Switch GeoIP database from MaxMind to IP2Location.

The IP2Location data is licensed under CC BY-SA, which
allows us to distribute the database with releases.

OpenRA.Game/Network/GeoIP.cs

@@ -11,63 +11,119 @@
 
 using System;
 using System.IO;
+using System.Linq;
 using System.Net;
-using ICSharpCode.SharpZipLib.GZip;
-using MaxMind.Db;
+using System.Net.Sockets;
+using System.Numerics;
+using ICSharpCode.SharpZipLib.Zip;
 
 namespace OpenRA.Network
 {
 	public class GeoIP
 	{
-		public class GeoIP2Record
+		class IP2LocationReader
 		{
-			[Constructor]
-			public GeoIP2Record(GeoIP2Country country)
+			public readonly DateTime Date;
+			readonly Stream stream;
+			readonly uint columnCount;
+			readonly uint v4Count;
+			readonly uint v4Offset;
+			readonly uint v6Count;
+			readonly uint v6Offset;
+
+			public IP2LocationReader(Stream source)
 			{
-				Country = country;
+				// Copy stream data for reuse
+				stream = new MemoryStream();
+				source.CopyTo(stream);
+				stream.Position = 0;
+
+				if (stream.ReadUInt8() != 1)
+					throw new InvalidDataException("Only IP2Location type 1 databases are supported.");
+
+				columnCount = stream.ReadUInt8();
+				var year = stream.ReadUInt8();
+				var month = stream.ReadUInt8();
+				var day = stream.ReadUInt8();
+				Date = new DateTime(2000 + year, month, day);
+
+				v4Count = stream.ReadUInt32();
+				v4Offset = stream.ReadUInt32();
+				v6Count = stream.ReadUInt32();
+				v6Offset = stream.ReadUInt32();
 			}
 
-			public GeoIP2Country Country { get; set; }
-		}
-
-		public class GeoIP2Country
-		{
-			[Constructor]
-			public GeoIP2Country(GeoIP2CountryNames names)
+			BigInteger AddressForIndex(long index, bool isIPv6)
 			{
-				Names = names;
+				var start = isIPv6 ? v6Offset : v4Offset;
+				var offset = isIPv6 ? 12 : 0;
+				stream.Seek(start + index * (4 * columnCount + offset) - 1, SeekOrigin.Begin);
+				return new BigInteger(stream.ReadBytes(isIPv6 ? 16 : 4).Append((byte)0).ToArray());
 			}
 
-			public GeoIP2CountryNames Names { get; set; }
-		}
-
-		public class GeoIP2CountryNames
-		{
-			[Constructor]
-			public GeoIP2CountryNames(string en)
+			string CountryForIndex(long index, bool isIPv6)
 			{
-				English = en;
+				// Read file offset for country entry
+				var start = isIPv6 ? v6Offset : v4Offset;
+				var offset = isIPv6 ? 12 : 0;
+				stream.Seek(start + index * (4 * columnCount + offset) + offset + 3, SeekOrigin.Begin);
+				var countryOffset = stream.ReadUInt32();
+
+				// Read length-prefixed country name
+				stream.Seek(countryOffset + 3, SeekOrigin.Begin);
+				var length = stream.ReadUInt8();
+
+				// "-" is used to represent an unknown country in the database
+				var country = stream.ReadASCII(length);
+				return country != "-" ? country : null;
 			}
 
-			public string English { get; set; }
+			public string LookupCountry(IPAddress ip)
+			{
+				var isIPv6 = ip.AddressFamily == AddressFamily.InterNetworkV6;
+				if (!isIPv6 && ip.AddressFamily != AddressFamily.InterNetwork)
+					return null;
+
+				// Locate IP using a binary search
+				// The IP2Location python parser has an additional
+				// optimization that can jump directly to the row, but this adds
+				// extra complexity that isn't obviously needed for our limited database size
+				long low = 0;
+				long high = isIPv6 ? v6Count : v4Count;
+
+				// Append an empty byte to force the data to be treated as unsigned
+				var ipNumber = new BigInteger(ip.GetAddressBytes().Reverse().Append((byte)0).ToArray());
+				while (low <= high)
+				{
+					var mid = (low + high) / 2;
+					var min = AddressForIndex(mid, isIPv6);
+					var max = AddressForIndex(mid + 1, isIPv6);
+					if (min <= ipNumber && ipNumber < max)
+						return CountryForIndex(mid, isIPv6);
+
+					if (ipNumber < min)
+						high = mid - 1;
+					else
+						low = mid + 1;
+				}
+
+				return null;
+			}
 		}
 
-		static Reader database;
+		static IP2LocationReader database;
 
-		public static void Initialize(string databasePath)
+		public static void Initialize(string databasePath = "IP2LOCATION-LITE-DB1.IPV6.BIN.ZIP")
 		{
-			if (string.IsNullOrEmpty(databasePath))
+			if (!File.Exists(databasePath))
 				return;
 
 			try
 			{
-				using (var fileStream = new FileStream(databasePath, FileMode.Open, FileAccess.Read))
+				using (var z = new ZipFile(databasePath))
 				{
-					if (databasePath.EndsWith(".gz"))
-						using (var gzipStream = new GZipInputStream(fileStream))
-							database = new Reader(gzipStream);
-					else
-						database = new Reader(fileStream);
+					var entry = z.FindEntry("IP2LOCATION-LITE-DB1.IPV6.BIN", false);
+					database = new IP2LocationReader(z.GetInputStream(entry));
 				}
 			}
 			catch (Exception e)
@@ -82,9 +138,7 @@ namespace OpenRA.Network
 			{
 				try
 				{
-					var record = database.Find<GeoIP2Record>(ip);
-					if (record != null)
-						return record.Country.Names.English;
+					return database.LookupCountry(ip);
 				}
 				catch (Exception e)
 				{