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 895C2156F4E for ; Tue, 9 Apr 2024 23:31:18 +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=1712705478; cv=none; b=ZYCBDO3B4Usn4aDpl+IHSAc4R73govzDToRPaL1wfc3L/iiKafKdKLBC81EQ0KdEhDuHMnjQWh3Ex2XCItRzaZsB5PPhUhu2QqEIyVFbiAdDiwHBttY1xZ6uJpRcISoJ1kGHK/eMIPOuipcF8nEg3y9kzCN9XrWpN2tEf0KqXOA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712705478; c=relaxed/simple; bh=o9L+f1xpCo7HGa4iQmVysPIL8tMgYLomWfPYYRBuA8U=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=GK1rkkWyapevChQAI49AoEwylhxXEVzYX9WFr3u2c67B3wqcY798XJEO5JxyoDOFG2/WUOWDvZKtUdKFU0Owc854EePJvSzt+NUgaY7HbNJbaOA7Uzj+H7H99LCiEsdrpPMJtKzXCIyLTwQwdNzkfy812j9v0Bv2FH12leYGKoY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ydmw07Ah; 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="Ydmw07Ah" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D912C433F1; Tue, 9 Apr 2024 23:31:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1712705478; bh=o9L+f1xpCo7HGa4iQmVysPIL8tMgYLomWfPYYRBuA8U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Ydmw07AhUlG5llXuvw1f33eWxvjqCYR7OtRP5kuVbsCz4tG4re4ePHStNPppamPEv atSviUUF1ksYt9vsRxwmbKxO+hXztoPT2RCbtQn97Ue56kduf0Khb2tMqAT+tG03dv X+4bDao1swNeAkui0FkAWzQ4YoVxiM1DKTekDVTPmfHp6LxtYtsnHmHi2jylq9ZIrz 8dLe/vmW9rrTlqcdKWM1owBPstRf4vhvbwDXVPjvjrd5ZfTZ7izIzmqfBV227ncGwR TtdPKgT4ijaiXTBQ1mBKdFa5yg1bIIbJWDJxp9h/NvgXTZN6VCOOj8Ezv0rXbwKMw6 UoIQ9USrJDihA== Date: Tue, 9 Apr 2024 16:31:16 -0700 From: Jakub Kicinski To: Yuri Benditovich Cc: Willem de Bruijn , "David S. Miller" , Eric Dumazet , Paolo Abeni , Shuah Khan , Jason Wang , yan@daynix.com, andrew@daynix.com, "netdev@vger.kernel.org" Subject: Re: [PATCH net] net: change maximum number of UDP segments to 128 Message-ID: <20240409163116.0b1525c5@kernel.org> In-Reply-To: <20240406185029.93335-1-yuri.benditovich@daynix.com> References: <20240406185029.93335-1-yuri.benditovich@daynix.com> 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 CC: netdev@ On Sat, 6 Apr 2024 21:50:29 +0300 Yuri Benditovich wrote: > Fixes: fc8b2a619469378 ("net: more strict VIRTIO_NET_HDR_GSO_UDP_L4 validation") > Fixes: line goes right above your sign-off, no empty lines in between them. > The mentioned above commit adds check of potential number > of UDP segments vs UDP_MAX_SEGMENTS in linux/virtio_net.h. > After this change certification test of USO guest-to-guest > transmit on Windows driver for virtio-net device fails, > for example with packet size of ~64K and mss of 536 bytes. > In general the USO should not be more restrictive than TSO. > Indeed, in case of unreasonably small mss a lot of segments > can cause queue overflow and packet loss on the destination. > Limit of 128 segments is good for any practical purpose, > with minimal meaningful mss of 536 the maximal UDP packet will > be divided to ~120 segments. > > Signed-off-by: Yuri Benditovich