// then the Dial will succeed, having simultaneously connected to itself.
	// This can only happen when we are letting the kernel pick a port (laddr == nil)
	// and when there is no listener for the destination address.
	// It's hard to argue this is anything other than a kernel bug. If we
	// see this happen, rather than expose the buggy effect to users, we

	// space. For some historical reason, it is used to
	// specify "any available address" on some operations
	// of IP node.
	//
	// When the IP node supports IPv4-mapped IPv6 address,
	// we allow a listener to listen to the wildcard
	// address of both IP addressing spaces by specifying
	// IPv6 wildcard address.
	if len(ip) == 0 || ip.Equal(IPv4zero) {
		ip = IPv6zero
	}