In some email I received from Christian E. Hopps, sie wrote:
[...]
> So the point jason is making is this:
> 
> Pass a pointer to the sockaddr, copy it into your happy structure you
> have now.. Don't poluute the API into the kernel with protocol specific
> stuff.

At present, it's not a "real" api..

> This change is so simple why are you fighting it?

because it would look like this:

struct foo {
	struct sockaddr *sa1;
	struct sockaddr *sm1;
	struct sockaddr *sa2;
	struct sockaddr *sm2;
	struct in_addr a4_1;
	struct in6_addr a6_1;
	struct in_addr m4_1;
	struct in6_addr m6_1;
	struct in_addr a4_2;
	struct in6_addr a6_2;
	struct in_addr m4_2;
	struct in6_addr m6_2;
};

Darren