Date: Thu, 11 Nov 2021 09:12:53 -0500 From: George Neville-Neil <gnn@neville-neil.com> To: Mike Karels <mike@karels.net> Cc: Gleb Smirnoff <glebius@freebsd.org>, 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: <C37059A2-BD20-4C99-A455-3AA9292EB57B@neville-neil.com> In-Reply-To: <90C05BCC-D4B6-43F9-95B1-D072EBA3703A@karels.net> References: <YYtpRVV0oZk4u9Z1@FreeBSD.org> <202111101536.1AAFa311018767@mail.karels.net> <YYv1oJN/pNp/%2Bn2m@FreeBSD.org> <90C05BCC-D4B6-43F9-95B1-D072EBA3703A@karels.net>
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I actually think that this is a reasonable solution. Best, George On 10 Nov 2021, at 17:26, Mike Karels wrote: > I’m 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 jobs, >> M> but it is subnetted in each case. I would peridically add an address, >> M> forgetting a mask, only to find that a route for 10/8 isolated the machine. >> >> The 10/8 can be used at home as a huge personal address space, just like >> a /64 IPv6 prefix. All addresses added without masks and everything works. >> >> 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, the >> M> main thought was that masks should be required. But it isn't practical to >> M> fail and return an error with no mask, at least not without a significant >> M> period with warnings, or some systems would stop coming up on the network. >> 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. >> >> -- >> Gleb Smirnoff
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