Add support for alternative names

[SchSeba]

This commit add the support for alternative names.

exposing the attributes in the link object.
also adding the add and delete functions

[aboch]

Thank you.
Can you pelase add some UT as well?

[hellt]

I would love to see this merged. Need it to set user-friendly names for otherwise restricted link length

[hellt]

@SchSeba I wonder, which func would one use to get the interface by its altname?

[SchSeba]

Hi @hellt,
it will be just as part of the link attrs you will have a list of them https://github.com/vishvananda/netlink/pull/862/files#diff-ff692b0e80c3a46490bdaf004f6628c003a4736c549aa8050a430246e70d6703R36

[hellt]

Hi @SchSeba
So to get a link by an alias one would need to list all links and then do a loop to the desired altname to be present in []AltNames?

I wonder, since we have LinkByAlias, wouldn't it be nice to have LinkByAltName?

[SchSeba]

The problem is that LinkByAltName will have to do "list all links and then do a loop to the desired altname to be present in []AltNames" because there is no API right now in the kernel.

btw I didn't try that but I think you can just use the LinkByName with the Alt name and it should work can you give it a try?

[hellt]

The problem is that LinkByAltName will have to do "list all links and then do a loop to the desired altname to be present in []AltNames" because there is no API right now in the kernel.

yes, this is also how LinkByAlias works as well for older kernels -

netlink/link_linux.go

Line 1845 in a4fcbb7

if err == unix.EINVAL {

I did try to use LinkByName and providing an alias, but I got a netlink error, smth about slice bounds out of range... So I had to revert back to using aliases, though AltNames is what I really want.

[SchSeba]

@aboch @vishvananda could you take a look at this PR ? :)

[SchSeba]

Hi @hellt be aware that now it works link netlink does you can do LinkByName and it will find the device base on the name or the altName

# ip link show enp8s0u2u1u2
26: ens1u2u1u2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 08:3a:88:61:c6:bf brd ff:ff:ff:ff:ff:ff
    altname enp8s0u2u1u2

[SchSeba]

@adrianchiris please take another look when you have time

[adrianchiris]

@SchSeba code changes look OK. thx for addressing my comments.

could you please update commit message to mention the changes in LinkByName()

[SchSeba]

Done thanks @adrianchiris !

[adrianchiris]

lgtm