Fix hostname env.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/server/container_create.go

@@ -334,6 +334,17 @@ func (c *criService) generateContainerSpec(id string, sandboxID string, sandboxP
 		g.AddProcessEnv("TERM", "xterm")
 	}
 
+	// Add HOSTNAME env.
+	hostname := sandboxConfig.GetHostname()
+	if sandboxConfig.GetLinux().GetSecurityContext().GetNamespaceOptions().GetNetwork() == runtime.NamespaceMode_NODE &&
+		hostname == "" {
+		hostname, err = c.os.Hostname()
+		if err != nil {
+			return nil, err
+		}
+	}
+	g.AddProcessEnv(hostnameEnv, hostname)
+
 	// Apply envs from image config first, so that envs from container config
 	// can override them.
 	if err := addImageEnvs(&g, imageConfig.Env); err != nil {

pkg/server/container_create_test.go

@@ -979,3 +979,45 @@ func TestMaskedAndReadonlyPaths(t *testing.T) {
 		assert.Equal(t, test.expectedReadonly, spec.Linux.ReadonlyPaths)
 	}
 }
+
+func TestHostname(t *testing.T) {
+	testID := "test-id"
+	testSandboxID := "sandbox-id"
+	testPid := uint32(1234)
+	config, sandboxConfig, imageConfig, specCheck := getCreateContainerTestData()
+	c := newTestCRIService()
+	c.os.(*ostesting.FakeOS).HostnameFn = func() (string, error) {
+		return "real-hostname", nil
+	}
+	for desc, test := range map[string]struct {
+		hostname    string
+		networkNs   runtime.NamespaceMode
+		expectedEnv string
+	}{
+		"should add HOSTNAME=sandbox.Hostname for pod network namespace": {
+			hostname:    "test-hostname",
+			networkNs:   runtime.NamespaceMode_POD,
+			expectedEnv: "HOSTNAME=test-hostname",
+		},
+		"should add HOSTNAME=sandbox.Hostname for host network namespace": {
+			hostname:    "test-hostname",
+			networkNs:   runtime.NamespaceMode_NODE,
+			expectedEnv: "HOSTNAME=test-hostname",
+		},
+		"should add HOSTNAME=os.Hostname for host network namespace if sandbox.Hostname is not set": {
+			hostname:    "",
+			networkNs:   runtime.NamespaceMode_NODE,
+			expectedEnv: "HOSTNAME=real-hostname",
+		},
+	} {
+		t.Logf("TestCase %q", desc)
+		sandboxConfig.Hostname = test.hostname
+		sandboxConfig.Linux.SecurityContext = &runtime.LinuxSandboxSecurityContext{
+			NamespaceOptions: &runtime.NamespaceOption{Network: test.networkNs},
+		}
+		spec, err := c.generateContainerSpec(testID, testSandboxID, testPid, config, sandboxConfig, imageConfig, nil)
+		require.NoError(t, err)
+		specCheck(t, testID, testSandboxID, testPid, spec)
+		assert.Contains(t, spec.Process.Env, test.expectedEnv)
+	}
+}

pkg/server/helpers.go

@@ -97,6 +97,8 @@ const (
 	etcHosts = "/etc/hosts"
 	// resolvConfPath is the abs path of resolv.conf on host or container.
 	resolvConfPath = "/etc/resolv.conf"
+	// hostnameEnv is the key for HOSTNAME env.
+	hostnameEnv = "HOSTNAME"
 )
 
 const (