[PATCH v12 11/19] net/pcap: support VLAN insert and strip

Stephen Hemminger
2026-02-02T23:14:01Z

Driver can easily insert VLAN tag strip and insertion similar
to how it is handled in virtio and af_packet.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
doc/guides/nics/features/pcap.ini | 1 +
doc/guides/nics/pcap_ring.rst | 11 ++++
doc/guides/rel_notes/release_26_03.rst | 4 ++
drivers/net/pcap/pcap_ethdev.c | 71 ++++++++++++++++++++++++--
4 files changed, 84 insertions(+), 3 deletions(-)

diff --git a/doc/guides/nics/features/pcap.ini b/doc/guides/nics/features/pcap.ini
index b0dac3cca7..814bc2119f 100644
--- a/doc/guides/nics/features/pcap.ini
+++ b/doc/guides/nics/features/pcap.ini
@@ -10,6 +10,7 @@ Scattered Rx = Y
Timestamp offload = Y
Basic stats = Y
Stats per queue = Y
+VLAN offload = Y
Multiprocess aware = Y
FreeBSD = Y
Linux = Y
diff --git a/doc/guides/nics/pcap_ring.rst b/doc/guides/nics/pcap_ring.rst
index 6955e91130..c005786ce3 100644
--- a/doc/guides/nics/pcap_ring.rst
+++ b/doc/guides/nics/pcap_ring.rst
@@ -213,6 +213,17 @@ Otherwise, the first 512 packets from the input pcap file will be discarded by t
an error if interface is down, and the PMD itself won't change the status
of the external network interface.

+Features and Limitations
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+* The PMD will re-insert the VLAN tag transparently to the packet if the kernel
+ strips it, as long as the ``RTE_ETH_RX_OFFLOAD_VLAN_STRIP`` is not enabled by the
+ application.
+
+* The PMD will transparently insert a VLAN tag to transmitted packets if
+ ``RTE_ETH_TX_OFFLOAD_VLAN_INSERT`` is enabled and the mbuf has ``RTE_MBUF_F_TX_VLAN``
+ set.
+

Rings-based PMD
~~~~~~~~~~~~~~~
diff --git a/doc/guides/rel_notes/release_26_03.rst b/doc/guides/rel_notes/release_26_03.rst
index a837bdb600..9d4bdfc985 100644
--- a/doc/guides/rel_notes/release_26_03.rst
+++ b/doc/guides/rel_notes/release_26_03.rst
@@ -59,6 +59,10 @@ New Features

* Added support for V4000 Krackan2e.

+* **Updated PCAP ethernet driver.**
+
+ * Added support for VLAN insertion and stripping.
+

Removed Items
-------------
diff --git a/drivers/net/pcap/pcap_ethdev.c b/drivers/net/pcap/pcap_ethdev.c
index dcfd636fa0..957da1e0ab 100644
--- a/drivers/net/pcap/pcap_ethdev.c
+++ b/drivers/net/pcap/pcap_ethdev.c
@@ -77,6 +77,7 @@ struct queue_missed_stat {
struct pcap_rx_queue {
uint16_t port_id;
uint16_t queue_id;
+ bool vlan_strip;
struct rte_mempool *mb_pool;
struct queue_stat rx_stat;
struct queue_missed_stat missed_stat;
@@ -107,6 +108,7 @@ struct pmd_internals {
bool single_iface;
bool phy_mac;
bool infinite_rx;
+ bool vlan_strip;
};

struct pmd_process_private {
@@ -271,7 +273,11 @@ eth_pcap_rx_infinite(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
bufs[i]->data_len = pcap_buf->data_len;
bufs[i]->pkt_len = pcap_buf->pkt_len;
bufs[i]->port = pcap_q->port_id;
- rx_bytes += pcap_buf->data_len;
+
+ if (pcap_q->vlan_strip)
+ rte_vlan_strip(bufs[i]);
+
+ rx_bytes += bufs[i]->data_len;

/* Enqueue packet back on ring to allow infinite rx. */
rte_ring_enqueue(pcap_q->pkts, pcap_buf);
@@ -337,6 +343,10 @@ eth_pcap_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
}

mbuf->pkt_len = len;
+
+ if (pcap_q->vlan_strip)
+ rte_vlan_strip(mbuf);
+
uint64_t us = (uint64_t)header->ts.tv_sec * US_PER_S + header->ts.tv_usec;

*RTE_MBUF_DYNFIELD(mbuf, timestamp_dynfield_offset, rte_mbuf_timestamp_t *) = us;
@@ -412,9 +422,16 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
uint32_t len, caplen;
const uint8_t *data;

+ if (mbuf->ol_flags & RTE_MBUF_F_TX_VLAN) {
+ /* if vlan insert fails treat it as error */
+ if (unlikely(rte_vlan_insert(&mbuf) != 0))
+ continue;
+ }
+
len = caplen = rte_pktmbuf_pkt_len(mbuf);

calculate_timestamp(&header.ts);
+
header.len = len;
header.caplen = caplen;

@@ -487,6 +504,12 @@ eth_pcap_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
uint32_t len = rte_pktmbuf_pkt_len(mbuf);
const uint8_t *data;

+ if (mbuf->ol_flags & RTE_MBUF_F_TX_VLAN) {
+ /* if vlan insert fails treat it as error */
+ if (unlikely(rte_vlan_insert(&mbuf) != 0))
+ continue;
+ }
+
if (unlikely(!rte_pktmbuf_is_contiguous(mbuf) && len > RTE_ETH_PCAP_SNAPSHOT_LEN)) {
static int warned;

@@ -733,8 +756,13 @@ eth_dev_stop(struct rte_eth_dev *dev)
}

static int
-eth_dev_configure(struct rte_eth_dev *dev __rte_unused)
+eth_dev_configure(struct rte_eth_dev *dev)
{
+ struct pmd_internals *internals = dev->data->dev_private;
+ struct rte_eth_conf *dev_conf = &dev->data->dev_conf;
+ const struct rte_eth_rxmode *rxmode = &dev_conf->rxmode;
+
+ internals->vlan_strip = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_VLAN_STRIP);
return 0;
}

@@ -750,7 +778,9 @@ eth_dev_info(struct rte_eth_dev *dev,
dev_info->max_rx_queues = dev->data->nb_rx_queues;
dev_info->max_tx_queues = dev->data->nb_tx_queues;
dev_info->min_rx_bufsize = 0;
- dev_info->tx_offload_capa = RTE_ETH_TX_OFFLOAD_MULTI_SEGS;
+ dev_info->tx_offload_capa = RTE_ETH_TX_OFFLOAD_MULTI_SEGS |
+ RTE_ETH_TX_OFFLOAD_VLAN_INSERT;
+ dev_info->rx_offload_capa = RTE_ETH_RX_OFFLOAD_VLAN_STRIP;

return 0;
}
@@ -897,6 +927,7 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
pcap_q->mb_pool = mb_pool;
pcap_q->port_id = dev->data->port_id;
pcap_q->queue_id = rx_queue_id;
+ pcap_q->vlan_strip = internals->vlan_strip;
dev->data->rx_queues[rx_queue_id] = pcap_q;

if (internals->infinite_rx) {
@@ -906,6 +937,7 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
uint64_t pcap_pkt_count = 0;
struct rte_mbuf *bufs[1];
pcap_t **pcap;
+ bool save_vlan_strip;

pp = rte_eth_devices[pcap_q->port_id].process_private;
pcap = &pp->rx_pcap[pcap_q->queue_id];
@@ -925,11 +957,20 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
if (!pcap_q->pkts)
return -ENOENT;

+ /*
+ * Temporarily disable offloads while filling the ring
+ * with raw packets. VLAN strip and timestamp will be
+ * applied later in eth_pcap_rx_infinite() on each copy.
+ */
+ save_vlan_strip = pcap_q->vlan_strip;
+ pcap_q->vlan_strip = false;
+
/* Fill ring with packets from PCAP file one by one. */
while (eth_pcap_rx(pcap_q, bufs, 1)) {
/* Check for multiseg mbufs. */
if (bufs[0]->nb_segs != 1) {
infinite_rx_ring_free(pcap_q->pkts);
+ pcap_q->vlan_strip = save_vlan_strip;
PMD_LOG(ERR,
"Multiseg mbufs are not supported in infinite_rx mode.");
return -EINVAL;
@@ -939,6 +980,9 @@ eth_rx_queue_setup(struct rte_eth_dev *dev,
(void * const *)bufs, 1, NULL);
}

+ /* Restore offloads for use during packet delivery */
+ pcap_q->vlan_strip = save_vlan_strip;
+
if (rte_ring_count(pcap_q->pkts) < pcap_pkt_count) {
infinite_rx_ring_free(pcap_q->pkts);
PMD_LOG(ERR,
@@ -1023,6 +1067,26 @@ eth_tx_queue_stop(struct rte_eth_dev *dev, uint16_t tx_queue_id)
return 0;
}

+static int
+eth_vlan_offload_set(struct rte_eth_dev *dev, int mask)
+{
+ struct pmd_internals *internals = dev->data->dev_private;
+ unsigned int i;
+
+ if (mask & RTE_ETH_VLAN_STRIP_MASK) {
+ bool vlan_strip = !!(dev->data->dev_conf.rxmode.offloads &
+ RTE_ETH_RX_OFFLOAD_VLAN_STRIP);
+
+ internals->vlan_strip = vlan_strip;
+
+ /* Update all RX queues */
+ for (i = 0; i < dev->data->nb_rx_queues; i++)
+ internals->rx_queue[i].vlan_strip = vlan_strip;
+ }
+
+ return 0;
+}
+
static const struct eth_dev_ops ops = {
.dev_start = eth_dev_start,
.dev_stop = eth_dev_stop,
@@ -1039,6 +1103,7 @@ static const struct eth_dev_ops ops = {
.link_update = eth_link_update,
.stats_get = eth_stats_get,
.stats_reset = eth_stats_reset,
+ .vlan_offload_set = eth_vlan_offload_set,
};

static int
--
2.51.0