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 848161E87B; Mon, 23 Jun 2025 22:05:45 +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=1750716345; cv=none; b=XuHZZZTKsUdJbmOE+jpfYkUgzBAwbIK4ULXJq4lCiIm4QzwZOwgdYpGA46pHvrXedLZ7HNzp2yW6l8wgedZh9g5R8A8Am08rGF3ggFp/TxlDg8RtXiACdQdpiY4ayD1AZKu1ajXm46w04vwg9E7c6klkStiImSGx6T14f9vRkfc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750716345; c=relaxed/simple; bh=pYAkAbY2p6AsIoSksAXZ/HZHu2sbbd7pqzXfsFFNoWg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BFxQSTENKmmKGfryV+bwGt9Gjq9pCKb4Vz6VugqYoBrI3d6uaOJMBmMzQ5o7j2BAag51ATBM0Hc/Y0m3juKkEovGrG0w68VskYza0OYbF5uNe7UM8cjOpUTp/XXKd6eutc1Q7GZOcmw0to9YAX49tk+crVku1d+SHtdHvPF4NHk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=udOQyuRP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="udOQyuRP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DF0BC4CEEA; Mon, 23 Jun 2025 22:05:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750716345; bh=pYAkAbY2p6AsIoSksAXZ/HZHu2sbbd7pqzXfsFFNoWg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=udOQyuRP1aSCaWjLORM/v/KA2qPj5xwi5Q3pD8yh0SC8aJ2Cm3DreOVvuQY9t7vG7 C4BuEX/t1PuywQMWgJ/Q39wbhhelsbp+97fOearLVEmhSoHNZJRXqYGau3cHFe48i/ i5g2irgfyECkof0+VyREb6oRLpXmvxpGAMN+ztXg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 314/411] tcp: always seek for minimal rtt in tcp_rcv_rtt_update() Date: Mon, 23 Jun 2025 15:07:38 +0200 Message-ID: <20250623130641.544852370@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130632.993849527@linuxfoundation.org> References: <20250623130632.993849527@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit b879dcb1aeeca278eacaac0b1e2425b1c7599f9f ] tcp_rcv_rtt_update() goal is to maintain an estimation of the RTT in tp->rcv_rtt_est.rtt_us, used by tcp_rcv_space_adjust() When TCP TS are enabled, tcp_rcv_rtt_update() is using EWMA to smooth the samples. Change this to immediately latch the incoming value if it is lower than tp->rcv_rtt_est.rtt_us, so that tcp_rcv_space_adjust() does not overshoot tp->rcvq_space.space and sk->sk_rcvbuf. Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20250513193919.1089692-8-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ipv4/tcp_input.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 8859a38b45d5e..000557f5c54bc 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -641,10 +641,12 @@ EXPORT_SYMBOL(tcp_initialize_rcv_mss); */ static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) { - u32 new_sample = tp->rcv_rtt_est.rtt_us; - long m = sample; + u32 new_sample, old_sample = tp->rcv_rtt_est.rtt_us; + long m = sample << 3; - if (new_sample != 0) { + if (old_sample == 0 || m < old_sample) { + new_sample = m; + } else { /* If we sample in larger samples in the non-timestamp * case, we could grossly overestimate the RTT especially * with chatty applications or bulk transfer apps which @@ -655,17 +657,9 @@ static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) * else with timestamps disabled convergence takes too * long. */ - if (!win_dep) { - m -= (new_sample >> 3); - new_sample += m; - } else { - m <<= 3; - if (m < new_sample) - new_sample = m; - } - } else { - /* No previous measure. */ - new_sample = m << 3; + if (win_dep) + return; + new_sample = old_sample - (old_sample >> 3) + sample; } tp->rcv_rtt_est.rtt_us = new_sample; -- 2.39.5