Real IP Lookup Module

This Go module provides functionality to accurately determine a client's IP address from HTTP requests, considering various headers that might contain the real IP address, especially when your application is behind a proxy or load balancer.

Features

LookupFromRequest: Retrieve the client IP address directly from an HTTP request with consideration for custom headers.
Middleware: An easy-to-integrate middleware function for HTTP servers that automatically sets the RemoteAddr field of the request to the client's real IP address.

Installation

To install the module, use the following command:

go get github.com/dmitrymomot/clientip

Usage

LookupFromRequest Function

LookupFromRequest retrieves the client IP address from the provided HTTP request. It checks a list of headers for the IP address and uses a default set if none are specified.

import "github.com/dmitrymomot/clientip"

func handler(w http.ResponseWriter, r *http.Request) {
    clientIP := clientip.LookupFromRequest(r)
    fmt.Fprintf(w, "Client IP: %s", clientIP)
}

With custom headers:

import "github.com/dmitrymomot/clientip"

func handler(w http.ResponseWriter, r *http.Request) {
    clientIP := clientip.LookupFromRequest(r, "X-Custom-Real-IP")
    fmt.Fprintf(w, "Client IP: %s", clientIP)
}

Middleware

The Middleware function returns a middleware handler that modifies the request's RemoteAddr based on the client IP address found in the specified headers.

import (
    "net/http"
    "github.com/dmitrymomot/clientip"
)

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/", handler)

    // Init the middleware with custom header. If not specified, the default headers are used.
    mdw := clientip.Middleware("X-Custom-Real-IP")

    http.ListenAndServe(":8080", mdw(mux))
}

func handler(w http.ResponseWriter, r *http.Request) {
    // The RemoteAddr now contains the real client IP
    fmt.Fprintf(w, "Client IP: %s", r.RemoteAddr)
}

Customization

Both LookupFromRequest and Middleware functions accept an optional list of headers to consider when looking for the client IP address. By default, a predefined set of common headers used for forwarding client IPs in proxy setups are checked.

Contributing

If you wish to contribute to this project, please fork the repository and submit a pull request.

License

This project is licensed under the Apache 2.0 - see the LICENSE file for details.

dmitrymomot / clientip