Gordon...

it is old and ugly, but you'd have to change about every imported
program on earth (tcpdump, dhcpd come to mind) to change this. You'd
also have to change very of our self-maintained network programs, but
that would be just our problem.

And we'd have to keep compatibility stuff for COMPAT_12 somewhere.

However, it is possible to make the name length aligned (just fill up
with zeros) to get the performance benefit you want.

In src/sys/net/if.c:if_attach() move the #define ROUNDUP to just
before the namelen=strlen(ifp->if_xname) assignment, and change the

namelen = strlen(ifp->if_xname);
	to
namelen = ROUNDUP(strlen(ifp->if_xname));

Regards,
	Ignatios