This is a note to let you know that I've just added the patch titled
tcp: Set INET_ECN_xmit configuration in tcp_reinit_congestion_control
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-set-inet_ecn_xmit-configuration-in-tcp_reinit_congestion_control.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Dec 2 12:09:18 PM CET 2020
From: Alexander Duyck <alexanderduyck@xxxxxx>
Date: Thu, 19 Nov 2020 13:23:58 -0800
Subject: tcp: Set INET_ECN_xmit configuration in tcp_reinit_congestion_control
From: Alexander Duyck <alexanderduyck@xxxxxx>
[ Upstream commit 55472017a4219ca965a957584affdb17549ae4a4 ]
When setting congestion control via a BPF program it is seen that the
SYN/ACK for packets within a given flow will not include the ECT0 flag. A
bit of simple printk debugging shows that when this is configured without
BPF we will see the value INET_ECN_xmit value initialized in
tcp_assign_congestion_control however when we configure this via BPF the
socket is in the closed state and as such it isn't configured, and I do not
see it being initialized when we transition the socket into the listen
state. The result of this is that the ECT0 bit is configured based on
whatever the default state is for the socket.
Any easy way to reproduce this is to monitor the following with tcpdump:
tools/testing/selftests/bpf/test_progs -t bpf_tcp_ca
Without this patch the SYN/ACK will follow whatever the default is. If dctcp
all SYN/ACK packets will have the ECT0 bit set, and if it is not then ECT0
will be cleared on all SYN/ACK packets. With this patch applied the SYN/ACK
bit matches the value seen on the other packets in the given stream.
Fixes: 91b5b21c7c16 ("bpf: Add support for changing congestion control")
Signed-off-by: Alexander Duyck <alexanderduyck@xxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp_cong.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -199,6 +199,11 @@ static void tcp_reinit_congestion_contro
icsk->icsk_ca_setsockopt = 1;
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
+ if (ca->flags & TCP_CONG_NEEDS_ECN)
+ INET_ECN_xmit(sk);
+ else
+ INET_ECN_dontxmit(sk);
+
if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
tcp_init_congestion_control(sk);
}
Patches currently in stable-queue which might be from alexanderduyck@xxxxxx are
queue-4.14/tcp-set-inet_ecn_xmit-configuration-in-tcp_reinit_congestion_control.patch
