[rancid] Re: clogin bug in $prompt matching, does not work well IOS XR

[Kristian Larsson]

On Tue, Jan 20, 2009 at 10:43:33AM -0700, Lance Vermilion wrote:
> Have you tried adding something like the following to you .cloginrc?

No.

> add userprompt AMS-CORE-1 "RP/0/RP1/CPU0:AMS-CORE-1"

This looks just like the prompt on the router,
which clogin already detects correctly.
Anyway, I just tried now adding it to my .cloginrc
and I'm running into the same problem.

The problem is _not_ with how clogin identifies
the prompt, it does this correctly so the value
stored in $prompt is correct.

The problem is when clogin matches $prompt towards
the lines received thereafter. Due to the way IOS
XR behaves the $prompt variable could appear
several times though not a complete line (with a
new line at the end) and this confuses clogin.

Please look at the strace output and you will see
how you receive parts of the line several times
before it is finally sent with an ending \n. That
is where the problem lies. Or so I believe ;-)

Kind regards,
  Kristian.



> On Tue, Jan 20, 2009 at 10:33 AM, Kristian Larsson
> <kristian at spritelink.net> wrote:
> > Hello!
> >
> > I have found what I believe is a bug in clogin.
> >
> > When using clogin to automatically send commands
> > and retrieve its output from an IOS XR device the
> > prompt is not correctly parsed.
> >
> > When clogin first logs in, it sends a simple
> > carriage return (\n) to the router to be able to
> > determine the prompt. Here's an strace of that..
> >
> > recvfrom(3, "RP/0/RP1/CPU0:AMS-CORE-1#", 6938, 0, NULL, NULL) = 25
> > write(1, "RP/0/RP1/CPU0:AMS-CORE-1#", 25) = 25
> > read(0, "\r", 8177)                     = 1
> > sendto(3, "\r\0", 2, 0, NULL, 0)        = 2
> > recvfrom(3, "\r\n\rRP/0/RP1/CPU0:AMS-CORE-1#", 6913, 0, NULL, NULL) = 28
> > write(1, "\r\n\rRP/0/RP1/CPU0:AMS-CORE-1#", 28) = 28
> >
> > So far, everything is fine and dandy. The router
> > is obviously called ams-core-1 and it has the
> > prompt RP/0/RP1/CPU0:AMS-CORE-1# which clogin
> > correctly identifies.
> > Here comes the next part, clogin sends 'terminal
> > length 0'...
> >
> > read(0, "terminal length 0\r", 8176)    = 18
> > sendto(3, "terminal length 0\r\0", 19, 0, NULL, 0) = 19
> > recvfrom(3, "terminal\rRP/0/RP1/CPU0:AMS-CORE-1#terminal length\rRP/0/RP1/CPU0:AMS-CORE-1#terminal length 0\r\n\r", 6885, 0, NULL, NULL) = 95
> >
> > So it reads 'terminal length 0' from clogin, sends
> > it to the CRS and then receives the output.
> >
> > Now, IOS XR does one thing a tad differently than
> > IOS, it has command completion on the space key
> > as well as on the tab key. My guess is that this
> > mechanism forces the IOS XR CLI to redraw the line
> > each and every time a space is entered.
> > If we examine the recvfrom line
> >
> > recvfrom(3, "terminal\rRP/0/RP1/CPU0:AMS-CORE-1#terminal length\rRP/0/RP1/CPU0:AMS-CORE-1#terminal length 0\r\n\r", 6885, 0, NULL, NULL) = 95
> >
> > we see that "terminal" is first echoed back to
> > the client. Then, as a space was entered, IOS XR
> > does a carriage return and redraws the entire line
> > starting with the prompt and filling up with
> > "terminal length" and the same thing over again to
> > "terminal length 0".
> >
> > As clogin merely looks for $prompt which is
> > 'RP/0/RP1/CPU0:AMS-CORE-1#', it will get a match
> > several times over and is thus unable to interpret
> > the situation correctly.
> >
> > I've tried modifying clogin in several ways
> >  - adding \n to prompt or several of the places
> > where $prompt is used and so forth but so far
> > without much luck. My TCL-fu is not strong enough.
> >
> > Could some TCL guru have a look at this? I could
> > probably arrange access to an IOS XR device for
> > testing.
> >
> > Oh, I'm running clogin version 2.3.2a9
> >
> > Kind regards,
> >   Kristian.
> >
> > --
> > Kristian Larsson                                        KLL-RIPE
> > Network Engineer / Internet Core        Tele2 / SWIPnet [AS1257]
> > +46 704 910401                                kll at spritelink.net
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> > http://www.shrubbery.net/mailman/listinfo.cgi/rancid-discuss
> >
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-- 
Kristian Larsson                                        KLL-RIPE
Network Engineer / Internet Core        Tele2 / SWIPnet [AS1257]
+46 704 910401			              kll at spritelink.net