This is a note to let you know that I've just added the patch titled
tcp: Return user_mss for TCP_MAXSEG in CLOSE/LISTEN state if user_mss set
to the 5.4-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-return-user_mss-for-tcp_maxseg-in-close-listen-s.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 023f8be6a04f25f46a0c2a31a1cf593bfa8f9d54
Author: Cambda Zhu <cambda@xxxxxxxxxxxxxxxxx>
Date: Sat May 27 12:03:17 2023 +0800
tcp: Return user_mss for TCP_MAXSEG in CLOSE/LISTEN state if user_mss set
[ Upstream commit 34dfde4ad87b84d21278a7e19d92b5b2c68e6c4d ]
This patch replaces the tp->mss_cache check in getting TCP_MAXSEG
with tp->rx_opt.user_mss check for CLOSE/LISTEN sock. Since
tp->mss_cache is initialized with TCP_MSS_DEFAULT, checking if
it's zero is probably a bug.
With this change, getting TCP_MAXSEG before connecting will return
default MSS normally, and return user_mss if user_mss is set.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Jack Yang <mingliang@xxxxxxxxxxxxxxxxx>
Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/netdev/CANn89i+3kL9pYtkxkwxwNMzvC_w3LNUum_2=3u+UyLBmGmifHA@xxxxxxxxxxxxxx/#t
Signed-off-by: Cambda Zhu <cambda@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/netdev/14D45862-36EA-4076-974C-EA67513C92F6@xxxxxxxxxxxxxxxxx/
Reviewed-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230527040317.68247-1-cambda@xxxxxxxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e427eabc7f278..fdf2ddc4864df 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3451,7 +3451,8 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
switch (optname) {
case TCP_MAXSEG:
val = tp->mss_cache;
- if (!val && ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
+ if (tp->rx_opt.user_mss &&
+ ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
val = tp->rx_opt.user_mss;
if (tp->repair)
val = tp->rx_opt.mss_clamp;
