Remove early yields in _iter_hosts in dhcp agent

There were early yields in the DHCP agent to handling skipping
lease setup for certain IPv6 addresses. However, the setup for
name resolution in _output_addn_hosts_file depends on the same
function so certain IPv6 addresses weren't getting name resolution.

This patch adjusts the function to return a flag indicating that
DHCP isn't required for the port so the callers setting up reservations
can skip based on that and the name resolution setup can continue
as normal.

Change-Id: I81b4669eadaa9119e08c6a5e1d2a7b5959babdcc
Closes-Bug: #1498665

neutron/agent/linux/dhcp.py

@@ -512,6 +512,7 @@ class Dnsmasq(DhcpLocalProcess):
                     # an IPv6 address because of stateless DHCPv6 network.
             host_name,  # Host name.
             name,  # Canonical hostname in the format 'hostname[.domain]'.
+            no_dhcp,  # A flag indicating that the address doesn't need DHCP.
         )
         """
         v6_nets = dict((subnet.id, subnet) for subnet in
@@ -526,17 +527,11 @@ class Dnsmasq(DhcpLocalProcess):
             if dns_assignment:
                 dns_ip_map = {d.ip_address: d for d in dns_assignment}
             for alloc in fixed_ips:
-                # Note(scollins) Only create entries that are
-                # associated with the subnet being managed by this
-                # dhcp agent
+                no_dhcp = False
                 if alloc.subnet_id in v6_nets:
                     addr_mode = v6_nets[alloc.subnet_id].ipv6_address_mode
-                    if addr_mode == constants.IPV6_SLAAC:
-                        continue
-                    elif addr_mode == constants.DHCPV6_STATELESS:
-                        alloc = hostname = fqdn = None
-                        yield (port, alloc, hostname, fqdn)
-                        continue
+                    no_dhcp = addr_mode in (constants.IPV6_SLAAC,
+                                            constants.DHCPV6_STATELESS)
 
                 # If dns_name attribute is supported by ports API, return the
                 # dns_assignment generated by the Neutron server. Otherwise,
@@ -550,7 +545,7 @@ class Dnsmasq(DhcpLocalProcess):
                     fqdn = hostname
                     if self.conf.dhcp_domain:
                         fqdn = '%s.%s' % (fqdn, self.conf.dhcp_domain)
-                yield (port, alloc, hostname, fqdn)
+                yield (port, alloc, hostname, fqdn, no_dhcp)
 
     def _get_port_extra_dhcp_opts(self, port):
         return getattr(port, edo_ext.EXTRADHCPOPTS, False)
@@ -582,9 +577,10 @@ class Dnsmasq(DhcpLocalProcess):
             timestamp = int(time.time()) + self.conf.dhcp_lease_duration
         dhcp_enabled_subnet_ids = [s.id for s in self.network.subnets
                                    if s.enable_dhcp]
-        for (port, alloc, hostname, name) in self._iter_hosts():
-            # don't write ip address which belongs to a dhcp disabled subnet.
-            if not alloc or alloc.subnet_id not in dhcp_enabled_subnet_ids:
+        for (port, alloc, hostname, name, no_dhcp) in self._iter_hosts():
+            # don't write ip address which belongs to a dhcp disabled subnet
+            # or an IPv6 SLAAC/stateless subnet
+            if no_dhcp or alloc.subnet_id not in dhcp_enabled_subnet_ids:
                 continue
 
             ip_address = self._format_address_for_dnsmasq(alloc.ip_address)
@@ -631,8 +627,8 @@ class Dnsmasq(DhcpLocalProcess):
                                    if s.enable_dhcp]
         # NOTE(ihrachyshka): the loop should not log anything inside it, to
         # avoid potential performance drop when lots of hosts are dumped
-        for (port, alloc, hostname, name) in self._iter_hosts():
-            if not alloc:
+        for (port, alloc, hostname, name, no_dhcp) in self._iter_hosts():
+            if no_dhcp:
                 if self._get_port_extra_dhcp_opts(port):
                     buf.write('%s,%s%s\n' %
                               (port.mac_address, 'set:', port.id))
@@ -726,7 +722,7 @@ class Dnsmasq(DhcpLocalProcess):
         file.
         """
         buf = six.StringIO()
-        for (port, alloc, hostname, fqdn) in self._iter_hosts():
+        for (port, alloc, hostname, fqdn, no_dhcp) in self._iter_hosts():
             # It is compulsory to write the `fqdn` before the `hostname` in
             # order to obtain it in PTR responses.
             if alloc:

neutron/tests/unit/agent/linux/test_dhcp.py

@@ -148,7 +148,9 @@ class FakePort4(object):
                                   'dddddddd-dddd-dddd-dddd-dddddddddddd'),
                  FakeIPAllocation('ffda:3ba5:a17a:4ba3:0216:3eff:fec2:771d',
                                   'eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee')]
-    dns_assignment = [FakeDNSAssignment('192.168.0.4')]
+    dns_assignment = [
+        FakeDNSAssignment('192.168.0.4'),
+        FakeDNSAssignment('ffda:3ba5:a17a:4ba3:0216:3eff:fec2:771d')]
     mac_address = '00:16:3E:C2:77:1D'
     device_id = 'fake_port4'
 
@@ -213,7 +215,8 @@ class FakeV6PortExtraOpt(object):
     device_owner = 'foo3'
     fixed_ips = [FakeIPAllocation('ffea:3ba5:a17a:4ba3:0216:3eff:fec2:771d',
                                   'eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee')]
-    dns_assignment = []
+    dns_assignment = [
+        FakeDNSAssignment('ffea:3ba5:a17a:4ba3:0216:3eff:fec2:771d')]
     mac_address = '00:16:3e:c2:77:1d'
     device_id = 'fake_port6'
 
@@ -232,7 +235,9 @@ class FakeDualPortWithV6ExtraOpt(object):
                                   'dddddddd-dddd-dddd-dddd-dddddddddddd'),
                  FakeIPAllocation('ffea:3ba5:a17a:4ba3:0216:3eff:fec2:771d',
                                   'eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee')]
-    dns_assignment = [FakeDNSAssignment('192.168.0.3')]
+    dns_assignment = [
+        FakeDNSAssignment('192.168.0.3'),
+        FakeDNSAssignment('ffea:3ba5:a17a:4ba3:0216:3eff:fec2:771d')]
     mac_address = '00:16:3e:c2:77:1d'
     device_id = 'fake_port6'