[rancid] duplicated characters

john heasley heas at shrubbery.net
Sat Sep 3 20:08:19 UTC 2011

Thu, Sep 01, 2011 at 02:27:10PM -0600, Corey Edwards:
> After a recent upgrade from Debian 5.0 to 6.0 I began seeing duplicate
> characters in config diffs. Here's an example:
> - access-list 102 deny   udp any any eq 135
> + access-list 102 denny   udp any any eq 135
> - access-list  110 deny   tcp any any eq 445 log
> + access-list 110 deny   tcp any any eq 445 log
> The next round of updates will revert the change back. I haven't found
> any pattern to which character it will be or even which router. It's
> only happening with my Cisco devices, not any of our others (Foundry
> switches, Mikrotiks or Lucent TNTs). I'm using 2.3.1, but a fresh
> install of 2.3.6 on the same server does the same thing. 2.3.6 on my
> Ubuntu 10.04 laptop works just fine.
> To verify whether the routers themselves were errant, I did a packet
> capture. That confirmed that the data from the router is correct. I
> turned on debugging in clogin. WriteTerm shows the duplicate characters.
> So then I put in a puts in run_commands in rancid and that also showed
> duplicate characters in $expect_out(buffer).
> I found this thread from 2004 which hinted at it being an issue with the
> telnet client. The OP eventually switched to ssh which in this case
> isn't an option.
> http://www.gossamer-threads.com/lists/rancid/users/720

i dont know what the fbsd fix was for this, but they fixed it somehow in
their tcl or expect port.

perhaps its related to a problem that came up in rancid 2.3.5 something
changed in debian's libc that caused problems with string handling
functions, which i believe was related to internationalization.

or could be a bug in buffer handling in expect or tcl.

either way, if you can capture clogin -d -c 'show running' o/p where this
occurs, it should at least reveal where the bug is.

you can also try rebuilding tcl and expect w/o internationalization.

> The incessant emails are driving me batty and making the cvs history
> significantly less useful. I'll debug whatever needs to be debugged but
> I'm fresh out of ideas of where to look. I started looking at expect but
> was quickly lost in the code.
> Any ideas?
> Corey
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