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 2D7192F4A0B; Wed, 16 Jul 2025 10:28:27 +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=1752661708; cv=none; b=RpqqW1Jaf0EFmTNrLxs187UBOVA38mLaKSESaBsXOKL7tnqCp65LQ/5htO/qWggdwq0zooQQLX3nsU1tv9M9nkxJ36Sh6CuwkJqNNil9pKij1ExGY7to+opgg+dfWfESQKk/XOICgKbAUMHIO27TQa8QH6jxJY1tpHDPVeX2BmM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752661708; c=relaxed/simple; bh=481cka8erGmjKbyjTt7K9jn11qoN9jnG5VVx4IklCeM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=MpTvC7T748hvF+M31NW5IlZ+m8mZP1ngTIpVFxmcihfa+yi6xOYXq4eSc4dfocjB2Qy12kSQxhLvrAXr30UIgC6TTZ2of09PfeVF253oYAs3L1WEGlgdz8OvFSKSiLyPPvVn5XFZeyG59OQZL4X7tw+zkRYWli3G6GrcXMPi7uk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BtCCEsGT; 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="BtCCEsGT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45A6AC4CEF0; Wed, 16 Jul 2025 10:28:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1752661707; bh=481cka8erGmjKbyjTt7K9jn11qoN9jnG5VVx4IklCeM=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=BtCCEsGTgsQwGuMt35pKV0JZkMensIQODAfEWoU6GiwPYYVZWiu8InG57PLetPinG Ehl4vZ9xfQGXWHG2dG7OQ2q9VfxuT5X6QkL3DnAi7HGLsT6hjRcv0hUFP/8XLq5apT WolbfftPuYhEqndSfxeS+ERvz5YbNIuRxloEuAnu/DG8uP7JPijApc7fzaqr7RNPNw kqFkWeSz4OlXlAfuX02R5LOl54cmwJQW6mPK6pjTlSxSIf8T+mSKBhLDTALDTw09Op EmFC/EwXKTwR8eA5Xd+DqAl7FNBTg4WZve8RqbDlcczIOB0Muw4VeTBy6ShKEd7L9b 3bAkY8Yv0YWAw== From: "Matthieu Baerts (NGI0)" Date: Wed, 16 Jul 2025 12:28:05 +0200 Subject: [PATCH net-next 3/4] mptcp: add TCP_MAXSEG sockopt support 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: <20250716-net-next-mptcp-tcp_maxseg-v1-3-548d3a5666f6@kernel.org> References: <20250716-net-next-mptcp-tcp_maxseg-v1-0-548d3a5666f6@kernel.org> In-Reply-To: <20250716-net-next-mptcp-tcp_maxseg-v1-0-548d3a5666f6@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=3597; i=matttbe@kernel.org; h=from:subject:message-id; bh=qOHsJBqU1N3UcL7j8IzEZR4JZWaMj7+gDpL8lzuOm88=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGDLK6/Zn7Yk+O3vm5zQu1+LG3pWHrifsYn4wQ3+rZsS9n csMNnkndpSyMIhxMciKKbJIt0Xmz3xexVvi5WcBM4eVCWQIAxenAEyk9yAjw47j5nsi/Mp0vtV1 OJ851LEp8NJmo2ksnbvFWm8XStmaOzH8FROT0N6XNv+jT/P8B3su9fp8Csw78yr9YNXGsPQ5TwK 1uAA= X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 From: Geliang Tang The TCP_MAXSEG socket option is currently not supported by MPTCP, mainly because it has never been requested before. But there are still valid use-cases, e.g. with HAProxy. This patch adds its support in MPTCP by propagating the value to all subflows. The get part looks at the value on the first subflow, to be as closed as possible to TCP. Only one value can be returned for the cached MSS, so this can come only from one subflow. Similar to mptcp_setsockopt_first_sf_only(), a generic helper mptcp_setsockopt_all_subflows() is added to set sockopt for each subflows of the mptcp socket. Add a new member for struct mptcp_sock to store the TCP_MAXSEG value, and return this value in getsockopt. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/515 Signed-off-by: Geliang Tang Reviewed-by: Matthieu Baerts (NGI0) Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/protocol.h | 1 + net/mptcp/sockopt.c | 26 ++++++++++++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 3dd11dd3ba16e8c1d3741b6eb5b526bb4beae15b..9c43a1f037e71243e202f907608ad42086dbde4b 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -326,6 +326,7 @@ struct mptcp_sock { int keepalive_cnt; int keepalive_idle; int keepalive_intvl; + int maxseg; struct work_struct work; struct sk_buff *ooo_last_skb; struct rb_root out_of_order_queue; diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index afa54fba51e215bc2efb21f16ed7d0a0fb120972..379a02a46b7bf706480cf66a88c6cf2357d2a62b 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -798,6 +798,23 @@ static int mptcp_setsockopt_first_sf_only(struct mptcp_sock *msk, int level, int return ret; } +static int mptcp_setsockopt_all_sf(struct mptcp_sock *msk, int level, + int optname, sockptr_t optval, + unsigned int optlen) +{ + struct mptcp_subflow_context *subflow; + + mptcp_for_each_subflow(msk, subflow) { + struct sock *ssk = mptcp_subflow_tcp_sock(subflow); + int ret = 0; + + ret = tcp_setsockopt(ssk, level, optname, optval, optlen); + if (ret) + return ret; + } + return 0; +} + static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname, sockptr_t optval, unsigned int optlen) { @@ -859,6 +876,11 @@ static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname, &msk->keepalive_cnt, val); break; + case TCP_MAXSEG: + msk->maxseg = val; + ret = mptcp_setsockopt_all_sf(msk, SOL_TCP, optname, optval, + optlen); + break; default: ret = -ENOPROTOOPT; } @@ -1406,6 +1428,9 @@ static int mptcp_getsockopt_sol_tcp(struct mptcp_sock *msk, int optname, return mptcp_put_int_option(msk, optval, optlen, msk->notsent_lowat); case TCP_IS_MPTCP: return mptcp_put_int_option(msk, optval, optlen, 1); + case TCP_MAXSEG: + return mptcp_getsockopt_first_sf_only(msk, SOL_TCP, optname, + optval, optlen); } return -EOPNOTSUPP; } @@ -1552,6 +1577,7 @@ static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk) tcp_sock_set_keepidle_locked(ssk, msk->keepalive_idle); tcp_sock_set_keepintvl(ssk, msk->keepalive_intvl); tcp_sock_set_keepcnt(ssk, msk->keepalive_cnt); + tcp_sock_set_maxseg(ssk, msk->maxseg); inet_assign_bit(TRANSPARENT, ssk, inet_test_bit(TRANSPARENT, sk)); inet_assign_bit(FREEBIND, ssk, inet_test_bit(FREEBIND, sk)); -- 2.48.1