[v5] net/af_packet: reinsert the stripped vlan tag
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Commit Message
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.cornea@gmail.com>
---
v5:
* Updated the af_packet documentation
* Updated the af_packet release notes
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 | 7 +++++++
doc/guides/rel_notes/release_21_11.rst | 5 +++++
drivers/net/af_packet/rte_eth_af_packet.c | 12 ++++++++++++
3 files changed, 24 insertions(+)
Comments
On Fri, 1 Oct 2021 11:35:01 +0300
Tudor Cornea <tudor.cornea@gmail.com> 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.cornea@gmail.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
On 10/1/2021 4:02 PM, Stephen Hemminger wrote:
> On Fri, 1 Oct 2021 11:35:01 +0300
> Tudor Cornea <tudor.cornea@gmail.com> 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.cornea@gmail.com>
>
>
> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Applied to dpdk-next-net/main, thanks.
Release notes slightly updated, to simplify the sentences, while merging.
@@ -65,3 +65,10 @@ 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
+---------------------------------------------
+
+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.
@@ -66,6 +66,11 @@ New Features
* Added rte_flow support for dual VLAN insert and strip actions.
+* **Updated af_packet ethdev driver.**
+
+ * Default VLAN strip behavior changed.
+ If previously, the VLAN tag was stripped by the kernel, if the application now requires the same behavior, it will need to enable ``DEV_RX_OFFLOAD_VLAN_STRIP``.
+
* **Updated Marvell cnxk crypto PMD.**
* Added AES-CBC SHA1-HMAC support in lookaside protocol (IPsec) for CN10K.
@@ -48,6 +48,7 @@ struct pkt_rx_queue {
struct rte_mempool *mb_pool;
uint16_t in_port;
+ uint8_t vlan_strip;
volatile unsigned long rx_pkts;
volatile unsigned long rx_bytes;
@@ -78,6 +79,7 @@ struct pmd_internals {
struct pkt_rx_queue *rx_queue;
struct pkt_tx_queue *tx_queue;
+ uint8_t vlan_strip;
};
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) {
mbuf->vlan_tci = ppd->tp_vlan_tci;
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 */
@@ -302,6 +307,11 @@ eth_dev_stop(struct rte_eth_dev *dev)
static int
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;
}
@@ -318,6 +328,7 @@ eth_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
dev_info->min_rx_bufsize = 0;
dev_info->tx_offload_capa = DEV_TX_OFFLOAD_MULTI_SEGS |
DEV_TX_OFFLOAD_VLAN_INSERT;
+ dev_info->rx_offload_capa = DEV_RX_OFFLOAD_VLAN_STRIP;
return 0;
}
@@ -448,6 +459,7 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
dev->data->rx_queues[rx_queue_id] = pkt_q;
pkt_q->in_port = dev->data->port_id;
+ pkt_q->vlan_strip = internals->vlan_strip;
return 0;
}