yggdrasil-go/src/multicast/multicast_unix.go

//go:build linux || netbsd || freebsd || openbsd || dragonflybsd
// +build linux netbsd freebsd openbsd dragonflybsd

package multicast

import (
	"syscall"

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

func (m *Multicast) _multicastStarted() {

}

func (m *Multicast) multicastReuse(network string, address string, c syscall.RawConn) error {
	var control error
	var reuseaddr error

	control = c.Control(func(fd uintptr) {
		// Previously we used SO_REUSEPORT here, but that meant that machines running
		// Yggdrasil nodes as different users would inevitably fail with EADDRINUSE.
		// The behaviour for multicast is similar with both, so we'll use SO_REUSEADDR
		// instead.
		reuseaddr = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_REUSEADDR, 1)
	})

	switch {
	case reuseaddr != nil:
		return reuseaddr
	default:
		return control
	}
}