On Sat, May 28, 2022 at 01:46:18PM -0700, Seth David Schoen wrote: > We're also interested in talking about whether there's an appropriate > path for supporting non-broadcast use of addresses within 127/8, our > most controversial change. In Linux and FreeBSD, we're experimenting > with the ideas of having a sysctl that defines the prefix length for > loopback on the 127 network (with the default value being 8), or making > the loopback interface honor netmasks in exactly the same way as other > network interfaces do (so if you set 255.0.0.0 as the mask on lo, then > it will believe 127.2.3.4 is reachable via loopback, while if you set > 255.255.255.255 as the mask, it will only believe 127.0.0.1 is > reachable). We think other systems will be willing to let people opt > into this change, but will likely not want to make it the default due to > concerns about possible existing uses for loopback addresses other than > 127.0.0.1.
There certainly are people using this behaviour of the loopback address(es) in creative ways on non-OpenBSD systems: https://timkay.com/solo/ Changing it on those systems will likely break various users' scripts in unexpected ways. The script linked above doesn't work in it's original form on OpenBSD precisely because of the different behaviour of the 127/8 subnet. Not that I really care, because a solution to the _real_ problem already exists. It's called IPv6.
