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From: Mike Karels <mike@karels.net>
To: Gleb Smirnoff <glebius@freebsd.org>
Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org,
dev-commits-src-main@freebsd.org
Subject: Re: git: 20d59403961d - main - kernel: deprecate Internet Class A/B/C
Date: Wed, 10 Nov 2021 16:26:29 -0600
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I=E2=80=99m going to top-post my reply to highlight this question:
It is proposed to revert the change to the default mask when setting
an Internet interface address without a mask, returning to the use of
the Class A/B/C mask as the default. We would still warn if there
was no mask supplied, except on loopback and point-to-point interfaces.
Does anyone object, or otherwise have comments?
Mike
On 10 Nov 2021, at 10:38, Gleb Smirnoff wrote:
> On Wed, Nov 10, 2021 at 09:36:03AM -0600, Mike Karels wrote:
> M> > The new /24 default is no better than classes. The only difference
> M> > that classes maintained POLA and new default doesn't. For example,
> M> > in my home network I have default router 10.0.0.1 and since it is
> M> > class A network on my VMs and test boxes I can type
> M>
> M> > # ifconfig vtnet0 10.6.6.6
> M>
> M> > and that is going to work. With this change no longer.
> M>
> M> I suspect that /8 is by far the minority these days, even with a
> M> "Class A" net. I also use net 10 at home, and at the last several j=
obs,
> M> but it is subnetted in each case. I would peridically add an addres=
s,
> M> forgetting a mask, only to find that a route for 10/8 isolated the m=
achine.
>
> The 10/8 can be used at home as a huge personal address space, just lik=
e
> a /64 IPv6 prefix. All addresses added without masks and everything wor=
ks.
>
> M> That said, my main objective was to deprecate usage without a mask, =
and
> M> to warn in that case. Both the kernel and ifconfig now warn when a =
default
> M> mask is used. In the discussion on freebsd-net and in the review, t=
he
> M> main thought was that masks should be required. But it isn't practi=
cal to
> M> fail and return an error with no mask, at least not without a signif=
icant
> M> period with warnings, or some systems would stop coming up on the ne=
twork.
> M>
> M> One reviewer was going to comment on the /24 default, but thought it=
was
> M> better than the previous. I'm open to hearing more opinions.
>
> Although I don't internally agree that we really need to police people =
to
> always specify masks, I would make step forward and agree with that. So=
,
> let's do print loud warning on every attempt to set IP address without =
a
> mask. But I can not agree that change from class based guess to /24 is =
a
> right thing to do. A proper deprecation process goes like this:
>
> Step 1: Print warning, don't change legacy behavior.
> <... people adopt ...>
> Step 2: Return error. Remove deprecated behavior.
>
> What we did is that we changed behavior together with warning. The new
> behavior is neither the legacy one nor the desired one, where mask is
> a must. Look from a user perspective: for class C nothing changed, but
> changed for A and B.
>
> --=20
> Gleb Smirnoff