add all files from Hong

plugins/plugin.go

@@ -0,0 +1,114 @@
+// Copyright 2018-present the CoreDHCP Authors. All rights reserved
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+
+package plugins
+
+import (
+	"errors"
+
+	"github.com/coredhcp/coredhcp/config"
+	"github.com/coredhcp/coredhcp/handler"
+	"github.com/coredhcp/coredhcp/logger"
+)
+
+var log = logger.GetLogger("plugins")
+
+// Plugin represents a plugin object.
+// Setup6 and Setup4 are the setup functions for DHCPv6 and DHCPv4 handlers
+// respectively. Both setup functions can be nil.
+type Plugin struct {
+	Name   string
+	Setup6 SetupFunc6
+	Setup4 SetupFunc4
+}
+
+// RegisteredPlugins maps a plugin name to a Plugin instance.
+var RegisteredPlugins = make(map[string]*Plugin)
+
+// SetupFunc6 defines a plugin setup function for DHCPv6
+type SetupFunc6 func(args ...string) (handler.Handler6, error)
+
+// SetupFunc4 defines a plugin setup function for DHCPv6
+type SetupFunc4 func(args ...string) (handler.Handler4, error)
+
+// RegisterPlugin registers a plugin.
+func RegisterPlugin(plugin *Plugin) error {
+	if plugin == nil {
+		return errors.New("cannot register nil plugin")
+	}
+	log.Printf("Registering plugin '%s'", plugin.Name)
+	if _, ok := RegisteredPlugins[plugin.Name]; ok {
+		// TODO this highlights that asking the plugins to register themselves
+		// is not the right approach. Need to register them in the main program.
+		log.Panicf("Plugin '%s' is already registered", plugin.Name)
+	}
+	RegisteredPlugins[plugin.Name] = plugin
+	return nil
+}
+
+// LoadPlugins reads a Config object and loads the plugins as specified in the
+// `plugins` section, in order. For a plugin to be available, it must have been
+// previously registered with plugins.RegisterPlugin. This is normally done at
+// plugin import time.
+// This function returns the list of loaded v6 plugins, the list of loaded v4
+// plugins, and an error if any.
+func LoadPlugins(conf *config.Config) ([]handler.Handler4, []handler.Handler6, error) {
+	log.Print("Loading plugins...")
+	handlers4 := make([]handler.Handler4, 0)
+	handlers6 := make([]handler.Handler6, 0)
+
+	if conf.Server6 == nil && conf.Server4 == nil {
+		return nil, nil, errors.New("no configuration found for either DHCPv6 or DHCPv4")
+	}
+
+	// now load the plugins. We need to call its setup function with
+	// the arguments extracted above. The setup function is mapped in
+	// plugins.RegisteredPlugins .
+
+	// Load DHCPv6 plugins.
+	if conf.Server6 != nil {
+		for _, pluginConf := range conf.Server6.Plugins {
+			if plugin, ok := RegisteredPlugins[pluginConf.Name]; ok {
+				log.Printf("DHCPv6: loading plugin `%s`", pluginConf.Name)
+				if plugin.Setup6 == nil {
+					log.Warningf("DHCPv6: plugin `%s` has no setup function for DHCPv6", pluginConf.Name)
+					continue
+				}
+				h6, err := plugin.Setup6(pluginConf.Args...)
+				if err != nil {
+					return nil, nil, err
+				} else if h6 == nil {
+					return nil, nil, config.ConfigErrorFromString("no DHCPv6 handler for plugin %s", pluginConf.Name)
+				}
+				handlers6 = append(handlers6, h6)
+			} else {
+				return nil, nil, config.ConfigErrorFromString("DHCPv6: unknown plugin `%s`", pluginConf.Name)
+			}
+		}
+	}
+	// Load DHCPv4 plugins. Yes, duplicated code, there's not really much that
+	// can be deduplicated here.
+	if conf.Server4 != nil {
+		for _, pluginConf := range conf.Server4.Plugins {
+			if plugin, ok := RegisteredPlugins[pluginConf.Name]; ok {
+				log.Printf("DHCPv4: loading plugin `%s`", pluginConf.Name)
+				if plugin.Setup4 == nil {
+					log.Warningf("DHCPv4: plugin `%s` has no setup function for DHCPv4", pluginConf.Name)
+					continue
+				}
+				h4, err := plugin.Setup4(pluginConf.Args...)
+				if err != nil {
+					return nil, nil, err
+				} else if h4 == nil {
+					return nil, nil, config.ConfigErrorFromString("no DHCPv4 handler for plugin %s", pluginConf.Name)
+				}
+				handlers4 = append(handlers4, h4)
+			} else {
+				return nil, nil, config.ConfigErrorFromString("DHCPv4: unknown plugin `%s`", pluginConf.Name)
+			}
+		}
+	}
+
+	return handlers4, handlers6, nil
+}