#!/bin/sh --
#
# CDDL HEADER START
#
# The contents of this file are subject to the terms of the
# Common Development and Distribution License (the "License").
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#
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# or http://www.opensolaris.org/os/licensing.
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#

# Check hostname configuration as per the sendmail code.
#
# See http://www.sendmail.org/sun-specific/migration.html#FQHN for details.
#
# Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
# Use is subject to license terms.
#

setvar PATH = "/bin:/usr/sbin"

# If $1 has a ".", accept it and exit.

proc accept_if_fully_qualified {
	match $1 {
	with *.*
		echo "Hostname $myhostname OK: fully qualified as $1"
		exit 0
		
	}
}

# Check the `getent hosts $1` output, skipping the 1st entry (IP address).

proc check_gethostbyname {
	for host in [$(getent hosts $1 | awk '{for (f=2; f <= NF; f++) print $f})]
	{
		accept_if_fully_qualified $host
	}
}

# Parse /etc/hosts, looking for $1 as an entry by itself, and try to find
# a long name on the same line.  First kill all comments, then check for
# $1 as a word by itself, then take just the first such line, then skip
# its first entry (IP address).

proc check_hosts_file {
	for entry in [$(sed -e 's/#.*$//' /etc/hosts | \
		awk '/[ 	]'$1'([ 	]|$)/ \
			{for (f=2; f <= NF; f++) print $f; exit})]
	{
		accept_if_fully_qualified $entry
	}
}

# Parse the output of `nslookup $1`, checking the Name and Aliases.

proc check_dns {
	for host in [$(nslookup $1 2>/dev/null | \
		awk '$1 == "Name:" || $1 == "Aliases:"{print $2})]
	{
		accept_if_fully_qualified $host
	}
}

# Check the `ypmatch $1 hosts` output, skipping the 1st entry (IP address).

proc check_nis {
	for hst in [$(ypmatch $1 hosts | awk '{for (f=2; f <= NF; f++) print $f})]
	{
		accept_if_fully_qualified $hst
	}
}

# Recommend how to reconfigure to get $1.$2 as the FQHN.
# $3 is the first entry for hosts in /etc/nsswitch.conf . 

proc suggest_fix_and_exit {
	setvar myhost = "$1"
	setvar suggested_domain = "$2"
	setvar fhe = "$3"
	setvar myipaddr = $(getent hosts $myhost | head -1 | awk '{print $1})

	# aliases: skip the 1st & 2nd entries: IP address & canonical name

	set -- '' '' '[ aliases ... ]'
	set -- $(grep "^$myipaddr[	 ]" /etc/hosts )
	setvar result = "$Status"
	shift 2
	echo "We recommend \c"
	if test "x$fhe" != "xfiles"  {
		echo "listing files first for hosts in /etc/nsswitch.conf"
		echo "and then \c"
	}
	if test $result = 0  {
		echo "changing the /etc/hosts entry:\n"
		echo "$myipaddr $myhost $ifsjoin(ARGV)\n"
		echo "to:\n"
	} else {
		echo "adding the /etc/hosts entry:\n"
	}
	echo "$myipaddr $myhost $myhost.$suggested_domain $ifsjoin(ARGV)"
	exit 0
}

# Fall back to the NIS domain, minus the first label.  If it is non-null,
# use it but recommend against it.  $2 is just informative, indicating whether
# we're checking the NIS domain.  $3 is to pass on.

proc check_nis_domain {
	setvar nisdomain = $(domainname)
	setvar realdomain = $(echo $nisdomain | sed 's/[^.]*\.//)
	if test "x$realdomain" != "x"  {
		echo "Hostname $1 can be fully qualified using NIS$2 domain"
		echo "	$nisdomain"
		echo "resulting in the name"
		echo "	$1.$realdomain"
		echo "but this is bad practice.\n"
		suggest_fix_and_exit $1 $realdomain $3
	}
}

# Goal: try to fully qualify `hostname` as sendmail would.
# Algorithm (stop as soon as a name with a dot is found):
#    1. gethostbyname (simulate with getent hosts)
#    2. fall back to individual hosts: methods in nsswitch.conf, using
#       only those that are configured, in their configured order
#       * files (parse /etc/hosts directly)
#       * dns (parse nslookup output)
#       * nis (parse ypmatch output)
#    3. fall back to the NIS domain name.
# If none of the above succeed, give up.  Recommend:
#    a. the domain entry in /etc/resolv.conf, if one exists
#    b. "pick.some.domain"

setvar myhostname = $(hostname)

check_gethostbyname $myhostname

setvar hosts_line = $(sed -n -e 's/^hosts:\([^#]*\).*/\1/p' /etc/nsswitch.conf)
setvar first_hosts_entry = $(echo $hosts_line | awk '{print $1})
setvar nis_domains = """"

for entry in [$hosts_line]
{
	match $entry {
	with files
		check_hosts_file $myhostname
		
	with dns
		check_dns $myhostname
		
	with nis
		check_nis $myhostname
		setvar nis_domains = ""$nis_domains nis""
		
	}
}

for entry in [$nis_domains]
{
	match $entry {
	with nis
		check_nis_domain $myhostname "" $first_hosts_entry
		
	}
}

setvar realdomain = $(awk '$1 ~ /^domain/ {print $2}' 2>/dev/null )
match $realdomain {
with *.*
	# OK
	
with *
	setvar realdomain = ""pick.some.domain""
	
}

echo "Hostname $myhostname could not be fully qualified."
suggest_fix_and_exit $myhostname $realdomain $first_hosts_entry