Hi Qi,
On 04/09/2018 03:16, Zhang, Qi Z wrote:
-----Original Message-----
From: Robert Shearman [mailto:robertshear...@gmail.com]
Sent: Monday, September 3, 2018 9:14 PM
To: Zhang, Qi Z <qi.z.zh...@intel.com>; dev@dpdk.org
Cc: Lu, Wenzhuo <wenzhuo...@intel.com>; Ananyev, Konstantin
<konstantin.anan...@intel.com>; Robert Shearman
<robert.shear...@att.com>
Subject: Re: [dpdk-dev] [PATCH] net/ixgbe: Strip SR-IOV transparent VLANs in
VF
Hi Qi,
On 03/09/2018 12:45, Zhang, Qi Z wrote:
Hi Robert:
-----Original Message-----
From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of
robertshear...@gmail.com
Sent: Saturday, August 25, 2018 12:35 AM
To: dev@dpdk.org
Cc: Lu, Wenzhuo <wenzhuo...@intel.com>; Ananyev, Konstantin
<konstantin.anan...@intel.com>; Robert Shearman
<robert.shear...@att.com>
Subject: [dpdk-dev] [PATCH] net/ixgbe: Strip SR-IOV transparent VLANs
in VF
From: Robert Shearman <robert.shear...@att.com>
SR-IOV VFs support "transparent" VLANs. Traffic from/to a VM
associated with a VF has a VLAN tag inserted/stripped in a manner
intended to be totally transparent to the VM. On a Linux hypervisor
the vlan can be specified by "ip link set <device> vf <n> vlan <v>".
The VM VF driver is not configured to use any VLAN and the VM should
never see the transparent VLAN for that reason. However, in practice
these VLAN headers are being received by the VM which discards the
packets as that VLAN is unknown to it. The Linux kernel ixbge driver
explicitly removes the VLAN in this case (presumably due to the
hardware not being able to do this) but the DPDK driver does not.
I'm not quite understand this part.
What does explicitly remove the VLAN means?, DPDK also discard
unmatched VLAN and strip vlan if vlan_strip is enabled what is the gap?
It will be better if you can give same examples
Sure. Typical use case for this is a hypervisor where it is necessary to provide
L2 access into the guests, but there are insufficient, and so the hypervisor is
using the PF and VFs are assigned to guests. In order to avoid having to
configure each guest to use the VLAN and to not send any untagged traffic it is
desirable to use transparent VLANs. For example:
Guest 1 = VLAN 10
Guest 2 = VLAN 20
ip link set eth0 vf 1 vlan 10
ip link set eth0 vf 2 vlan 20
Now this means that packets arriving tagged on the physical port should be
delivered to the guest and arrive in the guest untagged. Similarly, packets
transmitted untagged by the guest should gain a tag before they go out of the
physical port. What you get when using the Linux VF ixgbe driver inside the
VMs is exactly this since the driver knows that for this hardware the
transparent stripping isn't done in hardware and is done inside the driver.
What you get currently when using the DPDK VF ixgbe driver inside the VMs is
that packets arrive tagged (e.g. with VLAN tag 10) and these are then dropped
because the VM doesn't know about VLAN 10.
Transparent VLAN insertion works currently with both Linux and DPDK VF
drivers.
What do you mean "stripping isn't done in hardware" and "packets arrived
tagged"?
Let me explain how PMD driver works. (or it is expected)
if we enable vlan_strip, the VLAN header is expected to be stripped from packet
data by hardware.
And in rx descriptor, it still keep the stripped vlan information, so driver will set
mbuf->ol_flags with PKT_RX_VLAN | PKT_RX_VLAN_STRIPPED and also set stripped vlan
tag to mbuf->vlan_tci
So in my review, it is "stripping is done and packets arrived with untagged",
and application also know what exactly happened and make decision based on the requirement
So do you mean ixgbevf does not support vlan_strip as a hardware offload?, and
it should be done with software?
But in your code, I didn't see the part that vlan header is stripped from the packet
data. ( set mbuf->ol_flag and mbuf->vlan_tci does not mean the vlan is stripped)
I understand how the VLAN stripping hardware offload is supposed to
work, but this use case is distinct from VLAN stripping and it was my
mistake to use that loaded term in my explanation of the use case.
The expectation in this case is that the packet arrive completely
untagged, i.e. whether the VLAN has been stripped and placed in metadata
or not. The application running inside the VM expects the packet to
arrive is if the VLAN tag was never there.
The application cannot do the removal of the VLAN tag itself because in
this use case it is implicit that it shouldn't know about the tag and
the presence of the tag is driver/hardware specific.
Thanks for highlighting the PKT_RX_VLAN_STRIPPED flag - I should remove
that as well when the transparent VLAN filter triggers.
Thanks,
Rob
