Desired behaviour of "ifconfig -alias"

Brooks Davis brooks at FreeBSD.ORG
Mon Feb 12 18:41:04 UTC 2007

On Mon, Feb 12, 2007 at 07:23:33PM +0100, Oliver Fromme wrote:
> Brooks Davis wrote:
>  > Oliver Fromme wrote:
>  > > Brooks Davis wrote:
>  > > > ipv4_addrs_<interface> is a much better replacement IMO.  It's easy to
>  > > > use and doesn't required the hackish pseudo array traversal used by
>  > > > ifconfig_iface_aliasX.
>  > > 
>  > > That might work for simple cases, but how do you specify
>  > > other parameters beside the IPs if you need to?
>  > 
>  > What do you need to set?  It's sets IP and netmask.  It doesn't handle
>  > broadcast, but I'd be pretty suprised if that's needed often.
> True, not often, but sometimes.  I had cases like that in
> certain environments with bridged networks and arp proxies.
> I'm fine with your proposed syntax, as long as all the
> existing ifconfig possibilities continue to be possible,
> i.e. no regression.

FWIW, it's HEAD and 6.1.  We've actually got the aliases syntax labled
as deprecated in the manpage.  We might want to add a feature to set the
broadcast address.

>  > is needed?  Axing ifconfig_iface_aliasX is not needed, but reducing the
>  > visiability of the interface in the documentation is probably in order
>  > particularly since it's quite fragile since you have to renumber whenever
>  > you remove an entry.
> Yup, I agree, that's a PITA.  That could be solved in the
> shell code, though, by not enumerating until a number
> doesn't exist, but instead looking at the set of all
> shell variables that have been set, similar to this:
> set | grep "^ifconfig_${IFACE}_alias" | cut -f1 -d= | ...

Unfortuanly grep in in /usr/bin so can't be used.  You could do it
with sh variable mangling and case though.  Something like:

{ while read _var; do
	case $_var in
done } < `set`

-- Brooks
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