From 11f03096d5b8ca4b1b4e407c679c47fd33242b62 Mon Sep 17 00:00:00 2001
From: Marc Fiuczynski <mef@cs.princeton.edu>
Date: Fri, 1 Feb 2008 21:03:12 +0000
Subject: [PATCH] Generalized logic for setting up /etc/resolv.conf and
 /etc/hosts depending on whether myplc has DNS enabled or not.

If PLC's DNS (dnsmasq) is enabled, then:

1) /etc/resolv.conf will point at the local host and
   /etc/plc_resolv.conf points either at:

  a) the plc-config-tty configured DNS servers, or
  b) the servers specific in the original /etc/resolv.conf

2) /etc/plc_hosts will contain a list of the currently configured
   nodes. (This needs to be fixed, as the set of nodes and their
   network settings can change).

If PLC's DNS (dnsmasq) is disabled, then /etc/resolv.conf will either :
  a) remain untouched if PLC_NET_DNS{1,2} are not specified, or
  b) be backed up to /etc/resolv_plc.backup and a new /etc/resolv.conf
     will be generated with the PLC_NET_DNS{1,2} servers configured by
     plc-config-tty
---
 plc.d/dns | 67 ++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 56 insertions(+), 11 deletions(-)

diff --git a/plc.d/dns b/plc.d/dns
index b819e32..b195809 100755
--- a/plc.d/dns
+++ b/plc.d/dns
@@ -15,32 +15,77 @@
 . /etc/plc.d/functions
 . /etc/planetlab/plc_config
 
+SIGNATURE="; generated by /etc/plc.d/dns --- DO NOT REMOVE THIS TEXT!"
+
 # Be verbose
 set -x
 
 case "$1" in
     start)
-	[ $PLC_DNS_ENABLED -ne 1 ] && exit 0
+	if [ $PLC_DNS_ENABLED -eq 1 ] ; then
+	    MESSAGE=$"Starting DNS server"
+	    dialog "$MESSAGE"
 
-	MESSAGE=$"Starting DNS server"
-	dialog "$MESSAGE"
+	    dns-config
+	    check
+	fi
 
-	dns-config
-	check
+	# Set up nameservers
+	if [ -n "$PLC_NET_DNS1" -o -n "$PLC_NET_DNS2" ] ; then
+	    MESSAGE=$"Configuring resolv.conf"
+	    dialog "$MESSAGE"
 
-	plc_daemon dnsmasq
-	check
+	    rfile=$(mktemp)
+	    (
+		echo $SIGNATURE
+		[ -n "$PLC_NET_DNS1" ] && echo "nameserver $PLC_NET_DNS1"
+		[ -n "$PLC_NET_DNS2" -a "$PLC_NET_DNS1" != "$PLC_NET_DNS2" ] && echo "nameserver $PLC_NET_DNS2"
+	    ) > $rfile
+	    
+	    if [ $PLC_DNS_ENABLED -eq 1 ] ; then
+		ourfile=$(grep "$SIGNATURE" /etc/resolv.conf| wc -l)
+		if [ $ourfile -eq 0 ] ; then
+		    cp /etc/resolv.conf /etc/plc_resolv.conf
+		fi
+	    else
+		cp /etc/resolv.conf /etc/resolv_plc.backup
+	    fi
+	    mv -f $rfile /etc/resolv.conf
+	    chmod 444 /etc/resolv.conf
+	fi
+
+	if [ $PLC_DNS_ENABLED -eq 1 ] ; then
+	    plc_daemon dnsmasq
+	    check
+	fi
 
 	result "$MESSAGE"
 	;;
 
     stop)
-	[ $PLC_DNS_ENABLED -ne 1 ] && exit 0
-	MESSAGE=$"Stopping DNS server"
+	MESSAGE=$"Reverting /etc/resolv.conf and /etc/hosts"
 	dialog "$MESSAGE"
+	if [ $PLC_DNS_ENABLED -eq 1 ] ; then
+	    if [ -f "/etc/plc_resolv.conf" ] ; then
+		ourfile=$(grep "$SIGNATURE" /etc/plc_resolv.conf| wc -l)
+		if [ $ourfile -ne 0 ] ; then 
+		    dialog "WARNING: original /etc/resolv.conf was generated by etc/plc.d/dns"		
+		fi
+		mv -f /etc/plc_resolv.conf /etc/resolv.conf
+	    fi
+	    [ -f "/etc/plc_hosts" ] && rm -f /etc/plc_hosts
+	fi
+	if [ $PLC_DNS_ENABLED -eq 0 -a -f "/etc/resolv_plc.backup" ] ; then
+	    mv -f /etc/resolv_plc.backup /etc/resolv.conf
+	fi
+
+	if [ $PLC_DNS_ENABLED -eq 1 ] ; then
+	    MESSAGE=$"Stopping DNS server"
+	    dialog "$MESSAGE"
 
-	killproc plc_dnsmasq
-	check
+	    killproc plc_dnsmasq
+	    check
+	fi
 
 	result "$MESSAGE"
 	;;
-- 
2.43.0