protokube: support writing AAAA records to /etc/hosts

Though we likely want to stop using this code altogether, it is still
used on GCE (for now).  dns-controller will "gossip" AAAA records, and
they are valid (and work) in /etc/hosts.

Co-authored-by: John Gardiner Myers <[email protected]>

protokube/pkg/gossip/dns/hosts.go

@@ -38,20 +38,26 @@ func (h *HostsFile) Update(snapshot *DNSViewSnapshot) error {
 			klog.Warningf("ignoring unexpected lines in /etc/hosts: %v", badLines)
 		}
 
+		hostsToAddr := make(map[string][]string)
 		zones := snapshot.ListZones()
 		for _, zone := range zones {
 			records := snapshot.RecordsForZone(zone)
 
 			for _, record := range records {
-				if record.RrsType != "A" {
+				switch record.RrsType {
+				case "A", "AAAA":
+					hostsToAddr[record.Name] = append(hostsToAddr[record.Name], record.Rrdatas...)
+
+				default:
 					klog.Warningf("skipping record of unhandled type: %v", record)
-					continue
 				}
-
-				hostMap.ReplaceRecords(record.Name, record.Rrdatas)
 			}
 		}
 
+		for host, addresses := range hostsToAddr {
+			hostMap.ReplaceRecords(host, addresses)
+		}
+
 		return hostMap, nil
 	}