From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oa1-f50.google.com (mail-oa1-f50.google.com [209.85.160.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A5273BC676 for ; Wed, 11 Mar 2026 07:56:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773215803; cv=none; b=HrUH+Eti9QcsZiFwhlzVrlHxb8IGNWYOr4+W0EGKrP+iGbV/C/5hP0qcdEaod6rh2aD0tkzLchpBDfafBt8zpgXoIskxBWIVN72PWyh8OF3DYdr4xMwE81p4KzUHyLZj4xpfWha4VTvM0nyVjlWW1/xTHO782A/ZSQUnFkv4bko= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773215803; c=relaxed/simple; bh=9YrqMac2RvVbcQMvhIkvAs6CdxSyWCSfXy/rvRlKfmE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=U+MWM4Ln1rWq89dSnMrqbyLVDGowXM+0Gwf6XjdNEQAy2XriKC7moqFLcUz7o4JYJmvcZd0flq9HsWW/DT+wl33HQg1n91d2+gbTsK9p69SSQ6nD1i0eZyMk1HYMgfjygYqpW+6S0mVYTpQE2MzVTcRLZ4OyttWfU6RHPQYlKao= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=bf4OdtH7; arc=none smtp.client-ip=209.85.160.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bf4OdtH7" Received: by mail-oa1-f50.google.com with SMTP id 586e51a60fabf-409de4132b5so5818904fac.1 for ; Wed, 11 Mar 2026 00:56:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1773215797; x=1773820597; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=DQ1OrwVz8Z3OJFcYGZCm4ACsYMr8Af3yv6w/TQO392I=; b=bf4OdtH7dYvZH0Pm5BCE0v6Kyxgrqcm9ifR02nbDzdUgjo4ncoo7rOA6dUpoXbNOjl Cf18YTTMviUOYlpP6pO4GkC9utn3BDvSRM18341vKYC+if5y93YQ89ulI/GZlVhEIB6I 3RamUOhKpNPdZSdRSvU2vlG8WmcwO1I7w5cF6qDNtfbNMdWux7C4uOrzuWX9CE0Ms6oz EsIgclWrrW399y8mn/r12uYJRC4B+2LkZRW3YmZs+B6OvsmEDFFOHblSC1kG0ETkG/AU BzCvlhugDNX1fI/4IROI5CgS3sv3hosqE80Lk9ZkPMPB/Uo1ROn16Qfz4CiMFrDCA2k+ BAOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773215797; x=1773820597; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=DQ1OrwVz8Z3OJFcYGZCm4ACsYMr8Af3yv6w/TQO392I=; b=a8R8wXsiDy8nRH6PB6V3rl728kN+09dcpgc9vAg6yhunewoZQxMhvYoILvwS1msKYu oaMULTIgcVqGQ/rhpbhYp9ZmnW+hBkUXQKdji7pGtnhSTFaWpwc8jgcljWsagWRel89T B5FxYQ6N+xXmZ4ykanBQVidoj45cCuloocsD0rIMErUZpzKGs/Tyo5YEQeneI9s7CF7A Ao3glkY9eUT1yue+gx5mvTkxmDCr+E2voEWikddQcfLF6OiKRAdy3PX1yreEaObGBCBS X90Ce9os+mxDJb/0kxq5RFHYcpZxZt8bHfq6Ewuaf8k4Oi380kFiXm42YpZI5nR13Uu6 uQdA== X-Forwarded-Encrypted: i=1; AJvYcCUoSf2lbzZfmUPnD9NcL3ci5ytzC+Cb2T/1pvd5x/YJwC9i1vzrvTs+l5UNjZIIX/uwtJfXa/Y=@vger.kernel.org X-Gm-Message-State: AOJu0YzT/8Elr81NaYbaljmWwYzzSm/XOpiDPyFu3d8M+DraLA3LUAP6 S62IcCNgnyJYJxKuxE/d4Gw0CFi7JZyrqvX2Dlq3P4A+MnaShyhibccXFKERDGHu X-Gm-Gg: ATEYQzwmeK7aUPqyD8jn938oS1gEF+I52YTU2tv6hqnosT+/kXu/WlPO2IH/sJPHKFh BM5UnMYjTywl5hHFBM0PlnI7PnXCdxRdhqusDlbIhus0mTntfpgwFhkeXPcdd+gboZRQnnqhV52 P61xG6CIV2W650ksX/6EWx2q6iUj5cNEuYVAVxWcXEXeTYgIwmgQBKRCSQU0PFvL7UV1owaPN1L KefwLYEaZyzrk+UynPD4dQhziMqckid3N982BfWcRQZajU54RkFTuZKqg1zrox/KQj3/Yp8c2fY 9E1BrQZ1YvCyolqxiHzGOtypV20rjF1IRV8bJOHlrMguBdRWKIkJAR2lgjNw4l3miasyXQ9Xueh pSpa8c6wD3HxXH7OlWDlsUpdrFqTXHxpMWH1OoEflAk5juooBOcl4w+oqiAXJIIEIRTxK4MV/SU 67Zz8HQBt6F45rM6L1BOFnzO5s0hBV4LGkJZT8oXd94iWX9UrKeh7c10loAKLkvwGtyFOg8y278 nBiXCyoV45rI9vgQOXDMRaWGUeuyo06mwMMDqSbO1yicUXJ X-Received: by 2002:a05:6870:2e04:b0:409:7cfc:7392 with SMTP id 586e51a60fabf-4177c96b888mr1211062fac.42.1773215796875; Wed, 11 Mar 2026 00:56:36 -0700 (PDT) Received: from localhost.localdomain (108-212-132-20.lightspeed.irvnca.sbcglobal.net. [108.212.132.20]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4177e6ae0e3sm1568938fac.16.2026.03.11.00.56.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Mar 2026 00:56:36 -0700 (PDT) From: Wesley Atwell To: davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, ncardwell@google.com, dsahern@kernel.org, matttbe@kernel.org, martineau@kernel.org, netdev@vger.kernel.org, mptcp@lists.linux.dev Cc: kuniyu@google.com, horms@kernel.org, geliang@kernel.org, corbet@lwn.net, skhan@linuxfoundation.org, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, 0x7f454c46@gmail.com, linux-doc@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, atwellwea@gmail.com Subject: [PATCH net 5/7] mptcp: refresh tcp rcv_wnd snapshot when syncing receive windows Date: Wed, 11 Mar 2026 01:55:58 -0600 Message-Id: <20260311075600.948413-6-atwellwea@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260311075600.948413-1-atwellwea@gmail.com> References: <20260311075600.948413-1-atwellwea@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit MPTCP rewrites the TCP shadow receive window on subflows when shared receive-window state changes. Once tp->rcv_wnd carries paired snapshot semantics, those subflow shadow updates have to refresh the snapshot too. Convert the MPTCP window-sync write sites to use the helper and keep the aggregate receive-space arithmetic using the explicit rwnd-availability helper. Signed-off-by: Wesley Atwell --- net/mptcp/options.c | 12 ++++++++---- net/mptcp/protocol.h | 14 +++++++++++--- 2 files changed, 19 insertions(+), 7 deletions(-) diff --git a/net/mptcp/options.c b/net/mptcp/options.c index 43df4293f58b..6e6aa084cbfa 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -1073,9 +1073,12 @@ static void rwin_update(struct mptcp_sock *msk, struct sock *ssk, return; /* Some other subflow grew the mptcp-level rwin since rcv_wup, - * resync. + * resync. Keep the TCP shadow window in its advertised u32 domain + * and refresh the advertise-time scaling snapshot while doing so. */ - tp->rcv_wnd += mptcp_rcv_wnd - subflow->rcv_wnd_sent; + tcp_set_rcv_wnd(tp, min_t(u64, (u64)tp->rcv_wnd + + (mptcp_rcv_wnd - subflow->rcv_wnd_sent), + U32_MAX)); subflow->rcv_wnd_sent = mptcp_rcv_wnd; } @@ -1334,11 +1337,12 @@ static void mptcp_set_rwin(struct tcp_sock *tp, struct tcphdr *th) if (rcv_wnd_new != rcv_wnd_old) { raise_win: /* The msk-level rcv wnd is after the tcp level one, - * sync the latter. + * sync the latter and refresh its advertise-time scaling + * snapshot. */ rcv_wnd_new = rcv_wnd_old; win = rcv_wnd_old - ack_seq; - tp->rcv_wnd = min_t(u64, win, U32_MAX); + tcp_set_rcv_wnd(tp, min_t(u64, win, U32_MAX)); new_win = tp->rcv_wnd; /* Make sure we do not exceed the maximum possible diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 0bd1ee860316..4ea95c9c0c7a 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -408,11 +408,19 @@ static inline int mptcp_space_from_win(const struct sock *sk, int win) return __tcp_space_from_win(mptcp_sk(sk)->scaling_ratio, win); } +/* MPTCP exposes window space from the mptcp-level receive queue, so it tracks + * a separate backlog counter from the subflow backlog embedded in struct sock. + */ +static inline int mptcp_rwnd_avail(const struct sock *sk) +{ + return READ_ONCE(sk->sk_rcvbuf) - + READ_ONCE(mptcp_sk(sk)->backlog_len) - + tcp_rmem_used(sk); +} + static inline int __mptcp_space(const struct sock *sk) { - return mptcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) - - READ_ONCE(mptcp_sk(sk)->backlog_len) - - sk_rmem_alloc_get(sk)); + return mptcp_win_from_space(sk, mptcp_rwnd_avail(sk)); } static inline struct mptcp_data_frag *mptcp_send_head(const struct sock *sk) -- 2.34.1