netdev - Re: [PATCH v2] macvlan/macvtap: Fix vlan tagging on user read

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Message-ID: <m1d371zwaw.fsf@fess.ebiederm.org>
Date:	Fri, 20 Apr 2012 18:51:51 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Basil Gor <basil.gor@...il.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Basil Gor <basilgor@...il.com>
Subject: Re: [PATCH v2] macvlan/macvtap: Fix vlan tagging on user read

Basil Gor <basil.gor@...il.com> writes:

> Vlan tag is restored during buffer transmit to a network device (bridge
> port) in bridging code in case of tun/tap driver. In case of macvtap it
> has to be done explicitly. Otherwise vlan_tci is ignored and user always
> gets untagged packets.
>
> Scenario tested:
> kvm guests (that use vlans) migration from bridged network to macvtap
> revealed that packets delivered to guests are always untagged. Dumping
> and comparing sk_buff in case of tap and macvtap driver showed that
> macvtap does not restore vlan_tci.
>
> With current patch applied I was able to get working network, kvm guests
> get correctly tagged packets and can reach each other when macvtap in
> bridge mode (both with no vlans and through vlan interfaces).
>
> Changes from original version:
> vlan header restoring code is moved from macvtap_forward to
> macvtap_receive

I really think this is the wrong fix.

Eric
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