[823] forwarder setting with NetBSD/sparc

[Mark.Andrews at nominum.com]

	Looks like a reasonable analysis.  Patch shortly.

> 	with BIND823 on on NetBSD/sparc, there are problem reports like this:
> 	http://www.NetBSD.org/cgi-bin/query-pr-single.pl?number=12128
> 	to sumamrize, if we set multiple forwarders into named.conf, named
> 	will coredump. (there's some report that it does not happen on i386).
> 
> 	i looked at the code briefly, and found a possible source of problem.
> 	it would be good if you can check if my reasoning is correct.
> 
> 
> 	global variable fwddata[] keeps the all list forwarder data,
> 	created in find_forwarder().  fwddata->ref_count (in struct fwddata)
> 	does not count the pointer from fwddata.
> 
> 	when ftp->fwddata->ref_count reaches 0, we free ftp->fwddata
> 	(ns_config.c near line 2400).  we do not cleanup pointers from
> 	fwddata[] for this particular item, therefore, we leave a dangling
> 	pointer in fwddata[].
> 
> 	next time we visit find_forwarder(), we have possibility to touch
> 	dangling pointer in fwddata[].  the pointer would be returned to
> 	the caller of find_forwarder if we are (un)lucky, and the pointer
> 	will be kept into ftp->fwddata.  when the region gets reused, we will
> 	see coredump.
> 
> 
> 	solution would be to cleanup pointer from fwddata[], when a fwddata
> 	item goes away.
> 
> itojun
> 
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com