clientip

Overview ¶

Package clientip extracts real client IP addresses from HTTP requests.

This package handles various proxy headers in priority order to determine the actual client IP address, which is essential for rate limiting, geolocation, and security logging in web applications behind proxies, load balancers, or CDNs.

The package checks headers in this specific order:

1. CF-Connecting-IP (Cloudflare)
2. DO-Connecting-IP (DigitalOcean App Platform)
3. X-Forwarded-For (most common proxy header)
4. X-Real-IP (nginx and other proxies)
5. RemoteAddr (direct connection)

Basic usage:

import "github.com/dmitrymomot/forge/pkg/clientip"

func handleRequest(w http.ResponseWriter, r *http.Request) {
	clientIP := clientip.GetIP(r)
	log.Printf("Request from IP: %s", clientIP)

	// Use for rate limiting, geolocation, security logging, etc.
}

The GetIP function validates all IP addresses and handles edge cases:

• Invalid IP strings are rejected and fallback headers are checked
• IPv6 addresses are properly parsed and normalized
• X-Forwarded-For with multiple IPs uses the leftmost (original client) IP
• The special address 0.0.0.0 is rejected as invalid
• If no valid IP is found, returns the raw RemoteAddr as fallback

The function never panics and always returns a string, making it safe for production use in high-traffic applications.