Wireshark-bugs: [Wireshark-bugs] [Bug 2580] New: invalid checksum in udp header

From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Sat, 31 May 2008 11:59:08 -0700 (PDT)

http://bugs.wireshark.org/bugzilla/show_bug.cgi?id=2580

           Summary: invalid checksum in udp header
           Product: Wireshark
           Version: 1.0.0
          Platform: PC
        OS/Version: other
            Status: NEW
          Severity: Major
          Priority: Low
         Component: Wireshark
        AssignedTo: wireshark-bugs@xxxxxxxxxxxxx
        ReportedBy: rtrout@xxxxxxxxxxxxxxxxx


Build Information:
Paste the COMPLETE build information from "Help->About Wireshark", "wireshark
-v", or "tshark -v".
--
I send the following packet:
    {0x00, 0x16, 0x41, 0xE0, 0xF8, 0x59,//00:target ethernet address
     0x00, 0x50, 0xC2, 0x44, 0x20, 0x05,//06:source ethernet address
     0x08, 0x00,                        //0C:packet type
    //IP, header
     0x45, 0x00,                        //00:
     0x00, 48,                          //02:total length(IP + udp + userData)
     0x00, 0x00,                        //04:identification
     0x40, 0x00,                        //06:flags,fragment offset
     0x40,                              //08:TTL
     0x11,                              //09:protocol
     0x25, 0xE2,                        //10:IP checksum (computed)
     0x0A, 0x00, 0x00, 0x45,            //12:source      IP 10.0.0.69
     0x0A, 0x00, 0x00, 0x97,            //16:destination IP 10.0.0.151
    //UDP packet
     0x03, 0xE8,                        //20:source port=1000
     0x0B, 0xCC,                        //22:destn  port=0xBCC
     0x00, 26,                          //24:UDP length
     0x0F, 0xC7,                        //26:UDP checksum (computed)
     //data                             //28:
     'M', 'S', 'G', '=', 'U', 'D', 'P', ' ', //28-35
     'M', 'e', 's', 's', 'a', 'g', 'e', '.', //36-43
     0x0A, 0,  0,   0,                       //44-47
    };

Wire shark reports an invalid UDP checksum and suggests 0x0FC5.
I believe the checksum is correct since the packet gets through Windows sockets
just fine (and other packets with checksum errors do not).
If i change the checksum to 0x0FC5 it does not get through Windows.

Program is running on an embedded system with no operating system or IP stack.


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