Added UI for plugin system and upnp example

- Added wip UI for plugin tag system
- Added upnp port forwarder plugin
- Added error and fatal printout for plugins
- Optimized UI flow for plugin context window
- Added dev web server for plugin development purpose

example/plugins/upnp/mod/upnpc/upnpc.go

@@ -0,0 +1,135 @@
+package upnpc
+
+import (
+	"errors"
+	"fmt"
+	"sync"
+	"time"
+
+	"gitlab.com/NebulousLabs/go-upnp"
+)
+
+/*
+	uPNP Module
+
+	This module handles uPNP Connections to the gateway router and create a port forward entry
+	for the host system at the given port (set with -port paramter)
+*/
+
+type UPnPClient struct {
+	Connection    *upnp.IGD //UPnP conenction object
+	ExternalIP    string    //Storage of external IP address
+	RequiredPorts []int     //All the required ports will be recored
+	PolicyNames   sync.Map  //Name for the required port nubmer
+}
+
+// NewUPNPClient creates a new UPnPClient object
+func NewUPNPClient() (*UPnPClient, error) {
+	//Create uPNP forwarding in the NAT router
+	fmt.Println("Discovering UPnP router in Local Area Network...")
+	d, err := upnp.Discover()
+	if err != nil {
+		return &UPnPClient{}, err
+	}
+
+	// discover external IP
+	ip, err := d.ExternalIP()
+	if err != nil {
+		return &UPnPClient{}, err
+	}
+
+	//Create the final obejcts
+	newUPnPObject := &UPnPClient{
+		Connection:    d,
+		ExternalIP:    ip,
+		RequiredPorts: []int{},
+	}
+
+	return newUPnPObject, nil
+}
+
+// ForwardPort forwards a port to the host
+func (u *UPnPClient) ForwardPort(portNumber int, ruleName string) error {
+	fmt.Println("UPnP forwarding new port: ", portNumber, "for "+ruleName+" service")
+
+	//Check if port already forwarded
+	_, ok := u.PolicyNames.Load(portNumber)
+	if ok {
+		//Port already forward. Ignore this request
+		return errors.New("port already forwarded")
+	}
+
+	// forward a port
+	err := u.Connection.Forward(uint16(portNumber), ruleName)
+	if err != nil {
+		return err
+	}
+
+	u.RequiredPorts = append(u.RequiredPorts, portNumber)
+	u.PolicyNames.Store(portNumber, ruleName)
+	return nil
+}
+
+// ClosePort closes the port forwarding
+func (u *UPnPClient) ClosePort(portNumber int) error {
+	//Check if port is opened
+	portOpened := false
+	newRequiredPort := []int{}
+	for _, thisPort := range u.RequiredPorts {
+		if thisPort != portNumber {
+			newRequiredPort = append(newRequiredPort, thisPort)
+		} else {
+			portOpened = true
+		}
+	}
+
+	if portOpened {
+		//Update the port list
+		u.RequiredPorts = newRequiredPort
+
+		// Close the port
+		fmt.Println("Closing UPnP Port Forward: ", portNumber)
+		err := u.Connection.Clear(uint16(portNumber))
+
+		//Delete the name registry
+		u.PolicyNames.Delete(portNumber)
+
+		if err != nil {
+			fmt.Println(err)
+			return err
+		}
+	}
+	return nil
+}
+
+// Renew forward rules, prevent router lease time from flushing the Upnp config
+func (u *UPnPClient) RenewForwardRules() {
+	if u.Connection == nil {
+		//UPnP router gone
+		return
+	}
+	portsToRenew := u.RequiredPorts
+	for _, thisPort := range portsToRenew {
+		ruleName, ok := u.PolicyNames.Load(thisPort)
+		if !ok {
+			continue
+		}
+		u.ClosePort(thisPort)
+		time.Sleep(100 * time.Millisecond)
+		u.ForwardPort(thisPort, ruleName.(string))
+	}
+	fmt.Println("UPnP Port Forward rule renew completed")
+}
+
+func (u *UPnPClient) Close() error {
+	//Shutdown the default UPnP Object
+	if u != nil {
+		for _, portNumber := range u.RequiredPorts {
+			err := u.Connection.Clear(uint16(portNumber))
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}