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I am looking into a TCP capture with Wireshark and I am seeing numerous AJP errors that look similar to below coming from our Apache server. I'm wondering what is causing these errors and what I can do to resolve them?

AJP13 Error?[Unreassembled Packet [incorrect TCP checksum]]

Checksum: 0x66ff [incorrect, should be 0x0912 (maybe caused by "TCP checksum offload"?)]

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2 Answers 2

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Your network card has told the TCP stack that it can handle the TCP checksum calculation in hardware. This means the fields in the TCP header that are passed down the stack lack a checksum, as the card said it will add them before it puts them on the wire.

Unfortunately this means that anything snooping on the packet on the way out of the machine will see a packet without a correct checksum because the two bytes that make up the checksum retain the previous value of whatever data was written to that area of memory previously.

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You probably have a network card configured on your system to offload the tcp checksumming.

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Thanks. Sounds like this is nothing to worry about then. –  Taylor Leese Jun 5 '09 at 4:57
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