Re: [lwip-users] Unusual ARP behavior

[address@hidden]

Roger Cover wrote:
> I am confused about a couple of things here. Why does the stack send 4 
> duplicate ARP requests in 2 microseconds?
That's just the way lwIP ARP works: if it does not find a stable entry, 
it sends a request. In order to keep it simple, there is no check for 
the last request (or to limit the amount of requests).
> Why does it send another ARP request, after those have been answered, 239 
> microseconds later?
I would guess that at this point, the ARP response packets have not 
reached the ARP table yet. I guess the input packets are queued 
somewhere, and 239us is not such a long time for an embedded system...
> Why are no UDP packets passed out of the stack after these 5 ARP requests have 
> been answered?
That's a good question. Something seems to block the device between 
packets 30 and 35 (it does not respond to TCP SYN, too).
> Is there somewhere in the stack that it could reasonably remain for longer than 
> the 1.3 seconds my watchdog timer requires to reset my instrument?
No, not in the stack itself (unless it's a bug, of course, but that's 
unlikely to make it work again later). Sorry I can't help you further 
here...
Maybe the lwIP stats can help you?

Simon