From: Stephen Hemminger <shemminger@linux-foundation.org>
To: andrei radulescu-banu <iubica2@yahoo.com>
Cc: Patrick McHardy <kaber@trash.net>,
Krzysztof Halasa <khc@pm.waw.pl>,
linux-kernel@vger.kernel.org,
Linux Netdev List <netdev@vger.kernel.org>
Subject: Re: Linux, tcpdump and vlan
Date: Thu, 19 Jul 2007 17:21:05 +0100 [thread overview]
Message-ID: <20070719172105.01454686@oldman.hamilton.local> (raw)
In-Reply-To: <123837.78916.qm@web56604.mail.re3.yahoo.com>
On Thu, 19 Jul 2007 08:47:01 -0700 (PDT)
andrei radulescu-banu <iubica2@yahoo.com> wrote:
> The consensus seems to be that skb's need to carry vlan accelerated tags in their cb's, on rx as well as tx. VLAN_TX_SKB_CB() is perfect for that.
>
> > [Patrick] On the TX path, it could simply use the CB, but this is actually
> also wrong (for both macvlan and real devices) since qdiscs have
> ownership of the skb in between, and at least netem *does* modify
> the CB, breaking VLAN.
No, VLAN is wrong to expect the CB to survive through layers. The CB is
a private scribble area that can be used by which ever piece of code currently
"owns" the skb. If data needs to be passed from layer to layer, it needs to
be done as separate fields in the skb itself. If A passes an skb to B, then
the CB can be changed by B (or things it calls) before it arrives at C.
next prev parent reply other threads:[~2007-07-19 16:21 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-19 15:47 Linux, tcpdump and vlan andrei radulescu-banu
2007-07-19 16:21 ` Stephen Hemminger [this message]
2007-07-19 16:33 ` Patrick McHardy
2007-07-19 16:47 ` Ben Greear
-- strict thread matches above, loose matches on Subject: below --
2007-07-19 21:38 andrei radulescu-banu
2007-07-19 23:38 ` Ben Greear
2007-07-20 20:19 ` Krzysztof Halasa
2007-07-19 18:20 andrei radulescu-banu
2007-07-19 19:28 ` Stephen Hemminger
2007-07-19 17:46 andrei radulescu-banu
2007-07-19 16:02 andrei radulescu-banu
2007-07-20 19:58 ` Krzysztof Halasa
2007-07-20 20:34 ` Ben Greear
2007-07-21 11:32 ` Krzysztof Halasa
2007-07-21 17:57 ` Ben Greear
2007-07-21 21:15 ` Krzysztof Halasa
[not found] <878246.51044.qm@web56608.mail.re3.yahoo.com>
2007-07-18 22:57 ` Patrick McHardy
2007-07-18 23:22 ` Ben Greear
2007-07-18 23:34 ` Patrick McHardy
2007-07-19 0:01 ` Ben Greear
2007-07-19 0:19 ` Patrick McHardy
2007-07-19 13:28 ` Krzysztof Halasa
2007-07-19 13:41 ` Stephen Hemminger
2007-07-19 14:00 ` Patrick McHardy
2007-07-19 14:23 ` Krzysztof Halasa
2007-07-19 15:00 ` Stephen Hemminger
2007-07-19 15:45 ` Krzysztof Halasa
2007-07-19 15:20 ` Stephen Hemminger
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