How can I get the client's IP address in ASP.NET MVC?

Question

I'm totally new to the ASP.NET MVC stack, and I was wondering what happened to the simple Page object and the Request ServerVariables object?

Basically, I want to to pull out the client PC's IP address, but I fail to understand how the current MVC structure has changed all of this.

As far as I can understand, most of the variable objects has been replaced by the HttpRequest variants.

Anybody care to share some resources? There is really a sea of stuff to learn in the ASP.NET MVC world. :)

For example, I have a static class with this current function. How do I get the same result using ASP.NET MVC?

public static int getCountry(Page page)
{
    return getCountryFromIP(getIPAddress(page));
}

public static string getIPAddress(Page page)
{
    string szRemoteAddr = page.Request.ServerVariables["REMOTE_ADDR"];
    string szXForwardedFor = page.Request.ServerVariables["X_FORWARDED_FOR"];
    string szIP = "";

    if (szXForwardedFor == null)
    {
        szIP = szRemoteAddr;
    }
    else
    {
        szIP = szXForwardedFor;

        if (szIP.IndexOf(",") > 0)
        {
            string [] arIPs = szIP.Split(',');

            foreach (string item in arIPs)
            {
                if (!isPrivateIP(item))
                {
                    return item;
                }
            }
        }
    }
    return szIP;
}

And how do I call this function from the controller page?

Answer 1

The simple answer is to use the HttpRequest.UserHostAddress property.

Example: From within a Controller:

using System;
using System.Web.Mvc;

namespace Mvc.Controllers
{
    public class HomeController : ClientController
    {
        public ActionResult Index()
        {
            string ip = Request.UserHostAddress;

            ...
        }
    }
}

Example: From within a helper class:

using System.Web;

namespace Mvc.Helpers
{
    public static class HelperClass
    {
        public static string GetIPHelper()
        {
            string ip = HttpContext.Current.Request.UserHostAddress;
            ..
        }
    }
}

BUT, if the request has been passed on by one, or more, proxy servers then the IP address returned by HttpRequest.UserHostAddress property will be the IP address of the last proxy server that relayed the request.

Proxy servers MAY use the de facto standard of placing the client's IP address in the X-Forwarded-For HTTP header. Aside from there is no guarantee that a request has a X-Forwarded-For header, there is also no guarantee that the X-Forwarded-For hasn't been SPOOFED.

---

Original Answer

Request.UserHostAddress

The above code provides the Client's IP address without resorting to looking up a collection. The Request property is available within Controllers (or Views). Therefore instead of passing a Page class to your function you can pass a Request object to get the same result:

public static string getIPAddress(HttpRequestBase request)
{
    string szRemoteAddr = request.UserHostAddress;
    string szXForwardedFor = request.ServerVariables["X_FORWARDED_FOR"];
    string szIP = "";

    if (szXForwardedFor == null)
    {
        szIP = szRemoteAddr;
    }
    else
    {
        szIP = szXForwardedFor;
        if (szIP.IndexOf(",") > 0)
        {
            string [] arIPs = szIP.Split(',');

            foreach (string item in arIPs)
            {
                if (!isPrivateIP(item))
                {
                    return item;
                }
            }
        }
    }
    return szIP;
}

Answer 2

Request.ServerVariables["REMOTE_ADDR"] should work - either directly in a view or in the controller action method body (Request is a property of Controller class in MVC, not Page).

It is working.. but you have to publish on a real IIS not the virtual one.

Answer 3

A lot of the code here was very helpful, but I cleaned it up for my purposes and added some tests. Here's what I ended up with:

using System;
using System.Linq;
using System.Net;
using System.Web;

public class RequestHelpers
{
    public static string GetClientIpAddress(HttpRequestBase request)
    {
        try
        {
            var userHostAddress = request.UserHostAddress;

            // Attempt to parse.  If it fails, we catch below and return "0.0.0.0"
            // Could use TryParse instead, but I wanted to catch all exceptions
            IPAddress.Parse(userHostAddress);

            var xForwardedFor = request.ServerVariables["X_FORWARDED_FOR"];

            if (string.IsNullOrEmpty(xForwardedFor))
                return userHostAddress;

            // Get a list of public ip addresses in the X_FORWARDED_FOR variable
            var publicForwardingIps = xForwardedFor.Split(',').Where(ip => !IsPrivateIpAddress(ip)).ToList();

            // If we found any, return the last one, otherwise return the user host address
            return publicForwardingIps.Any() ? publicForwardingIps.Last() : userHostAddress;
        }
        catch (Exception)
        {
            // Always return all zeroes for any failure (my calling code expects it)
            return "0.0.0.0";
        }
    }

    private static bool IsPrivateIpAddress(string ipAddress)
    {
        // http://en.wikipedia.org/wiki/Private_network
        // Private IP Addresses are: 
        //  24-bit block: 10.0.0.0 through 10.255.255.255
        //  20-bit block: 172.16.0.0 through 172.31.255.255
        //  16-bit block: 192.168.0.0 through 192.168.255.255
        //  Link-local addresses: 169.254.0.0 through 169.254.255.255 (http://en.wikipedia.org/wiki/Link-local_address)

        var ip = IPAddress.Parse(ipAddress);
        var octets = ip.GetAddressBytes();

        var is24BitBlock = octets[0] == 10;
        if (is24BitBlock) return true; // Return to prevent further processing

        var is20BitBlock = octets[0] == 172 && octets[1] >= 16 && octets[1] <= 31;
        if (is20BitBlock) return true; // Return to prevent further processing

        var is16BitBlock = octets[0] == 192 && octets[1] == 168;
        if (is16BitBlock) return true; // Return to prevent further processing

        var isLinkLocalAddress = octets[0] == 169 && octets[1] == 254;
        return isLinkLocalAddress;
    }
}

And here are some NUnit tests against that code (I'm using Rhino Mocks to mock the HttpRequestBase, which is the M<HttpRequestBase> call below):

using System.Web;
using NUnit.Framework;
using Rhino.Mocks;
using Should;

[TestFixture]
public class HelpersTests : TestBase
{
    HttpRequestBase _httpRequest;

    private const string XForwardedFor = "X_FORWARDED_FOR";
    private const string MalformedIpAddress = "MALFORMED";
    private const string DefaultIpAddress = "0.0.0.0";
    private const string GoogleIpAddress = "74.125.224.224";
    private const string MicrosoftIpAddress = "65.55.58.201";
    private const string Private24Bit = "10.0.0.0";
    private const string Private20Bit = "172.16.0.0";
    private const string Private16Bit = "192.168.0.0";
    private const string PrivateLinkLocal = "169.254.0.0";

    [SetUp]
    public void Setup()
    {
        _httpRequest = M<HttpRequestBase>();
    }

    [TearDown]
    public void Teardown()
    {
        _httpRequest = null;
    }

    [Test]
    public void PublicIpAndNullXForwardedFor_Returns_CorrectIp()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(null);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(GoogleIpAddress);
    }

    [Test]
    public void PublicIpAndEmptyXForwardedFor_Returns_CorrectIp()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(string.Empty);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(GoogleIpAddress);
    }

    [Test]
    public void MalformedUserHostAddress_Returns_DefaultIpAddress()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(MalformedIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(null);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(DefaultIpAddress);
    }

    [Test]
    public void MalformedXForwardedFor_Returns_DefaultIpAddress()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(MalformedIpAddress);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(DefaultIpAddress);
    }

    [Test]
    public void SingleValidPublicXForwardedFor_Returns_XForwardedFor()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(MicrosoftIpAddress);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(MicrosoftIpAddress);
    }

    [Test]
    public void MultipleValidPublicXForwardedFor_Returns_LastXForwardedFor()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(GoogleIpAddress + "," + MicrosoftIpAddress);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(MicrosoftIpAddress);
    }

    [Test]
    public void SinglePrivateXForwardedFor_Returns_UserHostAddress()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(Private24Bit);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(GoogleIpAddress);
    }

    [Test]
    public void MultiplePrivateXForwardedFor_Returns_UserHostAddress()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        const string privateIpList = Private24Bit + "," + Private20Bit + "," + Private16Bit + "," + PrivateLinkLocal;
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(privateIpList);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(GoogleIpAddress);
    }

    [Test]
    public void MultiplePublicXForwardedForWithPrivateLast_Returns_LastPublic()
    {
        // Arrange
        _httpRequest.Stub(x => x.UserHostAddress).Return(GoogleIpAddress);
        const string privateIpList = Private24Bit + "," + Private20Bit + "," + MicrosoftIpAddress + "," + PrivateLinkLocal;
        _httpRequest.Stub(x => x.ServerVariables[XForwardedFor]).Return(privateIpList);

        // Act
        var ip = RequestHelpers.GetClientIpAddress(_httpRequest);

        // Assert
        ip.ShouldEqual(MicrosoftIpAddress);
    }
}

Answer 4

I had trouble using the above, and I needed the IP address from a controller. I used the following in the end:

System.Web.HttpContext.Current.Request.UserHostAddress

Answer 5

In a class you might call it like this:

public static string GetIPAddress(HttpRequestBase request) 
{
    string ip;
    try
    {
        ip = request.ServerVariables["HTTP_X_FORWARDED_FOR"];
        if (!string.IsNullOrEmpty(ip))
        {
            if (ip.IndexOf(",") > 0)
            {
                string[] ipRange = ip.Split(',');
                int le = ipRange.Length - 1;
                ip = ipRange[le];
            }
        } else
        {
            ip = request.UserHostAddress;
        }
    } catch { ip = null; }

    return ip; 
}

I used this in a razor app with great results.

Answer 6

How I account for my site being behind an Amazon AWS Elastic Load Balancer (ELB):

public class GetPublicIp {

    /// <summary>
    /// account for possbility of ELB sheilding the public IP address
    /// </summary>
    /// <returns></returns>
    public static string Execute() {
        try {
            Console.WriteLine(string.Join("|", new List<object> {
                    HttpContext.Current.Request.UserHostAddress,
                    HttpContext.Current.Request.Headers["X-Forwarded-For"],
                    HttpContext.Current.Request.Headers["REMOTE_ADDR"]
                })
            );

            var ip = HttpContext.Current.Request.UserHostAddress;
            if (HttpContext.Current.Request.Headers["X-Forwarded-For"] != null) {
                ip = HttpContext.Current.Request.Headers["X-Forwarded-For"];
                Console.WriteLine(ip + "|X-Forwarded-For");
            }
            else if (HttpContext.Current.Request.Headers["REMOTE_ADDR"] != null) {
                ip = HttpContext.Current.Request.Headers["REMOTE_ADDR"];
                Console.WriteLine(ip + "|REMOTE_ADDR");
            }
            return ip;
        }
        catch (Exception ex) {
            Console.Error.WriteLine(ex.Message);
        }
        return null;
    }
}