sandbox: Create and export KillContainer() to the API level

In order to support use cases such as containerd-shim-v2 where we
would have a long running process holding the sandbox pointer, there
would be no reason to call into the stateless function KillContainer(),
which would recreate a new sandbox pointer and the corresponding ones
for containers.

Fixes #903

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtcontainers/api.go

@@ -655,19 +655,7 @@ func KillContainer(ctx context.Context, sandboxID, containerID string, signal sy
 	}
 	defer s.releaseStatelessSandbox()
 
-	// Fetch the container.
+	return s.KillContainer(containerID, signal, all)
-	c, err := s.findContainer(containerID)
-	if err != nil {
-		return err
-	}
-
-	// Send a signal to the process.
-	err = c.kill(signal, all)
-	if err != nil {
-		return err
-	}
-
-	return nil
 }
 
 // PauseSandbox is the virtcontainers pausing entry point which pauses an

virtcontainers/interfaces.go

@@ -78,6 +78,7 @@ type VCSandbox interface {
 	DeleteContainer(contID string) (VCContainer, error)
 	StartContainer(containerID string) (VCContainer, error)
 	StopContainer(containerID string) (VCContainer, error)
+	KillContainer(containerID string, signal syscall.Signal, all bool) error
 	StatusContainer(containerID string) (ContainerStatus, error)
 	StatsContainer(containerID string) (ContainerStats, error)
 	EnterContainer(containerID string, cmd Cmd) (VCContainer, *Process, error)

virtcontainers/pkg/vcmock/sandbox.go

@@ -112,6 +112,11 @@ func (s *Sandbox) StopContainer(contID string) (vc.VCContainer, error) {
 	return &Container{}, nil
 }
 
+// KillContainer implements the VCSandbox function of the same name.
+func (s *Sandbox) KillContainer(contID string, signal syscall.Signal, all bool) error {
+	return nil
+}
+
 // StatusContainer implements the VCSandbox function of the same name.
 func (s *Sandbox) StatusContainer(contID string) (vc.ContainerStatus, error) {
 	return vc.ContainerStatus{}, nil

virtcontainers/sandbox.go

@@ -1336,6 +1336,18 @@ func (s *Sandbox) StopContainer(containerID string) (VCContainer, error) {
 	return c, nil
 }
 
+// KillContainer signals a container in the sandbox
+func (s *Sandbox) KillContainer(containerID string, signal syscall.Signal, all bool) error {
+	// Fetch the container.
+	c, err := s.findContainer(containerID)
+	if err != nil {
+		return err
+	}
+
+	// Send a signal to the process.
+	return c.kill(signal, all)
+}
+
 // DeleteContainer deletes a container from the sandbox
 func (s *Sandbox) DeleteContainer(containerID string) (VCContainer, error) {
 	if containerID == "" {