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 3063C26E146 for ; Tue, 11 Nov 2025 15:47:14 +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=1762876035; cv=none; b=oTwLY4AEwKHlEoEVPe24bBlkrTssdZsSVY690l1pMt0KEYYfUTiVy2bzL3vtEQs2wk1ezl4h/prsubyCGYIXA87x/UAxWZPLxl41x/2WgYbS3JTUpkoX1DcH5mlawJ8JfXU/BFE9vFa4WK7QHvZY3TNo6iJUZQfREZBew/jvRIY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762876035; c=relaxed/simple; bh=/8ePIaJg5isv8TlpN/VGfKw5Rm9eFEcKXACBIH3vp48=; h=Message-ID:Date:MIME-Version:Subject:From:To:References: In-Reply-To:Content-Type; b=JRYRUtXkF2S57nAzNIh6oPRjZ58nyt1FYT5xmgtPVCw1MmnMsmFndrpy/X2Ebd4lnxKsYvJI4U3VQRxrCzuth3yPT027YEQ7HfH++yzo9aa9IADoxrGhczEYikbJlcdIPTwyB0TJh5MKcH7LLdZ2KUfAPZnI3PbzyXG4UZVwXTE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FxyUUQnz; 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="FxyUUQnz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3DACBC4CEF7; Tue, 11 Nov 2025 15:47:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762876034; bh=/8ePIaJg5isv8TlpN/VGfKw5Rm9eFEcKXACBIH3vp48=; h=Date:Subject:From:To:References:In-Reply-To:From; b=FxyUUQnzbj5XCtN2VXFCcjDXrWGyBRSHERRDYNXZ25V7niF8pgtI29fBe01sKq+Hg k8dMSVCqD/XKvn/NdljH3ENKQLJbPZqYu0U9SM9bToyDdOlgAxwAhsTD3fVrYUshS9 x5ADkoPTCVJZo44ZiNe7WnIeq7RV6dzduHWkQ8CQHuLDaAWBmwn3ljP3uPp2i/YBsM 6xmbUTsDExs6c0aP0XROtmdK01f+85xBq8/oumnvJl5gIAIDrWhIm7FzpfYivAkCGo 1pC7OaL9bh4r/Fdc2dLZen5iJhacEMUr01fpo7FtZWnhJBjFPFskgItOeHcIcC0s2U +EGYTyfjK0uCg== Message-ID: Date: Tue, 11 Nov 2025 16:47:12 +0100 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-net] mptcp: fix ack generation for fallback msk Content-Language: en-GB, fr-BE From: Matthieu Baerts To: Paolo Abeni , mptcp@lists.linux.dev References: <14a868192851deb4145a90e3b7eec616544da262.1762474159.git.pabeni@redhat.com> Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Paolo, On 11/11/2025 16:30, Matthieu Baerts wrote: > Hi Paolo, > > On 07/11/2025 01:10, Paolo Abeni wrote: >> mptcp_cleanup_rbuf() need to know the last most recent, mptcp-level >> rcv_wnd sent, and such information is tracked into the msk->old_wspace >> field, updated at ack transmission time by mptcp_write_options(). >> >> Fallback socket do not add any mptcp options, such helper is never >> invoked, and msk->old_wspace value remain stale. That in turn makes >> ack generation at recvmsg() time quite randomic. >> >> Address the issue ensuring mptcp_write_options() is invoked even >> for fallback sockets, and just update the needed info in such a >> case. >> >> The issue went unnoticed for a long time, as mptcp overshot the> fallback socket receive buffer autotune significantly. > > Should we say "used to overshot"? :) > >> Fixes: e3859603ba13 ("mptcp: better msk receive window updates") >> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/594 > > Thank you for the fix! > > (...) > >> @@ -1643,6 +1660,9 @@ void mptcp_write_options(struct tcphdr *th, __be32 *ptr, struct tcp_sock *tp, >> opts->reset_transient, >> opts->reset_reason); >> return; >> + } else if (unlikely(!opts->suboptions)) { > > Small detail: do you mind if I add /* Fallback to TCP */ just above when > applying the patch? > >> + mptcp_track_rwin(tp); > > Should we eventually also call mptcp_track_rwin(tp) in case of MP_FAIL > without MP_RST? Or is this not needed? > > Other than that, it looks good to me, and I guess we can already apply > the patch: That's what I just did: I guess the modification for MP_FAIL, if really needed, can still be added later on. New patches for t/upstream-net and t/upstream: - c3a571ff59cc: mptcp: fix ack generation for fallback msk - Results: 751a2432b7d8..5b6b4e3aef4f (export-net) - Results: 247540d77d20..a96affe5f0a1 (export) Tests are now in progress: - export-net: https://github.com/multipath-tcp/mptcp_net-next/commit/7fade8917eeabe227b5ffae540e9cbe48d3e5046/checks - export: https://github.com/multipath-tcp/mptcp_net-next/commit/b10c1d3d1e5da09bbc2b81eca8f4339b84499268/checks Cheers, Matt -- Sponsored by the NGI0 Core fund.