FC: Fix error of overlong firecracker API unix socket

When sandbox id is too long, it will incur error of overlong firecracker
API unix socket.
In Linux, sun_path could maximumly contains 108 bytes in size.
http://man7.org/linux/man-pages/man7/unix.7.html
So here we try to truncate FC id to only keep the size of UUID(128bit).

Fixes: #2504

Signed-off-by: Penny Zheng <penny.zheng@arm.com>

virtcontainers/fc.go

@@ -180,6 +180,19 @@ func (fc *firecracker) trace(name string) (opentracing.Span, context.Context) {
 	return span, ctx
 }
 
+//At some cases, when sandbox id is too long, it will incur error of overlong
+//firecracker API unix socket(fc.socketPath).
+//In Linux, sun_path could maximumly contains 108 bytes in size.
+//(http://man7.org/linux/man-pages/man7/unix.7.html)
+func (fc *firecracker) truncateID(id string) string {
+	if len(id) > 32 {
+		//truncate the id to only leave the size of UUID(128bit).
+		return id[:32]
+	}
+
+	return id
+}
+
 // For firecracker this call only sets the internal structure up.
 // The sandbox will be created and started through startSandbox().
 func (fc *firecracker) createSandbox(ctx context.Context, id string, networkNS NetworkNamespace, hypervisorConfig *HypervisorConfig, stateful bool) error {
@@ -190,7 +203,7 @@ func (fc *firecracker) createSandbox(ctx context.Context, id string, networkNS N
 
 	//TODO: check validity of the hypervisor config provided
 	//https://github.com/kata-containers/runtime/issues/1065
-	fc.id = id
+	fc.id = fc.truncateID(id)
 	fc.state.set(notReady)
 	fc.config = *hypervisorConfig
 	fc.stateful = stateful

virtcontainers/fc_test.go

@@ -29,3 +29,19 @@ func TestFCGenerateSocket(t *testing.T) {
 	assert.NotEmpty(hvsock.UdsPath)
 	assert.NotZero(hvsock.Port)
 }
+
+func TestFCTruncateID(t *testing.T) {
+	assert := assert.New(t)
+
+	fc := firecracker{}
+
+	testLongID := "3ef98eb7c6416be11e0accfed2f4e6560e07f8e33fa8d31922fd4d61747d7ead"
+	expectedID := "3ef98eb7c6416be11e0accfed2f4e656"
+	id := fc.truncateID(testLongID)
+	assert.Equal(expectedID, id)
+
+	testShortID := "3ef98eb7c6416be11"
+	expectedID = "3ef98eb7c6416be11"
+	id = fc.truncateID(testShortID)
+	assert.Equal(expectedID, id)
+}