Merge pull request #419 from asridharan/cnitool

Added documentation for `cnitool`

Documentation/cnitool.md

@@ -0,0 +1,16 @@
+# Overview
+The `cnitool` is a utility that can be used to test a CNI plugin
+without the need for a container runtime. The `cnitool` takes a
+`network name` and a `network namespace` and a command to `ADD` or
+`DEL`,.i.e, attach or detach containers from a network. The `cnitool`
+relies on the following environment variables to operate properly:
+* `NETCONFPATH`: This environment variable needs to be set to a
+  directory. It defaults to `/etc/cni/net.d`. The `cnitool` searches
+  for CNI configuration files in this directory with the extension
+  `*.conf` or `*.json`. It loads all the CNI configuration files in
+  this directory and if it finds a CNI configuration with the `network
+  name` given to the cnitool it returns the corresponding CNI
+  configuration, else it returns `nil`.
+
+* `CNI_PATH`: For a given CNI configuration `cnitool` will search for
+  the corresponding CNI plugin in this path.

libcni/conf.go

@@ -16,7 +16,6 @@ package libcni
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -33,7 +32,13 @@ func (e NotFoundError) Error() string {
 	return fmt.Sprintf(`no net configuration with name "%s" in %s`, e.Name, e.Dir)
 }
 
-var NoConfigsFoundError = errors.New("no net configurations found")
+type NoConfigsFoundError struct {
+	Dir string
+}
+
+func (e NoConfigsFoundError) Error() string {
+	return fmt.Sprintf(`no net configurations found in %s`, e.Dir)
+}
 
 func ConfFromBytes(bytes []byte) (*NetworkConfig, error) {
 	conf := &NetworkConfig{Bytes: bytes}
@@ -149,7 +154,7 @@ func LoadConf(dir, name string) (*NetworkConfig, error) {
 	case err != nil:
 		return nil, err
 	case len(files) == 0:
-		return nil, NoConfigsFoundError
+		return nil, NoConfigsFoundError{Dir: dir}
 	}
 	sort.Strings(files)
 
@@ -187,16 +192,12 @@ func LoadConfList(dir, name string) (*NetworkConfigList, error) {
 	singleConf, err := LoadConf(dir, name)
 	if err != nil {
 		// A little extra logic so the error makes sense
-		switch {
+		if _, ok := err.(NoConfigsFoundError); len(files) != 0 && ok {
-		// neither configlists nor config files found
+			// Config lists found but no config files found
-		case len(files) == 0 && err == NoConfigsFoundError:
-			return nil, err
-		// config lists found but no config files found
-		case len(files) != 0 && err == NoConfigsFoundError:
 			return nil, NotFoundError{dir, name}
-		default: // either not found or parse error
-			return nil, err
 		}
+
+		return nil, err
 	}
 	return ConfListFromConf(singleConf)
 }

libcni/conf_test.go

@@ -61,7 +61,7 @@ var _ = Describe("Loading configuration from disk", func() {
 
 			It("returns a useful error", func() {
 				_, err := libcni.LoadConf(configDir, "some-plugin")
-				Expect(err).To(MatchError("no net configurations found"))
+				Expect(err).To(MatchError(libcni.NoConfigsFoundError{Dir: configDir}))
 			})
 		})
 
@@ -244,7 +244,7 @@ var _ = Describe("Loading configuration from disk", func() {
 
 			It("returns a useful error", func() {
 				_, err := libcni.LoadConfList(configDir, "some-plugin")
-				Expect(err).To(MatchError("no net configurations found"))
+				Expect(err).To(MatchError(libcni.NoConfigsFoundError{Dir: configDir}))
 			})
 		})