network: use `qubes-primary-dns` QubesDB entry if present

For a long time the DNS address was the same as default gateway. This is
still the case in R3.x, but using `qubes-gateway` configuration
parameter for it is misleading. It should be up to dom0 to provide DNS
address (whether the value is the same as gateway or not).

Fixes QubesOS/qubes-issues#1817

network/setup-ip

@@ -13,6 +13,7 @@ ip=`/usr/bin/qubesdb-read /qubes-ip 2> /dev/null`
 if [ x$ip != x ]; then
     netmask=`/usr/bin/qubesdb-read /qubes-netmask`
     gateway=`/usr/bin/qubesdb-read /qubes-gateway`
+    primary_dns=`/usr/bin/qubesdb-read /qubes-primary-dns 2>/dev/null || echo $gateway`
     secondary_dns=`/usr/bin/qubesdb-read /qubes-secondary-dns`
     /sbin/ethtool -K $INTERFACE sg off
     /sbin/ethtool -K $INTERFACE tx off
@@ -39,7 +40,7 @@ method=manual
 may-fail=false
 __EOF__
         if [ "x$disabledns" != "x1" ]; then
-            echo "dns=$gateway;$secondary_dns" >> $nm_config
+            echo "dns=$primary_dns;$secondary_dns" >> $nm_config
         fi
         if [ "x$disablegw" != "x1" ]; then
             echo "addresses1=$ip;32;$gateway" >> $nm_config
@@ -58,7 +59,7 @@ __EOF__
         if ! grep -rq "^/etc/resolv[.]conf$" "${PROTECTED_FILE_LIST}" 2>/dev/null; then
         echo > /etc/resolv.conf
             if [ "x$disabledns" != "x1" ]; then
-                echo "nameserver $gateway" > /etc/resolv.conf
+                echo "nameserver $primary_dns" > /etc/resolv.conf
                 echo "nameserver $secondary_dns" >> /etc/resolv.conf
             fi
         fi
@@ -67,8 +68,9 @@ __EOF__
     if [ "x$network" != "x" ] && [ "x$disabledns" != "x1" ]; then
         gateway=$(qubesdb-read /qubes-netvm-gateway)
         netmask=$(qubesdb-read /qubes-netvm-netmask)
+        primary_dns=$(qubesdb-read /qubes-netvm-primary-dns 2>/dev/null || echo $gateway)
         secondary_dns=$(qubesdb-read /qubes-netvm-secondary-dns)
-        echo "NS1=$gateway" > /var/run/qubes/qubes-ns
+        echo "NS1=$primary_dns" > /var/run/qubes/qubes-ns
         echo "NS2=$secondary_dns" >> /var/run/qubes/qubes-ns
         /usr/lib/qubes/qubes-setup-dnat-to-ns
     fi

vm-init.d/qubes-core-netvm

@@ -26,9 +26,10 @@ start()
 	if [ "x$network" != "x" ]; then
 		gateway=$(/usr/bin/qubesdb-read /qubes-netvm-gateway)
 		netmask=$(/usr/bin/qubesdb-read /qubes-netvm-netmask)
+		primary_dns=$(/usr/bin/qubesdb-read /qubes-netvm-primary-dns || echo $gateway)
 		secondary_dns=$(/usr/bin/qubesdb-read /qubes-netvm-secondary-dns)
 		modprobe netbk 2> /dev/null || modprobe xen-netback
-		echo "NS1=$gateway" > /var/run/qubes/qubes-ns
+		echo "NS1=$primary_dns" > /var/run/qubes/qubes-ns
 		echo "NS2=$secondary_dns" >> /var/run/qubes/qubes-ns
 		/usr/lib/qubes/qubes-setup-dnat-to-ns
 		echo "1" > /proc/sys/net/ipv4/ip_forward

vm-systemd/network-proxy-setup.sh

@@ -12,9 +12,10 @@ if [ "x$network" != "x" ]; then
 
     gateway=$(qubesdb-read /qubes-netvm-gateway)
     netmask=$(qubesdb-read /qubes-netvm-netmask)
+    primary_dns=$(qubesdb-read /qubes-netvm-primary-dns 2>/dev/null || echo $gateway)
     secondary_dns=$(qubesdb-read /qubes-netvm-secondary-dns)
     modprobe netbk 2> /dev/null || modprobe xen-netback || "${modprobe_fail_cmd}"
-    echo "NS1=$gateway" > /var/run/qubes/qubes-ns
+    echo "NS1=$primary_dns" > /var/run/qubes/qubes-ns
     echo "NS2=$secondary_dns" >> /var/run/qubes/qubes-ns
     /usr/lib/qubes/qubes-setup-dnat-to-ns
     echo "1" > /proc/sys/net/ipv4/ip_forward