netdev - Re: [PATCH 1/2] NET: Re-add VLAN tag for devices incapable of keeping it

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20071105.163542.157789854.davem@davemloft.net>
Date:	Mon, 05 Nov 2007 16:35:42 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	kaber@...sh.net
Cc:	djohnson+linux-kernel@...starentnetworks.com,
	jes@...ined-monkey.org, mchan@...adcom.com, ram.vepa@...erion.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	bguo@...starentnetworks.com
Subject: Re: [PATCH 1/2] NET: Re-add VLAN tag for devices incapable of
 keeping it

From: Patrick McHardy <kaber@...sh.net>
Date: Tue, 06 Nov 2007 01:21:09 +0100

> David Miller wrote:
> > From: Patrick McHardy <kaber@...sh.net>
> > Date: Mon, 05 Nov 2007 19:00:19 +0100
> > 
> >> This looks like a rather expensive operation for the unlikely case
> >> that packets will be received by a packet socket. IMO it should only
> >> be reconstructed if actually needed, by af_packet itself.
> > 
> > Completely agreed.  We should not do this by default when %99
> > of the networking stack simply does not care about this.
> 
> 
> I think there is one more case that matters, which is briding
> from a device with VLAN stripping for a VLAN not configured
> locally. The tag will be stripped and will be lost for forwarded
> packets. But I'm not exactly sure this really can be configured
> (time for bed so I'll check tommorrow).

If so then when such rules are loaded, just like PF_PACKET, it can set
the indication to start reconstituting VLAN headers stripped by HW.

> >> As we discussed some time back storing the VLAN tag in the CB on
> >> TX clashes with other users of the CB like qdiscs, so we need a
> >> new field in the skb for this anyway.
> > 
> > Someone will have to find a way to remove some other fields in
> > sk_buff before I'm going to allow more space to be eaten up
> > by this completely fringe case feature.
> 
> We have a two byte hole after tc_verd where we could fit this in.
> But I'm pretty sure we also could reuse some other fields on input,
> like queue_mapping or maybe even destructor for unowned skbs.

Two bytes is enough, so if there is a hole we can use it.
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html