FEATURE: /etc/resolv.conf improved handling

`resolv.search` attribute can override the search line.

Only the Frontend has access to the `Kickstart_PublicDNSServers`. For
all other nodes the Frontend will be the first nameserver IFF it is
serving DNS for any network (this was previously the case as well),
but the subsequent nameserver lines will come only from the
`Kickstart_PrivateDNSServers`.

common/src/stack/command/stack/commands/report/host/resolv/__init__.py

@@ -26,34 +26,26 @@ def resolv(self, host):
 			zones[row['network']] = row['zone']
 			dns[row['network']] = row['dns']
 
-		search = None
-		# The default search path should always have the
-		# hosts default network. If a host has no default
-		# network, or if the zone on the default network
-		# is empty, leave the search value out.
-		for intf in self.call('list.host.interface', [host, 'expanded=True']):
-			if intf['default'] is True and intf['zone']:
-				search = intf['zone']
-				break
+		# 'resolv.attr' attribute can be used the specify the search
+		# line
+
+		search = self.getHostAttr(host, 'resolv.search')
+
+		if not search:
+			# Otherwise the search line should be the zone of the
+			# host's default interface.
+			for intf in self.call('list.host.interface', 
+					      [host, 'expanded=True']):
+				if intf['default'] is True and intf['zone']:
+					search = intf['zone']
+					break
+
 		if search:
 			report.append(f'search {search}')
 
-		#
-		# If the default network is 'public' use the
-		# public DNS rather that the server on the boss.
-
-		#
-		# or
-		#
 
-		#
-		# if any network has 'dns' set to true, then the frontend
-		# is serving DNS for that network, so make sure the
-		# frontend is listed as the first DNS server, then list
-		# the public DNS server. The IP address of the DNS server
-		# should be the one on the network that serves out
-		# DNS. Not the primary network of the frontend.
-		#
+		# If any network has 'dns' set to true, list the Frontend as
+		# the first DNS server.
 
 		for row in self.call('list.host.interface', [ host ]):
 			network = row['network']
@@ -65,16 +57,31 @@ def resolv(self, host):
 				report.append(f'nameserver {frontend}')
 				break
 
-		remotedns = self.getHostAttr(host, 'Kickstart_PublicDNSServers')
+		# For the subsequent nameserver lines:
+	        #
+		# Frontend - Use the public DNS and if that doesn't exist use
+		# the private DNS. This is still legacy public/private
+		# HPC-nonsense, but we do this so that setup works and
+		# AWS/Docker does as well.
+		#
+		# Backends - Uses the private DNS, and ignore the public
+		# DNS. By default the private DNS attr is the Frontend which is
+		# already a forwarding nameserver.
+
+		remotedns = None
+		if self.db.getHostAppliance(host) == 'frontend':
+			remotedns = self.getHostAttr(host, 'Kickstart_PublicDNSServers')
+
 		if not remotedns:
 			remotedns = self.getHostAttr(host, 'Kickstart_PrivateDNSServers')
+
 		if remotedns:
 			servers = remotedns.strip().split(',')
 			for server in servers:
 				if server:
 					report.append(f'nameserver {server.strip()}')
 
-		return'\n'.join(report)
+		return '\n'.join(report)
 
 
 	def reportFile(self, file, contents, *, perms=None, host=None):