From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8B58710A1F; Thu, 17 Jul 2025 01:25:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752715553; cv=none; b=VYwmMbGcSC5BcIkgjGxnNtrE28ASPxuGCB1nKoT7lyV9DoqpHIIpUqyXkQdHmQoWaUdcpd6jVOKn9gi8GrkAwHegpFt4VRpLKplN1Ig/Iydk5DCAj6bgjcKct9Ddm+a6Cn+WSHcRPruyZr8eog4UesTDH/xciNbXDIHXjCcv6EU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752715553; c=relaxed/simple; bh=eJW4DqvpNT9WZHN3RA/qOqnzpM5aERTsDG8vrMculSo=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=uuWU51yhULpNM4dYMtYxA1ThQGlI1EopM6J8+m/Ccj6k9IVgu6H+iEZnpjQftXNU8gJXbQRfYywA075W/r+ARx4DBEoDKB0yBVijDlWBhd0FxeHiHxgKF1cSoSSML2UFAaviCMn1IcKYlmZZs5rQPjA+3cWzwqsSUN6RxX0F11Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RVbIPsGh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RVbIPsGh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37EACC4CEE7; Thu, 17 Jul 2025 01:25:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752715553; bh=eJW4DqvpNT9WZHN3RA/qOqnzpM5aERTsDG8vrMculSo=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=RVbIPsGhNQVhy08SIkFMzDX9E2ZHDYGh89e3uIeEPpmPlh83AIxGQNQRQb5G0KL55 mO0BZ5TQx07gVZg9HSW5YhW+dY2kCj1vT5frvFTbO3HBa/lWPGPdROFdhhK4N9v5kq B9OO0vX52zs9SBBtPN/AhJ0QV3f5HgNAIzrMgOQvDRj6M27mOzzDuznSzB/QdvydyV bRWY9Ko9VYTL2u2Cxv3YiI7OqDqF8gN/YLOJgMmGC/KXSaW63HfskGCC9MSHMeWjkd UJYaH1MqafFkrbArQzhNzQTdrjXRIPlSJxnvk+YJSFO0B2B+Bz71f9InJXcraWJ62i ykhdavSsQtRnw== Message-ID: Subject: Re: [PATCH net-next 2/4] tcp: add tcp_sock_set_maxseg From: Geliang Tang To: "Matthieu Baerts (NGI0)" , mptcp@lists.linux.dev, Mat Martineau , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Neal Cardwell , Kuniyuki Iwashima , David Ahern Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 17 Jul 2025 09:25:45 +0800 In-Reply-To: <20250716-net-next-mptcp-tcp_maxseg-v1-2-548d3a5666f6@kernel.org> References: <20250716-net-next-mptcp-tcp_maxseg-v1-0-548d3a5666f6@kernel.org> <20250716-net-next-mptcp-tcp_maxseg-v1-2-548d3a5666f6@kernel.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.56.0-1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Matt, On Wed, 2025-07-16 at 12:28 +0200, Matthieu Baerts (NGI0) wrote: > From: Geliang Tang > > Add a helper tcp_sock_set_maxseg() to directly set the TCP_MAXSEG > sockopt from kernel space. > > This new helper will be used in the following patch from MPTCP. > > Signed-off-by: Geliang Tang > Acked-by: Matthieu Baerts (NGI0) > Signed-off-by: Matthieu Baerts (NGI0) > --- >  include/linux/tcp.h |  1 + >  net/ipv4/tcp.c      | 23 ++++++++++++++--------- >  2 files changed, 15 insertions(+), 9 deletions(-) > > diff --git a/include/linux/tcp.h b/include/linux/tcp.h > index > 1a5737b3753d06165bc71e257a261bcd7a0085ce..57e478bfaef20369f5dba1cff54 > 0e52c9302ebf4 100644 > --- a/include/linux/tcp.h > +++ b/include/linux/tcp.h > @@ -621,6 +621,7 @@ void tcp_sock_set_nodelay(struct sock *sk); >  void tcp_sock_set_quickack(struct sock *sk, int val); >  int tcp_sock_set_syncnt(struct sock *sk, int val); >  int tcp_sock_set_user_timeout(struct sock *sk, int val); > +int tcp_sock_set_maxseg(struct sock *sk, int val); >   >  static inline bool dst_tcp_usec_ts(const struct dst_entry *dst) >  { > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c > index > 31149a0ac849192b46c67dd569efeeeb0a041a0b..c9cdc4e99c4f11a75471b8895b9 > c52ad8da3a7ff 100644 > --- a/net/ipv4/tcp.c > +++ b/net/ipv4/tcp.c > @@ -3751,6 +3751,19 @@ int tcp_set_window_clamp(struct sock *sk, int > val) >   return 0; >  } >   > +int tcp_sock_set_maxseg(struct sock *sk, int val) > +{ > + /* Values greater than interface MTU won't take effect. > However > + * at the point when this call is done we typically don't > yet > + * know which interface is going to be used > + */ > + if (val && (val < TCP_MIN_MSS || val > MAX_TCP_WINDOW)) > + return -EINVAL; > + > + tcp_sk(sk)->rx_opt.user_mss = val; > + return 0; > +} > + >  /* >   * Socket option code for TCP. >   */ > @@ -3883,15 +3896,7 @@ int do_tcp_setsockopt(struct sock *sk, int > level, int optname, >   >   switch (optname) { >   case TCP_MAXSEG: > - /* Values greater than interface MTU won't take > effect. However > - * at the point when this call is done we typically > don't yet > - * know which interface is going to be used > - */ > - if (val && (val < TCP_MIN_MSS || val > > MAX_TCP_WINDOW)) { > - err = -EINVAL; > - break; > - } > - tp->rx_opt.user_mss = val; > + tcp_sock_set_maxseg(sk, val); Sorry, I forgot to set the return value here, it should be: err = tcp_sock_set_maxseg(sk, val); I'll send a squash-to patch to fix this. Thanks, -Geliang >   break; >   >   case TCP_NODELAY: