[PATCH v13 08/16] net/pcap: support VLAN insert and strip
Stephen Hemminger
stephen at networkplumber.org
Tue Feb 10 01:00:39 CET 2026
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 at 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 | 117 ++++++++++++++++++++++++-
4 files changed, 129 insertions(+), 4 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 031eaa657e..c97ab7c3ca 100644
--- a/doc/guides/rel_notes/release_26_03.rst
+++ b/doc/guides/rel_notes/release_26_03.rst
@@ -63,6 +63,10 @@ New Features
* Added support for pre and post VF reset callbacks.
+* **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 b77fa85dd4..7fb6d98d75 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;
@@ -383,6 +393,56 @@ calculate_timestamp(struct timeval *ts) {
}
}
+
+/*
+ * If Vlan offload flag is present, insert the vlan.
+ * Returns the mbuf to send, or NULL on error.
+ */
+static inline int
+eth_pcap_tx_vlan(struct pcap_tx_queue *tx_queue, struct rte_mbuf **mbuf)
+{
+ struct rte_mbuf *mb = *mbuf;
+
+ if ((mb->ol_flags & RTE_MBUF_F_TX_VLAN) == 0)
+ return 0;
+
+ if (unlikely(mb->data_len < RTE_ETHER_HDR_LEN)) {
+ PMD_TX_LOG(ERR, "mbuf missing ether header");
+ goto error;
+ }
+
+ /* Need at another buffer to hold VLAN header? */
+ if (!RTE_MBUF_DIRECT(mb) || rte_mbuf_refcnt_read(mb) > 1) {
+ struct rte_mbuf *mh = rte_pktmbuf_alloc(mb->pool);
+ if (unlikely(mh == NULL)) {
+ PMD_TX_LOG(ERR, "mbuf pool exhausted on transmit vlan");
+ goto error;
+ }
+
+ /* Extract original ethernet header into new mbuf */
+ memcpy(rte_pktmbuf_mtod(mh, void *), rte_pktmbuf_mtod(mb, void *), RTE_ETHER_HDR_LEN);
+ mh->nb_segs = mb->nb_segs + 1;
+ mh->data_len = RTE_ETHER_HDR_LEN;
+ mh->pkt_len = mb->pkt_len;
+ mh->ol_flags = mb->ol_flags;
+
+ mb->data_len -= RTE_ETHER_HDR_LEN;
+ mh->next = mb;
+
+ *mbuf = mh;
+ }
+
+ int ret = rte_vlan_insert(mbuf);
+ if (unlikely(ret != 0)) {
+ PMD_TX_LOG(ERR, "Vlan insert failed: %s", strerror(-ret));
+ goto error;
+ }
+ return 0;
+error:
+ tx_queue->tx_stat.err_pkts++;
+ return -1;
+}
+
/*
* Callback to handle writing packets to a pcap file.
*/
@@ -408,13 +468,17 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
/* writes the nb_pkts packets to the previously opened pcap file
* dumper */
for (i = 0; i < nb_pkts; i++) {
- struct rte_mbuf *mbuf = bufs[i];
uint32_t len, caplen;
const uint8_t *data;
+ if (eth_pcap_tx_vlan(dumper_q, &bufs[i]) < 0)
+ continue;
+
+ struct rte_mbuf *mbuf = bufs[i];
len = caplen = rte_pktmbuf_pkt_len(mbuf);
calculate_timestamp(&header.ts);
+
header.len = len;
header.caplen = caplen;
@@ -493,6 +557,9 @@ eth_pcap_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
return 0;
for (i = 0; i < nb_pkts; i++) {
+ if (eth_pcap_tx_vlan(tx_queue, &bufs[i]) < 0)
+ continue;
+
struct rte_mbuf *mbuf = bufs[i];
uint32_t len = rte_pktmbuf_pkt_len(mbuf);
@@ -740,8 +807,13 @@ 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;
}
@@ -757,7 +829,9 @@ 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;
}
@@ -904,6 +978,7 @@ 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) {
@@ -913,6 +988,7 @@ 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];
@@ -932,11 +1008,20 @@ 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;
@@ -946,6 +1031,9 @@ 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,
@@ -1030,6 +1118,26 @@ 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,
@@ -1046,6 +1154,7 @@ 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
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