Added configmap option to disable IPv6 in nginx DNS resolver (#1992)

internal/ingress/controller/template/configmap.go

@@ -144,6 +144,7 @@ func ReadConfig(src map[string]string) config.Configuration {
 	to.HideHeaders = hideHeaderslist
 	to.HTTPRedirectCode = redirectCode
 	to.ProxyStreamResponses = streamResponses
+	to.DisableIpv6DNS = !ing_net.IsIPv6Enabled()
 
 	config := &mapstructure.DecoderConfig{
 		Metadata:         nil,

internal/ingress/controller/template/template.go

@@ -163,11 +163,16 @@ func formatIP(input string) string {
 }
 
 // buildResolvers returns the resolvers reading the /etc/resolv.conf file
-func buildResolvers(input interface{}) string {
+func buildResolvers(res interface{}, disableIpv6 interface{}) string {
 	// NGINX need IPV6 addresses to be surrounded by brackets
-	nss, ok := input.([]net.IP)
+	nss, ok := res.([]net.IP)
 	if !ok {
-		glog.Errorf("expected a '[]net.IP' type but %T was returned", input)
+		glog.Errorf("expected a '[]net.IP' type but %T was returned", res)
+		return ""
+	}
+	no6, ok := disableIpv6.(bool)
+	if !ok {
+		glog.Errorf("expected a 'bool' type but %T was returned", disableIpv6)
 		return ""
 	}
 
@@ -178,14 +183,21 @@ func buildResolvers(input interface{}) string {
 	r := []string{"resolver"}
 	for _, ns := range nss {
 		if ing_net.IsIPV6(ns) {
+			if no6 {
+				continue
+			}
 			r = append(r, fmt.Sprintf("[%v]", ns))
 		} else {
 			r = append(r, fmt.Sprintf("%v", ns))
 		}
 	}
-	r = append(r, "valid=30s;")
+	r = append(r, "valid=30s")
 
-	return strings.Join(r, " ")
+	if no6 {
+		r = append(r, "ipv6=off")
+	}
+
+	return strings.Join(r, " ") + ";"
 }
 
 // buildLocation produces the location string, if the ingress has redirects

internal/ingress/controller/template/template_test.go

@@ -28,6 +28,7 @@ import (
 
 	"encoding/base64"
 	"fmt"
+
 	"k8s.io/ingress-nginx/internal/file"
 	"k8s.io/ingress-nginx/internal/ingress"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/authreq"
@@ -352,7 +353,14 @@ func TestBuildResolvers(t *testing.T) {
 	ipList := []net.IP{ipOne, ipTwo}
 
 	validResolver := "resolver 192.0.0.1 [2001:db8:1234::] valid=30s;"
-	resolver := buildResolvers(ipList)
+	resolver := buildResolvers(ipList, false)
+
+	if resolver != validResolver {
+		t.Errorf("Expected '%v' but returned '%v'", validResolver, resolver)
+	}
+
+	validResolver = "resolver 192.0.0.1 valid=30s ipv6=off;"
+	resolver = buildResolvers(ipList, true)
 
 	if resolver != validResolver {
 		t.Errorf("Expected '%v' but returned '%v'", validResolver, resolver)