From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A4F79C433ED for ; Sun, 11 Apr 2021 22:20:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78EC661074 for ; Sun, 11 Apr 2021 22:20:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235903AbhDKWUa (ORCPT ); Sun, 11 Apr 2021 18:20:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235474AbhDKWU1 (ORCPT ); Sun, 11 Apr 2021 18:20:27 -0400 Received: from mail-oi1-x22d.google.com (mail-oi1-x22d.google.com [IPv6:2607:f8b0:4864:20::22d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0C851C061574 for ; Sun, 11 Apr 2021 15:20:11 -0700 (PDT) Received: by mail-oi1-x22d.google.com with SMTP id i81so11616513oif.6 for ; Sun, 11 Apr 2021 15:20:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:subject:to:cc:references:from:autocrypt:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=22ns3w2Lp6/GzZClkyqcdBBT7zw6HUfbfqljax9H/Yg=; b=BjxRFW8m2K7Yaa4oLc8oJ+/GvUlMA7JHu8kqUiFiileDxWAjMS49/XOoTa7mv7e3OA GdbASZn00ElgD+YXENBc7GhibV0XHQZm15AFuxiSCTc2pSlvJfLB/DN44Y4bTn6tGGVM afcVN41RsZVwzKcj9hofvGIUVrtXOki89uXYFr+CRiojQS0fVG4a/3wSCvFwVFcXy453 7gjkwT7asPrtgsDjNjZxTMOcqzBV2jZmoh/g0oIOc0KbEdUdynay9ckoM4QvpY1SD/9x 05f375hxwrG0uYc9rYe2uxSWrd1a/+T/RUNsvX89vVG2Vk/UUpt7Of1BxTcYCclRAQR1 aSeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=22ns3w2Lp6/GzZClkyqcdBBT7zw6HUfbfqljax9H/Yg=; b=e3qkiUwHHoHl/PfgSzmc+QHeP2AjfnstM0kWUemRscRMhYPaPmHMa89MjxVGp/lbTR 7EAo9sedumRs+lRxe1TejIcFBb3+2SSInTZmvqwymArsYM4BOGCV92rnP0wVDJX80gCS uQ/KK5aSP6LR9IPovbx9gpU2QbWlYcWzy1zbPu2ttIPCG2szjkvIu867p7V40Du2kc23 gxjJ18rkSoyzdhUiceZwHsQPdaj5n7SgNkwJiVtmteV57s2fQ6hQHYH2xvN4UarRZyaO FiWdXOa5rVovngauPZasVjoKJ4Coiq3U7em/i3zFVfhY01R36npvdUqy6bgk2Qm+avhe 0+pQ== X-Gm-Message-State: AOAM533IsxWcnPvv8dVx94C4L/XaK45Vds7H8f4Px3HYZ6rvXn7NM0c5 r4lo2Gjj4zgJO7L2rIaGar0= X-Google-Smtp-Source: ABdhPJz8sfyal/C6reF90xUhf+6LPls6O0TbCQB0Id9MxcT+HYKmLwKmDGMv6W0rLw21dUYow3UCVw== X-Received: by 2002:aca:482:: with SMTP id 124mr7761387oie.130.1618179610455; Sun, 11 Apr 2021 15:20:10 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id w5sm1253992oos.43.2021.04.11.15.20.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 11 Apr 2021 15:20:09 -0700 (PDT) Sender: Guenter Roeck Subject: Re: [PATCH net] virtio_net: Do not pull payload in skb->head To: Eric Dumazet Cc: Eric Dumazet , "David S . Miller" , Jakub Kicinski , netdev , Xuan Zhuo , "Michael S. Tsirkin" , Jason Wang , virtualization@lists.linux-foundation.org References: <20210402132602.3659282-1-eric.dumazet@gmail.com> <20210411134329.GA132317@roeck-us.net> <0f63dc52-ea72-16b6-7dcd-efb24de0c852@roeck-us.net> From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; keydata= xsFNBE6H1WcBEACu6jIcw5kZ5dGeJ7E7B2uweQR/4FGxH10/H1O1+ApmcQ9i87XdZQiB9cpN RYHA7RCEK2dh6dDccykQk3bC90xXMPg+O3R+C/SkwcnUak1UZaeK/SwQbq/t0tkMzYDRxfJ7 nyFiKxUehbNF3r9qlJgPqONwX5vJy4/GvDHdddSCxV41P/ejsZ8PykxyJs98UWhF54tGRWFl 7i1xvaDB9lN5WTLRKSO7wICuLiSz5WZHXMkyF4d+/O5ll7yz/o/JxK5vO/sduYDIlFTvBZDh gzaEtNf5tQjsjG4io8E0Yq0ViobLkS2RTNZT8ICq/Jmvl0SpbHRvYwa2DhNsK0YjHFQBB0FX IdhdUEzNefcNcYvqigJpdICoP2e4yJSyflHFO4dr0OrdnGLe1Zi/8Xo/2+M1dSSEt196rXaC kwu2KgIgmkRBb3cp2vIBBIIowU8W3qC1+w+RdMUrZxKGWJ3juwcgveJlzMpMZNyM1jobSXZ0 VHGMNJ3MwXlrEFPXaYJgibcg6brM6wGfX/LBvc/haWw4yO24lT5eitm4UBdIy9pKkKmHHh7s jfZJkB5fWKVdoCv/omy6UyH6ykLOPFugl+hVL2Prf8xrXuZe1CMS7ID9Lc8FaL1ROIN/W8Vk BIsJMaWOhks//7d92Uf3EArDlDShwR2+D+AMon8NULuLBHiEUQARAQABzTJHdWVudGVyIFJv ZWNrIChMaW51eCBhY2NvdW50KSA8bGludXhAcm9lY2stdXMubmV0PsLBgQQTAQIAKwIbAwYL CQgHAwIGFQgCCQoLBBYCAwECHgECF4ACGQEFAlVcphcFCRmg06EACgkQyx8mb86fmYFg0RAA nzXJzuPkLJaOmSIzPAqqnutACchT/meCOgMEpS5oLf6xn5ySZkl23OxuhpMZTVX+49c9pvBx hpvl5bCWFu5qC1jC2eWRYU+aZZE4sxMaAGeWenQJsiG9lP8wkfCJP3ockNu0ZXXAXwIbY1O1 c+l11zQkZw89zNgWgKobKzrDMBFOYtAh0pAInZ9TSn7oA4Ctejouo5wUugmk8MrDtUVXmEA9 7f9fgKYSwl/H7dfKKsS1bDOpyJlqhEAH94BHJdK/b1tzwJCFAXFhMlmlbYEk8kWjcxQgDWMu GAthQzSuAyhqyZwFcOlMCNbAcTSQawSo3B9yM9mHJne5RrAbVz4TWLnEaX8gA5xK3uCNCeyI sqYuzA4OzcMwnnTASvzsGZoYHTFP3DQwf2nzxD6yBGCfwNGIYfS0i8YN8XcBgEcDFMWpOQhT Pu3HeztMnF3HXrc0t7e5rDW9zCh3k2PA6D2NV4fews9KDFhLlTfCVzf0PS1dRVVWM+4jVl6l HRIAgWp+2/f8dx5vPc4Ycp4IsZN0l1h9uT7qm1KTwz+sSl1zOqKD/BpfGNZfLRRxrXthvvY8 BltcuZ4+PGFTcRkMytUbMDFMF9Cjd2W9dXD35PEtvj8wnEyzIos8bbgtLrGTv/SYhmPpahJA l8hPhYvmAvpOmusUUyB30StsHIU2LLccUPPOwU0ETofVZwEQALlLbQeBDTDbwQYrj0gbx3bq 7kpKABxN2MqeuqGr02DpS9883d/t7ontxasXoEz2GTioevvRmllJlPQERVxM8gQoNg22twF7 pB/zsrIjxkE9heE4wYfN1AyzT+AxgYN6f8hVQ7Nrc9XgZZe+8IkuW/Nf64KzNJXnSH4u6nJM J2+Dt274YoFcXR1nG76Q259mKwzbCukKbd6piL+VsT/qBrLhZe9Ivbjq5WMdkQKnP7gYKCAi pNVJC4enWfivZsYupMd9qn7Uv/oCZDYoBTdMSBUblaLMwlcjnPpOYK5rfHvC4opxl+P/Vzyz 6WC2TLkPtKvYvXmdsI6rnEI4Uucg0Au/Ulg7aqqKhzGPIbVaL+U0Wk82nz6hz+WP2ggTrY1w ZlPlRt8WM9w6WfLf2j+PuGklj37m+KvaOEfLsF1v464dSpy1tQVHhhp8LFTxh/6RWkRIR2uF I4v3Xu/k5D0LhaZHpQ4C+xKsQxpTGuYh2tnRaRL14YMW1dlI3HfeB2gj7Yc8XdHh9vkpPyuT nY/ZsFbnvBtiw7GchKKri2gDhRb2QNNDyBnQn5mRFw7CyuFclAksOdV/sdpQnYlYcRQWOUGY HhQ5eqTRZjm9z+qQe/T0HQpmiPTqQcIaG/edgKVTUjITfA7AJMKLQHgp04Vylb+G6jocnQQX JqvvP09whbqrABEBAAHCwWUEGAECAA8CGwwFAlVcpi8FCRmg08MACgkQyx8mb86fmYHNRQ/+ J0OZsBYP4leJvQF8lx9zif+v4ZY/6C9tTcUv/KNAE5leyrD4IKbnV4PnbrVhjq861it/zRQW cFpWQszZyWRwNPWUUz7ejmm9lAwPbr8xWT4qMSA43VKQ7ZCeTQJ4TC8kjqtcbw41SjkjrcTG wF52zFO4bOWyovVAPncvV9eGA/vtnd3xEZXQiSt91kBSqK28yjxAqK/c3G6i7IX2rg6pzgqh hiH3/1qM2M/LSuqAv0Rwrt/k+pZXE+B4Ud42hwmMr0TfhNxG+X7YKvjKC+SjPjqp0CaztQ0H nsDLSLElVROxCd9m8CAUuHplgmR3seYCOrT4jriMFBtKNPtj2EE4DNV4s7k0Zy+6iRQ8G8ng QjsSqYJx8iAR8JRB7Gm2rQOMv8lSRdjva++GT0VLXtHULdlzg8VjDnFZ3lfz5PWEOeIMk7Rj trjv82EZtrhLuLjHRCaG50OOm0hwPSk1J64R8O3HjSLdertmw7eyAYOo4RuWJguYMg5DRnBk WkRwrSuCn7UG+qVWZeKEsFKFOkynOs3pVbcbq1pxbhk3TRWCGRU5JolI4ohy/7JV1TVbjiDI HP/aVnm6NC8of26P40Pg8EdAhajZnHHjA7FrJXsy3cyIGqvg9os4rNkUWmrCfLLsZDHD8FnU mDW4+i+XlNFUPUYMrIKi9joBhu18ssf5i5Q= Message-ID: <271df9a8-1fdd-b65e-92c3-e66e2d332644@roeck-us.net> Date: Sun, 11 Apr 2021 15:20:07 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 4/11/21 2:43 PM, Eric Dumazet wrote: > On Sun, Apr 11, 2021 at 11:32 PM Guenter Roeck wrote: >> >> On 4/11/21 2:23 PM, Eric Dumazet wrote: >>> On Sun, Apr 11, 2021 at 10:37 PM Guenter Roeck wrote: >>>> >>>> On 4/11/21 8:06 AM, Eric Dumazet wrote: >>>>> On Sun, Apr 11, 2021 at 3:43 PM Guenter Roeck wrote: >>>>> >>>>>> This patch causes a virtio-net interface failure when booting sh4 images >>>>>> in qemu. The test case is nothing special: Just try to get an IP address >>>>>> using udhcpc. If it fails, udhcpc reports: >>>>>> >>>>>> udhcpc: started, v1.33.0 >>>>>> udhcpc: sending discover >>>>>> FAIL >>>>>> >>>>> >>>>> Can you investigate where the incoming packet is dropped ? >>>>> >>>> >>>> Unless I am missing something, packets are not dropped. It looks more >>>> like udhcpc gets bad indigestion in the receive path and exits immediately. >>>> Plus, it doesn't happen all the time; sometimes it receives the discover >>>> response and is able to obtain an IP address. >>>> >>>> Overall this is quite puzzling since udhcpc exits immediately when the problem >>>> is seen, no matter which option I give it on the command line; it should not >>>> really do that. >>> >>> >>> Could you strace both cases and report differences you can spot ? >>> >>> strace -o STRACE -f -s 1000 udhcpc >>> >> >> I'll give it a try. It will take a while; I'll need to add strace to my root >> file systems first. >> >> As a quick hack, I added some debugging into the kernel; it looks like >> the data part of the dhcp discover response may get lost with your patch >> in place. > > Data is not lost, the payload is whole contained in skb frags, which > was expected from my patch. > > Maybe this sh arch does something wrong in this case. > > This could be checksuming... > > Please check > > nstat -n > > nstat > Does that tell you anything ? / # nstat -n / # udhcpc -n -q udhcpc: started, v1.33.0 udhcpc: sending discover / # nstat #kernel IpInReceives 1 0.0 IpInDelivers 1 0.0 UdpIgnoredMulti 1 0.0 IpExtInBcastPkts 1 0.0 IpExtInOctets 576 0.0 IpExtInBcastOctets 576 0.0 IpExtInNoECTPkts 1 0.0 Also, one interesting detail is that the problem is not seen all the time, even with your patch in place. Not sure if I mentioned that before. strace output in the success case (same image, with patch in place) looks as follows. 130 write(2, "udhcpc: sending discover\n", 25) = 25 130 socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)) = 6 130 bind(6, {sa_family=AF_PACKET, sll_protocol=htons(ETH_P_IP), sll_ifindex=if_nametoindex("eth0"), sll_hatype=ARPHRD_NETROM, sll_pkttype=PACKET_HOST, sll_halen=6, sll_addr=[0xff, 0xff, 0xff, 0xf 130 sendto(6, "E\0\1H\0\0\0\0@\21y\246\0\0\0\0\377\377\377\377\0D\0C\0014\227r\1\1\6\0\5\16\36P\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0RT\0\0224V\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0 130 close(6) = 0 130 fcntl64(5, F_SETFD, FD_CLOEXEC) = 0 130 clock_gettime64(CLOCK_MONOTONIC, {tv_sec=25, tv_nsec=202168729}) = 0 130 poll([{fd=3, events=POLLIN}, {fd=5, events=POLLIN}], 2, 3000) = 1 ([{fd=5, revents=POLLIN}]) 130 read(3, 0x7bf47a73, 1) = -1 EAGAIN (Resource temporarily unavailable) 130 recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="E\20\2@\0\10\0\0@\21l\224\n\0\2\2\377\377\377\377\0C\0D\2,\230\23\2\1\6\0\5\16\36P\0\0\0\0\0\0\0\0\n\0\2\17\n\0\2\2\0\0\0\0RT\0\0 130 clock_gettime64(CLOCK_MONOTONIC, {tv_sec=25, tv_nsec=205504062}) = 0 130 fcntl64(5, F_SETFD, FD_CLOEXEC) = 0 130 socket(AF_INET, SOCK_RAW, IPPROTO_RAW) = 6 130 ioctl(6, SIOCGIFINDEX, {ifr_name="eth0", }) = 0 130 ioctl(6, SIOCGIFHWADDR, {ifr_name="eth0", ifr_hwaddr={sa_family=ARPHRD_ETHER, sa_data=52:54:00:12:34:56}}) = 0 130 close(6) = 0 130 clock_gettime64(CLOCK_MONOTONIC, {tv_sec=25, tv_nsec=208676862}) = 0 130 write(2, "udhcpc: sending select for 10.0.2.15\n", 37) = 37 130 socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)) = 6 130 bind(6, {sa_family=AF_PACKET, sll_protocol=htons(ETH_P_IP), sll_ifindex=if_nametoindex("eth0"), sll_hatype=ARPHRD_NETROM, sll_pkttype=PACKET_HOST, sll_halen=6, sll_addr=[0xff, 0xff, 0xff, 0xf 130 sendto(6, "E\0\1H\0\0\0\0@\21y\246\0\0\0\0\377\377\377\377\0D\0C\0014\25Y\1\1\6\0\5\16\36P\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0RT\0\0224V\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\ 130 close(6) = 0 130 fcntl64(5, F_SETFD, FD_CLOEXEC) = 0 130 clock_gettime64(CLOCK_MONOTONIC, {tv_sec=25, tv_nsec=213060729}) = 0 130 poll([{fd=3, events=POLLIN}, {fd=5, events=POLLIN}], 2, 3000) = 1 ([{fd=5, revents=POLLIN}]) 130 read(3, 0x7bf47a73, 1) = -1 EAGAIN (Resource temporarily unavailable) 130 recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="E\20\2@\0\t\0\0@\21l\223\n\0\2\2\377\377\377\377\0C\0D\2,\225\23\2\1\6\0\5\16\36P\0\0\0\0\0\0\0\0\n\0\2\17\n\0\2\2\0\0\0\0RT\0\02 130 clock_gettime64(CLOCK_MONOTONIC, {tv_sec=25, tv_nsec=215453662}) = 0 130 write(2, "udhcpc: lease of 10.0.2.15 obtained, lease time 86400\n", 54) = 54 In that case, the output of nstat is as follows. / # nstat #kernel IpInReceives 2 0.0 IpInDelivers 2 0.0 UdpIgnoredMulti 2 0.0 IpExtInBcastPkts 2 0.0 IpExtInOctets 1152 0.0 IpExtInBcastOctets 1152 0.0 IpExtInNoECTPkts 2 0.0 Guenter