From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 29644426EC5; Wed, 10 Jun 2026 15:22:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781104955; cv=none; b=tiE4H94YPsoJUsY2yvyM4oGX5N3FCynPTIK792en7VBfiPvexPlwEQXjTOvAXlGVX93SrWBWn5n+5+7Kdsmwiktplqdh3ACAi0hjKBT47ptfjuxYnyFzAL80WRog74LD848HA1arVeIW4hCH8Yl1vtDvuXqLNKZcQG0vkN8Ny5g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781104955; c=relaxed/simple; bh=+JK8R/7VtnPPWu0kAeq9/YQZvg1IJIk8ICcVdv06DO4=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=k8+91zV6QVYuV4u1Xhigo1bwwh6ex9fZuDU5AtmhuAykB+PvtjcBiDrI10EmhE4XCxOSjtHXjLTk+yZ2rRxWMLSgjfP3M9IM4RxcTqDqfrLDQgqeDjDwX0r9eI24juJVSIFPKbilD3gHOjg6jVCJE2dbUqTqigiE5L+ee5pavfo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HS6PxtTg; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HS6PxtTg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55DB21F00893; Wed, 10 Jun 2026 15:22:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781104953; bh=1z+b6EFtad9PbYUN1KmvNW1k3GO6SZb8m9ge86o3v+4=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=HS6PxtTgczGOj0boeuGs2k4xaiBszzZcoRNwdf9EDDPB/Ey5xslpVTfEUcFCNCpZo pI1+arO84XD96jJQXZAmuUc8OC2IibcKcxkYy3biGS/8YFehKd0gWlNpwo2IhRJ0Ez 50BlnUgkQbqfXnYuO+Vatgi7H+/CP+ZIE4GPuzJH91m+AvCKQEeAtIE/SZ6DPKgrwk HPo+UDK3Rhs2oRUO3D4ujt05fjM9zBSfS2U/3gW4X3AzKlgfDAcBBNp9/FiYzQaua7 17laYPwKaq+NfPyjJLK/dE9PD4AdFgm1mUOccEWYemf0NbuHOK+oSP9Q2pIaNLpk9z myIuhPcmCvj6w== Date: Wed, 10 Jun 2026 08:22:32 -0700 From: Jakub Kicinski To: Matthieu Baerts Cc: Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2 06/15] mptcp: pm: drop TCP TS with ADD_ADDRv6 + port Message-ID: <20260610082232.50d2a31b@kernel.org> In-Reply-To: <17ecf803-4ee9-4dbc-ae9f-34da6460b163@kernel.org> References: <20260605-net-next-mptcp-add-addr6-port-ts-v2-0-758e7ca73f4d@kernel.org> <20260605-net-next-mptcp-add-addr6-port-ts-v2-6-758e7ca73f4d@kernel.org> <17ecf803-4ee9-4dbc-ae9f-34da6460b163@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 10 Jun 2026 17:13:54 +0200 Matthieu Baerts wrote: > Hello, > > On 05/06/2026 19:21, Matthieu Baerts (NGI0) wrote: > > With TCP-timestamps (padded) taking 12 bytes and ADD_ADDR IPv6 + port > > taking 30 bytes, the 40-byte limit for the TCP options is reached. In > > this case, it is then not possible to send the signal. > > > > To be able to send this ADD_ADDR, the TCP timestamps option can now be > > dropped. This is done, when needed by setting the *drop_ts parameter > > from mptcp_established_options. This feature is controlled by a new > > net.mptcp.add_addr_v6_port_drop_ts sysctl knob, enabled by default. > > > > It is important to keep in mind that dropping the TCP timestamps option > > for one packet of the connection could eventually disrupt some > > middleboxes: even if it should be unlikely, they could drop the packet > > or even block the connection. That's why this new feature can be > > controlled by a sysctl knob. > FYI, Sashiko's new comments about this patch [1] are suggesting issues > when MPTCP is used in parallel with TCP MD5. But MPTCP cannot be used > with MD5 because there is not enough space in the TCP options. That's > why there is an explicit rejection when initiating the connection. > > So I think we can ignore these comments saying that more options could > be dropped, and the size can be negative. > > https://sashiko.dev/#/patchset/20260605-net-next-mptcp-add-addr6-port-ts-v2-0-758e7ca73f4d%40kernel.org?part=6 I'll probably pull today, but to explain the delay - Sashiko made me read the code and while I think the reports are false positives - the option handling does not read like awesome code. So the series fell down the priority list.