clientip

README

clientip

Go library to retrieve the client IP from HTTP requests.

This library is a port of github.com/pbojinov/request-ip with additional tooling for Go servers.

Installation

$ go get github.com/victorkt/clientip

Basic usage

package main

import (
	"fmt"
	"log"
	"net/http"

	"github.com/victorkt/clientip"
)

func main() {
	http.HandleFunc("/", HelloServer)
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}

func HelloServer(w http.ResponseWriter, r *http.Request) {
	ip := clientip.FromRequest(r)
	fmt.Fprintf(w, "Hello, your IP is %s!", ip)
}

Middleware

package main

import (
	"fmt"
	"log"
	"net/http"

	"github.com/victorkt/clientip"
)

func main() {
	handler := http.HandlerFunc(HelloServer)
	http.Handle("/", clientip.Middleware(handler))

	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}

func HelloServer(w http.ResponseWriter, r *http.Request) {
	ip := clientip.FromContext(r.Context())
	fmt.Fprintf(w, "Hello, your IP is %s!", ip)
}

How it works

The library will try to get the client IP from a list of headers and falls back on request.RemoteAddr

The order in which the headers are checked is:

1. X-Client-IP
2. X-Forwarded-For (Header may return multiple IP addresses in the format: "client IP, proxy 1 IP, proxy 2 IP", so we take the the first one.)
3. CF-Connecting-IP (Cloudflare)
4. Fastly-Client-Ip (Fastly CDN and Firebase hosting header when forwared to a cloud function)
5. True-Client-Ip (Akamai and Cloudflare)
6. X-Real-IP (Nginx proxy/FastCGI)
7. X-Cluster-Client-IP (Rackspace LB, Riverbed Stingray)
8. X-Forwarded and Forwarded-For (Variations of #2)
9. request.RemoteAddr

If a valid IP was found and it contains a port number, the port will be ignored. If no valid IP is found, it returns a nil net.IP

License

The MIT License (MIT) - 2020

Documentation

Index

• func FromContext(ctx context.Context) net.IP
• func FromRequest(r *http.Request) net.IP
• func Middleware(next http.Handler) http.Handler

Functions

func FromContext

func FromContext(ctx context.Context) net.IP

FromContext returns the client IP address stored in the context. The value will only be set in context when using the middleware.

func FromRequest

func FromRequest(r *http.Request) net.IP

FromRequest returns the client IP address from the HTTP request

func Middleware

func Middleware(next http.Handler) http.Handler

Middleware returns an HTTP handler that will add the client IP to the request context.