Date: Fri, 12 Mar 2010 00:30:00 -0800 From: Qing Li <qingli@freebsd.org> To: "Robert N. M. 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: <9ace436c1003120030m39f518basc77c7cff40299008@mail.gmail.com> In-Reply-To: <8726950E-5110-4FE1-90BB-B4205D637764@freebsd.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>
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I believe what Julian means is the following:
1. in the driver, I do this
ifp->if_flags |=3D IFF_KNOWS_LINK_STATE;
2. In route.h, I do this
if (ifp->flags & IFF_KNOWS_LINK_STATE) && (ifp->if_link_state =3D=3D
LINK_STATE_UP)
return 1;
-- Qing
On Fri, Mar 12, 2010 at 12:26 AM, Robert N. M. Watson
<rwatson@freebsd.org> wrote:
>
> On Mar 12, 2010, at 8:11 AM, Qing Li wrote:
>
>> I like Julian's suggestion because it is simple and very low risk.
>> And there isn't a need to check for interface type any more.
>> Here is why:
>>
>> 1. The interfaces that are popular and modern are already supporting
>> =A0 =A0link_state. So for these drivers, and there are just a few, I wil=
l go set
>> =A0 =A0its if_flags to include "can change link_state".
>>
>> 2. For the existing dated drivers, because that flag bit is never set,
>> =A0 =A0no check is done.
>>
>> 3. In the mean time, we try to convert the drivers progressively.
>>
>> 4. If one wants to do ECMP and not having packets go into a black
>> =A0 =A0hole when the physical link is down, that person can ping the ML
>> =A0 =A0and ask for driver compatibility list. If we haven't converted th=
at
>> =A0 =A0particular driver by then, we will update the driver if it's capa=
ble
>> =A0 =A0at that time.
>
>
> Today, we support three link state values:
>
> 170 /*
> 171 =A0* Values for if_link_state.
> 172 =A0*/
> 173 #define LINK_STATE_UNKNOWN =A0 =A0 =A00 =A0 =A0 =A0 /* link invalid/u=
nknown */
> 174 #define LINK_STATE_DOWN =A0 =A0 =A0 =A0 1 =A0 =A0 =A0 /* link is down=
*/
> 175 #define LINK_STATE_UP =A0 =A0 =A0 =A0 =A0 2 =A0 =A0 =A0 /* link is up=
*/
>
> I'm confused about Julian's proposal because it seems to me that we alrea=
dy 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.
>
> So the only question we don't know the answer to, at run-time, is whether=
a driver may *ever* set the link state (i.e., it thinks it knows how to), =
and hence whether or not tools like dhclient should try to wait for that to=
happen. That is the problem that an interface capability would solve.
>
> For the purposes of ECMP, you just need to decide on your policy: map UNK=
NOWN to either UP or DOWN for your purposes.
>
> Robert
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