Re: [lwip-users] Header Checksum error

[Simon Goldschmidt]

Roberto Romo <address@hidden> wrote:
> I founded an example for a TCP-echo-client from st I think. When I compile
> it and run it on my µc everything is ok,
> but when i capture the communication with  wireshark I see that the µc
> (IP: 192.168.1.5) sends an error:
> 
> - Header checksum: 0x0000 [incorrect, should be 0x0d6f (maybe caused by
> "IP checksum offload"?)

Is that so? Because from the image you attached, a packet from 192.168.1.4 *to* 
192.168.1.5 has a zero checksum. No I assume that .4 is your PC which has 
checksum offloading enabled. In that case, it's perfectly normal to see 
checksum errors: wireshark gets the outgoing packets before the driver (or even 
hardware) has filled in the checksums. 

However, communication should still work fine although wireshark reports an 
error. As a workaround, either disable checksum checks in the wireshark options 
or disable checksum offloading in your windows NIC's options.

Simon
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