SO_TIMESTAMP vs ICMP6?

I'm trying to build a program that sends and receives ICMP6 packets.  I
want accurate timestamps on the received packets.  So, I turned on
SO_TIMESTAMP on the socket.

It didn't work.  recvmsg returned zero bytes of control data.  (It
works as expected for IPv4.)

So I tried it on a 9.1 machine I have root access to at work, only to
find it doesn't work there either.

I've written a small test program.  It needs SOCK_RAW access, so it
needs to be run as root, but it's small enough to read over in full.
See {http,ftp}://ftp.rodents-montreal.org/mouse/misc/test-icmp6.c for
the source.  Run it with no args on a v6-capable machine; it uses ::1,
so you don't need a second machine.

I get "data 64, ctl 0".  The ctl number should be nonzero; the exact
value depends on things such as sizeof(struct timeval) on the relevant
system - with a little kernel bludgeoning, my dev system (my mutant
4.0.1, on i386) sees 24 there.

Could someone maybe test this to see if it works on -current?  If not,
I'll send-pr it, unless someone explains why it's not supposed to work
for IPv6.

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