cloud-config-url fails to parse if booting over PXE ipv6

[Federico Bosi]

On MAAS 3.4-RC1, I configured a subnet my:prefix:141::/80.
The rack controller has address my:prefix:141::rack.

MAAS correctly hands out DHCPv6 addresses but when the image boots, the cloud-config-url kernel parameter has the rack's ip without square brackets (see attachment) and fails saying it cannot parse the url as the added port makes in invalid.
The host then fails to enlist saying that no datasource can be found.

If in the custom kernel parameters I override it by adding
`cloud-config-url="http://[my:prefix:141::rack]:5248/MAAS/metadata/latest/enlist-preseed/?op=get_enlist_preseed"` the node enlists successfully.

[Jacopo Rota (r00ta)]

Hi Federico,

Thanks for reporting this. I'll take a look and get back to you by the end of the day

[Jacopo Rota (r00ta)]

Being busy with some urgent stuff. I'll get back to this by the end of the week

[Jacopo Rota (r00ta)]

I confirm in an ipv6 env in the grub.cfg we are not adding the brackets to the cloud_init config address.
The bug should be here https://github.com/maas/maas/blob/00e818eb2434af668fefed378bc9da36548bcd0c/src/maasserver/rpc/boot.py#L349