Re: [lwip-users] Not getting responses to some ARP requests

[Simon Goldschmidt]

> I’m seeing an odd problem with lwip (1.2) in which the system uses DHCP
> and
> gets an IP, and then it will respond to ARP queries from my laptop running
> netcat, but it fails to respond to other ARP queries.  The only difference
> that I can see in Wireshark ( other than the source IP of course ) is the
> packet size of the ARP request (60 bytes, vs 42 bytes from netcat).   Mine

This is normal: On the wire, every packet should be at least 60 bytes long. 
However, tracing your own outgoing packets, you only see the data being sent, 
not the trailer (18 bytes of zero, in your case): The trailer is appended by 
the ethernet driver or even the ethernet MAC in your PC.

Unfortunately, this doesn't help you very much because it doesn't explain why 
the device doesn't answer to some ARP requests. One thing I have in mind is 
that lwIP 1.2.0 was _not_ thread safe when processing ARP requests (1.3.0 now 
_is_ thread safe!). Another source of error could be the ethernetif (the 
driver) implementation...

> The etharp.c module is unmodified from the software framework provided by
> Atmel for the AVR32 processors.

Hmm, can't help you there: I don't know what Atmel ships, so I can't even know 
if that's unmodified from the original 1.2.0 distribution... Maybe you can ask 
Atmel for help?

The last idea to trace the problem would be to enable statistics and debug 
output on the lwIP device that fails and check if you see something strange 
there.

Simon
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