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 9A7752236E3; Fri, 18 Jul 2025 22:07:27 +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=1752876447; cv=none; b=NpQXX/7X7sVnl+sgvVjIYGaov3+0Q3ngz/IjPuf7Rm9LD9B2k07qQeXr3jsuOeHCrhefxJZy9Xz1mZjzVzP0Fi8Ka9LYq0ZwU7VtY0CU6OzYxIG4rn6VLl5VOtCfytr+LJryU6hmr7xqxpvQuquNhX6WImt/p3KdjzF/G5dx+Xw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752876447; c=relaxed/simple; bh=/SQtUJyCpLjbf+fckE/nrzvl+r8miFRFPNgU2sEtSZs=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=hefZavSF3tKi+9NEJKaT7x7dP8uvZyEC1F8xAJhGJ9NkLDhynIgqzsxBPC4QII+E9XhbxZSYmkwtYuzc1vj4BEOPeRSdYg652sXEMij47iqQ5gxTBeeGu2LW3nMqS4S07kNAqONoi8wrZSI2MlEZj6XRsFZw4o0lbzLeZ9/0198= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Lx8Ys5QY; 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="Lx8Ys5QY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD1F4C4CEF9; Fri, 18 Jul 2025 22:07:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752876447; bh=/SQtUJyCpLjbf+fckE/nrzvl+r8miFRFPNgU2sEtSZs=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Lx8Ys5QYkHmp2rZY76f0bnPRwRGeY37a5q1o0e6PwsQHTu5KPOuaxaXjE0UY/3lR7 oY//6LSBDM4syZDXtf+VLXaBEzx+DhL6u1dObTKKdAjW6JIyEGXoBO5WFFC1vgNhjB TVAgytCnaQbV8QbNHXA49HLSBjmyhj9LHqHCBxRTRAvkTp+n0Ko5zMlpwynOi+/wLn INj+Gdgj+nQlzbYKpqtkJIwQsEQSlHA5qqGrsjjBf36YulB2T3rWCPDasP3wljgapJ l1YvBOaMh0sxLBeMTq+FrzOMB2+z0aHO65h9si+c4xw6Trpt6H0NrNXJyaqKwoP+RA q6PgEYsOkOScA== From: "Matthieu Baerts (NGI0)" Date: Sat, 19 Jul 2025 00:06:57 +0200 Subject: [PATCH net-next v2 2/4] tcp: add tcp_sock_set_maxseg Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250719-net-next-mptcp-tcp_maxseg-v2-2-8c910fbc5307@kernel.org> References: <20250719-net-next-mptcp-tcp_maxseg-v2-0-8c910fbc5307@kernel.org> In-Reply-To: <20250719-net-next-mptcp-tcp_maxseg-v2-0-8c910fbc5307@kernel.org> To: mptcp@lists.linux.dev, Mat Martineau , Geliang Tang , "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, "Matthieu Baerts (NGI0)" , Geliang Tang X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=2363; i=matttbe@kernel.org; h=from:subject:message-id; bh=YqIJfnbK+sopMAVXCbVtu06VBqQwQt1h8xVTfpnCAag=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGDKqjk5KbW6/nxu+yvPzlymT9Xn8n4tkCM7vmDnbQevM+ 9xrks89OkpZGMS4GGTFFFmk2yLzZz6v4i3x8rOAmcPKBDKEgYtTACbSKMvI0FudbLa8qsjvcZqP 9pJtjq8fmrSs36v7kafhWKa31oavBxj+10zJKrwY0dHkyz373B5PoQO8U1xcj/FrH4nx6lkbces bOwA= X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 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) --- Notes: - v2: Set the return value of tcp_sock_set_maxseg() to err. --- 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..57e478bfaef20369f5dba1cff540e52c9302ebf4 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..71a956fbfc5533224ee00e792de2cfdccd4d40aa 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; + err = tcp_sock_set_maxseg(sk, val); break; case TCP_NODELAY: -- 2.50.0