gateway: fix the dns discovery method

strip the scheme from the endpoints to have a clean hostname for TCP proxy

Fixes #7452

etcdmain/gateway.go

@@ -24,6 +24,7 @@ import (
 	"github.com/coreos/etcd/pkg/transport"
 	"github.com/coreos/etcd/proxy/tcpproxy"
 	"github.com/spf13/cobra"
+    "strings"
 )
 
 var (
@@ -77,6 +78,23 @@ func newGatewayStartCommand() *cobra.Command {
 	return &cmd
 }
 
+func stripSchema(eps []string) []string {
+    var endpoints []string
+
+    for _, ep := range eps {
+
+        if strings.HasPrefix(ep, "https://") {
+            ep = ep[len("https://"):]
+        } else if strings.HasPrefix(ep, "http://") {
+            ep = ep[len("http://"):]
+        }
+
+        endpoints = append(endpoints, ep)
+    }
+
+    return endpoints
+}
+
 func startGateway(cmd *cobra.Command, args []string) {
 	endpoints := gatewayEndpoints
 	if gatewayDNSCluster != "" {
@@ -101,6 +119,9 @@ func startGateway(cmd *cobra.Command, args []string) {
 		}
 	}
 
+    // Strip the schema from the endpoints because we start just a TCP proxy
+    endpoints = stripSchema(endpoints)
+
 	if len(endpoints) == 0 {
 		plog.Fatalf("no endpoints found")
 	}