From: Laurent Vivier Date: Fri, 17 Jan 2025 11:17:09 +0000 (+0100) Subject: net/dump: Correctly compute Ethernet packet offset X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c6a1b591a68b4d7230d6c3f56965e18080d737e5;p=users%2Fdwmw2%2Fqemu.git net/dump: Correctly compute Ethernet packet offset 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 Reviewed-by: Michael Tokarev Signed-off-by: Michael Tokarev --- diff --git a/net/dump.c b/net/dump.c index d7dd2ce461..140215aa10 100644 --- a/net/dump.c +++ b/net/dump.c @@ -155,7 +155,8 @@ static ssize_t filter_dump_receive_iov(NetFilterState *nf, NetClientState *sndr, { NetFilterDumpState *nfds = FILTER_DUMP(nf); - dump_receive_iov(&nfds->ds, iov, iovcnt, qemu_get_vnet_hdr_len(nf->netdev)); + dump_receive_iov(&nfds->ds, iov, iovcnt, flags & QEMU_NET_PACKET_FLAG_RAW ? + 0 : qemu_get_vnet_hdr_len(nf->netdev)); return 0; }