There's a long history of using loX interfaces for such things. What might make sense is to restrict it on lo0 ?
>On Tue, Apr 16, 2024 at 08:37:49AM -0600, Florian Obser wrote: >> CVSROOT: /cvs >> Module name: src >> Changes by: [email protected] 2024/04/16 08:37:49 >> >> Modified files: >> sys/netinet6 : in6.c >> >> Log message: >> Destination addresses make no sense on loopback interfaces. >> >> While here use (variable & FLAG) or !(variable & FLAG) consistently in >> in6_update_ifa(). >> >> Discussed with claudio >> OK denis > >This change introduced 15 regress failures, all related to inet6. > > https://regress.basename.se/ > >Excerpt from sys/net/mpath showing the symptom: > > doas -n /sbin/ifconfig lo19 inet6 fc00::19 alias > ifconfig: lo19: SIOCIFAFATTACH: Invalid argument > ifconfig: SIOCAIFADDR: Invalid argument > >
