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

[Ashish Anand]

Oh and just so there was no confusion, I turned down eth0 while doing the
experiment so the only active interface is ppp0, besides loopback ofcourse.
So the routing etc. from the linux box doesn't seem to be the issue to me.



Ashish Anand wrote:
> 
> 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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> 
> 

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