Date sent:      	Sat, 2 Jan 1999 15:39:55 +0100 (MET)
From:           	Urban Widmark <urban@svenskatest.se>
To:             	r.oosterloo@mediaresultant.nl
Copies to:      	linux-ppp@vger.rutgers.edu, nerijusb@prototechnika.lt
Subject:        	RE: callback

On Thu, 31 Dec 1998 r.oosterloo@mediaresultant.nl wrote:

> In theory, it should work. Check the file README.cbcp in the
> ppp-2.3.5.tar.gz. It describes the changes you have to make to the source
> before you compile it.
> I compiled it like that and when i dial into an NT with dialback, it does
> some dialback negotiation, but it doesn't hang up so that the NT can call
> back. Maybe it works better for you. Good Luck!
> 
> Greetings!
> 

It is possible to get CBCP working (NT callback). I had some problems with
the CBCP code in ppp-2.3.5, maybe you have run into the same problem.

Does the server agree on callback?
Have you run it with debug option?
Do you get "AdminDefined", where the number to call is set on the server?

For me both the server and the client seemed to agree on 'AdminDefined'
callback.But they never stopped negotiating this, and the server kept
requesting this. Here is some debug output:

Sep  7 18:17:48 nirvana pppd[228]: rcvd [CBCP Request id=0x59 <AdminDefined delay = 0>]
Sep  7 18:17:48 nirvana pppd[228]: length: 3
Sep  7 18:17:48 nirvana pppd[228]: user admin defined allowed
Sep  7 18:17:48 nirvana pppd[228]: cbcp_resp cb_type=8
Sep  7 18:17:48 nirvana pppd[228]: cbcp_resp CONF_ADMIN
Sep  7 18:17:48 nirvana pppd[228]: sent [CBCP Response id=0x59 <AdminDefined delay = 0 number = >]
Sep  7 18:17:50 nirvana pppd[228]: rcvd [CBCP Request id=0x5a <AdminDefined delay = 0>]
Sep  7 18:17:50 nirvana pppd[228]: length: 3
Sep  7 18:17:50 nirvana pppd[228]: user admin defined allowed
Sep  7 18:17:50 nirvana pppd[228]: cbcp_resp cb_type=8
Sep  7 18:17:50 nirvana pppd[228]: cbcp_resp CONF_ADMIN
Sep  7 18:17:50 nirvana pppd[228]: sent [CBCP Response id=0x5a <AdminDefined delay = 0 number = >]

and so on ... notice the response/request id increasing. It turns out I
wasn't talking to an NT, but to a Cisco 3600 (or?).

I believe this is due to a bug in the ppp-2.3.5 code where pppd adds a 0
value for the callback number which is wrong according to the draft
specification of CBCP. Here is a patch against ppp-2.3.5 (apply in the
pppd directory)

--- cbcp.c.org  Tue Sep  7 20:07:55 1998
+++ cbcp.c      Tue Sep  7 20:08:25 1998
@@ -343,10 +343,9 @@
     if (cb_type & ( 1 << CB_CONF_ADMIN ) ) {
        syslog(LOG_DEBUG, "cbcp_resp CONF_ADMIN");
         PUTCHAR(CB_CONF_ADMIN, bufp);
-       len = 3 + 1;
+       len = 3;
        PUTCHAR(len , bufp);
        PUTCHAR(5, bufp); /* delay */
-       PUTCHAR(0, bufp);
        cbcp_send(us, CBCP_RESP, buf, len);
        return;
     }

With this patch applied cbcp works for me, without it nothing happens.
There is one warning about an "id mismatch", but that may be the server
getting it wrong. Could you please try my patch and see if it works for
you too?

Of course you need to get the other authentication right (chap or
similar).

Please let me know if (either of) you do/do not get it to work
using/without using this patch. So I can send some info to the ppp
maintainers.

/Urban

---
Urban Widmark                           urban@svenskatest.se
Svenska Test AB                         +46 90 71 71 23


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