Re: [lwip-users] low level output question

[address@hidden]

John Kennedy wrote:
> Yes, I'm sending a ping from my PC to my embedded system running lwip.  With no 
> breakpoints set wireshark shows an ARP request going out and the ARP response 
> returning from lwip.  Then the PC sends an ICMP (ping request) to the embedded 
> system.  So the ARP response packet generated by lwip is correct.  I was just 
> puzzled because when I set the breakpoint the pbuf length is 1518?
Hm, that does sound strange. Without breakpoints, the packets shown in 
wireshark are correct? Event the ping responses? If so, I don't have a 
clue what's going wrong: there should be no packets with lenght=1518 
involved in these packets. And 1518 is even too long for an ethernet 
packet, 1514 should be the maximum (if you didn't misconfigured lwIP).

I think the pbufs in the pool (PBUF_POOL type) have their length set to 
the maximum (which is 1518 because of memory alignment) if they are not 
used (i.e. currently *in* the pool). Could it be that you are seeing 
such a pbuf pointer? You didn't yet write what's in the pbuf's payload.

Simon