Subject: Re: [PATCH net-next 0/5] net: Extend address label support

From: Stephen Hemminger <[email-masked]>
Date: Fri, 10 Mar 2023 19:41:25 -0800

On Fri, 10 Mar 2023 12:44:53 +0100
Petr Machata <[email-masked]> wrote:

> IPv4 addresses can be tagged with label strings. Unlike IPv6 addrlabels,
> which are used for prioritization of IPv6 addresses, these "ip address
> labels" are simply tags that the userspace can assign to IP addresses
> arbitrarily.
> 
> IPv4 has had support for these tags since before Linux was tracked in GIT.
> However it has never been possible to change the label after it is once
> defined. This limits usefulness of this feature. A userspace that wants to
> change a label might drop and recreate the address, but that disrupts
> routing and is just impractical.
> 
> IPv6 addresses lack support for address labels (in the sense of address
> tags) altogether.
> 
> In this patchset, extend IPv4 to allow changing the label defined at an
> address (in patch #1). Then, in patches #2 and #3, extend IPv6 with a suite
> of address label operations fully analogous with those defined for IPv4.
> Then in patches #4 and #5 add selftest coverage for the feature.
> 
> An example session with the feature in action:
> 
> 	# ip address add dev d 2001:db8:1::1/64 label foo
> 	# ip address show dev d
> 	4: d: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc [...]
> 	    link/ether 06:29:74:fd:1f:eb brd ff:ff:ff:ff:ff:ff
> 	    inet6 2001:db8:1::1/64 scope global foo <--
> 	    valid_lft forever preferred_lft forever
> 	    inet6 fe80::429:74ff:fefd:1feb/64 scope link d
> 	    valid_lft forever preferred_lft forever
> 
> 	# ip address replace dev d 2001:db8:1::1/64 label bar
> 	# ip address show dev d
> 	4: d: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc [...]
> 	    link/ether 06:29:74:fd:1f:eb brd ff:ff:ff:ff:ff:ff
> 	    inet6 2001:db8:1::1/64 scope global bar <--
> 	    valid_lft forever preferred_lft forever
> 	    inet6 fe80::429:74ff:fefd:1feb/64 scope link d
> 	    valid_lft forever preferred_lft forever
> 
> 	# ip address del dev d 2001:db8:1::1/64 label foo
> 	RTNETLINK answers: Cannot assign requested address
> 	# ip address del dev d 2001:db8:1::1/64 label bar

This would add a lot of naming confusion with existing IPv6 address labels.
And MPLS labels.

See man ip-addrlabel for more info.  Can't think of better term for this.
Tag would raise conflicts with vlan/vxlan tag term.
Name would be confusing vs DNS naming.

Also, most of the real world manages addresses through automated services so
doing it with ip address isn't going to help.