Implement WebClientIPHeader telemetry initializer

src/ApplicationInsights.AspNet/DataCollection/WebClientIpHeaderTelemetryInitializer.cs

@@ -9,15 +9,69 @@ namespace Microsoft.ApplicationInsights.AspNet.DataCollection
 	using Microsoft.AspNet.Http;
 	using Microsoft.AspNet.Http.Interfaces;
 	using Microsoft.ApplicationInsights.AspNet.Implementation;
+	using System.Collections.Generic;
+	using System.Net.Sockets;
+	using System.Net;
 
+	/// <summary>
+	/// This telemetry initializer extracts client IP address and populates telemetry.Context.Location.Ip property.
+	/// Lot's of code reuse from Microsoft.ApplicationInsights.Extensibility.Web.TelemetryInitializers.WebClientIpHeaderTelemetryInitializer
+	/// </summary>
 	public class WebClientIpHeaderTelemetryInitializer : ITelemetryInitializer
 	{
 		private IServiceProvider serviceProvider;
 
-        public WebClientIpHeaderTelemetryInitializer(IServiceProvider serviceProvider)
+		private readonly char[] HeaderValuesSeparatorDefault = new char[] { ',' };
+		private const string HeaderNameDefault = "X-Forwarded-For";
+
+		private char[] headerValueSeparators;
+
+		private readonly ICollection<string> headerNames;
+
+
+		public WebClientIpHeaderTelemetryInitializer(IServiceProvider serviceProvider)
 		{
 			this.serviceProvider = serviceProvider;
-        }
+			this.headerNames = new List<string>();
+			this.HeaderNames.Add(HeaderNameDefault);
+			this.UseFirstIp = true;
+			this.headerValueSeparators = HeaderValuesSeparatorDefault;
+		}
+
+		/// <summary>
+		/// Gets or sets comma separated list of request header names that is used to check client id.
+		/// </summary>
+		public ICollection<string> HeaderNames
+		{
+			get
+			{
+				return this.headerNames;
+			}
+		}
+
+		/// <summary>
+		/// Gets or sets a header values separator.
+		/// </summary>
+		public string HeaderValueSeparators
+		{
+			get
+			{
+				return string.Concat(this.headerValueSeparators);
+			}
+
+			set
+			{
+				if (!string.IsNullOrEmpty(value))
+				{
+					this.headerValueSeparators = value.ToCharArray();
+				}
+			}
+		}
+
+		/// <summary>
+		/// Gets or sets a value indicating whether the first or the last IP should be used from the lists of IPs in the header.
+		/// </summary>
+		public bool UseFirstIp { get; set; }
 
 		public void Initialize(ITelemetry telemetry)
 		{
@@ -30,18 +84,73 @@ namespace Microsoft.ApplicationInsights.AspNet.DataCollection
 			{
 				var context = this.serviceProvider.GetService<HttpContextHolder>().Context;
 
-				var connectionFeature = context.GetFeature<IHttpConnectionFeature>();
-
-				if (connectionFeature != null)
+				string resultIp = null;
+				foreach (var name in this.HeaderNames)
 				{
-					string ip = connectionFeature.RemoteIpAddress.ToString();
-					request.Context.Location.Ip = ip;
-					if (request != telemetry)
+					var headerValue = context.Request.Headers[name];
+					if (!string.IsNullOrEmpty(headerValue))
 					{
-						telemetry.Context.Location.Ip = ip;
+						var ip = GetIpFromHeader(headerValue);
+						ip = CutPort(ip);
+						if (IsCorrectIpAddress(ip))
+						{
+							resultIp = ip;
+							break;
+						}
 					}
 				}
+
+				if (string.IsNullOrEmpty(resultIp))
+				{
+					var connectionFeature = context.GetFeature<IHttpConnectionFeature>();
+
+					if (connectionFeature != null)
+					{
+						resultIp = connectionFeature.RemoteIpAddress.ToString();
+					}
+				}
+
+				request.Context.Location.Ip = resultIp;
+				telemetry.Context.Location.Ip = resultIp;
 			}
 		}
+
+		private static string CutPort(string address)
+		{
+			// For Web sites in Azure header contains ip address with port e.g. 50.47.87.223:54464
+			int portSeparatorIndex = address.IndexOf(":", StringComparison.OrdinalIgnoreCase);
+
+			if (portSeparatorIndex > 0)
+			{
+				return address.Substring(0, portSeparatorIndex);
+			}
+
+			return address;
+		}
+
+		private static bool IsCorrectIpAddress(string address)
+		{
+			IPAddress outParameter;
+			address = address.Trim();
+
+			// Core SDK does not support setting Location.Ip to malformed ip address
+			if (IPAddress.TryParse(address, out outParameter))
+			{
+				// Also SDK supports only ipv4!
+				if (outParameter.AddressFamily == AddressFamily.InterNetwork)
+				{
+					return true;
+				}
+			}
+
+			return false;
+		}
+
+		private string GetIpFromHeader(string clientIpsFromHeader)
+		{
+			var ips = clientIpsFromHeader.Split(this.headerValueSeparators, StringSplitOptions.RemoveEmptyEntries);
+			return this.UseFirstIp ? ips[0].Trim() : ips[ips.Length - 1].Trim();
+		}
+
 	}
 }