Date: Thu, 11 Mar 2010 15:30:25 -0800 From: Qing Li <qingli@freebsd.org> To: Robert Watson <rwatson@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r205024 - head/sys/net Message-ID: <9ace436c1003111530s3bd0de9cq451671909fb6aa64@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1003112128020.97017@fledge.watson.org> References: <201003111756.o2BHukJu042449@svn.freebsd.org> <alpine.BSF.2.00.1003112128020.97017@fledge.watson.org>
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> > A couple of questions: > > (1) It used to be the case that quite a few interface drivers and types > didn't have a notion of "link up" -- especially older ethernet devices. = =A0Do > those all have the same problem? =A0It was probably a design oversight th= at >=A0devices don't declare an explicit capability for "can report link state= ". > What you raised is definitely a possibility and these fixes take the similar approach. I am going to try and go through each of these drivers in /sys/dev/ and converting them, very soon. > > (2) While loopback interfaces don't really have a link state, they can be >=A0administratively down -- should/do you check that as well as link state= ? > And more generally, even if link is up, administratively down should be >=A0obeyed? > For loopback interfaces, althgouth administrative these can be taken down= , I personally cannot think one practical usage case where ECMP across loopback interfaces would be interesting or usefaul. So I can think of very little reason to be concerned in the loopback case. > > Finally, it would be neat if there were a way to have information beyond > link state influence the choice to balance to a particular route/interfac= e. > =A0For example, imagine if I have a router with ECMP, and on the other si= de on > a single ethernet segment, I have two DSL modems. =A0The ethernet link wi= ll > remain up, but I may (via out-of-band mechanisms, such as SNMP or an acti= ve > probe) be able to tell that one of the DSL lines is down. =A0Is there a w= ay to > push that information into the kernel currently without deleting the rout= es, > and instead say "yeah, but for ECMP purposes this is 'down'"? > The above really falls into policy based routing. And policy based routing infrastrucutre is something I have already been working on but cannot yet push back into -current. In fact Julian and I had a conversation about this topic during the FIBs implementation time in late 2008. This infrastructure enhancement is definitely coming but I cannot yet prv= oide a timeline for merge back. It's mostly a time issue. Let me know if I have answered these questions to your satisfaction. -- Qing
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