#!/bin/ksh
# $Id: resolver,v 1.8 2011/12/01 21:03:53 ksb Exp $
# check nameservers, missing, etc.				(ksb, petef)
#
PATH=$PATH:/usr/local/libexec

#****p* netlint/resolver
# NAME
#   resolver
# DESCRIPTION
#   Every host uses DNS to resolve hostnames in a modern installation.
# IMPACT
#   Minor network disruptions will create strange behavior of applications,
#   slow boots the node, and 30 second timeouts to start an ssh session.
#***

progname=`basename $0`
: ${RESCONF=/etc/resolv.conf}
: ${CARP:=echo}
# go find the AndIt function from netlint
. $NETLINT_FUNCS
if [ _-V = _$1 ] ; then
	echo "$progname: "'$Id: resolver,v 1.8 2011/12/01 21:03:53 ksb Exp $'
	[ -s "$RESCONF" ] || echo "$progname: $RESCONF: missing?"
	typeset -f AndIt >/dev/null || echo "$progname: AndIt not defined in $NETLINT_FUNCS"
	exit 0
fi

#****a* resolver/RESOLVER_MISSING
# NAME
#   RESOLVER_MISSING
# FORMAT
#   RESOLVER_MISSING: path
# DESCRIPTION
#   Netlint looks for the system resolver configuration in:
#   * $RESCONF
#   * /etc/resolv.conf
# REMEDIATION
#   When it cannot find the resolver configuration you should check:
#   * The size and existance of /etc/resolv.conf
#   * The modes on the file: should be world readable, only writable by root
#   * The sanity of $RESCONF in netlints environment
#***

if [ ! -s "$RESCONF" ] ; then
	$CARP "RESOLVER_MISSING: $RESCONF"
	exit 0
fi
TFILE=/tmp/rnle.$$

if [ `uname` = Linux ] ; then
        awk '/^nameserver/ {print $2}' $RESCONF |
        xapply -S /bin/ksh -f "nslookup www.fedex.com %1 | head -1 | grep -v timed >/dev/null || echo '%1'" - >$TFILE
else
        awk '/^nameserver/ {print $2}' $RESCONF |
        xapply -S /bin/ksh -f "nslookup www.fedex.com %1 >/dev/null || echo '%1'" -      >$TFILE
fi

# We must point this out because some people do not read well -- ksb
# The RE below could be more egrep-ish if we had egrep everyplace, we don't.
awk '/^nameserver/ {print $2}' $RESCONF |
grep -v '^[0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*[.][0-9][0-9]*$' |
xapply -S /bin/ksh -f "$CARP 'RESOLVER_BADIP: %1'" -

#****a* resolver/RESOLVER_DEAD
# NAME
#   RESOLVER_DEAD
# FORMAT
#   RESOLVER_DEAD: list
# DESCRIPTION
#   This is almost always a real issue: the IPs named in the list are not
#   really running a named (BIND), or that name server is refusing to serve us.
# REMEDIATION
#   Either changing our list of resolvers, or assuring that the listed IPs do,
#   in fact, reply to our requests.
#***

if [ -s $TFILE ] ; then
	$CARP "RESOLVER_DEAD:" `cat $TFILE`
fi

#****a* resolver/RESOLVER_DATA
# NAME
#   RESOLVER_DATA
# FORMAT
#   RESOLVER_DATA: no subnets from netlint
# DESCRIPTION
#   The netlint program didn't include an environment varaible "SUBNET_LIST" in
#   out envronment (or we were not called from netlint).
# REMEDIATION
#   Make sure that the correct version of netlint and the
#   plugins are installed on the host.
#***

#****a* resolver/RESOLVER_NOLOCAL
# NAME
#   RESOLVER_NOLOCAL
# FORMAT
#   RESOLVER_NOLOCAL: subnets
# DESCRIPTION
#   The node has no nameserver listed in the resolver configuration which is
#   also on the local subnet. Because a host might have to run
#   static.routes before it has a good route off the local network it is
#   important to have a local name server.
# REMEDIATION
#   Make at least 2 hosts on the local network a caching name server to serve
#   client nodes.
#***

# make sure there's a nameserver on a local subnet
if [ -z "$SUBNET_LIST" ]; then
	$CARP "RESOLVER_DATA: no subnets from netlint"
else
	LOCALNS=false
	for ns in `awk '/^nameserver/ {print $2;}' /etc/resolv.conf`; do
		if [ "$ns" = "0.0.0.0"  -o  "$ns" = "127.0.0.1" ] ; then
			LOCALNS=true
			continue
		fi
		for pair in $SUBNET_LIST; do
			if [ ${pair%%/*} = `AndIt $ns ${pair#*/}` ] ; then
				LOCALNS=true
			fi
		done
	done
	$LOCALNS || $CARP "RESOLVER_NOLOCAL: $SUBNET_LIST"
fi

rm $TFILE

exit 0