On Thu, 23 Feb 2006, Colm MacCarthaigh wrote:
> Sub-interfaces can be bonded to for example, which allows
> applications to listen on a sub-set of addresses, or to prefer a
> specific source address, without having to specify a list of which
> addresses. This is probably the biggest effect/difference.
This doesn't ring true to me.
Selecting "interfaces" is typically done either by local address or
else by ifindex (see, e.g. the multicast sockopts). I can't think of
a sockopt that passes in or back device labels.
Addresses with labels do not have a distinct ifindex, you could only
ever 'pick' them by address. For which it doesn't matter whether or
not the address has a label.
'virtual interfaces' simply don't exist as far as userspace ought to
be concerned, not on Linux, not on BSD.
The only system I know of where additional addresses actually /do/
come wrapped up with additional interface structures is Solaris. (And
even there the sanest way for userspace to deal with it is to think
of it as behaving just like BSD - simply because other parts of
Solaris kernel do so, e.g PF_ROUTE - if you intend to make use of
1. I can think of ioctls where the 'label' matters, but only on
Paul Jakma paul at clubi.iepaul at jakma.org Key ID: 64A2FF6A
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