shim: Add trace config option

Add a new `enable_tracing` option to `configuration.toml` to enable
shim tracing.

Fixes #934.

Signed-off-by: James O. D. Hunt <[email protected]>

cli/config/configuration.toml.in

@@ -212,6 +212,17 @@ path = "@SHIMPATH@"
 # (default: disabled)
 #enable_debug = true
 
+# If enabled, the shim will create opentracing.io traces and spans.
+# (See https://www.jaegertracing.io/docs/getting-started).
+#
+# Note: By default, the shim runs in a separate network namespace. Therefore,
+# to allow it to send trace details to the Jaeger agent running on the host,
+# it is necessary to set 'disable_new_netns=true' so that it runs in the host
+# network namespace.
+#
+# (default: disabled)
+#enable_tracing = true
+
 [agent.@PROJECT_TYPE@]
 # There is no field for this section. The goal is only to be able to
 # specify which type of agent the user wants to use.

pkg/katautils/config.go

@@ -121,8 +121,9 @@ type runtime struct {
 }
 
 type shim struct {
-	Path  string `toml:"path"`
-	Debug bool   `toml:"enable_debug"`
+	Path    string `toml:"path"`
+	Debug   bool   `toml:"enable_debug"`
+	Tracing bool   `toml:"enable_tracing"`
 }
 
 type agent struct {
@@ -344,6 +345,10 @@ func (s shim) debug() bool {
 	return s.Debug
 }
 
+func (s shim) trace() bool {
+	return s.Tracing
+}
+
 func (n netmon) enable() bool {
 	return n.Enable
 }
@@ -459,6 +464,7 @@ func newShimConfig(s shim) (vc.ShimConfig, error) {
 	return vc.ShimConfig{
 		Path:  path,
 		Debug: s.debug(),
+		Trace: s.trace(),
 	}, nil
 }
 
@@ -710,7 +716,13 @@ func checkNetNsConfig(config oci.RuntimeConfig) error {
 		if config.InterNetworkModel != vc.NetXConnectNoneModel {
 			return fmt.Errorf("config disable_new_netns only works with 'none' internetworking_model")
 		}
+	} else if config.ShimConfig.(vc.ShimConfig).Trace {
+		// Normally, the shim runs in a separate network namespace.
+		// But when tracing, the shim process needs to be able to talk
+		// to the Jaeger agent running in the host network namespace.
+		return errors.New("Shim tracing requires disable_new_netns for Jaeger agent communication")
 	}
+
 	return nil
 }
 

pkg/katautils/config_test.go

@@ -1148,6 +1148,10 @@ func TestShimDefaults(t *testing.T) {
 	assert.False(s.debug())
 	s.Debug = true
 	assert.True(s.debug())
+
+	assert.False(s.trace())
+	s.Tracing = true
+	assert.True(s.trace())
 }
 
 func TestGetDefaultConfigFilePaths(t *testing.T) {
@@ -1538,3 +1542,41 @@ func TestCheckFactoryConfig(t *testing.T) {
 		}
 	}
 }
+
+func TestCheckNetNsConfigShimTrace(t *testing.T) {
+	assert := assert.New(t)
+
+	type testData struct {
+		disableNetNs bool
+		networkModel vc.NetInterworkingModel
+		shimTrace    bool
+		expectError  bool
+	}
+
+	data := []testData{
+		{false, vc.NetXConnectMacVtapModel, false, false},
+		{false, vc.NetXConnectMacVtapModel, true, true},
+		{true, vc.NetXConnectMacVtapModel, true, true},
+		{true, vc.NetXConnectMacVtapModel, false, true},
+		{true, vc.NetXConnectNoneModel, false, false},
+		{true, vc.NetXConnectNoneModel, true, false},
+	}
+
+	for i, d := range data {
+		config := oci.RuntimeConfig{
+			DisableNewNetNs:   d.disableNetNs,
+			InterNetworkModel: d.networkModel,
+			ShimConfig: vc.ShimConfig{
+				Trace: d.shimTrace,
+			},
+		}
+
+		err := checkNetNsConfig(config)
+
+		if d.expectError {
+			assert.Error(err, "test %d (%+v)", i, d)
+		} else {
+			assert.NoError(err, "test %d (%+v)", i, d)
+		}
+	}
+}

virtcontainers/kata_shim.go

@@ -57,5 +57,9 @@ func (s *kataShim) start(sandbox *Sandbox, params ShimParams) (int, error) {
 		args = append(args, "-log", "debug")
 	}
 
+	if config.Trace {
+		args = append(args, "-trace")
+	}
+
 	return startShim(args, params)
 }

virtcontainers/shim.go

@@ -56,6 +56,7 @@ type ShimParams struct {
 type ShimConfig struct {
 	Path  string
 	Debug bool
+	Trace bool
 }
 
 // Set sets a shim type based on the input string.