I'm not a subscriber on the list, please cc the answers, if any ;). This script is generated with 2.6.6-kernel (patched with lufs and lirc but that should be of no consequence): --8<-- verse# tcpdump -c1 -w log 'dst port 4343' & [1] 1225 verse# tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes verse# echo -n foo | nc -q1 -u -b 192.168.2.255 4343 1 packets captured 3 packets received by filter 0 packets dropped by kernel [1] + done tcpdump -c1 -w log 'dst port 4343' verse# tethereal -V -r log (headers of little interest removed: full 85-byte dump available at http://www.modeemi.cs.tut.fi/~flux/udpbug/eth0-dump.pcap) Frame 1 (45 bytes on wire, 45 bytes captured) Packet Length: 45 bytes Capture Length: 45 bytes Ethernet II, Src: 00:00:b4:a6:2d:90, Dst: ff:ff:ff:ff:ff:ff Destination: ff:ff:ff:ff:ff:ff (Broadcast) Source: 00:00:b4:a6:2d:90 (EdimaxCo_a6:2d:90) Type: IP (0x0800) Internet Protocol, Src Addr: 192.168.2.2 (192.168.2.2), Dst Addr: 192.168.2.255 (192.168.2.255) Total Length: 31 Protocol: UDP (0x11) Header checksum: 0xed39 (correct) Source: 192.168.2.2 (192.168.2.2) Destination: 192.168.2.255 (192.168.2.255) User Datagram Protocol, Src Port: 1027 (1027), Dst Port: 4343 (4343) Source port: 1027 (1027) Destination port: 4343 (4343) Length: 11 Checksum: 0x866e (incorrect, should be 0x8f1c) Data (3 bytes) 0000 66 6f 6f foo --8<-- As you can see, udp-checksum is not correct according to ethereal (and tcpdump). eth0 is rtl8139, however the bug appears with eth1 too, which is 3com 3c905B. Needless to say, the checksum is similarly corrupted when the other hosts receive it, which causes them to drop the packet. Loopback-interface seems to be working OK. The bug appears only when using udp broadcast; sending a udp packet to a host succeeds. The machine can broadcast ping ok. I have no similar problems with other hosts in the network (running 2.6.2, 2.6.5, 2.4.20 and 2.4.18). The bug appeared with kernels compiled both with gcc-2.95.4 and gcc-3.3.4, both from Debian Unstable. Kernel configuration and other information is available at: http://www.modeemi.cs.tut.fi/~flux/udpbug/ -- _____________________________________________________________________ / __// /__ ____ __ http://www.modeemi.fi/~flux/\ \ / /_ / // // /\ \/ / \ / /_/ /_/ \___/ /_/\_\@modeemi.fi \/ - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
