From: Greg Rose <gvrose8192@gmail.com>
To: carl h <heyen2000@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: vlan tagging problem
Date: Tue, 11 Apr 2017 13:49:38 -0700 [thread overview]
Message-ID: <1491943778.30720.10.camel@gmail.com> (raw)
In-Reply-To: <CABM+yxmxfFZRtOyKbU3f1MpseQYRCReHj5uqtE3rKhaV0cUb7A@mail.gmail.com>
On Tue, 2017-04-11 at 15:36 -0400, carl h wrote:
> Hi
>
> Hope this is right place to ask this. Looking for help regarding vlan
> tagging done by the 8021q driver.
>
> I tried to manually configure a vlan on my target device. I use these
> 2 vlan config commands, then I ping an IP address and sniff the
> packets to look for the vlan tag in the messages.
>
> vconfig add esw0
> ifconfig esw0.10 10.93.1.2 netmask 255.255.255.0
>
> Despite my attempts, tagging does not occur in any outgoing packets.
> However when I tried the exact same method and commands on my Ubuntu
> workstation vlan tagging did work without problems.
>
> Target: mips32, Linux 2.6.39, 802.1Q driver version 1.8
>
> I have looked at the source for the 8021q.ko driver and I keep running
> into a dead end trying to figure out where the 4 bytes of vlan data
> gets added to the IP header. There are 2 key functions where vlan
> information is deciphered and added to a structure that contains vlan
> info, but the information never gets added to the header for some
> reason.
>
> vlan_dev_hard_header()
> vlan_dev_hard_start_xmit()
>
> It is clear in the code where vlan information in receive packets gets
> removed, but not so clear in the transmit direction where this is
> supposed to happen.
>
> Could someone explain to me what I'm missing, and where and how vlan
> info gets added to the header for outgoing packets?
>
> thx
> /carl
The Ethernet HW probably inserts the VLAN tag for you as an 'offload'.
Run 'ethtool -k <interface>' and check the offloads. You can change the
offload settings with 'ethtool -K..'.
- Greg Rose
next prev parent reply other threads:[~2017-04-11 20:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-11 19:36 vlan tagging problem carl h
2017-04-11 20:49 ` Greg Rose [this message]
2017-04-12 9:45 ` Michal Kubecek
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