pkg/invoke: ensure that custom env vars are prepended to the env

pkg/invoke/args.go

@@ -57,13 +57,16 @@ func (args *Args) AsEnv() []string {
 		pluginArgsStr = stringify(args.PluginArgs)
 	}
 
-	env = append(env,
-		"CNI_COMMAND="+args.Command,
-		"CNI_CONTAINERID="+args.ContainerID,
-		"CNI_NETNS="+args.NetNS,
-		"CNI_ARGS="+pluginArgsStr,
-		"CNI_IFNAME="+args.IfName,
-		"CNI_PATH="+args.Path)
+	// Ensure that the custom values are first, so any value present in
+	// the process environment won't override them.
+	env = append([]string{
+		"CNI_COMMAND=" + args.Command,
+		"CNI_CONTAINERID=" + args.ContainerID,
+		"CNI_NETNS=" + args.NetNS,
+		"CNI_ARGS=" + pluginArgsStr,
+		"CNI_IFNAME=" + args.IfName,
+		"CNI_PATH=" + args.Path,
+	}, env...)
 	return env
 }
 

pkg/invoke/args_test.go

@@ -0,0 +1,60 @@
+// Copyright 2017 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package invoke_test
+
+import (
+	"os"
+
+	"github.com/containernetworking/cni/pkg/invoke"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Args", func() {
+	Describe("AsEnv", func() {
+		It("places the CNI_ environment variables ahead of any ambient variables", func() {
+			args := invoke.Args{
+				Command:     "ADD",
+				ContainerID: "some-container-id",
+				NetNS:       "/some/netns/path",
+				PluginArgs: [][2]string{
+					[2]string{"KEY1", "VALUE1"},
+					[2]string{"KEY2", "VALUE2"},
+				},
+				IfName: "eth7",
+				Path:   "/some/cni/path",
+			}
+			const numCNIEnvVars = 6
+
+			latentVars := os.Environ()
+
+			cniEnv := args.AsEnv()
+			Expect(cniEnv).To(HaveLen(len(latentVars) + numCNIEnvVars))
+			Expect(cniEnv[0:numCNIEnvVars]).To(Equal([]string{
+				"CNI_COMMAND=ADD",
+				"CNI_CONTAINERID=some-container-id",
+				"CNI_NETNS=/some/netns/path",
+				"CNI_ARGS=KEY1=VALUE1;KEY2=VALUE2",
+				"CNI_IFNAME=eth7",
+				"CNI_PATH=/some/cni/path",
+			}))
+
+			for i := range latentVars {
+				Expect(cniEnv[numCNIEnvVars+i]).To(Equal(latentVars[i]))
+			}
+		})
+	})
+})