pkg,plugins: update for Result struct Interface index changes

It's a pointer now, so we need to use the helper function to set
the field and also test for nil before accessing it.

plugins/meta/portmap/main.go

@@ -164,9 +164,14 @@ func parseConfig(stdin []byte, ifName string) (*PortMapConf, error) {
 			}
 
 			// Skip known non-sandbox interfaces
-			intIdx := ip.Interface
-			if intIdx >= 0 && intIdx < len(conf.PrevResult.Interfaces) && conf.PrevResult.Interfaces[intIdx].Name != ifName {
-				continue
+			if ip.Interface != nil {
+				intIdx := *ip.Interface
+				if intIdx >= 0 &&
+					intIdx < len(conf.PrevResult.Interfaces) &&
+					(conf.PrevResult.Interfaces[intIdx].Name != ifName ||
+						conf.PrevResult.Interfaces[intIdx].Sandbox == "") {
+					continue
+				}
 			}
 			switch ip.Version {
 			case "6":

plugins/meta/portmap/portmap_integ_test.go

@@ -134,7 +134,8 @@ var _ = Describe("portmap integration tests", func() {
 		var contIP net.IP
 
 		for _, ip := range result.IPs {
-			if result.Interfaces[ip.Interface].Sandbox == "" {
+			intfIndex := *ip.Interface
+			if result.Interfaces[intfIndex].Sandbox == "" {
 				continue
 			}
 			contIP = ip.Address.IP

plugins/meta/portmap/portmap_test.go

@@ -124,6 +124,34 @@ var _ = Describe("portmapping configuration", func() {
 			_, err := parseConfig(configBytes, "container")
 			Expect(err).To(MatchError("Invalid host port number: 0"))
 		})
+
+		It("Does not fail on missing prevResult interface index", func() {
+			configBytes := []byte(`{
+	"name": "test",
+	"type": "portmap",
+	"cniVersion": "0.3.1",
+	"runtimeConfig": {
+		"portMappings": [
+			{ "hostPort": 8080, "containerPort": 80, "protocol": "tcp"}
+		]
+	},
+	"conditionsV4": ["a", "b"],
+	"prevResult": {
+		"interfaces": [
+			{"name": "host"}
+		],
+		"ips": [
+			{
+				"version": "4",
+				"address": "10.0.0.1/24",
+				"gateway": "10.0.0.1"
+			}
+		]
+	}
+}`)
+			_, err := parseConfig(configBytes, "container")
+			Expect(err).NotTo(HaveOccurred())
+		})
 	})
 
 	Describe("Generating chains", func() {