netdev - Re: hypothetical vlan rx path question

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Message-ID: <20110713141127.23703590@nehalam.ftrdhcpuser.net>
Date:	Wed, 13 Jul 2011 14:11:27 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Jiri Pirko <jpirko@...hat.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	eric.dumazet@...il.com, nicolas.2p.debian@...il.com,
	andy@...yhouse.net, greearb@...delatech.com, mirqus@...il.com,
	bhutchings@...arflare.com
Subject: Re: hypothetical vlan rx path question

On Wed, 13 Jul 2011 22:49:46 +0200
Jiri Pirko <jpirko@...hat.com> wrote:

> Hi guys.
> 
> Consider following code taken from 8139cp.c
> 
> 
> static inline void cp_rx_skb (struct cp_private *cp, struct sk_buff *skb,
> 			      struct cp_desc *desc)
> {
> 	skb->protocol = eth_type_trans (skb, cp->dev);
> 
> 	cp->dev->stats.rx_packets++;
> 	cp->dev->stats.rx_bytes += skb->len;
> 
> #if CP_VLAN_TAG_USED
> 	if (cp->vlgrp && (desc->opts2 & cpu_to_le32(RxVlanTagged))) {
> 		vlan_hwaccel_receive_skb(skb, cp->vlgrp,
> 					 swab16(le32_to_cpu(desc->opts2) & 0xffff));
> 	} else
> #endif
> 		netif_receive_skb(skb);
> }
> 
> 
> Now my question is why the check for cp->vlgrp is needed here. Because
> in hypothetical case it might be possible to receive vlan packet as
> non-vlan packet (vlan tag would be lost).
> 
> This is present in many drivers.
> 
> How about to kill this check entirely and let the later code to deside
> what to do with the packet?
> 
> Thanks.
> 
> Jirka

All this is moot with new vlan model. It should always just put
tagged packet up.

I think all drivers with .ndo_vlan_rx_register need to be still converted.
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