/*
 *	slookup.c - dns lookup stream utility
 *
 *	Heikki Hannikainen <hessu@hes.iki.fi> 1998, 2004
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *	
 */


  slookup is a simple program to do parallelized DNS lookups in a
convenient way (useful for log parsing scripts and one-liners). It reads
names (MX/A lookups) or addresses (in dotted-quad format) on stdin and
writes the results on stdout. One record per line. Beware, output is
written in the order the DNS replies are received, which is usually
different from the input order if parallel lookups are done.

To install:

	$ make
	# make install
	
	This puts the binary in /usr/local/bin.

Usage: slookup [-v] [-f <children>] [-p] [-t A|PTR|MX|NS]
	-v	Verbose
	-f	Number of children to Fork for Fast parallel lookups
	-p	Use persistent TCP connection(s) to DNS server
	-t	Specify query type

  Currently, slookup being a small and dumb program, -v is a NOP.

  Output from slookup comes in the form
  
<question> <+|-> <response|error message>

  Question is the string that was asked on stdin. + means that the query
succeeded, - means that it failed. For failed requests, an error message
stating the reason is printed. For successful requests, a list of
responses is printed.

$ echo cache.inet.fi | slookup -t a
cache.inet.fi + A 192.89.123.14 A 192.89.123.19 A 192.89.123.16 A 192.89.123.21
$ echo hes.iki.fi | slookup -t mx
hes.iki.fi + MX 20 blues.hes.iki.fi MX 10 hes.iki.fi
$ echo 194.251.245.42 | slookup -t ptr
194.251.245.42 + PTR hes.iki.fi
$ echo asdf.hes.iki.fi | slookup -t a  
asdf.hes.iki.fi - Unknown host

  To demonstrate the parallel lookups, one could create a file "foo"
containing a few names to look up:

$ cat > foo
hes.iki.fi
pp.inet.fi
asdf.hes.iki.fi
www.inet.fi
<CTRL-D>
$

  And then run slookup with a few children several times:

$ slookup -t a -f 4 < foo
hes.iki.fi + A 194.251.245.42
pp.inet.fi - No address associated with name
asdf.hes.iki.fi - Unknown host
www.inet.fi + A 194.251.244.140
$ slookup -t a -f 4 < foo
hes.iki.fi + A 194.251.245.42
www.inet.fi + A 194.251.244.140
asdf.hes.iki.fi - Unknown host
pp.inet.fi - No address associated with name
$

Tested on systems:

	Solaris 2.6 / UltraSparc / gcc 2.7.2.3
	RedHat Linux 7.0 / 2.2.17 / glibc-2.1.94 / gcc 2.96
	Debian sarge / 2.6.8.1 / glibc-2.3.2 / gcc 3.3.5
	Debian etch / 2.6.15 / glibc-2.3.6 / gcc 4.0.3
	FreeBSD 5.3-RELEASE / gcc 3.4.2
	FreeBSD 6.0-RELEASE / gcc 3.4.4

	Will fail on many platforms which miss snprintf().