Date: Wed, 10 Nov 2021 16:26:29 -0600 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 Message-ID: <90C05BCC-D4B6-43F9-95B1-D072EBA3703A@karels.net> In-Reply-To: <YYv1oJN/pNp/%2Bn2m@FreeBSD.org> References: <YYtpRVV0oZk4u9Z1@FreeBSD.org> <202111101536.1AAFa311018767@mail.karels.net> <YYv1oJN/pNp/%2Bn2m@FreeBSD.org>
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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
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