Re: [lwip-users] eCos - PPP - TCP - LwIP

[Jonathan Larmour]

Kieran Mansley wrote:
> On Mon, 2007-02-19 at 07:16 -0800, Ashish Anand wrote:
> > [1] No issue of firewall, since I used "service iptables stop".

Ok, sigh. I go back to my other suggestion of more extensive debug I'm afraid.

> > [2] When I telnet, I get something similar:
> >
> >  ip_input: iphdr->dest 0xfb0000e0 netif->ip_addr 0x401a8c0 (0xe0, 
> > > > > > > 0x1a8c0, 
> > > > > > > 0xfb00000)ip_input: iphdr->dest 0xfb0000e0 netif->ip_addr 0x100007f 
> > > > > > > (0xe0, 
> > > > > > > 0x7f, 0xfb000000) 
> > > > > > > ip_input: packet not for us. 
> > > > > > > ip_forward: not bouncing packets back on incoming interface. 
> > Except that this time, the (hex) IP address is 192.168.1.4 (board IP)
> > instead of the MDNS IP.

I don't see any different to the previous ip_input debug output you posted.

> > So even these packets are considered "not for us"!
> >
> > It's really strange, why all this complication is arising!
>
> I may have got confused here, but let me summarise what I think is
> happening:
>  - you receive two packets.
>  - the first is for a multicast IP address.
>  - the second is a SYN to the board IP address.
>  - both are rejected as "not for us"
>
> The multicast packet is rejected because it is multicast and we don't
> support generic multicast traffic (there are some special cases where it
> is supported, but on the whole not).
>
> The second can only be rejected with that error because your board does
> not have the IP address you think it does.  The debug statement above
> shows the packet's IP address to be 0xfb0000e0 (i.e 14.0.0.251) and the
> netif/board IP address to be  0x100007f (ie. 127.0.0.16).

/me passes Kieran a new hex converter ;-).

0xfb0000e0 == 224.0.0.51.
0x100007f == 127.0.0.1.

ip_input is making debug output for each netif interface. So:

ip_input: iphdr->dest 0xfb0000e0 netif->ip_addr 0x401a8c0 (0xe0, 0x1a8c0,
0xfb00000)

means the destination is the multicast addr, but the netif addr is 
0x401a8c0 == 192.168.1.4, which must be the PPP interface.

The second line:
ip_input: iphdr->dest 0xfb0000e0 netif->ip_addr 0x100007f (0xe0, 0x7f, 
0xfb000000)
is ip_input's attempt to match the multicast addr against the loopback 
interface.

These lines are just ip_inputs attempts to direct the (single) multicast 
packet, which it fails to do.

The real problem appears to be that the telnet SYN is never even seen.

Jifl
--
eCosCentric    http://www.eCosCentric.com/    The eCos and RedBoot experts
 Meet us at Embedded Systems Conference - SV, April 3rd-5th.  Stand #2248
Company legal info, address and number:   http://www.ecoscentric.com/legal
------["The best things in life aren't things."]------      Opinions==mine