Date: Fri, 12 Mar 2010 08:49:40 +0000 From: "Robert N. M. Watson" <rwatson@freebsd.org> To: Julian Elischer <julian@elischer.org> Cc: svn-src-head@freebsd.org, Qing Li <qingli@freebsd.org>, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r205024 - head/sys/net Message-ID: <385F840D-4011-443C-8FC9-FAB9FDF211DF@freebsd.org> In-Reply-To: <4B99FF0A.5080504@elischer.org> References: <201003111756.o2BHukJu042449@svn.freebsd.org> <alpine.BSF.2.00.1003112128020.97017@fledge.watson.org> <9ace436c1003111530s3bd0de9cq451671909fb6aa64@mail.gmail.com> <5ADB6F0D-11F1-4F9F-87A0-64F57063981E@freebsd.org> <9ace436c1003112352l3b2505ceq63d9c78954520497@mail.gmail.com> <A543276F-1982-4F12-B325-7277C2B42C92@freebsd.org> <9ace436c1003120011v3c627aadka2e57615ae01fe6f@mail.gmail.com> <8726950E-5110-4FE1-90BB-B4205D637764@freebsd.org> <9ace436c1003120030m39f518basc77c7cff40299008@mail.gmail.com> <DEE37FC3-0843-4121-A001-51AB80FE2B32@freebsd.org> <4B99FE46.6090001@elischer.org> <4B99FF0A.5080504@elischer.org>
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On Mar 12, 2010, at 8:44 AM, Julian Elischer wrote: >>>>> I'm confused about Julian's proposal because it seems to me that = we already know when a driver hasn't set or is unable to determine the = link state: it will (should) be set to LINK_STATE_UNKNOWN by default. >=20 > the question is whether there is any other meaning for this state. > For example "I have not started up yet" Right now LINK_STATE_UNKNOWN conflates three different conditions: (1) I haven't and won't ever set the link state (2) I haven't yet, but may in the future set the link state (3) I wanted to check the link state, and the hardware is $*$**=A3*@@ so = I left or set this value instead My preferred solution is to advertise driver capabilities via the driver = capabilities flag, if_capabilities, and define a new flag = IFCAP_LINKSTATE (or something similar) that allows a driver to declare = that it is able to determine link state. If the flag is set, then = components like ECMP, but also dhclient, can reasonably expect that the = driver will do its best to provide link state information, addressing = the difference between (1) and (2) when a value of LINK_STATE_UNKNOWN is = found. If we are able to explicitly handle (3) in any of our drivers, then a = new link state definition should be defined, LINK_STATE_ERROR, which = should be set by the driver if it declared ICAP_LINKSTATE but was = unable, due to hardware failure, to check it. Robert=
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