Azure function client ip

Question

I pass traffic through API Management to c# Function App. How can I get the client IP?

Answer 1

Hello @Casper Rubæk - Thanks for confirming in the private comments. Posting the below as a resolution to this thread:

Since APIM is in front of the Function App, and given how APIM maintains Client IP through context variable as follows: context.Request.IpAddress

The Client IP needs to be passed along to the Function App by way of defining a header via a small policy snippet:

<set-header name="X-Forwarded-Client-Ip" exists-action="override">  
     <value>@(context.Request.IpAddress)</value>  
</set-header>  

The corresponding value then can be accessed in your HttpTrigger function via HttpRequest object as follows:

#r "Newtonsoft.Json"  
  
using System.Net;  
using Microsoft.AspNetCore.Mvc;  
using Microsoft.Extensions.Primitives;  
using Newtonsoft.Json;  
  
public static async Task<IActionResult> Run(HttpRequest req, ILogger log)  
{  
   ....  
  
   var clientIP = req.Headers["X-Forwarded-Client-Ip"];  
   ....  
}  

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Answer 2

Hi @Casper Rubæk ,

Thanks for reaching out to Q&A forum.

In the function app, the list of client ip that is getting blocked due to ip restriction is available in the "Diagnose and solve problems" blade in portal. However, if you are looking to get all the client ips that are sending requests to the function app, then you will have to write your own logic/code to get the client ip.
Please refer to this article to get the client ip using C# : Get client ip using C#

Application insights temporarily collect the client ip addresses you can also explore it: https://learn.microsoft.com/en-us/azure/azure-monitor/app/ip-collection?tabs=net#default-behavior

I hope this helps! Feel free to reach out to me if you have any further queries or concerns.

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