Re: change to deprecate broadcast on host 0 of a subnet
- In reply to: Mike Karels : "change to deprecate broadcast on host 0 of a subnet"
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Date: Wed, 15 Sep 2021 15:57:34 UTC
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