Re: ifconfig v2

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>>         inet 169.254.162.222 prefixlen 16
>>         inet6 fe80::226:2dff:fef3:c8c7%wm0 prefixlen 64 scopeid 0x1

> If you want to do that, please use

>    inet 169.253.162.222/16

> which is more standard notation (so-called "CIDR" notation) for IPv4.

Indeed, some programs accept it for v6 as well.  But - unless you also
propose to break noncontiguous netmasks completely - you have to be
prepared to report the mask as other than a width if it's
noncontiguous.

Not that noncontiguous masks are common.  I'm the only person I have
ever even heard of who ran one other than for testing.  But, if they're
possible for userland to create even by mistake (which is not the same
as being possible for ifconfig to set), they really should be reported
when querying, for much the same reason you bring up with respect to
broadcast addresses below: if it goes wonky it needs to be mentioned.
Indeed, I had an unpleasant bug once which arose from certain bits
being ignored when printed but accepted, and used, when set wrong; if
they'd been reported it would have been much easier to find and thus
fix.

Not that that's a reason to not report it as a CIDR width if it _is_ a
contiguous mask, of course.

> Also, my recent experience is that while rarely is the broadcast
> address useful, when it's wrong, you are not likely to query
> specifically for it, and removing it means you're less likely to
> notice the problem.

This is true.  If you really want to delete it from the common case, I
would suggest reporting it by default iff it's not set to the default
for the address-and-mask in question.

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