On 9/29/2021 3:08 PM, Tudor Cornea wrote: > The af_packet pmd driver binds to a raw socket and allows > sending and receiving of packets through the kernel. > > Since commit [1], the kernel strips the vlan tags early in > __netif_receive_skb_core(), so we receive untagged packets while > running with the af_packet pmd. > > Luckily for us, the skb vlan-related fields are still populated from the > stripped vlan tags, so we end up having all the information > that we need in the mbuf. > > Having the pmd driver support DEV_RX_OFFLOAD_VLAN_STRIP allows the > application to control the desired vlan stripping behavior, > until we have a way to describe offloads that can't be disabled by > pmd drivers. > > This patch will cause a change in the default way that the af_packet > pmd treats received vlan-tagged frames. While previously, the > application was required to check the PKT_RX_VLAN_STRIPPED flag, after > this patch, the pmd will re-insert the vlan tag transparently to the > user, unless the DEV_RX_OFFLOAD_VLAN_STRIP is enabled in > rxmode.offloads. > > I've attempted a preliminary benchmark to understand if the change could > cause a sizable performance hit. > > Setup: > Two virtual machines running on top of an ESXi hypervisor > > Tx: DPDK app (running on top of vmxnet3 PMD) > Rx: af_packet (running on top of a kernel vmxnet3 interface) > Packet size :68 (packet contains a vlan tag) > > Rates: > Tx - 1.419 Mpps > Rx (without vlan insertion) - 1227636 pps > Rx (with vlan insertion) - 1220081 pps > > At a first glance, we don't seem to have a large degradation in terms > of packet rate. > > [1] > https://github.com/torvalds/linux/commit/bcc6d47903612c3861201cc3a866fb604f26b8b2 > > Signed-off-by: Tudor Cornea <tudor.cor...@gmail.com> > > --- > v4: > * Updated the af_packet documentation > v3: > * Updated release note and documentation > * Updated commit with performance measurements > v2: > * Added DEV_RX_OFFLOAD_VLAN_STRIP to rxmode->offloads > --- > doc/guides/nics/af_packet.rst | 5 +++++ > doc/guides/rel_notes/release_21_11.rst | 4 ++++ > drivers/net/af_packet/rte_eth_af_packet.c | 12 ++++++++++++ > 3 files changed, 21 insertions(+) > > diff --git a/doc/guides/nics/af_packet.rst b/doc/guides/nics/af_packet.rst > index efd6f1c..c87310b 100644 > --- a/doc/guides/nics/af_packet.rst > +++ b/doc/guides/nics/af_packet.rst > @@ -65,3 +65,8 @@ framecnt=512): > .. code-block:: console > > > --vdev=eth_af_packet0,iface=tap0,blocksz=4096,framesz=2048,framecnt=512,qpairs=1,qdisc_bypass=0 > + > +Features and Limitations of the af_packet PMD > +--------------------------------------------- > + > +Af_packet PMD now works with VLAN's on Linux
Thanks Tudor. I see this is suggested by Stephen, but I think 'now' is confusing in the driver guide. Also driver was already working with VLAN, the change is VLAN is not force stripped anymore. I think following part from your previous version is better, what do you think something like following? " The PMD will re-insert the VLAN tag transparently to the packet if the kernel strips it, as long as the ``DEV_RX_OFFLOAD_VLAN_STRIP`` is not enabled by application. " > diff --git a/doc/guides/rel_notes/release_21_11.rst > b/doc/guides/rel_notes/release_21_11.rst > index ad7c1af..095fd5b 100644 > --- a/doc/guides/rel_notes/release_21_11.rst > +++ b/doc/guides/rel_notes/release_21_11.rst > @@ -66,6 +66,10 @@ New Features > > * Added rte_flow support for dual VLAN insert and strip actions. > > +* **Updated af_packet ethdev driver.** > + > + * Added DEV_RX_OFFLOAD_VLAN_STRIP capability. > + I think change in the default behavior is more important in the release notes, again what do you think to have your following update here: " Default VLAN strip behavior changed. If previously, the vlan tag was stripped, if the application now requires the same behavior, it will need to configure ``DEV_RX_OFFLOAD_VLAN_STRIP``. "
