cloudmap: resolve hostnames before registering (#137)

AWS load balancers are DNS-based rather than IP-based.
This means that we need to resolve those host names before registering
endpoints to the service registry, as they only accept IPs.

This commit introduces this change and allows the operator to work fine
with EKS as well.

Author: asimpleidea

pkg/servregistry/aws/cloudmap/handler.go

@@ -1,4 +1,4 @@
-// Copyright © 2021 Cisco
+// Copyright © 2021, 2022 Cisco
 //
 // SPDX-License-Identifier: Apache-2.0
 //
@@ -23,6 +23,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"fmt"
+	"net"
 	"time"
 
 	sr "github.com/CloudNativeSDWAN/cnwan-operator/pkg/servregistry"
@@ -96,20 +97,50 @@ func (h *Handler) ExtractData(ns *corev1.Namespace, serv *corev1.Service) (*sr.N
 
 	// Get the endpoints from the service
 	// First, build the ips
-	ips := []string{}
-	ips = append(ips, serv.Spec.ExternalIPs...)
+	// De-duplicate and chek the original host name
+	ipsSet := map[string]string{}
+
+	for _, ip := range serv.Spec.ExternalIPs {
+		ipsSet[ip] = ""
+	}
 
 	// Get data from load balancers
 	for _, ing := range serv.Status.LoadBalancer.Ingress {
-		ips = append(ips, ing.IP)
+		if ing.IP != "" {
+			ipsSet[ing.IP] = ing.Hostname
+			continue
+		}
+
+		if ing.Hostname != "" {
+			addrs, err := net.LookupHost(ing.Hostname)
+			if err != nil {
+				// TODO: this needs to be logged
+				continue
+			}
+
+			// TODO: log to what this has been resolved to.
+			for _, addr := range addrs {
+				if _, exists := ipsSet[addr]; !exists {
+					ipsSet[addr] = ing.Hostname
+				}
+			}
+		}
 	}
 
 	endpointsData := []*sr.Endpoint{}
 	for _, port := range serv.Spec.Ports {
-		for _, ip := range ips {
+		for addr, hostname := range ipsSet {
+			metadata := map[string]string{}
+
+			if hostname != "" {
+				metadata = map[string]string{
+					"cnwan.io/hostname": hostname,
+					"cnwan.io/resolved": time.Now().Format(time.RFC822),
+				}
+			}
 
 			// Create an hashed name for this
-			toBeHashed := fmt.Sprintf("%s-%d", ip, port.Port)
+			toBeHashed := fmt.Sprintf("%s-%d", addr, port.Port)
 			h := sha256.New()
 			h.Write([]byte(toBeHashed))
 			hash := hex.EncodeToString(h.Sum(nil))
@@ -120,9 +151,9 @@ func (h *Handler) ExtractData(ns *corev1.Namespace, serv *corev1.Service) (*sr.N
 				Name:     name,
 				NsName:   namespaceData.Name,
 				ServName: serviceData.Name,
-				Address:  ip,
+				Address:  addr,
 				Port:     port.Port,
-				Metadata: map[string]string{},
+				Metadata: metadata,
 			})
 		}
 	}