[ovs-dev] [ovs-discuss] fix the mod_vlan_vid actions with OpenFlow13.

[Eric Garver]

On Tue, Aug 21, 2018 at 02:23:33AM +0000, wangyunjian wrote:
> 
> 
> > -----Original Message-----
> > From: Eric Garver [mailto:e at erig.me]
> > Sent: Monday, August 20, 2018 9:15 PM
> > To: wangyunjian <wangyunjian at huawei.com>
> > Cc: dev at openvswitch.org; ovs-discuss at openvswitch.org; Zhoulei (stone,
> > Cloud Networking) <stone.zhou at huawei.com>; thomasfherbert at gmail.com
> > Subject: Re: [ovs-discuss] [ovs-dev] fix the mod_vlan_vid actions with
> > OpenFlow13.
> > 
> > On Mon, Aug 20, 2018 at 02:17:34AM +0000, wangyunjian wrote:
> > >
> > >
> > [..]
> > > > > On Fri, Aug 17, 2018 at 12:15:30PM +0000, wangyunjian wrote:
> > > > > > The datapath flow which pushs double vlan was found using
> > > > > > ovs-appctl dpctl/dump-flows, but the flow was set mod_vlan_vid
> > actions.
> > > > > > This problem is discovered from "Add support for 802.1ad (QinQ
> > > > tunneling)".
> > > > >
> > > > > Thanks for reporting. Can you say what version of OVS you're using?
> > > > > Including any extra patches you may have applied.
> > > >
> > > > The version of OVS is master branch(git log "
> > > > be5e6d6822e60b5b84ac65dcd1b249145356a809
> > > > ofp-ed-props: Fix hang for crafted OpenFlow encap/decap properties".).
> > > >
> > > > >
> > > > > > My test steps:
> > > > > >
> > > > > > 1) ovs-vsctl add-br ovsbr0 -- set bridge ovsbr0 datapath_type=netdev
> > > > > >    ovs-vsctl add-port ovsbr0 eth2 -- set Interface eth2
> > > > > > type=dpdk
> > > > > options:dpdk-devargs=0000:03:00.0
> > > > > >    ovs-ofctl  -O OpenFlow13 add-flow ovsbr0 "
> > > > > > table=0,priority=2,in_port=1
> > > > > actions=mod_vlan_vid:3,NORMAL"
> > 
> > What happens if you add a wildcard VLAN match here?
> > e.g. vlan_tci=0x1000/0x1000
> 
> The packet is set vlan_vid ok with adding the wildcard VLAN match.
> 
> linux-jrWzwZ:/data/wyj/git/ovs # ovs-ofctl -O OpenFlow13 add-flow ovsbr0 "cookie=0xb043f0d196265635,table=0,priority=2,in_port=1,vlan_tci=0x1000/0x1000 actions=mod_vlan_vid:2,NORMAL"
> linux-jrWzwZ:/data/wyj/git/ovs # tcpdump -i ovsbr0 -ne
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on ovsbr0, link-type EN10MB (Ethernet), capture size 65535 bytes
> 10:06:53.284556 90:17:ac:b0:0a:ff > Broadcast, ethertype 802.1Q (0x8100), length 64: vlan 2, p 0, ethertype ARP, Request who-has 3.3.3.18 tell 3.3.3.17, length 46
> 10:06:54.286542 90:17:ac:b0:0a:ff > Broadcast, ethertype 802.1Q (0x8100), length 64: vlan 2, p 0, ethertype ARP, Request who-has 3.3.3.18 tell 3.3.3.17, length 46
> 10:06:56.283594 90:17:ac:b0:0a:ff > Broadcast, ethertype 802.1Q (0x8100), length 64: vlan 2, p 0, ethertype ARP, Request who-has 3.3.3.18 tell 3.3.3.17, length 46

The mod_vlan_vid will implicitly insert a PUSH_VLAN action if the
match/flow does not qualify a vlan regardless of the specified OF
version. This is done on the ovs-ofctl side before the flow is sent over
to ovs-vswitchd - long before any packets are involved.

You have two options:

    1) qualify the VLAN as you've done above

    2) Use set_vlan_vid action with "-O OpenFlow11" or greater. It will
       _not_ attempt to push a VLAN.

This worked before 802.1ad/QinQ support only by accident because the
PUSH_VLAN action blindly overwrote the existing VLAN.

Hope that helps.
Eric.