[Click] SetUDPChecksum dropping packets

[Robert Ross]

We have found what appears to be a bug (or undocumented feature) in SetUDPChecksum where packets sent into this element are somehow discarded.  In the attached config, you will see an ElementClass called FixChecksumsDebug which counts packets into each checksum fixer and counts packets out the other side.  We have found that, under specific circumstances, packets sent into SetUDPChecksum never come out the other side.  This is true of the latest version from SVN.

As to the particular situations for this problem, it seems to happen only with fragmented packets.  In a set of packet fragments, the first portion (offset +0) always seems to be discarded when going through SetUDPChecksum.  There is no indication that I have found as to the reason for the discard.

Has anyone else seen this issue?  Does SetUDPChecksum have a second output that is undocumented?  Any suggestions?

Thanks,

Robert Ross
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