[lwip-users] Re: [lwip] RFC: ARP (timing) behaviour

[leon . woestenberg]

Hello Scott,

> While on the subject of ARP, what is the maximum it'll delay the packet?
> 
> It seems that I've had UDP packets delayed from transmission for up to 60
> seconds. Seem familiar? ;-)
>
Hmm, this may have been a result of the old etharp.c code. Currently, queued
packets are dropped from pending ARP entries on every call to etharp_tmr(),
as can be seen
in the code below. So, at most 10 seconds if you follow the advice:
 
Leon.

If you call etharp_tmr() every 10 seconds,
{
  ...
  ++ctime;
  /* remove expired entries from the ARP table */
  ...

    } else if((arp_table[i].state == ETHARP_STATE_PENDING) &&
              (ctime - arp_table[i].ctime >= ARP_MAXPENDING)) {
      arp_table[i].state = ETHARP_STATE_EMPTY;
      /* remove any queued packet */
      pbuf_free(arp_table[i].p);      
      arp_table[i].p = NULL;
}

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