virtcontainers: Initial import

This is a virtcontainers 1.0.8 import into Kata Containers runtime.

virtcontainers is a Go library designed to manage hardware virtualized
pods and containers. It is the core Clear Containers framework and will
become the core Kata Containers framework, as discussed at
https://github.com/kata-containers/runtime/issues/33

Some more more pointers:

virtcontainers README, including some design and architecure notes:
https://github.com/containers/virtcontainers/blob/master/README.md

virtcontainers 1.0 API:
https://github.com/containers/virtcontainers/blob/master/documentation/api/1.0/api.md

Fixes #40

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

virtcontainers/hook.go

@@ -0,0 +1,160 @@
+//
+// Copyright (c) 2017 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+package virtcontainers
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"time"
+
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/sirupsen/logrus"
+)
+
+// Hook represents an OCI hook, including its required parameters.
+type Hook struct {
+	Path    string
+	Args    []string
+	Env     []string
+	Timeout int
+}
+
+// Hooks gathers all existing OCI hooks list.
+type Hooks struct {
+	PreStartHooks  []Hook
+	PostStartHooks []Hook
+	PostStopHooks  []Hook
+}
+
+// Logger returns a logrus logger appropriate for logging Hooks messages
+func (h *Hooks) Logger() *logrus.Entry {
+	return virtLog.WithField("subsystem", "hooks")
+}
+
+func buildHookState(processID int) specs.State {
+	return specs.State{
+		Pid: processID,
+	}
+}
+
+func (h *Hook) runHook() error {
+	state := buildHookState(os.Getpid())
+	stateJSON, err := json.Marshal(state)
+	if err != nil {
+		return err
+	}
+
+	var stdout, stderr bytes.Buffer
+	cmd := &exec.Cmd{
+		Path:   h.Path,
+		Args:   h.Args,
+		Env:    h.Env,
+		Stdin:  bytes.NewReader(stateJSON),
+		Stdout: &stdout,
+		Stderr: &stderr,
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		return err
+	}
+
+	if h.Timeout == 0 {
+		err = cmd.Wait()
+		if err != nil {
+			return fmt.Errorf("%s: stdout: %s, stderr: %s", err, stdout.String(), stderr.String())
+		}
+	} else {
+		done := make(chan error)
+
+		go func() { done <- cmd.Wait() }()
+
+		select {
+		case err := <-done:
+			if err != nil {
+				return fmt.Errorf("%s: stdout: %s, stderr: %s", err, stdout.String(), stderr.String())
+			}
+		case <-time.After(time.Duration(h.Timeout) * time.Second):
+			return fmt.Errorf("Hook timeout")
+		}
+	}
+
+	return nil
+}
+
+func (h *Hooks) preStartHooks() error {
+	if len(h.PreStartHooks) == 0 {
+		return nil
+	}
+
+	for _, hook := range h.PreStartHooks {
+		err := hook.runHook()
+		if err != nil {
+			h.Logger().WithFields(logrus.Fields{
+				"hook-type": "pre-start",
+				"error":     err,
+			}).Error("hook error")
+
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (h *Hooks) postStartHooks() error {
+	if len(h.PostStartHooks) == 0 {
+		return nil
+	}
+
+	for _, hook := range h.PostStartHooks {
+		err := hook.runHook()
+		if err != nil {
+			// In case of post start hook, the error is not fatal,
+			// just need to be logged.
+			h.Logger().WithFields(logrus.Fields{
+				"hook-type": "post-start",
+				"error":     err,
+			}).Info("hook error")
+		}
+	}
+
+	return nil
+}
+
+func (h *Hooks) postStopHooks() error {
+	if len(h.PostStopHooks) == 0 {
+		return nil
+	}
+
+	for _, hook := range h.PostStopHooks {
+		err := hook.runHook()
+		if err != nil {
+			// In case of post stop hook, the error is not fatal,
+			// just need to be logged.
+			h.Logger().WithFields(logrus.Fields{
+				"hook-type": "post-stop",
+				"error":     err,
+			}).Info("hook error")
+		}
+	}
+
+	return nil
+}