github.com/anonymouse64/snapd@v0.0.0-20210824153203-04c4c42d842d/netutil/metered.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2018 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package netutil
    21  
    22  import (
    23  	"fmt"
    24  
    25  	"github.com/godbus/dbus"
    26  
    27  	"github.com/snapcore/snapd/logger"
    28  )
    29  
    30  const (
    31  	// https://developer.gnome.org/NetworkManager/stable/nm-dbus-types.html#NMMetered
    32  	NetworkManagerMeteredUnknown  = 0
    33  	NetworkManagerMeteredYes      = 1
    34  	NetworkManagerMeteredNo       = 2
    35  	NetworkManagerMeteredGuessYes = 3
    36  	NetworkManagerMeteredGuessNo  = 4
    37  )
    38  
    39  // IsOnMeteredConnection checks whether the current default network connection
    40  // is metered. If the state can not be determined, returns false and an error.
    41  func IsOnMeteredConnection() (bool, error) {
    42  	// obtain a shared connection to system bus, no need to close it
    43  	conn, err := dbus.SystemBus()
    44  	if err != nil {
    45  		return false, fmt.Errorf("cannot connect to system bus: %v", err)
    46  	}
    47  
    48  	return isNMOnMetered(conn)
    49  }
    50  
    51  func isNMOnMetered(conn *dbus.Conn) (bool, error) {
    52  	nmObj := conn.Object("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager")
    53  	// https://developer.gnome.org/NetworkManager/stable/gdbus-org.freedesktop.NetworkManager.html
    54  	dbusV, err := nmObj.GetProperty("org.freedesktop.NetworkManager.Metered")
    55  	if err != nil {
    56  		return false, err
    57  	}
    58  	v, ok := dbusV.Value().(uint32)
    59  	if !ok {
    60  		return false, fmt.Errorf("network manager returned invalid value for metering verification: %s", dbusV)
    61  	}
    62  	logger.Debugf("metered state reported by NetworkManager: %s", dbusV)
    63  
    64  	return v == NetworkManagerMeteredGuessYes || v == NetworkManagerMeteredYes, nil
    65  }