Milter-greylist

On Tue, Oct 12, 2004 at 09:53:26AM +0200, Emmanuel Dreyfus wrote:
> But that kills backward compatibility.

Why? I don't say you should use the UDP socket except for checking
if you can bind to the IP address of a specific peer which means
it is a local address.

> We could also check that the address is non local.

That's exactly what I'm suggesting, isn't it?

The implementation could look like this:

int
IsLocalAddress(const struct sockaddr *sa)
{
	struct sockaddr_in	sin;
	struct sockaddr_in6	sin6;
	socklen_t		length;
	int			sfd, islocal;

	switch (sa->sa_family) {
	case AF_INET:
		length = sizeof (sin);
		(void) memcpy(&sin, sa, sizeof (sin));
		sin.sin_port = 0;
		sa = (struct sockaddr *)&sin;
		break;
	case AF_INET6:
		length = sizeof (sin6);
		(void) memcpy(&sin, sa, sizeof (sin));
		sin6.sin6_port = 0;
		sin6.sin6_flowinfo = 0;
		sin6.sin6_scope_id = 0;
		sa = (struct sockaddr *)&sin6;
		break;
	default:
		/* error handling */
		[...]
	}

	if ((sfd = socket(sa->sa_family, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
		/* error handling */
		[...]
	}

	if (bind(sfd, sa, length) < 0) {
		if (errno != EADDRNOTAVAIL) {
			/* error handling */
			[...]
		}
		islocal = 0;
	} else {
		islocal = 1;
	}

	(void) close(sfd);

	return (islocal);
}

	Kind regards

-- 
Matthias Scheler                                  http://scheler.de/~matthias/