netdev - Re: [PATCH net v3] tcp: Return user_mss for TCP_MAXSEG in CLOSE/LISTEN state if user

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Message-ID: <CANn89iLHO7Cma9kdjVTkAy8Z3QvdG-8U4=ob=TSofA5nojWV+w@mail.gmail.com>
Date: Sat, 27 May 2023 11:03:43 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Cambda Zhu <cambda@...ux.alibaba.com>
Cc: netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>, 
	Jason Xing <kerneljasonxing@...il.com>, "David S. Miller" <davem@...emloft.net>, 
	David Ahern <dsahern@...nel.org>, Jakub Kicinski <kuba@...nel.org>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Dust Li <dust.li@...ux.alibaba.com>, 
	Tony Lu <tonylu@...ux.alibaba.com>, Jack Yang <mingliang@...ux.alibaba.com>
Subject: Re: [PATCH net v3] tcp: Return user_mss for TCP_MAXSEG in
 CLOSE/LISTEN state if user_mss set

On Sat, May 27, 2023 at 6:04 AM Cambda Zhu <cambda@...ux.alibaba.com> wrote:
>
> 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@...ux.alibaba.com>
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Link: https://lore.kernel.org/netdev/CANn89i+3kL9pYtkxkwxwNMzvC_w3LNUum_2=3u+UyLBmGmifHA@mail.gmail.com/#t
> Signed-off-by: Cambda Zhu <cambda@...ux.alibaba.com>
> Link: https://lore.kernel.org/netdev/14D45862-36EA-4076-974C-EA67513C92F6@linux.alibaba.com/
> Reviewed-by: Jason Xing <kerneljasonxing@...il.com>
> ---

Reviewed-by: Eric Dumazet <edumazet@...gle.com>