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

[Ashish Anand]

Yes yes yes.......I used Ethereal.
The 254 IP is some process in the Linux box (MDNS Protocol - Ignore that).
I was monitoring the ppp interface through Ethereal and when I telnet to the
board, it shows TCP syn packets going out to the board. But there is no
SYN/ACK coming back from the board.

>From the numerous code examples I have seen till now, no one seems to be
setting up any routing tables through manual C code. Do you want me to put
up my code?


Jonathan Larmour wrote:
> 
> Ashish Anand wrote:
>> 
>> 
>> Jonathan Larmour wrote:
>>> Ashish Anand wrote:
>>>> I turned on debugging. This is what I get when I try to telnet to the
>>>> board
>>>> (192.168.1.4) from 192.168.1.3...... (0x401a8c0 is 192.168.1.4, the
>>>> board):
>>>>
>>>> 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.
>>>>
>>>>
>>>> So basically, the data link layer (PPP) is up. But I am not able to do
>>>> much
>>>> at the network layer (IP/ICMP).
>>> Try debugging the netif layer. See if the PPP layer does set the IP
>>> address 
>>> for the ppp interface, and if so, to what.
>>>
>>>
>> 
>> I have done that. The board is being assigned the correct IP as specified
>> by
>> my PPP Server. I am able to printf the board IP, the server IP and
>> netmask
>> also. So it's not a data link layer issue probably.
> 
> Sorry, yes, if I had read your earlier output more carefully I'd have seen 
> that. The destination address in the IP header field above is 224.0.0.251
> 
> That's a multicast address (see 
> http://en.wikipedia.org/wiki/Multicast_address ). In fact specifically
> that 
> is Rendezvous/multicastDNS. Are you sure this only happens at the point
> you 
> do the telnet? I suspect in fact this packet comes from some other process 
> on your host which is sending them, and it's sending it to all connected 
> interfaces including ppp.
> 
> If so, then that means IP connectivity in general is working as far as the 
> target is concerned, and the problem may in fact be the host. Perhaps the 
> routing tables? Perhaps using tcpdump or ethereal on the various
> interfaces 
> on the host may show you where the packets are going, at the point you 
> actually initiate the telnet.
> 
> Jifl
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