[PATCH v1] net/virtio-user: implement MAC setting for Vhost-kernel

[PATCH v1] net/virtio-user: implement MAC setting for Vhost-kernel

[Maxime Coquelin]

This patch implements MAC address setting with Vhost-kernel
backends.

With this, it is possible to set the TAP interface MAC address
using the Ethdev API.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---

Change from RFC: Rebased on latest main

---

 drivers/net/virtio/virtio_user/vhost_kernel.c | 23 +++++++++++++++++++
 .../net/virtio/virtio_user/vhost_kernel_tap.c |  2 +-
 .../net/virtio/virtio_user/vhost_kernel_tap.h |  2 +-
 .../net/virtio/virtio_user/virtio_user_dev.c  |  2 +-
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c b/drivers/net/virtio/virtio_user/vhost_kernel.c
index e42bb35935..4ff47c2327 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
@@ -12,6 +12,7 @@
 #include <rte_memory.h>

 #include "vhost.h"
+#include "virtio.h"
 #include "virtio_user_dev.h"
 #include "vhost_kernel_tap.h"

@@ -152,6 +153,9 @@ vhost_kernel_get_features(struct virtio_user_dev *dev, uint64_t *features)
 	if (tap_flags & IFF_MULTI_QUEUE)
 		*features |= (1ull << VIRTIO_NET_F_MQ);

+	/* vhost_kernel supports setting tap MAC address. */
+	*features |= (1ull << VIRTIO_NET_F_MAC);
+
 	return 0;
 }

@@ -371,6 +375,24 @@ vhost_kernel_set_status(struct virtio_user_dev *dev __rte_unused, uint8_t status
 	return -ENOTSUP;
 }

+static int
+vhost_kernel_set_config(struct virtio_user_dev *dev,
+			const uint8_t *data, uint32_t off, uint32_t len)
+{
+	struct vhost_kernel_data *backend_data = dev->backend_data;
+
+	if (off == offsetof(struct virtio_net_config, mac)) {
+		if (len != RTE_ETHER_ADDR_LEN) {
+			PMD_DRV_LOG(ERR, "Invalid MAC address length");
+			return -EINVAL;
+		}
+
+		return tap_set_mac(backend_data->tapfds[0], data);
+	}
+
+	return -ENOTSUP;
+}
+
 /**
  * Set up environment to talk with a vhost kernel backend.
  *
@@ -613,6 +635,7 @@ struct virtio_user_backend_ops virtio_ops_kernel = {
 	.set_vring_addr = vhost_kernel_set_vring_addr,
 	.get_status = vhost_kernel_get_status,
 	.set_status = vhost_kernel_set_status,
+	.set_config = vhost_kernel_set_config,
 	.enable_qp = vhost_kernel_enable_queue_pair,
 	.update_link_state = vhost_kernel_update_link_state,
 	.get_intr_fd = vhost_kernel_get_intr_fd,
diff --git a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
index 611e2e25ec..3e13f8f65b 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
@@ -112,7 +112,7 @@ tap_get_flags(int tapfd, unsigned int *tap_flags)
 }

 int
-tap_set_mac(int tapfd, uint8_t *mac)
+tap_set_mac(int tapfd, const uint8_t *mac)
 {
 	struct ifreq ifr;

diff --git a/drivers/net/virtio/virtio_user/vhost_kernel_tap.h b/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
index 636a0481be..0b9258dcb7 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
+++ b/drivers/net/virtio/virtio_user/vhost_kernel_tap.h
@@ -40,6 +40,6 @@ int tap_support_features(unsigned int *tap_features);
 int tap_open(const char *ifname, unsigned int r_flags, bool multi_queue);
 int tap_get_name(int tapfd, char **ifname);
 int tap_get_flags(int tapfd, unsigned int *tap_flags);
-int tap_set_mac(int tapfd, uint8_t *mac);
+int tap_set_mac(int tapfd, const uint8_t *mac);

 #endif
diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c b/drivers/net/virtio/virtio_user/virtio_user_dev.c
index 187f81b066..d5475bc4eb 100644
--- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
+++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
@@ -790,7 +790,7 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, uint16_t queues,
 	if (!packed_vq)
 		dev->unsupported_features |= (1ull << VIRTIO_F_RING_PACKED);

-	if (dev->mac_specified)
+	if (dev->mac_specified || (dev->device_features & (1ull << VIRTIO_NET_F_MAC)))
 		dev->frontend_features |= (1ull << VIRTIO_NET_F_MAC);
 	else
 		dev->unsupported_features |= (1ull << VIRTIO_NET_F_MAC);
--
2.49.0

Re: [PATCH v1] net/virtio-user: implement MAC setting for Vhost-kernel

[Stephen Hemminger]

On Wed, 21 May 2025 16:23:05 +0200
Maxime Coquelin <maxime.coquelin@redhat.com> wrote:

> iff --git a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
> index 611e2e25ec..3e13f8f65b 100644
> --- a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
> +++ b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
> @@ -112,7 +112,7 @@ tap_get_flags(int tapfd, unsigned int *tap_flags)
>  }
> 
>  int
> -tap_set_mac(int tapfd, uint8_t *mac)
> +tap_set_mac(int tapfd, const uint8_t *mac)
>  {
>  	struct ifreq ifr;

Since static building of DPDK does not have namespaces, it would be
good if virtio use of tap and tap device did not get name conflicts.

I.e make all the global function names start with "virtio_tap_" prefix