Date: Fri, 04 Jun 2021 21:31:54 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 256393] Issue with recreation of ppp/tun interfaces Message-ID: <bug-256393-7501-6JLLDRgQez@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-256393-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-256393-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D256393 --- Comment #21 from Rodney W. Grimes <rgrimes@FreeBSD.org> --- (In reply to Alexander V. Chernikov from comment #19 > Do I understand correctly that you're suggesting that loopback routes sho= uld be installed by the routing daemons instead of kernel? Suggest? No, my words are stronger than that. The KERNEL should NOT implem= ent ANY routing policies. A loopback route IS a routing policy. Further loopback routes are a micro-optimazation that was originally done to short circuit the MTU of 1500 on ethernet, and much short in the days of IM= P's and slip lines to use the larger MTU of the loopback interfaces. A BSD sys= tem can run perfectly fine with NONE of these loopback routes, they are nothing more than an optimization. > If yes, I'm not sure how one would handle non-router cases (e.g. a server= with a single interface). Well this use to be handled by a simple static route, but someone couldnt handle the fact that the route goes away if you down the interface and thou= ght that the kernel should maintain this route for them. This is arguable a la= ck of skill or understanding that if you take an interface down ALL routes are gona go away, and you need to re install them.=20=20 > I'm also not sure how can this work with modern routing software. IIRC fr= r does not care about any route which is not RTF_GATEWAY. It is certainly p= ossible to configure such routes in bird, but it has to be done on per-pref= ix basis. I'll discuss this with the FRR folks, but I do believe that software already knows how to maintain loopback routes. Usually on a "router" you do NOT wa= nt these routes in place, as this hides interface errors for locally sent pack= ets to a local address. > Could you share a bit more details on what is the proposed alternative? = Well I think part of why we are here right now is that routed is trying to = maintain these routes and it is conflicting/having issue with what the kern= el is doing. I also know of older routing code that maintained these witho= ut issue. And finally these routes are a micro optimazation that are simpl= y not needed in most cases. --=20 You are receiving this mail because: You are on the CC list for the bug.=
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