api: To watch the vm console in FetchSandbox api

When do sandbox release, the kataBuiltInProxy will
be closed, and it will stop the watch of vm's console;
Thus it needs to restart the proxy to monitor the vm
console once to restore the sandbox.

Fixes: #441

Signed-off-by: fupan <lifupan@gmail.com>

virtcontainers/agent.go

@@ -140,6 +140,9 @@ type agent interface {
 	// disconnect will disconnect the connection to the agent
 	disconnect() error
 
+	// start the proxy
+	startProxy(sandbox *Sandbox) error
+
 	// createSandbox will tell the agent to perform necessary setup for a Sandbox.
 	createSandbox(sandbox *Sandbox) error
 

virtcontainers/api.go

@@ -110,7 +110,21 @@ func FetchSandbox(sandboxID string) (VCSandbox, error) {
 	defer unlockSandbox(lockFile)
 
 	// Fetch the sandbox from storage and create it.
-	return fetchSandbox(sandboxID)
+	sandbox, err := fetchSandbox(sandboxID)
+	if err != nil {
+		return nil, err
+	}
+
+	// If the proxy is KataBuiltInProxyType type, it needs to restart the proxy to watch the
+	// guest console if it hadn't been watched.
+	if isProxyBuiltIn(sandbox.config.ProxyType) {
+		err = sandbox.startProxy()
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return sandbox, nil
 }
 
 // StartSandbox is the virtcontainers sandbox starting entry point.

virtcontainers/cc_proxy.go

@@ -41,3 +41,8 @@ func (p *ccProxy) start(sandbox *Sandbox, params proxyParams) (int, string, erro
 func (p *ccProxy) stop(sandbox *Sandbox, pid int) error {
 	return nil
 }
+
+// The ccproxy doesn't need to watch the vm console, thus return false always.
+func (p *ccProxy) consoleWatched() bool {
+	return false
+}

virtcontainers/hyperstart_agent.go

@@ -340,8 +340,11 @@ func (h *hyper) exec(sandbox *Sandbox, c Container, cmd Cmd) (*Process, error) {
 	return process, nil
 }
 
-// startSandbox is the agent Sandbox starting implementation for hyperstart.
-func (h *hyper) startSandbox(sandbox *Sandbox) error {
+func (h *hyper) startProxy(sandbox *Sandbox) error {
+	if h.proxy.consoleWatched() {
+		return nil
+	}
+
 	// Start the proxy here
 	pid, uri, err := h.proxy.start(sandbox, proxyParams{})
 	if err != nil {
@@ -357,6 +360,17 @@ func (h *hyper) startSandbox(sandbox *Sandbox) error {
 
 	h.Logger().WithField("proxy-pid", pid).Info("proxy started")
 
+	return nil
+}
+
+// startSandbox is the agent Sandbox starting implementation for hyperstart.
+func (h *hyper) startSandbox(sandbox *Sandbox) error {
+
+	err := h.startProxy(sandbox)
+	if err != nil {
+		return err
+	}
+
 	if err := h.register(); err != nil {
 		return err
 	}

virtcontainers/kata_agent.go

@@ -419,11 +419,15 @@ func (k *kataAgent) generateInterfacesAndRoutes(networkNS NetworkNamespace) ([]*
 	return ifaces, routes, nil
 }
 
-func (k *kataAgent) startSandbox(sandbox *Sandbox) error {
+func (k *kataAgent) startProxy(sandbox *Sandbox) error {
 	if k.proxy == nil {
 		return errorMissingProxy
 	}
 
+	if k.proxy.consoleWatched() {
+		return nil
+	}
+
 	// Get agent socket path to provide it to the proxy.
 	agentURL, err := k.agentURL()
 	if err != nil {
@@ -454,6 +458,15 @@ func (k *kataAgent) startSandbox(sandbox *Sandbox) error {
 		"proxy-url":  uri,
 	}).Info("proxy started")
 
+	return nil
+}
+
+func (k *kataAgent) startSandbox(sandbox *Sandbox) error {
+	err := k.startProxy(sandbox)
+	if err != nil {
+		return err
+	}
+
 	hostname := sandbox.config.Hostname
 	if len(hostname) > maxHostnameLen {
 		hostname = hostname[:maxHostnameLen]

virtcontainers/kata_builtin_proxy.go

@@ -21,11 +21,16 @@ type kataBuiltInProxy struct {
 	conn      net.Conn
 }
 
+// check if the proxy has watched the vm console.
+func (p *kataBuiltInProxy) consoleWatched() bool {
+	return p.conn != nil
+}
+
 // start is the proxy start implementation for kata builtin proxy.
 // It starts the console watcher for the guest.
 // It returns agentURL to let agent connect directly.
 func (p *kataBuiltInProxy) start(sandbox *Sandbox, params proxyParams) (int, string, error) {
-	if p.conn != nil {
+	if p.consoleWatched() {
 		return -1, "", fmt.Errorf("kata builtin proxy running for sandbox %s", p.sandboxID)
 	}
 

virtcontainers/kata_proxy.go

@@ -17,6 +17,11 @@ import (
 type kataProxy struct {
 }
 
+// The kata proxy doesn't need to watch the vm console, thus return false always.
+func (p *kataProxy) consoleWatched() bool {
+	return false
+}
+
 // start is kataProxy start implementation for proxy interface.
 func (p *kataProxy) start(sandbox *Sandbox, params proxyParams) (int, string, error) {
 	if sandbox.agent == nil {

virtcontainers/no_proxy.go

@@ -35,3 +35,8 @@ func (p *noProxy) start(sandbox *Sandbox, params proxyParams) (int, string, erro
 func (p *noProxy) stop(sandbox *Sandbox, pid int) error {
 	return nil
 }
+
+// The noproxy doesn't need to watch the vm console, thus return false always.
+func (p *noProxy) consoleWatched() bool {
+	return false
+}

virtcontainers/noop_agent.go

@@ -16,6 +16,11 @@ import (
 type noopAgent struct {
 }
 
+//start the proxy to watch the vm console. It does nothing.
+func (n *noopAgent) startProxy(sandbox *Sandbox) error {
+	return nil
+}
+
 // init initializes the Noop agent, i.e. it does nothing.
 func (n *noopAgent) init(sandbox *Sandbox, config interface{}) error {
 	return nil

virtcontainers/noop_proxy.go

@@ -22,3 +22,8 @@ func (p *noopProxy) start(sandbox *Sandbox, params proxyParams) (int, string, er
 func (p *noopProxy) stop(sandbox *Sandbox, pid int) error {
 	return nil
 }
+
+// The noopproxy doesn't need to watch the vm console, thus return false always.
+func (p *noopProxy) consoleWatched() bool {
+	return false
+}

virtcontainers/proxy.go

@@ -170,4 +170,7 @@ type proxy interface {
 	// stop terminates a proxy instance after all communications with the
 	// agent inside the VM have been properly stopped.
 	stop(sandbox *Sandbox, pid int) error
+
+	//check if the proxy has watched the vm console.
+	consoleWatched() bool
 }

virtcontainers/sandbox.go

@@ -352,6 +352,17 @@ type SandboxConfig struct {
 	SharePidNs bool
 }
 
+func (s *Sandbox) startProxy() error {
+
+	// If the proxy is KataBuiltInProxyType type, it needs to restart the proxy
+	// to watch the guest console if it hadn't been watched.
+	if s.agent == nil {
+		return fmt.Errorf("sandbox %s missed agent pointer", s.ID())
+	}
+
+	return s.agent.startProxy(s)
+}
+
 // valid checks that the sandbox configuration is valid.
 func (sandboxConfig *SandboxConfig) valid() bool {
 	if sandboxConfig.ID == "" {