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

[Jonathan Larmour]

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.

But the board is clearly able to receive broadcast IP packets, and 
netif->ip_addr is also clearly set correctly. If it gets sent down the 
link, it really should be able to be seen. You could enable the PPP 
debugging (PPP_DEBUG) specifically to see if _any_ event happens on the 
target when the SYNs are sent.

Is there any chance your linux host is packet filtering (i.e. firewalling) 
outbound packets? Just because you can see it in ethereal, doesn't mean the 
firewall allowed it through.

> 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?

If you see the TCP syns going out the right interface, there doesn't seem 
much point.

Jifl

> 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
> > --
> > 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
> >
> >
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--
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