To control the Network Manager on Ubuntu with DBUS and C#/Mono. D-BUS documentation: * The D-BUS Network Manager: http://projects.gnome.org/NetworkManager/developers/api/09/spec.html#org.freedesktop.NetworkManager.Settings.Connection * The D-BUS C# free library: https://github.com/mono/dbus-sharp and http://www.ndesk.org/DBus_Documentation * D-B…

NewtworkManagerConnection.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Net;
using DBus;

namespace IPChangerPrototype
{
  public enum Method
	{
		Manual,
		Auto,
		AutoAddressesOnly,
	}
	
	/// <summary>
	/// IP address extension.
	/// Some useful methods to convert IP address to integer or to netmask.
	/// All computations are using the little endian ordering.
	/// </summary>
	static class IPAddressExtension
	{		
		public static uint ToUint(this IPAddress ip)
		{
			return (uint)ip.GetAddressBytes()[0] | (uint)ip.GetAddressBytes()[1] << 8 | (uint)ip.GetAddressBytes()[2] << 16 | (uint)ip.GetAddressBytes()[3] << 24; // Little endian.
		}
		
		static readonly uint[] mod37BitPosition =
			{
			  32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13, 4,
			  7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9, 5,
			  20, 8, 19, 18
			};
		
		/// <summary>
		/// The computation method of the number of trailing zero came from http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightModLookup
		/// </summary>
		/// <returns>
		/// The netmask.
		/// </returns>
		/// <param name='ip'>
		/// Ip.
		/// </param>
		public static uint ToNetmask(this IPAddress ip)
		{
			uint ipUint = ~ip.ToUint();
			return mod37BitPosition[(-ipUint & ipUint) % 37];
		}
		
		public static IPAddress FromNetmask(uint netmask)
		{
			return new IPAddress(uint.MaxValue >> 32 - (int)netmask);
		}
	}
	
	/// <summary>
	/// Connection to remotely control the netowrk manager via D-BUS.
	/// 
	/// D-BUS documentation:
	///   * The D-BUS Network Manager: http://projects.gnome.org/NetworkManager/developers/api/09/spec.html#org.freedesktop.NetworkManager.Settings.Connection
	///   * The D-BUS C# free library: https://github.com/mono/dbus-sharp and http://www.ndesk.org/DBus_Documentation
	///   * D-BUS tutorial: http://dbus.freedesktop.org/doc/dbus-tutorial.html
	/// </summary>
	class NewtworkManagerConnection
	{		
		readonly string BUS_NAME = "org.freedesktop.NetworkManager";
				
		public Method Method { get; set; }		
		public IPAddress IP { get; set; }		
		public IPAddress Netmask { get; set; }		
		public IPAddress Gateway { get; set; }		
		public IEnumerable<IPAddress> DNS { get; set; }
		
		/// <summary>
		/// Automatically load data from the current active connection.
		/// </summary>/
		public NewtworkManagerConnection()
		{
			this.LoadFromActiveConnection();
		}
		
		public bool SetIP(string ipStr)
		{
			IPAddress ip;
			if (IPAddress.TryParse(ipStr, out ip))
			{
				this.IP = ip;
				return true;	
			}			
			return false;
		}
		
		public bool SetNetmask(string netmaskStr)
		{
			IPAddress ip;
			if (IPAddress.TryParse(netmaskStr, out ip))
			{
				this.Netmask = ip;
				return true;	
			}			
			return false;			
		}
		
		public bool SetGateway(string gatewayStr)
		{
			IPAddress ip;
			if (IPAddress.TryParse(gatewayStr, out ip))
			{
				this.Gateway = ip;
				return true;
			}			
			return false;				
		}
		
		public bool SetDNS(IEnumerable<string> dnsStr)
		{
			IEnumerable<IPAddress> ips = dnsStr.Aggregate(
				new List<IPAddress>(),
				(list, dns) =>
					{						
						IPAddress ip;
						if (IPAddress.TryParse(dns, out ip))
							list.Add(ip);
						return list;	
					}
			);
			
			if (ips.Any())
			{
				this.DNS = ips;
				return true;
			}
			
			return false;
		}
		
		public void SaveToActiveConnection()
		{
			var bus = Bus.System;		
		
			org.freedesktop.DBus.Properties networkManagerProperties = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, new ObjectPath("/org/freedesktop/NetworkManager"));						
			ObjectPath[] objPathActiveConnections = networkManagerProperties.Get(BUS_NAME, "ActiveConnections") as ObjectPath[];
			
			if (objPathActiveConnections.Length > 0)
			{	
				org.freedesktop.DBus.Properties activeConnectionProperties = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, objPathActiveConnections[0]);										
				ObjectPath objPathConnection = activeConnectionProperties.Get("org.freedesktop.NetworkManager.Connection.Active", "Connection") as ObjectPath;
				IConnection connection = bus.GetObject<IConnection>(BUS_NAME, objPathConnection);
				
				var settings = connection.GetSettings();
				
				IDictionary<string, object> settingIPv4 = settings["ipv4"];							
				
				if (this.Method == Method.AutoAddressesOnly)
				{
					settingIPv4["ignore-auto-dns"] = true;
					settingIPv4["dns"] = this.DNSAddresses;
				}
				
				if (this.Method == Method.Auto || this.Method == Method.AutoAddressesOnly)
				{
					settingIPv4["method"] = "auto";	
				}
				else
				{
					settingIPv4["method"] = "manual";
					settingIPv4["addresses"] = new uint[][] { this.Address };
					settingIPv4["dns"] = this.DNSAddresses;
				}
				
				connection.Update(settings);
			}
			
			bus.Close();
		}
		
		public override string ToString()
		{
			return string.Format("[NewtworkManagerConnection: Method={0}, IP={1}, SubNetworkMask={2}, Gateway={3}, DNS={4}]", this.Method, this.IP, this.Netmask, this.Gateway, this.DNS);
		}

		[Interface("org.freedesktop.NetworkManager.Settings.Connection")]
		interface IConnection
		{
			IDictionary<string, IDictionary<string, object>> GetSettings();
			void Update(IDictionary<string, IDictionary<string, object>> settings);
		}
		
		void LoadFromActiveConnection()
		{			
			var bus = Bus.System;
		
			org.freedesktop.DBus.Properties networkManagerProperties = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, new ObjectPath("/org/freedesktop/NetworkManager"));						
			ObjectPath[] objPathActiveConnections = networkManagerProperties.Get(BUS_NAME, "ActiveConnections") as ObjectPath[];
			
			if (objPathActiveConnections.Length > 0)
			{			
				org.freedesktop.DBus.Properties activeConnectionProperties = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, objPathActiveConnections[0]);		
				
				// First, set the IP/mask/gateway from the device of the current active connection.
				ObjectPath[] objPathDevices = activeConnectionProperties.Get("org.freedesktop.NetworkManager.Connection.Active", "Devices") as ObjectPath[];
				if (objPathDevices.Length > 0)
				{				
					ObjectPath objPathIp4Config = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, objPathDevices[0]).Get("org.freedesktop.NetworkManager.Device", "Ip4Config") as ObjectPath;
					
					uint[][] addresses = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, objPathIp4Config).Get("org.freedesktop.NetworkManager.IP4Config", "Addresses") as uint[][];					
					if (addresses.Length > 0)
						this.Address = addresses[0];
					
					uint[] dns = bus.GetObject<org.freedesktop.DBus.Properties>(BUS_NAME, objPathIp4Config).Get("org.freedesktop.NetworkManager.IP4Config", "Nameservers") as uint[];										
					this.DNSAddresses = dns;
				}				
				
				ObjectPath objPathConnection = activeConnectionProperties.Get("org.freedesktop.NetworkManager.Connection.Active", "Connection") as ObjectPath;
				
				IConnection connection = bus.GetObject<IConnection>(BUS_NAME, objPathConnection);
				
				var settings = connection.GetSettings();
				
				IDictionary<string, object> settingIPv4;
				if (settings.TryGetValue("ipv4", out settingIPv4))
				{					
					this.Method = Method.Manual; // Default method.
					object method;
					if (settingIPv4.TryGetValue("method", out method) && method is string)
					{
						object ignoreAutoDns;
						settingIPv4.TryGetValue("ignore-auto-dns", out ignoreAutoDns);
						
						if (method as string == "auto")
							this.Method = ignoreAutoDns is bool && (bool)ignoreAutoDns ? Method.AutoAddressesOnly : Method.Auto;
					}
					
					object addresses;
					if (settingIPv4.TryGetValue("addresses", out addresses) && addresses is uint[][] && (addresses as uint[][]).Length > 0)	
						this.Address = (addresses as uint[][])[0];
					
					object dns;
					if (settingIPv4.TryGetValue("dns", out dns) && dns is uint[] && (dns as uint[]).Length > 0)
						this.DNSAddresses = dns as uint[];
				}
			}
			
			bus.Close();		
		}
		
		uint[] Address
		{
			get
			{
				uint[] result = new uint[3];	
				result[0] = this.IP.ToUint();				
				result[1] = this.Netmask.ToNetmask();
				result[2] = this.Gateway.ToUint();				
				return result;
			}
			set
			{
				Debug.Assert(value.Length == 3);
				
				this.IP = new IPAddress(value[0]);
				this.Netmask = IPAddressExtension.FromNetmask(value[1]);
				this.Gateway = new IPAddress(value[2]);
			}
		}
		
		uint[] DNSAddresses
		{
			get
			{					
				return this.DNS.Select(ip => ip.ToUint()).ToArray();
			}
			set
			{
				this.DNS = value.Select(ip => new IPAddress(ip));
			}
		}
	}
}