From sasha@direct1.com Thu Jun 17 00:56:37 1999
Date: Wed, 16 Jun 1999 14:49:22 +0000
From: Sasha Pachev <sasha@direct1.com>
To: brad@mrunix.net
Subject: Patch to do reverse DNS lookup

Brad:

I really liked you Webalizer. Compiled right out of the box, make
install fix the config file to tell it where my logs are and where to
put the results, and lo and behold, got a beautiful report with all the
stuff I needed, with only one exception. I configure my Apache not to do
reverse lookups, but I wanted to see them in the reports. 

Well, here is the beauty of open source - I wrote a patch to do it,
first just dumb straighforward way, too slow , then optimized a bit to
cache previous lookups, still too slow because  some stupid DNS servers
are just down, and the default resovler timeouts are set too high, so I
added a hack to do a forced timeout of gethostbyaddr(). The hack is
really ugly, that's why I call it a hack, but I could not come up with
anything cleaner. gethostbyaddr() will retry if you terminate a select()
with SIGALRM, so I really had only two choices - either mess with _res
structure in the signal handler before returning control to
gethostbyaddr() or do longjmp() back out of gethostbyaddr().   Of the
two evils I chose the latter. Let me know if you are aware of a better
solution.

On some systems it may cause a resource leak if gethostbyaddr()
allocates resources that it frees only after select() that I am timing
out. I am also not doing a proper cleanup of the DNS cache resources,
because this will be done by the system on exit anyway. In the future,
this may be useful right before generating a report to re-claim some
memory so there would be enough to do the job. 

Anyway, here is the patch for version 1.22_06. To apply just run patch <
reverse_lookup.patch in the source directory. It adds three options to
the config file: ReverseLookup, DNSCache , and DNSTimeout . Let me know
what you think. Also, if there are any features that you are working on
and would like to delegate, I am available.

-- 
Sasha Pachev
http://www.sashanet.com/ (home)
http://www.direct1.com/ (work)