Refactor network and veth creation

Remove veth interfaces on the host if an error occurs.
Provide the host interface name, temporary peer interface name and the
name of the peer once it is inside the container's namespace in the
Network config.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

linux_init.go

@@ -29,13 +29,23 @@ type pid struct {
 	Pid int `json:"pid"`
 }
 
+// network is an internal struct used to setup container networks.
+type network struct {
+	configs.Network
+
+	// TempVethPeerName is a unique tempory veth peer name that was placed into
+	// the container's namespace.
+	TempVethPeerName string `json:"temp_veth_peer_name"`
+}
+
 // Process is used for transferring parameters from Exec() to Init()
 type initConfig struct {
-	Args   []string        `json:"args"`
-	Env    []string        `json:"env"`
-	Cwd    string          `json:"cwd"`
-	User   string          `json:"user"`
-	Config *configs.Config `json:"config"`
+	Args     []string        `json:"args"`
+	Env      []string        `json:"env"`
+	Cwd      string          `json:"cwd"`
+	User     string          `json:"user"`
+	Config   *configs.Config `json:"config"`
+	Networks []*network      `json:"network"`
 }
 
 type initer interface {
@@ -184,18 +194,15 @@ func setupUser(config *initConfig) error {
 	return nil
 }
 
-// setupVethNetwork uses the Network config if it is not nil to initialize
-// the new veth interface inside the container for use by changing the name to eth0
-// setting the MTU and IP address along with the default gateway
-func setupNetwork(config *configs.Config) error {
+// setupNetwork sets up and initializes any network interface inside the container.
+func setupNetwork(config *initConfig) error {
 	for _, config := range config.Networks {
 		strategy, err := getStrategy(config.Type)
 		if err != nil {
 			return err
 		}
-		err1 := strategy.Initialize(config)
-		if err1 != nil {
-			return err1
+		if err := strategy.initialize(config); err != nil {
+			return err
 		}
 	}
 	return nil