On 12 Sep 2021, at 15:25, Mike Karels wrote:
Long ago (4.2BSD), the IP broadcast address was the lowest address on
a
network, the one with a host part of 0. In RFC1122, the broadcast
address
was standardized using a host part of all ones. 4.3BSD changed its
default, and made the broadcast address settable with ifconfig.
However,
FreeBSD *still* broadcasts packets sent to the lowest address on a
subnet.
I have a change in review to stop broadcasting the lowest address on a
subnet by default, but added a sysctl to revert to the current
behavior.
I really doubt that anyone is still using a 0-based broadcast address.
This change allows host 0 on a subnet to be used as an assigned host
address, as long as the systems on that network support it (including
routers). Linux already has this change.
The review is https://reviews.freebsd.org/D31861. See also
https:/datatracker.ietf.org/draft-schoen-intarea-lowest-address/ and
I think it is:
https://datatracker.ietf.org/doc/draft-schoen-intarea-lowest-address/
some of the discussion in https://reviews.freebsd.org/D19316.
Comments are welcome on the review. I will wait a couple of days
for comments before proceeding. I am also interested in comments on
whether this should be MFC'ed to 13-stable after a suitable delay.
I would have even gone one further step back and put this under
EXPERIMENTAL
in HEAD and wait until this draft has gone anywhere but with your sysctl
I think
it is fine (from reading the email not the recent review).
I would prefer if the current behaviour stayed default (would also MFC
better)
and then flip if this will indeed go anywhere.
My personal note on this is: it is riding a dead horse, driven by
economics,
and it feels 30 year too late to still do this and change this historic
behaviour.
/bz
