Re: [lwip-users] SYN/ACK issue in TCP client/server implementation under eCos with LwIP-TCP/IP stack on ARM Evaluator 7T board

[Kieran Mansley]

On Mon, 2007-03-05 at 01:54 -0800, Ashish Anand wrote:
> Why would I be able to PING the board? I have not implemented any ICMP code
> in my program (I'm assuming that I must write some code to make the board
> ack ICMP packets). So, as of now, no, I can't PING my board, and all this
> while I wasn't expecting to be able to either :-)
> 
> Correct me if I'm wrong!

lwIP includes ICMP code.

> Secondly, here's some good looking debug stuff:

[snip]

> ip_input: iphdr->dest 0x401a8c0 netif->ip_addr 0x401a8c0 (0x1a8c0, 0x1a8c0,
> 0x4)
> ip_input: iphdr->dest 0x401a8c0 netif->ip_addr 0x100007f (0xc0, 0x7f,
> 0x401a800)
> ip_input: packet not for us.
> ip_forward: not bouncing packets back on incoming interface.

This is the interesting bit.  The lwIP receive code gets two packets:
the first it matches and passes through, the second it says is not for
us due to the IP address in the packet being different to the
interface's address.  The first packet getting through suggests that
something is right however.  I'd look into what happens to this first
packet and check out if it is the one you're interesting in (the reply
to the SYN) or if that one is the one that gets dropped.

Kieran