Allow CNAME records when specified as MINIO_PUBLIC_IPS (#8662)

This is necessary for `m3` global bucket support

cmd/common-main.go

@@ -188,7 +188,6 @@ func handleCommonEnvVars() {
 				for _, addr := range addrs {
 					domainIPs.Add(addr)
 				}
-				continue
 			}
 			domainIPs.Add(endpoint)
 		}

cmd/config/etcd/dns/etcd_dns.go

@@ -154,6 +154,8 @@ func (c *CoreDNS) list(key string) ([]SrvRecord, error) {
 
 // Put - Adds DNS entries into etcd endpoint in CoreDNS etcd message format.
 func (c *CoreDNS) Put(bucket string) error {
+	c.Delete(bucket) // delete any existing entries.
+
 	for ip := range c.domainIPs {
 		bucketMsg, err := newCoreDNSMsg(ip, c.domainPort, defaultTTL)
 		if err != nil {

cmd/endpoint.go

@@ -694,17 +694,23 @@ func updateDomainIPs(endPoints set.StringSet) {
 				continue
 			}
 		}
-		IPs, err := getHostIP(host)
-		if err != nil {
-			continue
+
+		if net.ParseIP(host) == nil {
+			IPs, err := getHostIP(host)
+			if err != nil {
+				continue
+			}
+
+			IPsWithPort := IPs.ApplyFunc(func(ip string) string {
+				return net.JoinHostPort(ip, port)
+			})
+
+			ipList = ipList.Union(IPsWithPort)
 		}
 
-		IPsWithPort := IPs.ApplyFunc(func(ip string) string {
-			return net.JoinHostPort(ip, port)
-		})
-
-		ipList = ipList.Union(IPsWithPort)
+		ipList.Add(net.JoinHostPort(host, port))
 	}
+
 	globalDomainIPs = ipList.FuncMatch(func(ip string, matchString string) bool {
 		host, _, err := net.SplitHostPort(ip)
 		if err != nil {