From: Patrick McHardy <kaber@trash•net>
To: Urs Thuermann <urs@isnogud•escape.de>
Cc: David Miller <davem@davemloft•net>,
Thomas Gleixner <tglx@linutronix•de>,
Oliver Hartkopp <oliver.hartkopp@volkswagen•de>,
netdev@vger•kernel.org
Subject: Re: [patch 5/7] CAN: Add virtual CAN netdevice driver
Date: Sun, 03 Jun 2007 20:27:17 +0200 [thread overview]
Message-ID: <46630805.9070309@trash.net> (raw)
In-Reply-To: <ygfsl9azsji.fsf@janus.isnogud.escape.de>
Urs Thuermann wrote:
> Patrick McHardy <kaber@trash•net> writes:
>
>>And it allows you have both loopback and non-loopback devices
>>in case that would be useful.
>
>
> That sounds very promising. I also was unhappy with the fixed number
> of vcan devices at module load time and have thought about ioctl's to
> add/delete devices and to change the loopback flag. A more general
> approach like the one you seem to be working on is preferable of
> course.
I got a bit delayed, but I hope to have the patches in postable state
tommorrow.
>>Qdiscs might change skb->cb. Maybe use skb->sk?
>
>
> When we decided to use skb->cb it seemed the only possible option.
> We need a field that we can set to zero to indicate we don't want the
> driver to loop back the packet and the value in that field must
> survive the path
>
> can_send()
> dev_queue_xmit()
> ...
> dev->hard_start_xmit()
>
> netif_rx()
> can_rcv()
>
> I think I misread the comment
>
> * @cb: Control buffer. Free for use by every layer. Put private vars here
>
> to mean I can use it for this purpose and since it worked as intended
> we felt ok with this. Now I see, it states exactly the opposite that
> I can't count on the value being preserved across layers.
Yes, that comment is a bit misleading.
> skb->sk can't be used since we shouldn't set it to zero before
> dev_queue_xmit() as Oliver already pointed out. IIRC, skb->sk
> couldn't also be used in rx half of that path, since it was set to
> null somewhere in netif_rx() but now, reading the src, I can't see
> where this would happen. Maybe this has changed or my memory has some
> bit errors. I'll look at it again. Even if it turns out skb->sk can
> be used in rx path, the need remains to pass down a flag from
> can_send() to dev->hard_start_xmit() indicating whether to loop back
> or not.
That flag is a socket flag acording to Oliver, so you can use the flag
itself. You could keep skb->sk for the RX path (don't call skb_orphan
in your hard_start_xmit function), if that doesn't work worst case would
be to use a flag in the skb (we still have 2 unused bits) until you've
figured out a better way.
next prev parent reply other threads:[~2007-06-03 18:29 UTC|newest]
Thread overview: 97+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-30 13:11 [patch 0/7] CAN: Add new PF_CAN protocol family, update Urs Thuermann
2007-05-30 13:11 ` [patch 1/7] CAN: Allocate protocol numbers for PF_CAN Urs Thuermann
2007-05-30 13:11 ` [patch 2/7] CAN: Add PF_CAN core module Urs Thuermann
2007-05-30 13:11 ` [patch 3/7] CAN: Add raw protocol Urs Thuermann
2007-05-30 13:11 ` [patch 4/7] CAN: Add broadcast manager (bcm) protocol Urs Thuermann
2007-05-30 13:11 ` [patch 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-05-30 17:13 ` Patrick McHardy
2007-05-30 18:39 ` Oliver Hartkopp
2007-05-30 19:16 ` Patrick McHardy
2007-05-30 19:48 ` Oliver Hartkopp
2007-05-30 19:58 ` Patrick McHardy
2007-05-31 5:13 ` Oliver Hartkopp
2007-05-31 20:25 ` Oliver Hartkopp
2007-06-01 14:54 ` Patrick McHardy
2007-06-02 9:51 ` Oliver Hartkopp
2007-06-02 19:58 ` Oliver Hartkopp
2007-06-03 19:16 ` Oliver Hartkopp
2007-06-04 11:53 ` Patrick McHardy
2007-06-04 12:44 ` Urs Thuermann
2007-06-06 11:39 ` Patrick McHardy
2007-06-04 12:17 ` Urs Thuermann
2007-06-04 16:32 ` Oliver Hartkopp
2007-06-04 18:26 ` Oliver Hartkopp
2007-06-02 8:09 ` Urs Thuermann
2007-06-03 18:27 ` Patrick McHardy [this message]
2007-05-30 17:28 ` Stephen Hemminger
2007-05-30 18:57 ` Oliver Hartkopp
2007-05-30 19:01 ` Stephen Hemminger
2007-05-30 19:25 ` Oliver Hartkopp
2007-05-30 13:11 ` [patch 6/7] CAN: Add maintainer entries Urs Thuermann
2007-05-30 13:11 ` [patch 7/7] CAN: Add documentation Urs Thuermann
-- strict thread matches above, loose matches on Subject: below --
2007-11-16 15:02 [PATCH 0/7] CAN: New PF_CAN protocol family for 2.6.25, update Urs Thuermann
2007-11-16 15:02 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-11-14 12:13 [PATCH 0/7] CAN: New PF_CAN protocol family for 2.6.25 Urs Thuermann
2007-11-14 12:13 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-11-14 12:51 ` Patrick McHardy
2007-11-14 13:36 ` Urs Thuermann
2007-11-14 13:45 ` Patrick McHardy
2007-10-05 10:49 [PATCH 0/7] CAN: Add new PF_CAN protocol family, try #10 Urs Thuermann
2007-10-05 10:49 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-10-02 13:10 [PATCH 0/7] CAN: Add new PF_CAN protocol family, try #9 Urs Thuermann
2007-10-02 13:10 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-10-02 14:20 ` Arnaldo Carvalho de Melo
2007-10-02 15:07 ` Oliver Hartkopp
2007-10-02 16:46 ` Arnaldo Carvalho de Melo
2007-10-02 21:02 ` Oliver Hartkopp
2007-10-02 21:43 ` Arnaldo Carvalho de Melo
2007-10-02 21:50 ` David Miller
2007-10-03 7:06 ` Oliver Hartkopp
2007-10-02 21:52 ` Stephen Hemminger
2007-10-02 22:04 ` David Miller
2007-10-03 17:47 ` Oliver Hartkopp
2007-10-04 11:52 ` Urs Thuermann
2007-09-25 12:20 [PATCH 0/7] CAN: Add new PF_CAN protocol family, try #8 Urs Thuermann
2007-09-25 12:20 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-09-25 13:26 ` YOSHIFUJI Hideaki / 吉藤英明
2007-09-25 14:00 ` Urs Thuermann
2007-09-25 14:47 ` Patrick McHardy
2007-09-25 17:55 ` Oliver Hartkopp
2007-09-25 17:53 ` Patrick McHardy
2007-09-25 19:09 ` Oliver Hartkopp
2007-09-20 18:43 [PATCH 0/7] CAN: Add new PF_CAN protocol family, try #7 Urs Thuermann
2007-09-20 18:43 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-09-27 15:54 ` Eric W. Biederman
2007-09-27 16:16 ` Eric W. Biederman
2007-09-27 19:18 ` David Miller
2007-09-28 8:48 ` Oliver Hartkopp
2007-09-28 16:52 ` Eric W. Biederman
2007-09-28 18:33 ` Oliver Hartkopp
2007-09-17 10:03 [PATCH 0/7] CAN: Add new PF_CAN protocol family, try #6 Urs Thuermann
2007-09-17 10:03 ` [PATCH 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-09-18 15:02 ` Patrick McHardy
2007-09-18 22:24 ` Urs Thuermann
2007-09-19 6:26 ` Oliver Hartkopp
2007-09-19 8:41 ` Patrick McHardy
2007-08-04 2:06 [patch 0/7] CAN: Add new PF_CAN protocol family, try #5 Urs Thuermann
2007-08-04 2:07 ` [patch 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-06-22 3:44 [patch 0/7] CAN: Add new PF_CAN protocol family, try #3 Urs Thuermann
2007-06-22 3:44 ` [patch 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
2007-06-22 11:02 ` Patrick McHardy
2007-06-22 12:22 ` Urs Thuermann
2007-06-22 12:38 ` Patrick McHardy
2007-06-23 12:05 ` Oliver Hartkopp
2007-06-23 12:52 ` Patrick McHardy
2007-06-23 15:13 ` Oliver Hartkopp
2007-06-23 16:25 ` Patrick McHardy
2007-06-23 16:42 ` Oliver Hartkopp
2007-06-23 17:13 ` Patrick McHardy
2007-07-04 11:37 ` Urs Thuermann
2007-07-04 14:01 ` Patrick McHardy
2007-07-09 11:37 ` Urs Thuermann
2007-07-09 14:18 ` Patrick McHardy
2007-07-09 15:27 ` Oliver Hartkopp
2007-07-11 19:41 ` Oliver Hartkopp
2007-07-11 22:52 ` Patrick McHardy
2007-07-16 6:05 ` Oliver Hartkopp
2007-07-16 8:37 ` David Miller
2007-07-16 13:08 ` Patrick McHardy
2007-07-16 16:27 ` Oliver Hartkopp
2007-07-16 13:07 ` Patrick McHardy
2007-07-16 16:00 ` Oliver Hartkopp
2007-06-23 21:01 ` David Miller
2007-06-23 21:44 ` Oliver Hartkopp
2007-06-23 20:51 ` David Miller
2007-06-23 21:49 ` Oliver Hartkopp
2007-05-16 14:51 [patch 0/7] CAN: Add new PF_CAN protocol family Urs Thuermann
2007-05-16 14:51 ` [patch 5/7] CAN: Add virtual CAN netdevice driver Urs Thuermann
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