* [PATCH net] tcp: fix incorrect ca_state in tail loss probe
@ 2013-10-12 17:16 Yuchung Cheng
2013-10-14 5:55 ` Neal Cardwell
0 siblings, 1 reply; 3+ messages in thread
From: Yuchung Cheng @ 2013-10-12 17:16 UTC (permalink / raw)
To: davem, ncardwell, nanditad
Cc: netdev, michael, jwboyer, sesse, dormando, Yuchung Cheng
On receiving an ACK that covers the loss probe sequence, TLP
immediately sets the congestion state to Open, even though some packets
are not recovered and retransmisssion are on the way. The later ACks
may trigger a WARN_ON check in step D of tcp_fastretrans_alert(), e.g.,
https://bugzilla.redhat.com/show_bug.cgi?id=989251
The fix is to follow the similar procedure in recovery by calling
tcp_try_keep_open(). The sender switches to Open state if no packets
are retransmissted. Otherwise it goes to Disorder and let subsequent
ACKs move the state to Recovery or Open.
Reported-By: Michael Sterrett <michael@sterretts.net>
Tested-By: Dormando <dormando@rydia.net>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
---
net/ipv4/tcp_input.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 113dc5f..53974c7 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3291,7 +3291,7 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
tcp_init_cwnd_reduction(sk, true);
tcp_set_ca_state(sk, TCP_CA_CWR);
tcp_end_cwnd_reduction(sk);
- tcp_set_ca_state(sk, TCP_CA_Open);
+ tcp_try_keep_open(sk);
NET_INC_STATS_BH(sock_net(sk),
LINUX_MIB_TCPLOSSPROBERECOVERY);
}
--
1.8.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net] tcp: fix incorrect ca_state in tail loss probe
2013-10-12 17:16 [PATCH net] tcp: fix incorrect ca_state in tail loss probe Yuchung Cheng
@ 2013-10-14 5:55 ` Neal Cardwell
2013-10-18 17:29 ` Nandita Dukkipati
0 siblings, 1 reply; 3+ messages in thread
From: Neal Cardwell @ 2013-10-14 5:55 UTC (permalink / raw)
To: Yuchung Cheng
Cc: David Miller, Nandita Dukkipati, Netdev, michael, jwboyer,
Steinar H. Gunderson, dormando
On Sat, Oct 12, 2013 at 1:16 PM, Yuchung Cheng <ycheng@google.com> wrote:
> On receiving an ACK that covers the loss probe sequence, TLP
> immediately sets the congestion state to Open, even though some packets
> are not recovered and retransmisssion are on the way. The later ACks
> may trigger a WARN_ON check in step D of tcp_fastretrans_alert(), e.g.,
> https://bugzilla.redhat.com/show_bug.cgi?id=989251
>
> The fix is to follow the similar procedure in recovery by calling
> tcp_try_keep_open(). The sender switches to Open state if no packets
> are retransmissted. Otherwise it goes to Disorder and let subsequent
> ACKs move the state to Recovery or Open.
>
> Reported-By: Michael Sterrett <michael@sterretts.net>
> Tested-By: Dormando <dormando@rydia.net>
> Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Nice catch!
neal
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net] tcp: fix incorrect ca_state in tail loss probe
2013-10-14 5:55 ` Neal Cardwell
@ 2013-10-18 17:29 ` Nandita Dukkipati
0 siblings, 0 replies; 3+ messages in thread
From: Nandita Dukkipati @ 2013-10-18 17:29 UTC (permalink / raw)
To: Neal Cardwell
Cc: Yuchung Cheng, David Miller, Netdev, michael, jwboyer,
Steinar H. Gunderson, dormando
On Sun, Oct 13, 2013 at 10:55 PM, Neal Cardwell <ncardwell@google.com> wrote:
>
> On Sat, Oct 12, 2013 at 1:16 PM, Yuchung Cheng <ycheng@google.com> wrote:
> > On receiving an ACK that covers the loss probe sequence, TLP
> > immediately sets the congestion state to Open, even though some packets
> > are not recovered and retransmisssion are on the way. The later ACks
> > may trigger a WARN_ON check in step D of tcp_fastretrans_alert(), e.g.,
> > https://bugzilla.redhat.com/show_bug.cgi?id=989251
> >
> > The fix is to follow the similar procedure in recovery by calling
> > tcp_try_keep_open(). The sender switches to Open state if no packets
> > are retransmissted. Otherwise it goes to Disorder and let subsequent
> > ACKs move the state to Recovery or Open.
> >
> > Reported-By: Michael Sterrett <michael@sterretts.net>
> > Tested-By: Dormando <dormando@rydia.net>
> > Signed-off-by: Yuchung Cheng <ycheng@google.com>
>
> Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Nandita Dukkipati <nanditad@google.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-10-12 17:16 [PATCH net] tcp: fix incorrect ca_state in tail loss probe Yuchung Cheng
2013-10-14 5:55 ` Neal Cardwell
2013-10-18 17:29 ` Nandita Dukkipati
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