xmit_time, tp->rack.mstamp,
- end_seq, tp->rack.end_seq))
- return;
-
rtt_us = tcp_stamp_us_delta(tp->tcp_mstamp, xmit_time);
- if (sacked & TCPCB_RETRANS) {
+ if (rtt_us < tcp_min_rtt(tp) && (sacked & TCPCB_RETRANS)) {
/* If the sacked packet was retransmitted, it's ambiguous
* whether the retransmission or the original (or the prior
* retransmission) was sacked.
@@ -134,13 +129,15 @@ void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq,
* so it's at least one RTT (i.e., retransmission is at least
* an RTT later).
*/
- if (rtt_us < tcp_min_rtt(tp))
- return;
+ return;
}
- tp->rack.rtt_us = rtt_us;
- tp->rack.mstamp = xmit_time;
- tp->rack.end_seq = end_seq;
tp->rack.advanced = 1;
+ tp->rack.rtt_us = rtt_us;
+ if (tcp_rack_sent_after(xmit_time, tp->rack.mstamp,
+ end_seq, tp->rack.end_seq)) {
+ tp->rack.mstamp = xmit_time;
+ tp->rack.end_seq = end_seq;
+ }
}
/* We have waited long enough to accommodate reordering. Mark the expired