package util

import (
	"log"
	"net"
)

// get the local ip and port based on our destination ip
func LocalIPPort(dstip net.IP) (net.IP, int) {
	serverAddr, err := net.ResolveUDPAddr("udp", dstip.String()+":12345")
	if err != nil {
		log.Fatal(err)
	}

	// We don't actually connect to anything, but we can determine
	// based on our destination ip what source ip we should use.
	if con, err := net.DialUDP("udp", nil, serverAddr); err == nil {
		defer con.Close()
		if udpaddr, ok := con.LocalAddr().(*net.UDPAddr); ok {
			return udpaddr.IP, udpaddr.Port
		}
	}
	return nil, -1
}