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Sat, 18 Jan 2025 02:12:19 -0800 (PST) Received: from [10.4.77.176] ([118.103.63.141]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21c2d4027e3sm28792505ad.222.2025.01.18.02.12.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Jan 2025 02:12:19 -0800 (PST) Message-ID: Date: Sat, 18 Jan 2025 19:12:16 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] net/dump: Correctly compute Ethernet packet offset To: Laurent Vivier , qemu-devel@nongnu.org Cc: Jason Wang References: <20250117111709.970789-1-lvivier@redhat.com> <20250117111709.970789-3-lvivier@redhat.com> Content-Language: en-US From: Akihiko Odaki In-Reply-To: <20250117111709.970789-3-lvivier@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2607:f8b0:4864:20::629; envelope-from=akihiko.odaki@gmail.com; helo=mail-pl1-x629.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 2025/01/17 20:17, Laurent Vivier wrote: > When a packet is sent with QEMU_NET_PACKET_FLAG_RAW by QEMU it > never includes virtio-net header even if qemu_get_vnet_hdr_len() > is not 0, and filter-dump is not managing this case. > > The only user of QEMU_NET_PACKET_FLAG_RAW is announce_self, > we can show the problem using it and tcpddump: > > - QEMU parameters: > > .. -monitor stdio \ > -netdev bridge,id=netdev0,br=virbr0 \ > -device virtio-net,mac=9a:2b:2c:2d:2e:2f,netdev=netdev0 \ > -object filter-dump,netdev=netdev0,file=log.pcap,id=pcap0 > > - HMP command: > > (qemu) announce_self > > - TCP dump: > > $ tcpdump -nxr log.pcap > > without the fix: > > 08:00:06:04:00:03 > 2e:2f:80:35:00:01, ethertype Unknown (0x9a2b), length 50: > 0x0000: 2c2d 2e2f 0000 0000 9a2b 2c2d 2e2f 0000 > 0x0010: 0000 0000 0000 0000 0000 0000 0000 0000 > 0x0020: 0000 0000 > > with the fix: > > ARP, Reverse Request who-is 9a:2b:2c:2d:2e:2f tell 9a:2b:2c:2d:2e:2f, length 46 > 0x0000: 0001 0800 0604 0003 9a2b 2c2d 2e2f 0000 > 0x0010: 0000 9a2b 2c2d 2e2f 0000 0000 0000 0000 > 0x0020: 0000 0000 0000 0000 0000 0000 0000 > > Fixes: 481c52320a26 ("net: Strip virtio-net header when dumping") > Cc: akihiko.odaki@daynix.com > Signed-off-by: Laurent Vivier Reviewed-by: Akihiko Odaki