backport of commit 067afcd (#24204)

Co-authored-by: Daniel Bennett <dbennett@hashicorp.com>

command/agent/consul/connect.go

@@ -154,7 +154,7 @@ func connectSidecarProxy(info structs.AllocInfo, proxy *structs.ConsulProxy, cPo
 		Mode:                mode,
 		LocalServiceAddress: proxy.LocalServiceAddress,
 		LocalServicePort:    proxy.LocalServicePort,
-		Config:              connectProxyConfig(proxy.Config, cPort, info),
+		Config:              connectProxyConfig(proxy.Config, cPort, info, networks),
 		Upstreams:           connectUpstreams(proxy.Upstreams),
 		Expose:              expose,
 	}, nil
@@ -243,11 +243,13 @@ func connectMeshGateway(in structs.ConsulMeshGateway) api.MeshGatewayConfig {
 	return gw
 }
 
-func connectProxyConfig(cfg map[string]interface{}, port int, info structs.AllocInfo) map[string]interface{} {
+func connectProxyConfig(cfg map[string]interface{}, port int, info structs.AllocInfo, networks structs.Networks) map[string]interface{} {
 	if cfg == nil {
 		cfg = make(map[string]interface{})
 	}
-	cfg["bind_address"] = "0.0.0.0"
+	if _, ok := cfg["bind_address"]; !ok {
+		cfg["bind_address"] = connectProxyBindAddress(networks)
+	}
 	cfg["bind_port"] = port
 
 	tags := map[string]string{
@@ -260,6 +262,15 @@ func connectProxyConfig(cfg map[string]interface{}, port int, info structs.Alloc
 	return cfg
 }
 
+func connectProxyBindAddress(networks structs.Networks) string {
+	for _, n := range networks {
+		if n.Mode == "bridge" && n.IsIPv6() {
+			return "::"
+		}
+	}
+	return "0.0.0.0"
+}
+
 // injectNomadInfo merges nomad information into cfg=>envoy_stats_tags
 //
 // cfg must not be nil

command/agent/consul/connect_test.go

@@ -409,22 +409,44 @@ func TestConnect_connectProxyConfig(t *testing.T) {
 	ci.Parallel(t)
 
 	t.Run("nil map", func(t *testing.T) {
-		require.Equal(t, map[string]interface{}{
+		must.Eq(t, map[string]any{
 			"bind_address":     "0.0.0.0",
 			"bind_port":        42,
 			"envoy_stats_tags": []string{"nomad.alloc_id=test_alloc1"},
-		}, connectProxyConfig(nil, 42, structs.AllocInfo{AllocID: "test_alloc1"}))
+		}, connectProxyConfig(nil, 42, structs.AllocInfo{AllocID: "test_alloc1"}, nil))
 	})
 
 	t.Run("pre-existing map", func(t *testing.T) {
-		require.Equal(t, map[string]interface{}{
+		must.Eq(t, map[string]any{
 			"bind_address":     "0.0.0.0",
 			"bind_port":        42,
 			"foo":              "bar",
 			"envoy_stats_tags": []string{"nomad.alloc_id=test_alloc2"},
-		}, connectProxyConfig(map[string]interface{}{
+		}, connectProxyConfig(map[string]any{
 			"foo": "bar",
-		}, 42, structs.AllocInfo{AllocID: "test_alloc2"}))
+		}, 42, structs.AllocInfo{AllocID: "test_alloc2"}, nil))
+	})
+
+	t.Run("bind_address override", func(t *testing.T) {
+		must.Eq(t, map[string]any{
+			"bind_address":     "anything",
+			"bind_port":        42,
+			"envoy_stats_tags": []string{"nomad.alloc_id=custom_bind_alloc"},
+		}, connectProxyConfig(map[string]any{
+			"bind_address": "anything",
+		}, 42, structs.AllocInfo{AllocID: "custom_bind_alloc"}, nil))
+	})
+
+	t.Run("bind_address ipv6", func(t *testing.T) {
+		must.Eq(t, map[string]any{
+			"bind_address":     "::",
+			"bind_port":        42,
+			"envoy_stats_tags": []string{"nomad.alloc_id=ipv6_alloc"},
+		}, connectProxyConfig(map[string]any{
+			"bind_address": "::",
+		}, 42, structs.AllocInfo{AllocID: "ipv6_alloc"}, []*structs.NetworkResource{
+			{Mode: "bridge", IP: "fd00:a110:c8::1"},
+		}))
 	})
 }
 

nomad/structs/structs.go

@@ -3037,6 +3037,11 @@ func (n *NetworkResource) PortLabels() map[string]int {
 	return labelValues
 }
 
+func (n *NetworkResource) IsIPv6() bool {
+	ip := net.ParseIP(n.IP)
+	return ip != nil && ip.To4() == nil
+}
+
 // Networks defined for a task on the Resources struct.
 type Networks []*NetworkResource