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 119FC211719 for ; Wed, 22 Jan 2025 11:13:30 +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=1737544411; cv=none; b=CzLRXGEywwAPQ/oesn0fe7oG8jgYUl3PXjskX7c5P+54n8t0MYD41Fr+kl5AfhphgpMG0EjlJqkCBvhxzVdJSxUqjVYN4w+p8b1lq+qQzQlSvunrV90b+nB/Muty0wTRzDJlPiJKSSvGVaLGZBDTajhTUF8f+prXF5UnNfftJF8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737544411; c=relaxed/simple; bh=5xSq2J9thkYhOloVPtapma3uWO0iRDgJjeFp695AZN0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tm42wlDeoxO/vG5Ki8iIrhg3oQ7APWtzINWJodlQFvR27Hq8M518H11E8ogaR1gik4x7lV39XupuxCfm9gNNBqnMwJUuYzAz7zGK9WWFtESzn4+oq1+nrR9d45ZzVp/Krtt6eI7R+RQLIckSxFEn6k3sBS1XBzC3fb8mC//IV8E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q8te+jBV; 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="Q8te+jBV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7D446C4CED6; Wed, 22 Jan 2025 11:13:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737544410; bh=5xSq2J9thkYhOloVPtapma3uWO0iRDgJjeFp695AZN0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Q8te+jBVWcJn0Fof0ij6iqXdv1eXYgTGUcFC8LRez+eArkgadhqW/0qASiomur4I3 7jJN5aYQ+zpNh1+hx2UU8BiOCudJjAJAbXKFHR/cbnRn50el8TvPOsPaEU5hJOSkX6 K6Trj1Oe8+xc2Q5PEJEJC48zDPu5T3aXkV2CFxN9S+uvVpzXhkKZpPPaOLIxxpTqua 3rTqevun8WfU0KvXBMLDLmheG9wvg5VeJcAJLlw7eg0sUA9p4j+LoHYgXe3jg1DyFg j+4A6lz8/7kgBYdvU1zDo8lZueRPNIPJkQQ09KxqGpFF8NWljsHjQilPw8oJwgWQaE uTn6ZC3Z6FYTQ== Message-ID: <9b376aa3-a7b1-4791-9013-ac250d9f1393@kernel.org> Date: Wed, 22 Jan 2025 12:13:26 +0100 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: FAILED: patch "[PATCH] mptcp: be sure to send ack when mptcp-level window re-opens" failed to apply to 5.15-stable tree Content-Language: en-GB To: gregkh@linuxfoundation.org, pabeni@redhat.com, kuba@kernel.org Cc: stable@vger.kernel.org References: <2025012037-siesta-sulfite-8b05@gregkh> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Greg, On 20/01/2025 14:38, gregkh@linuxfoundation.org wrote: > > The patch below does not apply to the 5.15-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to . Thank you for the notification! > ------------------ original commit in Linus's tree ------------------ > > From 2ca06a2f65310aeef30bb69b7405437a14766e4d Mon Sep 17 00:00:00 2001 > From: Paolo Abeni > Date: Mon, 13 Jan 2025 16:44:56 +0100 > Subject: [PATCH] mptcp: be sure to send ack when mptcp-level window re-opens > > mptcp_cleanup_rbuf() is responsible to send acks when the user-space > reads enough data to update the receive windows significantly. > > It tries hard to avoid acquiring the subflow sockets locks by checking > conditions similar to the ones implemented at the TCP level. > > To avoid too much code duplication - the MPTCP protocol can't reuse the > TCP helpers as part of the relevant status is maintained into the msk > socket - and multiple costly window size computation, mptcp_cleanup_rbuf > uses a rough estimate for the most recently advertised window size: > the MPTCP receive free space, as recorded as at last-ack time. > > Unfortunately the above does not allow mptcp_cleanup_rbuf() to detect > a zero to non-zero win change in some corner cases, skipping the > tcp_cleanup_rbuf call and leaving the peer stuck. > > After commit ea66758c1795 ("tcp: allow MPTCP to update the announced > window"), MPTCP has actually cheap access to the announced window value. > Use it in mptcp_cleanup_rbuf() for a more accurate ack generation. FYI, we are currently not planning to backport this patch: it depends on commits ea66758c1795 ("tcp: allow MPTCP to update the announced window") -- mentioned above -- and f3589be0c420 ("mptcp: never shrink offered window") which are not in this v5.15 version, and linked to new features. The issue fixed by the patch here has not been seen on a v5.15 kernel so far, and probably only visible with other changes that have been done later on. In other words, it looks OK not to backport this patch. Cheers, Matt -- Sponsored by the NGI0 Core fund.