Re: [lwip-users] Force PPP TermReq (Lwip 2.0.0 RC2)

[Patrick Klos]

On 8/4/2016 6:30 PM, Sylvain Rochet wrote:
> Hello,
>
> On Thu, Aug 04, 2016 at 10:15:56AM -0400, Patrick Klos wrote:
> > Again, the TermReq packet is an LCP packet.  If your peer is ignoring
> > all LCP packets (as you stated earlier), it's just ignore that packet
> > as well. I'm sure you could find a way to get LwIP to send the packet
> > - just not sure if it'll help given your symptoms.
> The issue here is probably a LCP magic (=cookie) mismatch. Once a LCP
> session negotiated the magic, which is usually the first thing it
> negotiates, it only accept LCP packets with the magic set.

That's not how the Magic-Number option is used.  The Magic-Number is 
primarily used to detect when the link is (or becomes) looped back. If 
the sender receives an LCP Configure-Request (or other LCP packets which 
explicitly include the Magic-Number) with the it's own Magic-Number, 
it's safe to assume the link is in some kind of loopback mode.  You can 
get the full explanation in RFC 1661, but you get the idea.

Once negotiated, the value set by the Magic-Number option is used in LCP 
Echo-Request, LCP Echo-Reply, LCP Discard-Request, and some 
Quality-Protocol packets, but none of the other LCP packets (unless 
negotiations start over).

> It means sending the TermReq packet with a new random magic is not going
> to work anyway, this is what the magic is for actually, to protect the
> LCP channel for outsiders, hey ;-)

The Terminate-Request does not have a Magic-Number in it.  You can send 
it at any time and the peer's LCP state is required to drop out of the 
Opened state.

> Greg, please use LCP echo request/reply mechanism, that's the only
> viable solution. I hope you can configure LCP request/reply interval and
> count timeout on the PPP peer.

At this point, I think a packet (or byte) trace is the best diagnostic 
to show what's happening here.

Patrick Klos
Laufer Wind