Since march 2021 setting AUTOCONF{4,6} sets UP as well unconditionally. I have lots of hostname.if files containing only "inet6 autoconf" without "up" and it works, but I noticed this isn't documented anywhere.
Neither do we remove UP and/or RUNNING on `-autoconf' and neither do we document this. This is a good start, I think. Feedback? OK? Index: ifconfig.8 =================================================================== RCS file: /cvs/src/sbin/ifconfig/ifconfig.8,v retrieving revision 1.379 diff -u -p -r1.379 ifconfig.8 --- ifconfig.8 11 Nov 2021 09:39:16 -0000 1.379 +++ ifconfig.8 13 Nov 2021 23:01:33 -0000 @@ -163,6 +163,9 @@ automatically configures IPv4 addresses for interfaces with .Sy AUTOCONF4 set. +.Pp +Automatically mark the interface as +.Dq up . .It Cm -autoconf Unset the .Sy AUTOCONF4