From: Pengcheng Yang yangpc@wangsu.com
commit 62d9f1a6945ba69c125e548e72a36d203b30596e upstream.
Upon receiving a cumulative ACK that changes the congestion state from Disorder to Open, the TLP timer is not set. If the sender is app-limited, it can only wait for the RTO timer to expire and retransmit.
The reason for this is that the TLP timer is set before the congestion state changes in tcp_ack(), so we delay the time point of calling tcp_set_xmit_timer() until after tcp_fastretrans_alert() returns and remove the FLAG_SET_XMIT_TIMER from ack_flag when the RACK reorder timer is set.
This commit has two additional benefits: 1) Make sure to reset RTO according to RFC6298 when receiving ACK, to avoid spurious RTO caused by RTO timer early expires. 2) Reduce the xmit timer reschedule once per ACK when the RACK reorder timer is set.
Fixes: df92c8394e6e ("tcp: fix xmit timer to only be reset if data ACKed/SACKed") Link: https://lore.kernel.org/netdev/1611311242-6675-1-git-send-email-yangpc@wangs... Signed-off-by: Pengcheng Yang yangpc@wangsu.com Acked-by: Neal Cardwell ncardwell@google.com Acked-by: Yuchung Cheng ycheng@google.com Cc: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/1611464834-23030-1-git-send-email-yangpc@wangsu.co... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- include/net/tcp.h | 2 +- net/ipv4/tcp_input.c | 10 ++++++---- net/ipv4/tcp_recovery.c | 5 +++-- 3 files changed, 10 insertions(+), 7 deletions(-)
--- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1969,7 +1969,7 @@ void tcp_v4_init(void); void tcp_init(void);
/* tcp_recovery.c */ -extern void tcp_rack_mark_lost(struct sock *sk); +extern bool tcp_rack_mark_lost(struct sock *sk); extern void tcp_rack_advance(struct tcp_sock *tp, u8 sacked, u32 end_seq, u64 xmit_time); extern void tcp_rack_reo_timeout(struct sock *sk); --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2803,7 +2803,8 @@ static void tcp_rack_identify_loss(struc if (sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION) { u32 prior_retrans = tp->retrans_out;
- tcp_rack_mark_lost(sk); + if (tcp_rack_mark_lost(sk)) + *ack_flag &= ~FLAG_SET_XMIT_TIMER; if (prior_retrans > tp->retrans_out) *ack_flag |= FLAG_LOST_RETRANS; } @@ -3688,15 +3689,16 @@ static int tcp_ack(struct sock *sk, cons
if (tp->tlp_high_seq) tcp_process_tlp_ack(sk, ack, flag); - /* If needed, reset TLP/RTO timer; RACK may later override this. */ - if (flag & FLAG_SET_XMIT_TIMER) - tcp_set_xmit_timer(sk);
if (tcp_ack_is_dubious(sk, flag)) { is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit); }
+ /* If needed, reset TLP/RTO timer when RACK doesn't set. */ + if (flag & FLAG_SET_XMIT_TIMER) + tcp_set_xmit_timer(sk); + if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) sk_dst_confirm(sk);
--- a/net/ipv4/tcp_recovery.c +++ b/net/ipv4/tcp_recovery.c @@ -102,13 +102,13 @@ static void tcp_rack_detect_loss(struct } }
-void tcp_rack_mark_lost(struct sock *sk) +bool tcp_rack_mark_lost(struct sock *sk) { struct tcp_sock *tp = tcp_sk(sk); u32 timeout;
if (!tp->rack.advanced) - return; + return false;
/* Reset the advanced flag to avoid unnecessary queue scanning */ tp->rack.advanced = 0; @@ -118,6 +118,7 @@ void tcp_rack_mark_lost(struct sock *sk) inet_csk_reset_xmit_timer(sk, ICSK_TIME_REO_TIMEOUT, timeout, inet_csk(sk)->icsk_rto); } + return !!timeout; }
/* Record the most recently (re)sent time among the (s)acked packets