Desired behaviour of "ifconfig -alias"

Oliver Fromme olli at
Tue Feb 13 07:57:33 UTC 2007

Kevin Way wrote:
 > Oliver Fromme wrote:
 > > But you called it "confusing".  That's just your personal
 > > perception.  It doesn't mean it is confusing to everybody.
 > >   
 > If asked what -alias does, would you really reply "it removes the
 > primary IP,
 > while leaving the alias?"  Be honest here.

No, I wouldn't answer that, because there is no such thing
as a primary IP.  All IPs on an interface are equal.  The
term alias exists only for historical reasons, and it's
clearly becoming obsolete.

If asked what "-alias" does, I would reply that it is an
alias for "delete" or "remove", which removes an IP address
from an interface.  According to the docs, the IP address
to be removed must be specified.  The docs don't mention
what happens if none is specified, so the behaviour is
undefined and should not be relied on.  It just happens
that the behaviour is to remove an arbitrary IP address
(which happens to be the first one).

That behaviour should be documented in the manual page.

 > >  Also note that it doesn't hurt anybody.  
 > If you run RELENG_6_2, and a jail fails to start, this command is  called. 
 > And instead of unaliasing the jail's alias, it (because of a bug in the
 > shipped
 > rc.d scripts), it removes the primary IP.

That's clearly a bug in the scripts then.  They shouldn't
call a command that can cause undefined behaviour.

I'm not against changing the behaviour for the -alias
parameter, if it's done carefully and in -current first,
as I wrote earlier.  However, the behaviour for "delete"
and "remove" should stay as-is (and be documented in the
man page) because it makes sense.

Best regards

Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
Handelsregister: Registergericht Muenchen, HRA 74606,  Geschäftsfuehrung:
secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün-
chen, HRB 125758,  Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart
Any opinions expressed in this message are personal to the author and may
not necessarily reflect the opinions of secnetix GmbH & Co KG in any way.
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