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tcp: disable TFO blackhole logic by default

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Multiple complaints have been raised from the TFO users on the internet
stating that the TFO blackhole logic is too aggressive and gets falsely
triggered too often.
(e.g. https://blog.apnic.net/2021/07/05/tcp-fast-open-not-so-fast/)
Considering that most middleboxes no longer drop TFO packets, we decide
to disable the blackhole logic by setting
/proc/sys/net/ipv4/tcp_fastopen_blackhole_timeout_set to 0 by default.

Fixes: cf1ef3f071 ("net/tcp_fastopen: Disable active side TFO in certain scenarios")
Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Wang 2021-07-21 10:27:38 -07:00 committed by David S. Miller
parent 02dc2ee7c7
commit 213ad73d06
3 changed files with 10 additions and 3 deletions
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2
Documentation/networking/ip-sysctl.rst
View File

@ -826,7 +826,7 @@ tcp_fastopen_blackhole_timeout_sec - INTEGER
initial value when the blackhole issue goes away.
0 to disable the blackhole detection.
By default, it is set to 1hr.
By default, it is set to 0 (feature is disabled).
tcp_fastopen_key - list of comma separated 32-digit hexadecimal INTEGERs
The list consists of a primary key and an optional backup key. The

9
net/ipv4/tcp_fastopen.c
View File

@ -507,6 +507,9 @@ void tcp_fastopen_active_disable(struct sock *sk)
{
struct net *net = sock_net(sk);
if (!sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout)
return;
/* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */
WRITE_ONCE(net->ipv4.tfo_active_disable_stamp, jiffies);
@ -526,10 +529,14 @@ void tcp_fastopen_active_disable(struct sock *sk)
bool tcp_fastopen_active_should_disable(struct sock *sk)
{
unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
int tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
unsigned long timeout;
int tfo_da_times;
int multiplier;
if (!tfo_bh_timeout)
return false;
tfo_da_times = atomic_read(&sock_net(sk)->ipv4.tfo_active_disable_times);
if (!tfo_da_times)
return false;

2
net/ipv4/tcp_ipv4.c
View File

@ -2965,7 +2965,7 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_comp_sack_nr = 44;
net->ipv4.sysctl_tcp_fastopen = TFO_CLIENT_ENABLE;
spin_lock_init(&net->ipv4.tcp_fastopen_ctx_lock);
net->ipv4.sysctl_tcp_fastopen_blackhole_timeout = 60 * 60;
net->ipv4.sysctl_tcp_fastopen_blackhole_timeout = 0;
atomic_set(&net->ipv4.tfo_active_disable_times, 0);
/* Reno is always built in */