Implement selecting tunnel port

This is useful for when you want to use boringproxy more like a
normal reverse proxy, ie if boringproxy and your service are on
the same machine, you can just use the port of the service as the
tunnel port and boringproxy will forward directly to it without
using SSH.

This would normally be used with no client set.

api.go

@@ -282,6 +282,16 @@ func (a *Api) CreateTunnel(tokenData TokenData, params url.Values) (*Tunnel, err
 		clientAddr = "127.0.0.1"
 	}
 
+	tunnelPort := 0
+	tunnelPortParam := params.Get("tunnel-port")
+	if tunnelPortParam != "" && tunnelPortParam != "Random" {
+		var err error
+		tunnelPort, err = strconv.Atoi(tunnelPortParam)
+		if err != nil {
+			return nil, errors.New("Invalid tunnel-port parameter")
+		}
+	}
+
 	allowExternalTcp := params.Get("allow-external-tcp") == "on"
 
 	passwordProtect := params.Get("password-protect") == "on"
@@ -312,6 +322,7 @@ func (a *Api) CreateTunnel(tokenData TokenData, params url.Values) (*Tunnel, err
 		ClientName:       clientName,
 		ClientPort:       clientPort,
 		ClientAddress:    clientAddr,
+		TunnelPort:       tunnelPort,
 		AllowExternalTcp: allowExternalTcp,
 		AuthUsername:     username,
 		AuthPassword:     password,

tunnel_manager.go

@@ -70,12 +70,21 @@ func (m *TunnelManager) RequestCreateTunnel(tunReq Tunnel) (Tunnel, error) {
 	m.mutex.Lock()
 	defer m.mutex.Unlock()
 
-	port, err := randomOpenPort()
-	if err != nil {
-		return Tunnel{}, err
+	if tunReq.TunnelPort == 0 {
+		var err error
+		tunReq.TunnelPort, err = randomOpenPort()
+		if err != nil {
+			return Tunnel{}, err
+		}
+	} else {
+		for _, tun := range m.db.GetTunnels() {
+			if tunReq.TunnelPort == tun.TunnelPort {
+				return Tunnel{}, errors.New("Tunnel port already in use")
+			}
+		}
 	}
 
-	privKey, err := m.addToAuthorizedKeys(tunReq.Domain, port, tunReq.AllowExternalTcp, tunReq.SshKey)
+	privKey, err := m.addToAuthorizedKeys(tunReq.Domain, tunReq.TunnelPort, tunReq.AllowExternalTcp, tunReq.SshKey)
 	if err != nil {
 		return Tunnel{}, err
 	}
@@ -84,7 +93,6 @@ func (m *TunnelManager) RequestCreateTunnel(tunReq Tunnel) (Tunnel, error) {
 	tunReq.ServerPort = m.config.SshServerPort
 	tunReq.ServerPublicKey = ""
 	tunReq.Username = m.user.Username
-	tunReq.TunnelPort = port
 	tunReq.TunnelPrivateKey = privKey
 
 	m.db.SetTunnel(tunReq.Domain, tunReq)

webui/index.tmpl

@@ -89,6 +89,10 @@
                  <input type="text" id="domain" name="domain" required>
                  <input type="hidden" id="tunnel-owner" name="owner" value="{{$.UserId}}">
                </div>
+               <div class='input'>
+                 <label for="tunnel-port">Tunnel Port:</label>
+                 <input type="text" id="tunnel-port" name="tunnel-port" value="Random">
+               </div>
 
                <!--
                <div class='input'>