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net/af_packet: reinsert stripped VLAN tag

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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/bcc6d47903612c3861201cc3a866fb60

Signed-off-by: Tudor Cornea <tudor.cornea@gmail.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
This commit is contained in:
Tudor Cornea 2021-10-01 11:35:01 +03:00 committed by Ferruh Yigit
parent 1cd22be207
commit d41d39bcf7
3 changed files with 24 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
doc/guides/nics/af_packet.rst
View File

@ -65,3 +65,10 @@ framecnt=512):
.. code-block:: console .. code-block:: console
--vdev=eth_af_packet0,iface=tap0,blocksz=4096,framesz=2048,framecnt=512,qpairs=1,qdisc_bypass=0 --vdev=eth_af_packet0,iface=tap0,blocksz=4096,framesz=2048,framecnt=512,qpairs=1,qdisc_bypass=0
Features and Limitations
------------------------
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 the
application.

5
doc/guides/rel_notes/release_21_11.rst
View File

@ -67,6 +67,11 @@ New Features
Added macros ETH_RSS_IPV4_CHKSUM and ETH_RSS_L4_CHKSUM, now IPv4 and Added macros ETH_RSS_IPV4_CHKSUM and ETH_RSS_L4_CHKSUM, now IPv4 and
TCP/UDP/SCTP header checksum field can be used as input set for RSS. TCP/UDP/SCTP header checksum field can be used as input set for RSS.
* **Updated af_packet ethdev driver.**
* Default VLAN strip behavior was changed. VLAN tag won't be stripped
unless ``DEV_RX_OFFLOAD_VLAN_STRIP`` offload is enabled.
* **Updated Broadcom bnxt PMD.** * **Updated Broadcom bnxt PMD.**
* Added flow offload support for Thor. * Added flow offload support for Thor.

12
drivers/net/af_packet/rte_eth_af_packet.c
View File

@ -48,6 +48,7 @@ struct pkt_rx_queue {
struct rte_mempool *mb_pool; struct rte_mempool *mb_pool;
uint16_t in_port; uint16_t in_port;
uint8_t vlan_strip;
volatile unsigned long rx_pkts; volatile unsigned long rx_pkts;
volatile unsigned long rx_bytes; volatile unsigned long rx_bytes;
@ -78,6 +79,7 @@ struct pmd_internals {
struct pkt_rx_queue *rx_queue; struct pkt_rx_queue *rx_queue;
struct pkt_tx_queue *tx_queue; struct pkt_tx_queue *tx_queue;
uint8_t vlan_strip;
}; };
static const char *valid_arguments[] = { static const char *valid_arguments[] = {
@ -148,6 +150,9 @@ eth_af_packet_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
if (ppd->tp_status & TP_STATUS_VLAN_VALID) { if (ppd->tp_status & TP_STATUS_VLAN_VALID) {
mbuf->vlan_tci = ppd->tp_vlan_tci; mbuf->vlan_tci = ppd->tp_vlan_tci;
mbuf->ol_flags |= (PKT_RX_VLAN | PKT_RX_VLAN_STRIPPED); mbuf->ol_flags |= (PKT_RX_VLAN | PKT_RX_VLAN_STRIPPED);
if (!pkt_q->vlan_strip && rte_vlan_insert(&mbuf))
PMD_LOG(ERR, "Failed to reinsert VLAN tag");
} }
/* release incoming frame and advance ring buffer */ /* release incoming frame and advance ring buffer */
@ -322,6 +327,11 @@ eth_dev_stop(struct rte_eth_dev *dev)
static int static int
eth_dev_configure(struct rte_eth_dev *dev __rte_unused) eth_dev_configure(struct rte_eth_dev *dev __rte_unused)
{ {
struct rte_eth_conf *dev_conf = &dev->data->dev_conf;
const struct rte_eth_rxmode *rxmode = &dev_conf->rxmode;
struct pmd_internals *internals = dev->data->dev_private;
internals->vlan_strip = !!(rxmode->offloads & DEV_RX_OFFLOAD_VLAN_STRIP);
return 0; return 0;
} }
@ -338,6 +348,7 @@ eth_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
dev_info->min_rx_bufsize = 0; dev_info->min_rx_bufsize = 0;
dev_info->tx_offload_capa = DEV_TX_OFFLOAD_MULTI_SEGS | dev_info->tx_offload_capa = DEV_TX_OFFLOAD_MULTI_SEGS |
DEV_TX_OFFLOAD_VLAN_INSERT; DEV_TX_OFFLOAD_VLAN_INSERT;
dev_info->rx_offload_capa = DEV_RX_OFFLOAD_VLAN_STRIP;
return 0; return 0;
} }
@ -468,6 +479,7 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
dev->data->rx_queues[rx_queue_id] = pkt_q; dev->data->rx_queues[rx_queue_id] = pkt_q;
pkt_q->in_port = dev->data->port_id; pkt_q->in_port = dev->data->port_id;
pkt_q->vlan_strip = internals->vlan_strip;
return 0; return 0;
} }