Provide interface to categorize errors

- Package types to define the interfaces libnetwork errors
  may implement, so that caller can categorize them.

Signed-off-by: Alessandro Boch <aboch@docker.com>

driverapi/driverapi.go

@@ -1,24 +1,11 @@
 package driverapi
 
 import (
-	"errors"
-	"fmt"
 	"net"
 
 	"github.com/docker/libnetwork/types"
 )
 
-var (
-	// ErrEndpointExists is returned if more than one endpoint is added to the network
-	ErrEndpointExists = errors.New("Endpoint already exists (Only one endpoint allowed)")
-	// ErrNoNetwork is returned if no network with the specified id exists
-	ErrNoNetwork = errors.New("No network exists")
-	// ErrNoEndpoint is returned if no endpoint with the specified id exists
-	ErrNoEndpoint = errors.New("No endpoint exists")
-	// ErrNotImplemented is returned when a Driver has not implemented an API yet
-	ErrNotImplemented = errors.New("The API is not implemented yet")
-)
-
 // NetworkPluginEndpointType represents the Endpoint Type used by Plugin system
 const NetworkPluginEndpointType = "NetworkDriver"
 
@@ -124,14 +111,6 @@ type JoinInfo interface {
 	SetResolvConfPath(string) error
 }
 
-// ErrActiveRegistration represents an error when a driver is registered to a networkType that is previously registered
-type ErrActiveRegistration string
-
-// Error interface for ErrActiveRegistration
-func (ar ErrActiveRegistration) Error() string {
-	return fmt.Sprintf("Driver already registered for type %q", string(ar))
-}
-
 // DriverCallback provides a Callback interface for Drivers into LibNetwork
 type DriverCallback interface {
 	// RegisterDriver provides a way for Remote drivers to dynamically register new NetworkType and associate with a driver instance

driverapi/errors.go

@@ -0,0 +1,56 @@
+package driverapi
+
+import (
+	"fmt"
+)
+
+// ErrNoNetwork is returned if no network with the specified id exists
+type ErrNoNetwork string
+
+func (enn ErrNoNetwork) Error() string {
+	return fmt.Sprintf("No network (%s) exists", string(enn))
+}
+
+// NotFound denotes the type of this error
+func (enn ErrNoNetwork) NotFound() {}
+
+// ErrEndpointExists is returned if more than one endpoint is added to the network
+type ErrEndpointExists string
+
+func (ee ErrEndpointExists) Error() string {
+	return fmt.Sprintf("Endpoint (%s) already exists (Only one endpoint allowed)", string(ee))
+}
+
+// Forbidden denotes the type of this error
+func (ee ErrEndpointExists) Forbidden() {}
+
+// ErrNotImplemented is returned when a Driver has not implemented an API yet
+type ErrNotImplemented struct{}
+
+func (eni *ErrNotImplemented) Error() string {
+	return "The API is not implemented yet"
+}
+
+// NotImplemented denotes the type of this error
+func (eni *ErrNotImplemented) NotImplemented() {}
+
+// ErrNoEndpoint is returned if no endpoint with the specified id exists
+type ErrNoEndpoint string
+
+func (ene ErrNoEndpoint) Error() string {
+	return fmt.Sprintf("No endpoint (%s) exists", string(ene))
+}
+
+// NotFound denotes the type of this error
+func (ene ErrNoEndpoint) NotFound() {}
+
+// ErrActiveRegistration represents an error when a driver is registered to a networkType that is previously registered
+type ErrActiveRegistration string
+
+// Error interface for ErrActiveRegistration
+func (ar ErrActiveRegistration) Error() string {
+	return fmt.Sprintf("Driver already registered for type %q", string(ar))
+}
+
+// Forbidden denotes the type of this error
+func (ar ErrActiveRegistration) Forbidden() {}