From: Ben Greear <greearb@candelatech•com>
To: hadi@cyberus•ca
Cc: Thomas Graf <tgraf@suug•ch>, Patrick McHardy <kaber@trash•net>,
David Miller <davem@davemloft•net>,
netdev@vger•kernel.org
Subject: Re: [PATCH 2/3] [VLAN]: Update iif when receiving via VLAN device
Date: Fri, 30 Jun 2006 08:40:00 -0700 [thread overview]
Message-ID: <44A545D0.6060504@candelatech.com> (raw)
In-Reply-To: <1151678118.5270.45.camel@jzny2>
jamal wrote:
> On Fri, 2006-30-06 at 16:15 +0200, Thomas Graf wrote:
>>You agreed in
>>your last posting that the 3rd option, being that not caring about
>>whether a device might disappear but having a way to check for it,
>>is what we agreed on and what makes most sense,
>
>
> yes, i recalled that as the last discussion we had.
>
>
>>yet you fail to see
>>that using ifindex is exactly what reflects this descision.
>>
>
>
> The choice is between using an ifindex and a pointer to the device.
> Why is it solvable via an ifindex but not a device pointer?
> I may have misunderstood you, so look at this as a fresh opportunity to
> enlighten me. Forget about all the discussion weve had thus far.
If you use a pointer, without taking it's reference, then that device
can go away, and leave you with a stale memory access, ie kernel crash
or worse.
If you take a reference for every packet (which means an atomic op), then
you slow down every packet, even those that will never use the reference.
If you instead use the if-index, then you do not need to take a reference
for every packet, but only when you actually want to look at that device.
If the device has since disappeared, then you get a null when trying to find
by reference, and the code can take appropriate action. No chance for
access of stale memory.
Ben
--
Ben Greear <greearb@candelatech•com>
Candela Technologies Inc http://www.candelatech.com
next prev parent reply other threads:[~2006-06-30 15:40 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-26 14:54 [PATCHSET] Towards accurate incoming interface information Thomas Graf
2006-06-25 22:00 ` [PATCH 1/3] [NET]: Use interface index to keep input device information Thomas Graf
2006-06-25 22:00 ` [PATCH 2/3] [VLAN]: Update iif when receiving via VLAN device Thomas Graf
2006-06-26 17:04 ` Patrick McHardy
2006-06-26 17:46 ` David Miller
2006-06-26 18:24 ` Patrick McHardy
2006-06-26 18:44 ` Thomas Graf
2006-06-26 22:29 ` Patrick McHardy
2006-06-26 22:49 ` Patrick McHardy
2006-06-27 10:03 ` Thomas Graf
2006-06-27 13:07 ` jamal
2006-06-28 10:18 ` Thomas Graf
2006-06-28 12:22 ` jamal
2006-06-28 13:01 ` Thomas Graf
2006-06-28 13:46 ` jamal
2006-06-29 8:51 ` Thomas Graf
2006-06-29 20:55 ` Thomas Graf
2006-06-29 23:23 ` jamal
2006-06-29 23:39 ` Thomas Graf
2006-06-29 23:47 ` David Miller
2006-06-30 0:08 ` jamal
2006-06-30 0:12 ` David Miller
2006-06-30 0:26 ` jamal
2006-06-30 0:29 ` David Miller
2006-06-30 0:44 ` Ben Greear
2006-06-30 0:48 ` jamal
2006-06-30 0:55 ` Thomas Graf
2006-06-30 1:18 ` jamal
2006-06-30 0:03 ` jamal
2006-06-30 0:46 ` Thomas Graf
2006-06-30 1:11 ` jamal
2006-06-30 13:08 ` Thomas Graf
2006-06-30 13:20 ` Nicolas Dichtel
2006-06-30 13:57 ` jamal
2006-06-30 14:15 ` Thomas Graf
2006-06-30 14:35 ` jamal
2006-06-30 15:40 ` Ben Greear [this message]
2006-06-30 16:32 ` Thomas Graf
2006-06-30 17:13 ` Thomas Graf
2006-06-30 17:18 ` Patrick McHardy
2006-06-30 17:32 ` jamal
2006-06-30 17:42 ` Patrick McHardy
2006-06-30 17:44 ` Thomas Graf
2006-06-30 19:40 ` jamal
2006-06-30 20:17 ` David Miller
2006-06-30 17:42 ` Thomas Graf
2006-06-30 19:34 ` jamal
2006-06-30 20:08 ` Thomas Graf
2006-06-30 20:42 ` jamal
2006-06-30 17:27 ` Ben Greear
2006-06-30 21:09 ` jamal
2006-06-30 21:20 ` Thomas Graf
2006-06-30 21:35 ` jamal
2006-06-30 23:22 ` Thomas Graf
2006-07-01 2:23 ` jamal
2006-07-01 11:51 ` Thomas Graf
2006-07-01 13:47 ` jamal
2006-06-30 17:19 ` jamal
2006-06-30 17:33 ` Patrick McHardy
2006-06-30 19:59 ` jamal
2006-06-30 20:30 ` Thomas Graf
2006-06-30 20:33 ` David Miller
2006-06-30 20:54 ` jamal
2006-06-30 21:10 ` Thomas Graf
2006-06-30 21:31 ` jamal
2006-06-30 23:45 ` Thomas Graf
2006-07-01 2:59 ` jamal
2006-07-01 11:28 ` Thomas Graf
2006-07-01 13:35 ` jamal
2006-07-08 10:54 ` Thomas Graf
2006-07-08 14:14 ` Jamal Hadi Salim
2006-07-08 14:29 ` Jamal Hadi Salim
2006-07-08 23:46 ` Thomas Graf
2006-07-08 23:48 ` Thomas Graf
2006-07-09 12:52 ` Jamal Hadi Salim
2006-07-09 13:17 ` Jamal Hadi Salim
2006-07-09 13:33 ` Thomas Graf
2006-07-09 14:03 ` Jamal Hadi Salim
2006-07-09 14:19 ` Thomas Graf
2006-07-09 15:00 ` Jamal Hadi Salim
2006-07-09 15:54 ` Thomas Graf
2006-07-09 23:06 ` Jamal Hadi Salim
2006-07-01 2:47 ` Patrick McHardy
2006-06-30 17:34 ` Thomas Graf
[not found] ` <44A52435.20909@6wind.com>
2006-06-30 13:36 ` Thomas Graf
2006-06-30 13:43 ` Nicolas Dichtel
2006-06-30 17:01 ` Patrick McHardy
2006-06-30 17:02 ` Patrick McHardy
2006-06-25 22:00 ` [PATCH 3/3] [PKT_SCHED]: Add iif meta match Thomas Graf
2006-06-27 15:07 ` [PATCHSET] Towards accurate incoming interface information Thomas Graf
2006-06-27 20:24 ` David Miller
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