package dialer

import (
	"net"
	"syscall"

	"golang.org/x/sys/unix"
)

func bindToInterface(i *net.Interface) controlFunc {
	return func(network, address string, c syscall.RawConn) error {
		ipStr, _, _ := net.SplitHostPort(address)
		if ip := net.ParseIP(ipStr); ip != nil && !ip.IsGlobalUnicast() {
			return nil
		}

		return c.Control(func(fd uintptr) {
			switch network {
			case "tcp4", "udp4":
				unix.SetsockoptInt(int(fd), syscall.IPPROTO_IP, syscall.IP_BOUND_IF, i.Index)
			case "tcp6", "udp6":
				unix.SetsockoptInt(int(fd), syscall.IPPROTO_IPV6, syscall.IPV6_BOUND_IF, i.Index)
			}
		})
	}
}