From: David Wei <dw@davidwei.uk>

Add a ynl netdev family operation called bind-queue that creates a new
rx queue in a virtual netdev (i.e. netkit or veth) and binds it to an rx
queue in a real netdev. This forms a queue pair, where the peer queue of
the pair in the virtual netdev acts as a proxy for the peer queue in the
real netdev. Thus, the peer queue in the virtual netdev can be used by
processes running in a container to use both memory providers (io_uring
zero-copy rx and devmem) and AF_XDP. An early implementation had only
driver-specific integration [0], but in order for other virtual devices
to reuse, it makes sense to have this as a generic API.

src-ifindex and src-queue-id is the real netdev and its rx queue id
respectively. dst-ifindex is the virtual netdev. Note that this op doesn't
take dst-queue-id because a new rx queue is created. The virtual netdev
must have real_num_rx_queues less than num_rx_queues at the time of
calling bind-queue. The queue-type must be rx as only rx queues are
supported for now.

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://bpfconf.ebpf.io/bpfconf2025/bpfconf2025_material/lsfmmbpf_2025_netkit_borkmann.pdf [0]
---
 Documentation/netlink/specs/netdev.yaml | 60 +++++++++++++++++++++++++
 include/uapi/linux/netdev.h             | 12 +++++
 net/core/netdev-genl-gen.c              | 25 +++++++++++
 net/core/netdev-genl-gen.h              |  1 +
 net/core/netdev-genl.c                  |  5 +++
 tools/include/uapi/linux/netdev.h       | 12 +++++
 6 files changed, 115 insertions(+)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index e00d3fa1c152..20bb00b7e9ac 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -561,6 +561,46 @@ attribute-sets:
         type: u32
         checks:
           min: 1
+  -
+    name: queue-pair
+    attributes:
+      -
+        name: queue-type
+        doc: |
+          Queue type as rx, tx, for src-queue-id and dst-queue-id.
+          Currently only pairing queues of type rx is supported.
+        type: u32
+        enum: queue-type
+      -
+        name: src-ifindex
+        doc: |
+          Specifies the netdev ifindex of the physical device to pair
+          src-queue-id from.
+        type: u32
+        checks:
+          min: 1
+          max: s32-max
+      -
+        name: src-queue-id
+        doc: |
+          Specifies the netdev queue id of the physical device with
+          src-ifindex to pair a queue from.
+        type: u32
+      -
+        name: dst-ifindex
+        doc: |
+          Specifies the netdev ifindex of the virtual device to pair
+          a new queue with the src-queue-id from src-ifindex.
+        type: u32
+        checks:
+          min: 1
+          max: s32-max
+      -
+        name: dst-queue-id
+        doc: |
+          Specifies the new netdev queue id of the virtual device after
+          a successful pairing operation.
+        type: u32
 
 operations:
   list:
@@ -772,6 +812,26 @@ operations:
           attributes:
             - id
 
+    -
+      name: bind-queue
+      doc: |
+        Bind a physical netdevice queue to a virtual one. The binding
+        creates a queue pair, where a queue can reference its peer queue.
+        This is useful for memory providers and AF_XDP operations which
+        take an ifindex and queue id to allow auch applications to bind
+        against virtual devices in containers.
+      attribute-set: queue-pair
+      do:
+        request:
+          attributes:
+            - queue-type
+            - src-ifindex
+            - src-queue-id
+            - dst-ifindex
+        reply:
+          attributes:
+            - dst-queue-id
+
 kernel-family:
   headers: ["net/netdev_netlink.h"]
   sock-priv: struct netdev_nl_sock
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 48eb49aa03d4..4ef04d0bc412 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -210,6 +210,17 @@ enum {
 	NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
 };
 
+enum {
+	NETDEV_A_QUEUE_PAIR_QUEUE_TYPE = 1,
+	NETDEV_A_QUEUE_PAIR_SRC_IFINDEX,
+	NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID,
+	NETDEV_A_QUEUE_PAIR_DST_IFINDEX,
+	NETDEV_A_QUEUE_PAIR_DST_QUEUE_ID,
+
+	__NETDEV_A_QUEUE_PAIR_MAX,
+	NETDEV_A_QUEUE_PAIR_MAX = (__NETDEV_A_QUEUE_PAIR_MAX - 1)
+};
+
 enum {
 	NETDEV_CMD_DEV_GET = 1,
 	NETDEV_CMD_DEV_ADD_NTF,
@@ -226,6 +237,7 @@ enum {
 	NETDEV_CMD_BIND_RX,
 	NETDEV_CMD_NAPI_SET,
 	NETDEV_CMD_BIND_TX,
+	NETDEV_CMD_BIND_QUEUE,
 
 	__NETDEV_CMD_MAX,
 	NETDEV_CMD_MAX = (__NETDEV_CMD_MAX - 1)
diff --git a/net/core/netdev-genl-gen.c b/net/core/netdev-genl-gen.c
index e9a2a6f26cb7..69f8126c3e42 100644
--- a/net/core/netdev-genl-gen.c
+++ b/net/core/netdev-genl-gen.c
@@ -26,6 +26,16 @@ static const struct netlink_range_validation netdev_a_napi_defer_hard_irqs_range
 	.max	= S32_MAX,
 };
 
+static const struct netlink_range_validation netdev_a_queue_pair_src_ifindex_range = {
+	.min	= 1ULL,
+	.max	= S32_MAX,
+};
+
+static const struct netlink_range_validation netdev_a_queue_pair_dst_ifindex_range = {
+	.min	= 1ULL,
+	.max	= S32_MAX,
+};
+
 /* Common nested types */
 const struct nla_policy netdev_page_pool_info_nl_policy[NETDEV_A_PAGE_POOL_IFINDEX + 1] = {
 	[NETDEV_A_PAGE_POOL_ID] = NLA_POLICY_FULL_RANGE(NLA_UINT, &netdev_a_page_pool_id_range),
@@ -106,6 +116,14 @@ static const struct nla_policy netdev_bind_tx_nl_policy[NETDEV_A_DMABUF_FD + 1]
 	[NETDEV_A_DMABUF_FD] = { .type = NLA_U32, },
 };
 
+/* NETDEV_CMD_BIND_QUEUE - do */
+static const struct nla_policy netdev_bind_queue_nl_policy[NETDEV_A_QUEUE_PAIR_DST_IFINDEX + 1] = {
+	[NETDEV_A_QUEUE_PAIR_QUEUE_TYPE] = NLA_POLICY_MAX(NLA_U32, 1),
+	[NETDEV_A_QUEUE_PAIR_SRC_IFINDEX] = NLA_POLICY_FULL_RANGE(NLA_U32, &netdev_a_queue_pair_src_ifindex_range),
+	[NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID] = { .type = NLA_U32, },
+	[NETDEV_A_QUEUE_PAIR_DST_IFINDEX] = NLA_POLICY_FULL_RANGE(NLA_U32, &netdev_a_queue_pair_dst_ifindex_range),
+};
+
 /* Ops table for netdev */
 static const struct genl_split_ops netdev_nl_ops[] = {
 	{
@@ -204,6 +222,13 @@ static const struct genl_split_ops netdev_nl_ops[] = {
 		.maxattr	= NETDEV_A_DMABUF_FD,
 		.flags		= GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd		= NETDEV_CMD_BIND_QUEUE,
+		.doit		= netdev_nl_bind_queue_doit,
+		.policy		= netdev_bind_queue_nl_policy,
+		.maxattr	= NETDEV_A_QUEUE_PAIR_DST_IFINDEX,
+		.flags		= GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group netdev_nl_mcgrps[] = {
diff --git a/net/core/netdev-genl-gen.h b/net/core/netdev-genl-gen.h
index cf3fad74511f..309248fe2b9e 100644
--- a/net/core/netdev-genl-gen.h
+++ b/net/core/netdev-genl-gen.h
@@ -35,6 +35,7 @@ int netdev_nl_qstats_get_dumpit(struct sk_buff *skb,
 int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info);
 int netdev_nl_napi_set_doit(struct sk_buff *skb, struct genl_info *info);
 int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info);
+int netdev_nl_bind_queue_doit(struct sk_buff *skb, struct genl_info *info);
 
 enum {
 	NETDEV_NLGRP_MGMT,
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 470fabbeacd9..ce1018ea390f 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1120,6 +1120,11 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
 	return err;
 }
 
+int netdev_nl_bind_queue_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	return -EOPNOTSUPP;
+}
+
 void netdev_nl_sock_priv_init(struct netdev_nl_sock *priv)
 {
 	INIT_LIST_HEAD(&priv->bindings);
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index 48eb49aa03d4..4ef04d0bc412 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -210,6 +210,17 @@ enum {
 	NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
 };
 
+enum {
+	NETDEV_A_QUEUE_PAIR_QUEUE_TYPE = 1,
+	NETDEV_A_QUEUE_PAIR_SRC_IFINDEX,
+	NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID,
+	NETDEV_A_QUEUE_PAIR_DST_IFINDEX,
+	NETDEV_A_QUEUE_PAIR_DST_QUEUE_ID,
+
+	__NETDEV_A_QUEUE_PAIR_MAX,
+	NETDEV_A_QUEUE_PAIR_MAX = (__NETDEV_A_QUEUE_PAIR_MAX - 1)
+};
+
 enum {
 	NETDEV_CMD_DEV_GET = 1,
 	NETDEV_CMD_DEV_ADD_NTF,
@@ -226,6 +237,7 @@ enum {
 	NETDEV_CMD_BIND_RX,
 	NETDEV_CMD_NAPI_SET,
 	NETDEV_CMD_BIND_TX,
+	NETDEV_CMD_BIND_QUEUE,
 
 	__NETDEV_CMD_MAX,
 	NETDEV_CMD_MAX = (__NETDEV_CMD_MAX - 1)
-- 
2.43.0

From: David Wei <dw@davidwei.uk>

Implement netdev_nl_bind_queue_doit() that creates an rx queue in a
virtual netdev and then binds it to an rxq in a real netdev to create
a queue pair.

Example with ynl client:

  # ./pyynl/cli.py \
      --spec ~/netlink/specs/netdev.yaml \
      --do bind-queue \
      --json '{"src-ifindex": 4, "src-queue-id": 15, "dst-ifindex": 8, "queue-type": "rx"}'
  {'dst-queue-id': 1}

Note that the netdevice locking order is always from the virtual to
the physical device.

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 include/net/netdev_queues.h   |   5 ++
 include/net/netdev_rx_queue.h |  36 ++++++++-
 net/core/netdev-genl.c        | 141 +++++++++++++++++++++++++++++++++-
 net/core/netdev_rx_queue.c    |  61 +++++++++++++++
 4 files changed, 240 insertions(+), 3 deletions(-)

diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
index cd00e0406cf4..286d5edce07d 100644
--- a/include/net/netdev_queues.h
+++ b/include/net/netdev_queues.h
@@ -130,6 +130,10 @@ void netdev_stat_queue_sum(struct net_device *netdev,
  * @ndo_queue_get_dma_dev: Get dma device for zero-copy operations to be used
  *			   for this queue. Return NULL on error.
  *
+ * @ndo_queue_create: Create a new RX queue which can be bound to another queue.
+ *		      Ops on this queue are redirected to the peer queue e.g.
+ *		      when opening a memory provider.
+ *
  * Note that @ndo_queue_mem_alloc and @ndo_queue_mem_free may be called while
  * the interface is closed. @ndo_queue_start and @ndo_queue_stop will only
  * be called for an interface which is open.
@@ -149,6 +153,7 @@ struct netdev_queue_mgmt_ops {
 						  int idx);
 	struct device *		(*ndo_queue_get_dma_dev)(struct net_device *dev,
 							 int idx);
+	int			(*ndo_queue_create)(struct net_device *dev);
 };
 
 bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx);
diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index 8cdcd138b33f..db3ef94c0744 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -28,6 +28,7 @@ struct netdev_rx_queue {
 #endif
 	struct napi_struct		*napi;
 	struct pp_memory_provider_params mp_params;
+	struct netdev_rx_queue		*peer;
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -56,6 +57,37 @@ get_netdev_rx_queue_index(struct netdev_rx_queue *queue)
 	return index;
 }
 
-int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq);
+static inline void __netdev_rx_queue_peer(struct netdev_rx_queue *src_rxq,
+					  struct netdev_rx_queue *dst_rxq)
+{
+	src_rxq->peer = dst_rxq;
+	dst_rxq->peer = src_rxq;
+}
 
-#endif
+static inline void __netdev_rx_queue_unpeer(struct netdev_rx_queue *src_rxq,
+					    struct netdev_rx_queue *dst_rxq)
+{
+	src_rxq->peer = NULL;
+	dst_rxq->peer = NULL;
+}
+
+static inline bool netdev_rx_queue_peered(struct net_device *dev,
+					  u16 queue_id)
+{
+	if (queue_id < dev->real_num_rx_queues)
+		return dev->_rx[queue_id].peer;
+	return false;
+}
+
+void netdev_rx_queue_peer(struct net_device *src_dev,
+			  struct netdev_rx_queue *src_rxq,
+			  struct netdev_rx_queue *dst_rxq);
+void netdev_rx_queue_unpeer(struct net_device *src_dev,
+			    struct netdev_rx_queue *src_rxq,
+			    struct netdev_rx_queue *dst_rxq);
+int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq);
+struct netdev_rx_queue *
+netif_get_rx_queue_peer_locked(struct net_device **dev,
+			       unsigned int *rxq_idx,
+			       bool *needs_unlock);
+#endif /* _LINUX_NETDEV_RX_QUEUE_H */
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index ce1018ea390f..579469abac8c 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1122,7 +1122,146 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
 
 int netdev_nl_bind_queue_doit(struct sk_buff *skb, struct genl_info *info)
 {
-	return -EOPNOTSUPP;
+	u32 src_ifidx, src_qid, dst_ifidx, dst_qid, q_type;
+	struct netdev_rx_queue *src_rxq, *dst_rxq, *tmp_rxq;
+	struct net_device *src_dev, *dst_dev;
+	struct sk_buff *rsp;
+	int err = 0;
+	void *hdr;
+
+	if (GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_QUEUE_TYPE) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_SRC_IFINDEX) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID) ||
+	    GENL_REQ_ATTR_CHECK(info, NETDEV_A_QUEUE_PAIR_DST_IFINDEX))
+		return -EINVAL;
+
+	src_ifidx = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_SRC_IFINDEX]);
+	src_qid = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID]);
+	dst_ifidx = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_DST_IFINDEX]);
+	q_type = nla_get_u32(info->attrs[NETDEV_A_QUEUE_PAIR_QUEUE_TYPE]);
+
+	if (q_type != NETDEV_QUEUE_TYPE_RX) {
+		NL_SET_ERR_MSG(info->extack, "Only binding of RX queue supported");
+		return -EOPNOTSUPP;
+	}
+	if (dst_ifidx == src_ifidx) {
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination driver cannot be same as source driver");
+		return -EOPNOTSUPP;
+	}
+
+	rsp = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!rsp)
+		return -ENOMEM;
+
+	hdr = genlmsg_iput(rsp, info);
+	if (!hdr) {
+		err = -EMSGSIZE;
+		goto err_genlmsg_free;
+	}
+
+	/* Locking order is always from the virtual to the physical device
+	 * since this is also the same order when applications open the
+	 * memory provider later on.
+	 */
+	dst_dev = netdev_get_by_index_lock(genl_info_net(info), dst_ifidx);
+	if (!dst_dev) {
+		err = -ENODEV;
+		goto err_genlmsg_free;
+	}
+	if (dst_dev->dev.parent) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination device is not a virtual device");
+		goto err_unlock_dst_dev;
+	}
+	if (!dst_dev->queue_mgmt_ops ||
+	    !dst_dev->queue_mgmt_ops->ndo_queue_create) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination driver does not support queue management operations");
+		goto err_unlock_dst_dev;
+	}
+	if (dst_dev->real_num_rx_queues < 1) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination device must have at least one real RX queue");
+		goto err_unlock_dst_dev;
+	}
+
+	src_dev = netdev_get_by_index_lock(genl_info_net(info), src_ifidx);
+	if (!src_dev) {
+		err = -ENODEV;
+		goto err_unlock_dst_dev;
+	}
+	if (!src_dev->dev.parent) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device is a virtual device");
+		goto err_unlock_src_dev;
+	}
+	if (!netif_device_present(src_dev)) {
+		err = -ENODEV;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device has been removed from the system");
+		goto err_unlock_src_dev;
+	}
+	if (!src_dev->queue_mgmt_ops) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source driver does not support queue management operations");
+		goto err_unlock_src_dev;
+	}
+	if (src_qid >= src_dev->num_rx_queues) {
+		err = -ERANGE;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device queue is out of range");
+		goto err_unlock_src_dev;
+	}
+
+	src_rxq = __netif_get_rx_queue(src_dev, src_qid);
+	if (src_rxq->peer) {
+		err = -EBUSY;
+		NL_SET_ERR_MSG(info->extack,
+			       "Source device queue is already bound");
+		goto err_unlock_src_dev;
+	}
+
+	tmp_rxq = __netif_get_rx_queue(dst_dev, dst_dev->real_num_rx_queues - 1);
+	if (tmp_rxq->peer && tmp_rxq->peer->dev != src_dev) {
+		err = -EOPNOTSUPP;
+		NL_SET_ERR_MSG(info->extack,
+			       "Binding multiple queues from difference source devices not supported");
+		goto err_unlock_src_dev;
+	}
+
+	err = dst_dev->queue_mgmt_ops->ndo_queue_create(dst_dev);
+	if (err <= 0) {
+		NL_SET_ERR_MSG(info->extack,
+			       "Destination device is unable to create a new queue");
+		goto err_unlock_src_dev;
+	}
+
+	dst_qid = err - 1;
+	dst_rxq = __netif_get_rx_queue(dst_dev, dst_qid);
+
+	netdev_rx_queue_peer(src_dev, src_rxq, dst_rxq);
+
+	nla_put_u32(rsp, NETDEV_A_QUEUE_PAIR_DST_QUEUE_ID, dst_qid);
+	genlmsg_end(rsp, hdr);
+
+	netdev_unlock(src_dev);
+	netdev_unlock(dst_dev);
+
+	return genlmsg_reply(rsp, info);
+
+err_unlock_src_dev:
+	netdev_unlock(src_dev);
+err_unlock_dst_dev:
+	netdev_unlock(dst_dev);
+err_genlmsg_free:
+	nlmsg_free(rsp);
+	return err;
 }
 
 void netdev_nl_sock_priv_init(struct netdev_nl_sock *priv)
diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index c7d9341b7630..916ca8d7ae7c 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -18,6 +18,67 @@ bool netif_rxq_has_unreadable_mp(struct net_device *dev, int idx)
 }
 EXPORT_SYMBOL(netif_rxq_has_unreadable_mp);
 
+void netdev_rx_queue_peer(struct net_device *src_dev,
+			  struct netdev_rx_queue *src_rxq,
+			  struct netdev_rx_queue *dst_rxq)
+{
+	netdev_assert_locked(src_dev);
+	netdev_assert_locked(dst_rxq->dev);
+
+	netdev_hold(src_dev, &src_rxq->dev_tracker, GFP_KERNEL);
+	__netdev_rx_queue_peer(src_rxq, dst_rxq);
+}
+
+void netdev_rx_queue_unpeer(struct net_device *src_dev,
+			    struct netdev_rx_queue *src_rxq,
+			    struct netdev_rx_queue *dst_rxq)
+{
+	WARN_ON_ONCE(READ_ONCE(dst_rxq->dev->reg_state) != NETREG_UNREGISTERING);
+
+	netdev_assert_locked(dst_rxq->dev);
+	netdev_assert_locked(src_dev);
+
+	__netdev_rx_queue_unpeer(src_rxq, dst_rxq);
+	netdev_put(src_dev, &src_rxq->dev_tracker);
+}
+
+static struct netdev_rx_queue *
+__netif_get_rx_queue_peer(struct net_device **dev, unsigned int *rxq_idx,
+			  bool virt_to_phys_only)
+{
+	struct net_device *req_dev = *dev;
+	struct netdev_rx_queue *rxq = __netif_get_rx_queue(req_dev, *rxq_idx);
+
+	if (rxq->peer) {
+		if (virt_to_phys_only &&
+		    req_dev->dev.parent)
+			return NULL;
+		rxq = rxq->peer;
+		*rxq_idx = get_netdev_rx_queue_index(rxq);
+		*dev = rxq->dev;
+	}
+	return rxq;
+}
+
+struct netdev_rx_queue *
+netif_get_rx_queue_peer_locked(struct net_device **dev, unsigned int *rxq_idx,
+			       bool *needs_unlock)
+{
+	struct net_device *req_dev = *dev;
+	struct netdev_rx_queue *rxq;
+
+	/* Locking order is always from the virtual to the physical device
+	 * see netdev_nl_bind_queue_doit().
+	 */
+	netdev_ops_assert_locked(req_dev);
+	rxq = __netif_get_rx_queue_peer(dev, rxq_idx, true);
+	if (rxq && req_dev != *dev) {
+		*needs_unlock = true;
+		netdev_lock(*dev);
+	}
+	return rxq;
+}
+
 int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 {
 	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);
-- 
2.43.0

From: David Wei <dw@davidwei.uk>

Add a nested peer field to the queue-get response that returns the peered
ifindex and queue id.

Example with ynl client:

  # ip netns exec foo ./pyynl/cli.py \
      --spec ~/netlink/specs/netdev.yaml \
      --do queue-get \
      --json '{"ifindex": 3, "id": 1, "type": "rx"}'
  {'id': 1, 'ifindex': 3, 'peer': {'id': 15, 'ifindex': 4, 'netns-id': 21}, 'type': 'rx'}

Note that the caller of netdev_nl_queue_fill_one() holds the netdevice
lock. For the queue-get we do not lock both devices. When queues get
{un,}peered, both devices are locked, thus if netdev_rx_queue_peered()
returns true, the peer pointer points to a valid device. The netns-id
is fetched via peernet2id_alloc() similarly as done in OVS.

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 Documentation/netlink/specs/netdev.yaml | 24 ++++++++++++++++++
 include/net/netdev_rx_queue.h           |  3 +++
 include/uapi/linux/netdev.h             | 10 ++++++++
 net/core/netdev-genl.c                  | 33 +++++++++++++++++++++++--
 net/core/netdev_rx_queue.c              |  8 ++++++
 tools/include/uapi/linux/netdev.h       | 10 ++++++++
 6 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index 20bb00b7e9ac..a3c562dfd205 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -297,6 +297,24 @@ attribute-sets:
   -
     name: xsk-info
     attributes: []
+  -
+    name: peer-info
+    attributes:
+      -
+        name: id
+        doc: Queue index of the netdevice to which the peer queue belongs.
+        type: u32
+      -
+        name: ifindex
+        doc: ifindex of the netdevice to which the peer queue belongs.
+        type: u32
+      -
+        name: netns-id
+        doc: |
+          Network namespace of the netdevice to which the peer queue belongs.
+          This is populated if the netdevices are not in the same network
+          namespace.
+        type: s32
   -
     name: queue
     attributes:
@@ -338,6 +356,11 @@ attribute-sets:
         doc: XSK information for this queue, if any.
         type: nest
         nested-attributes: xsk-info
+      -
+        name: peer
+        doc: Whether this queue was bound to another peer queue.
+        type: nest
+        nested-attributes: peer-info
   -
     name: qstats
     doc: |
@@ -723,6 +746,7 @@ operations:
             - dmabuf
             - io-uring
             - xsk
+            - peer
       dump:
         request:
           attributes:
diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index db3ef94c0744..ea23cca947bb 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -90,4 +90,7 @@ struct netdev_rx_queue *
 netif_get_rx_queue_peer_locked(struct net_device **dev,
 			       unsigned int *rxq_idx,
 			       bool *needs_unlock);
+struct netdev_rx_queue *
+netif_get_rx_queue_peer_any(struct net_device **dev,
+			    unsigned int *rxq_idx);
 #endif /* _LINUX_NETDEV_RX_QUEUE_H */
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 4ef04d0bc412..d4d5d9f86eee 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -150,6 +150,15 @@ enum {
 	NETDEV_A_XSK_INFO_MAX = (__NETDEV_A_XSK_INFO_MAX - 1)
 };
 
+enum {
+	NETDEV_A_PEER_INFO_ID = 1,
+	NETDEV_A_PEER_INFO_IFINDEX,
+	NETDEV_A_PEER_INFO_NETNS_ID,
+
+	__NETDEV_A_PEER_INFO_MAX,
+	NETDEV_A_PEER_INFO_MAX = (__NETDEV_A_PEER_INFO_MAX - 1)
+};
+
 enum {
 	NETDEV_A_QUEUE_ID = 1,
 	NETDEV_A_QUEUE_IFINDEX,
@@ -158,6 +167,7 @@ enum {
 	NETDEV_A_QUEUE_DMABUF,
 	NETDEV_A_QUEUE_IO_URING,
 	NETDEV_A_QUEUE_XSK,
+	NETDEV_A_QUEUE_PEER,
 
 	__NETDEV_A_QUEUE_MAX,
 	NETDEV_A_QUEUE_MAX = (__NETDEV_A_QUEUE_MAX - 1)
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 579469abac8c..28658b5cd7a4 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -393,6 +393,7 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
 	struct pp_memory_provider_params *params;
 	struct netdev_rx_queue *rxq;
 	struct netdev_queue *txq;
+	struct nlattr *nest;
 	void *hdr;
 
 	hdr = genlmsg_iput(rsp, info);
@@ -410,6 +411,34 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
 		if (nla_put_napi_id(rsp, rxq->napi))
 			goto nla_put_failure;
 
+		if (netdev_rx_queue_peered(netdev, q_idx)) {
+			struct net_device *p_netdev = netdev;
+			struct net *net, *p_net;
+			u32 p_q_idx = q_idx;
+
+			nest = nla_nest_start(rsp, NETDEV_A_QUEUE_PEER);
+			if (!nest)
+				goto nla_put_failure;
+
+			netif_get_rx_queue_peer_any(&p_netdev, &p_q_idx);
+			if (nla_put_u32(rsp, NETDEV_A_PEER_INFO_ID, p_q_idx) ||
+			    nla_put_u32(rsp, NETDEV_A_PEER_INFO_IFINDEX,
+					READ_ONCE(p_netdev->ifindex)))
+				goto nla_put_failure;
+
+			rcu_read_lock();
+			p_net = dev_net_rcu(p_netdev);
+			net = dev_net_rcu(netdev);
+			if (!net_eq(net, p_net)) {
+				s32 id = peernet2id_alloc(net, p_net, GFP_ATOMIC);
+
+				if (nla_put_s32(rsp, NETDEV_A_PEER_INFO_NETNS_ID, id))
+					goto nla_put_failure_unlock;
+			}
+			rcu_read_unlock();
+			nla_nest_end(rsp, nest);
+		}
+
 		params = &rxq->mp_params;
 		if (params->mp_ops &&
 		    params->mp_ops->nl_fill(params->mp_priv, rsp, rxq))
@@ -419,7 +448,6 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
 			if (nla_put_empty_nest(rsp, NETDEV_A_QUEUE_XSK))
 				goto nla_put_failure;
 #endif
-
 		break;
 	case NETDEV_QUEUE_TYPE_TX:
 		txq = netdev_get_tx_queue(netdev, q_idx);
@@ -434,9 +462,10 @@ netdev_nl_queue_fill_one(struct sk_buff *rsp, struct net_device *netdev,
 	}
 
 	genlmsg_end(rsp, hdr);
-
 	return 0;
 
+nla_put_failure_unlock:
+	rcu_read_unlock();
 nla_put_failure:
 	genlmsg_cancel(rsp, hdr);
 	return -EMSGSIZE;
diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index 916ca8d7ae7c..8ee289316c06 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -79,6 +79,14 @@ netif_get_rx_queue_peer_locked(struct net_device **dev, unsigned int *rxq_idx,
 	return rxq;
 }
 
+struct netdev_rx_queue *
+netif_get_rx_queue_peer_any(struct net_device **dev, unsigned int *rxq_idx)
+{
+	netdev_ops_assert_locked(*dev);
+	/* Retrieves both virt-to-phys and phys-to-virt peering. */
+	return __netif_get_rx_queue_peer(dev, rxq_idx, false);
+}
+
 int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 {
 	struct netdev_rx_queue *rxq = __netif_get_rx_queue(dev, rxq_idx);
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index 4ef04d0bc412..d4d5d9f86eee 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -150,6 +150,15 @@ enum {
 	NETDEV_A_XSK_INFO_MAX = (__NETDEV_A_XSK_INFO_MAX - 1)
 };
 
+enum {
+	NETDEV_A_PEER_INFO_ID = 1,
+	NETDEV_A_PEER_INFO_IFINDEX,
+	NETDEV_A_PEER_INFO_NETNS_ID,
+
+	__NETDEV_A_PEER_INFO_MAX,
+	NETDEV_A_PEER_INFO_MAX = (__NETDEV_A_PEER_INFO_MAX - 1)
+};
+
 enum {
 	NETDEV_A_QUEUE_ID = 1,
 	NETDEV_A_QUEUE_IFINDEX,
@@ -158,6 +167,7 @@ enum {
 	NETDEV_A_QUEUE_DMABUF,
 	NETDEV_A_QUEUE_IO_URING,
 	NETDEV_A_QUEUE_XSK,
+	NETDEV_A_QUEUE_PEER,
 
 	__NETDEV_A_QUEUE_MAX,
 	NETDEV_A_QUEUE_MAX = (__NETDEV_A_QUEUE_MAX - 1)
-- 
2.43.0

Similar to AF_XDP, do not allow queues in a physical netdev to be
resized by ethtool -L when they are peered.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 include/linux/ethtool.h |  1 +
 net/ethtool/channels.c  | 12 ++++++------
 net/ethtool/common.c    | 10 +++++++++-
 net/ethtool/ioctl.c     |  4 ++--
 4 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index c2d8b4ec62eb..151fc920234d 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -1481,4 +1481,5 @@ struct ethtool_forced_speed_map {
 
 void
 ethtool_forced_speed_maps_init(struct ethtool_forced_speed_map *maps, u32 size);
+bool ethtool_channel_busy(struct net_device *dev, u32 channel);
 #endif /* _LINUX_ETHTOOL_H */
diff --git a/net/ethtool/channels.c b/net/ethtool/channels.c
index ca4f80282448..b3de8064275c 100644
--- a/net/ethtool/channels.c
+++ b/net/ethtool/channels.c
@@ -1,7 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
-#include <net/xdp_sock_drv.h>
-
 #include "netlink.h"
 #include "common.h"
 
@@ -169,14 +167,16 @@ ethnl_set_channels(struct ethnl_req_info *req_info, struct genl_info *info)
 	if (ret)
 		return ret;
 
-	/* Disabling channels, query zero-copy AF_XDP sockets */
+	/* ensure channels are not busy at the moment */
 	from_channel = channels.combined_count +
 		       min(channels.rx_count, channels.tx_count);
-	for (i = from_channel; i < old_total; i++)
-		if (xsk_get_pool_from_qid(dev, i)) {
-			GENL_SET_ERR_MSG(info, "requested channel counts are too low for existing zerocopy AF_XDP sockets");
+	for (i = from_channel; i < old_total; i++) {
+		if (ethtool_channel_busy(dev, i)) {
+			GENL_SET_ERR_MSG(info,
+					 "requested channel counts are too low due to busy queues (AF_XDP or queue peering)");
 			return -EINVAL;
 		}
+	}
 
 	ret = dev->ethtool_ops->set_channels(dev, &channels);
 	return ret < 0 ? ret : 1;
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 55223ebc2a7e..a67382c2208b 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -6,13 +6,15 @@
 #include <linux/rtnetlink.h>
 #include <linux/ptp_clock_kernel.h>
 #include <linux/phy_link_topology.h>
+
 #include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
+#include <net/xdp_sock_drv.h>
 
 #include "netlink.h"
 #include "common.h"
 #include "../core/dev.h"
 
-
 const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_SG_BIT] =               "tx-scatter-gather",
 	[NETIF_F_IP_CSUM_BIT] =          "tx-checksum-ipv4",
@@ -1101,6 +1103,12 @@ EXPORT_SYMBOL(ethtool_get_ts_info_by_layer);
 
 const struct ethtool_phy_ops *ethtool_phy_ops;
 
+bool ethtool_channel_busy(struct net_device *dev, u32 channel)
+{
+	return netdev_rx_queue_peered(dev, channel) ||
+	       xsk_get_pool_from_qid(dev, channel);
+}
+
 void ethtool_set_ethtool_phy_ops(const struct ethtool_phy_ops *ops)
 {
 	ASSERT_RTNL();
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index fa83ddade4f8..9ed87a18e48a 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2282,12 +2282,12 @@ static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 	if (ret)
 		return ret;
 
-	/* Disabling channels, query zero-copy AF_XDP sockets */
+	/* Disabling channels, query busy queues (AF_XDP, queue peering) */
 	from_channel = channels.combined_count +
 		min(channels.rx_count, channels.tx_count);
 	to_channel = curr.combined_count + max(curr.rx_count, curr.tx_count);
 	for (i = from_channel; i < to_channel; i++)
-		if (xsk_get_pool_from_qid(dev, i))
+		if (ethtool_channel_busy(dev, i))
 			return -EINVAL;
 
 	ret = dev->ethtool_ops->set_channels(dev, &channels);
-- 
2.43.0

From: David Wei <dw@davidwei.uk>

When a process in a container wants to setup a memory provider, it will
use the virtual netdev and a mapped rxq, and call net_mp_{open,close}_rxq
to try and restart the queue. At this point, proxy the queue restart on
the real rxq in the physical netdev.

For memory providers (io_uring zero-copy rx and devmem), it causes the
real rxq in the physical netdev to be filled from a memory provider that
has DMA mapped memory from a process within a container.

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 include/net/page_pool/memory_provider.h |  4 +-
 net/core/netdev_rx_queue.c              | 57 +++++++++++++++++--------
 2 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/include/net/page_pool/memory_provider.h b/include/net/page_pool/memory_provider.h
index ada4f968960a..b6f811c3416b 100644
--- a/include/net/page_pool/memory_provider.h
+++ b/include/net/page_pool/memory_provider.h
@@ -23,12 +23,12 @@ bool net_mp_niov_set_dma_addr(struct net_iov *niov, dma_addr_t addr);
 void net_mp_niov_set_page_pool(struct page_pool *pool, struct net_iov *niov);
 void net_mp_niov_clear_page_pool(struct net_iov *niov);
 
-int net_mp_open_rxq(struct net_device *dev, unsigned ifq_idx,
+int net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
 		    struct pp_memory_provider_params *p);
 int __net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
 		      const struct pp_memory_provider_params *p,
 		      struct netlink_ext_ack *extack);
-void net_mp_close_rxq(struct net_device *dev, unsigned ifq_idx,
+void net_mp_close_rxq(struct net_device *dev, unsigned int rxq_idx,
 		      struct pp_memory_provider_params *old_p);
 void __net_mp_close_rxq(struct net_device *dev, unsigned int rxq_idx,
 			const struct pp_memory_provider_params *old_p);
diff --git a/net/core/netdev_rx_queue.c b/net/core/netdev_rx_queue.c
index 8ee289316c06..b4ff3497e086 100644
--- a/net/core/netdev_rx_queue.c
+++ b/net/core/netdev_rx_queue.c
@@ -170,48 +170,63 @@ int __net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
 		      struct netlink_ext_ack *extack)
 {
 	struct netdev_rx_queue *rxq;
+	bool needs_unlock = false;
 	int ret;
 
 	if (!netdev_need_ops_lock(dev))
 		return -EOPNOTSUPP;
-
 	if (rxq_idx >= dev->real_num_rx_queues) {
 		NL_SET_ERR_MSG(extack, "rx queue index out of range");
 		return -ERANGE;
 	}
-	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);
 
+	rxq_idx = array_index_nospec(rxq_idx, dev->real_num_rx_queues);
+	rxq = netif_get_rx_queue_peer_locked(&dev, &rxq_idx, &needs_unlock);
+	if (!rxq) {
+		NL_SET_ERR_MSG(extack, "rx queue peered to a virtual netdev");
+		return -EBUSY;
+	}
+	if (!dev->dev.parent) {
+		NL_SET_ERR_MSG(extack, "rx queue is mapped to a virtual netdev");
+		ret = -EBUSY;
+		goto out;
+	}
 	if (dev->cfg->hds_config != ETHTOOL_TCP_DATA_SPLIT_ENABLED) {
 		NL_SET_ERR_MSG(extack, "tcp-data-split is disabled");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 	if (dev->cfg->hds_thresh) {
 		NL_SET_ERR_MSG(extack, "hds-thresh is not zero");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 	if (dev_xdp_prog_count(dev)) {
 		NL_SET_ERR_MSG(extack, "unable to custom memory provider to device with XDP program attached");
-		return -EEXIST;
+		ret = -EEXIST;
+		goto out;
 	}
-
-	rxq = __netif_get_rx_queue(dev, rxq_idx);
 	if (rxq->mp_params.mp_ops) {
 		NL_SET_ERR_MSG(extack, "designated queue already memory provider bound");
-		return -EEXIST;
+		ret = -EEXIST;
+		goto out;
 	}
 #ifdef CONFIG_XDP_SOCKETS
 	if (rxq->pool) {
 		NL_SET_ERR_MSG(extack, "designated queue already in use by AF_XDP");
-		return -EBUSY;
+		ret = -EBUSY;
+		goto out;
 	}
 #endif
-
 	rxq->mp_params = *p;
 	ret = netdev_rx_queue_restart(dev, rxq_idx);
 	if (ret) {
 		rxq->mp_params.mp_ops = NULL;
 		rxq->mp_params.mp_priv = NULL;
 	}
+out:
+	if (needs_unlock)
+		netdev_unlock(dev);
 	return ret;
 }
 
@@ -226,38 +241,44 @@ int net_mp_open_rxq(struct net_device *dev, unsigned int rxq_idx,
 	return ret;
 }
 
-void __net_mp_close_rxq(struct net_device *dev, unsigned int ifq_idx,
+void __net_mp_close_rxq(struct net_device *dev, unsigned int rxq_idx,
 			const struct pp_memory_provider_params *old_p)
 {
 	struct netdev_rx_queue *rxq;
+	bool needs_unlock = false;
 	int err;
 
-	if (WARN_ON_ONCE(ifq_idx >= dev->real_num_rx_queues))
+	if (WARN_ON_ONCE(rxq_idx >= dev->real_num_rx_queues))
 		return;
 
-	rxq = __netif_get_rx_queue(dev, ifq_idx);
+	rxq = netif_get_rx_queue_peer_locked(&dev, &rxq_idx, &needs_unlock);
+	if (WARN_ON_ONCE(!rxq))
+		return;
 
 	/* Callers holding a netdev ref may get here after we already
 	 * went thru shutdown via dev_memory_provider_uninstall().
 	 */
 	if (dev->reg_state > NETREG_REGISTERED &&
 	    !rxq->mp_params.mp_ops)
-		return;
+		goto out;
 
 	if (WARN_ON_ONCE(rxq->mp_params.mp_ops != old_p->mp_ops ||
 			 rxq->mp_params.mp_priv != old_p->mp_priv))
-		return;
+		goto out;
 
 	rxq->mp_params.mp_ops = NULL;
 	rxq->mp_params.mp_priv = NULL;
-	err = netdev_rx_queue_restart(dev, ifq_idx);
+	err = netdev_rx_queue_restart(dev, rxq_idx);
 	WARN_ON(err && err != -ENETDOWN);
+out:
+	if (needs_unlock)
+		netdev_unlock(dev);
 }
 
-void net_mp_close_rxq(struct net_device *dev, unsigned ifq_idx,
+void net_mp_close_rxq(struct net_device *dev, unsigned int rxq_idx,
 		      struct pp_memory_provider_params *old_p)
 {
 	netdev_lock(dev);
-	__net_mp_close_rxq(dev, ifq_idx, old_p);
+	__net_mp_close_rxq(dev, rxq_idx, old_p);
 	netdev_unlock(dev);
 }
-- 
2.43.0

Move NETDEV_XDP_ACT_ZC into xdp_sock_drv.h header such that external code
can reuse it, and rename it into more generic NETDEV_XDP_ACT_XSK.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
---
 include/net/xdp_sock_drv.h | 4 ++++
 net/xdp/xsk_buff_pool.c    | 6 +-----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 4f2d3268a676..242e34f771cc 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -12,6 +12,10 @@
 #define XDP_UMEM_MIN_CHUNK_SHIFT 11
 #define XDP_UMEM_MIN_CHUNK_SIZE (1 << XDP_UMEM_MIN_CHUNK_SHIFT)
 
+#define NETDEV_XDP_ACT_XSK	(NETDEV_XDP_ACT_BASIC |		\
+				 NETDEV_XDP_ACT_REDIRECT |	\
+				 NETDEV_XDP_ACT_XSK_ZEROCOPY)
+
 struct xsk_cb_desc {
 	void *src;
 	u8 off;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index aa9788f20d0d..26165baf99f4 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -158,10 +158,6 @@ static void xp_disable_drv_zc(struct xsk_buff_pool *pool)
 	}
 }
 
-#define NETDEV_XDP_ACT_ZC	(NETDEV_XDP_ACT_BASIC |		\
-				 NETDEV_XDP_ACT_REDIRECT |	\
-				 NETDEV_XDP_ACT_XSK_ZEROCOPY)
-
 int xp_assign_dev(struct xsk_buff_pool *pool,
 		  struct net_device *netdev, u16 queue_id, u16 flags)
 {
@@ -203,7 +199,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 		/* For copy-mode, we are done. */
 		return 0;
 
-	if ((netdev->xdp_features & NETDEV_XDP_ACT_ZC) != NETDEV_XDP_ACT_ZC) {
+	if ((netdev->xdp_features & NETDEV_XDP_ACT_XSK) != NETDEV_XDP_ACT_XSK) {
 		err = -EOPNOTSUPP;
 		goto err_unreg_pool;
 	}
-- 
2.43.0

Small refactor to move the pool registration into xsk_reg_pool_at_qid,
such that the netdev and queue_id can be registered there. No change
in functionality.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 net/xdp/xsk.c           | 5 +++++
 net/xdp/xsk_buff_pool.c | 5 -----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 7b0c68a70888..0e9a385f5680 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -141,6 +141,11 @@ int xsk_reg_pool_at_qid(struct net_device *dev, struct xsk_buff_pool *pool,
 			      dev->real_num_rx_queues,
 			      dev->real_num_tx_queues))
 		return -EINVAL;
+	if (xsk_get_pool_from_qid(dev, queue_id))
+		return -EBUSY;
+
+	pool->netdev = dev;
+	pool->queue_id = queue_id;
 
 	if (queue_id < dev->real_num_rx_queues)
 		dev->_rx[queue_id].pool = pool;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 26165baf99f4..62a176996f02 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -173,11 +173,6 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 	if (force_zc && force_copy)
 		return -EINVAL;
 
-	if (xsk_get_pool_from_qid(netdev, queue_id))
-		return -EBUSY;
-
-	pool->netdev = netdev;
-	pool->queue_id = queue_id;
 	err = xsk_reg_pool_at_qid(netdev, pool, queue_id);
 	if (err)
 		return err;
-- 
2.43.0

Add another small helper called xp_pool_bindable and move the current
dev_get_min_mp_channel_count test into this helper. Pass in the pool
object, such that we derive the netdev from the prior registered pool.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 net/xdp/xsk_buff_pool.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 62a176996f02..701be6a5b074 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -54,6 +54,11 @@ int xp_alloc_tx_descs(struct xsk_buff_pool *pool, struct xdp_sock *xs)
 	return 0;
 }
 
+static bool xp_pool_bindable(struct xsk_buff_pool *pool)
+{
+	return dev_get_min_mp_channel_count(pool->netdev) == 0;
+}
+
 struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 						struct xdp_umem *umem)
 {
@@ -204,7 +209,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
 		goto err_unreg_pool;
 	}
 
-	if (dev_get_min_mp_channel_count(netdev)) {
+	if (!xp_pool_bindable(pool)) {
 		err = -EBUSY;
 		goto err_unreg_pool;
 	}
-- 
2.43.0

Change the xsk_rcv_check test for inbound packets to use the xs->pool->netdev
and xs->pool->queue_id of the bound socket rather than xs->dev and xs->queue_id
since the latter could point to a virtual device with mapped rxq rather than
the physical backing device of the pool.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 net/xdp/xsk.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 0e9a385f5680..985e0cac965d 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -340,15 +340,13 @@ static int xsk_rcv_check(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 {
 	if (!xsk_is_bound(xs))
 		return -ENXIO;
-
-	if (xs->dev != xdp->rxq->dev || xs->queue_id != xdp->rxq->queue_index)
+	if (xs->pool->netdev   != xdp->rxq->dev ||
+	    xs->pool->queue_id != xdp->rxq->queue_index)
 		return -EINVAL;
-
 	if (len > xsk_pool_get_rx_frame_size(xs->pool) && !xs->sg) {
 		xs->rx_dropped++;
 		return -ENOSPC;
 	}
-
 	return 0;
 }
 
-- 
2.43.0

Similarly what we do for net_mp_{open,close}_rxq for mapped queues,
proxy also the xsk_{reg,clear}_pool_at_qid via __netif_get_rx_queue_peer
such that when a virtual netdev picked a mapped rxq, the request gets
through to the real rxq in the physical netdev.

Change the function signatures for queue_id to unsigned int in order
to pass the queue_id parameter into __netif_get_rx_queue_peer. The
proxying is only relevant for queue_id < dev->real_num_rx_queues since
right now its only supported for rxqs.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 include/net/xdp_sock_drv.h |  4 ++--
 net/xdp/xsk.c              | 33 ++++++++++++++++++++++++++++-----
 net/xdp/xsk.h              |  5 ++---
 3 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 242e34f771cc..25c37fab00bc 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -29,7 +29,7 @@ bool xsk_tx_peek_desc(struct xsk_buff_pool *pool, struct xdp_desc *desc);
 u32 xsk_tx_peek_release_desc_batch(struct xsk_buff_pool *pool, u32 max);
 void xsk_tx_release(struct xsk_buff_pool *pool);
 struct xsk_buff_pool *xsk_get_pool_from_qid(struct net_device *dev,
-					    u16 queue_id);
+					    unsigned int queue_id);
 void xsk_set_rx_need_wakeup(struct xsk_buff_pool *pool);
 void xsk_set_tx_need_wakeup(struct xsk_buff_pool *pool);
 void xsk_clear_rx_need_wakeup(struct xsk_buff_pool *pool);
@@ -296,7 +296,7 @@ static inline void xsk_tx_release(struct xsk_buff_pool *pool)
 }
 
 static inline struct xsk_buff_pool *
-xsk_get_pool_from_qid(struct net_device *dev, u16 queue_id)
+xsk_get_pool_from_qid(struct net_device *dev, unsigned int queue_id)
 {
 	return NULL;
 }
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 985e0cac965d..9e55ea0f5fde 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -23,6 +23,8 @@
 #include <linux/netdevice.h>
 #include <linux/rculist.h>
 #include <linux/vmalloc.h>
+
+#include <net/netdev_queues.h>
 #include <net/xdp_sock_drv.h>
 #include <net/busy_poll.h>
 #include <net/netdev_lock.h>
@@ -111,7 +113,7 @@ bool xsk_uses_need_wakeup(struct xsk_buff_pool *pool)
 EXPORT_SYMBOL(xsk_uses_need_wakeup);
 
 struct xsk_buff_pool *xsk_get_pool_from_qid(struct net_device *dev,
-					    u16 queue_id)
+					    unsigned int queue_id)
 {
 	if (queue_id < dev->real_num_rx_queues)
 		return dev->_rx[queue_id].pool;
@@ -122,12 +124,19 @@ struct xsk_buff_pool *xsk_get_pool_from_qid(struct net_device *dev,
 }
 EXPORT_SYMBOL(xsk_get_pool_from_qid);
 
-void xsk_clear_pool_at_qid(struct net_device *dev, u16 queue_id)
+void xsk_clear_pool_at_qid(struct net_device *dev, unsigned int queue_id)
 {
+	bool needs_unlock = false;
+
+	if (queue_id < dev->real_num_rx_queues)
+		WARN_ON_ONCE(!netif_get_rx_queue_peer_locked(&dev, &queue_id,
+							     &needs_unlock));
 	if (queue_id < dev->num_rx_queues)
 		dev->_rx[queue_id].pool = NULL;
 	if (queue_id < dev->num_tx_queues)
 		dev->_tx[queue_id].pool = NULL;
+	if (needs_unlock)
+		netdev_unlock(dev);
 }
 
 /* The buffer pool is stored both in the _rx struct and the _tx struct as we do
@@ -135,14 +144,26 @@ void xsk_clear_pool_at_qid(struct net_device *dev, u16 queue_id)
  * This might also change during run time.
  */
 int xsk_reg_pool_at_qid(struct net_device *dev, struct xsk_buff_pool *pool,
-			u16 queue_id)
+			unsigned int queue_id)
 {
+	bool needs_unlock = false;
+	int ret = 0;
+
 	if (queue_id >= max_t(unsigned int,
 			      dev->real_num_rx_queues,
 			      dev->real_num_tx_queues))
 		return -EINVAL;
 	if (xsk_get_pool_from_qid(dev, queue_id))
 		return -EBUSY;
+	if (queue_id < dev->real_num_rx_queues) {
+		if (!netif_get_rx_queue_peer_locked(&dev, &queue_id,
+						    &needs_unlock))
+			return -EBUSY;
+	}
+	if (xsk_get_pool_from_qid(dev, queue_id)) {
+		ret = -EBUSY;
+		goto out;
+	}
 
 	pool->netdev = dev;
 	pool->queue_id = queue_id;
@@ -151,8 +172,10 @@ int xsk_reg_pool_at_qid(struct net_device *dev, struct xsk_buff_pool *pool,
 		dev->_rx[queue_id].pool = pool;
 	if (queue_id < dev->real_num_tx_queues)
 		dev->_tx[queue_id].pool = pool;
-
-	return 0;
+out:
+	if (needs_unlock)
+		netdev_unlock(dev);
+	return ret;
 }
 
 static int __xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff_xsk *xskb, u32 len,
diff --git a/net/xdp/xsk.h b/net/xdp/xsk.h
index a4bc4749faac..54d9a7736fd2 100644
--- a/net/xdp/xsk.h
+++ b/net/xdp/xsk.h
@@ -41,8 +41,7 @@ static inline struct xdp_sock *xdp_sk(struct sock *sk)
 
 void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
 			     struct xdp_sock __rcu **map_entry);
-void xsk_clear_pool_at_qid(struct net_device *dev, u16 queue_id);
+void xsk_clear_pool_at_qid(struct net_device *dev, unsigned int queue_id);
 int xsk_reg_pool_at_qid(struct net_device *dev, struct xsk_buff_pool *pool,
-			u16 queue_id);
-
+			unsigned int queue_id);
 #endif /* XSK_H_ */
-- 
2.43.0

Add a single device mode for netkit instead of netkit pairs. The primary
target for the paired devices is to connect network namespaces, of course,
and support has been implemented in projects like Cilium [0]. For the rxq
binding the plan is to support two main scenarios related to single device
mode:

* For the use-case of io_uring zero-copy, the control plane can either
  set up a netkit pair where the peer device can perform rxq binding which
  is then tied to the lifetime of the peer device, or the control plane
  can use a regular netkit pair to connect the hostns to a Pod/container
  and dynamically add/remove rxq bindings through a single device without
  having to interrupt the device pair. In the case of io_uring, the memory
  pool is used as skb non-linear pages, and thus the skb will go its way
  through the regular stack into netkit. Things like the netkit policy when
  no BPF is attached or skb scrubbing etc apply as-is in case the paired
  devices are used, or if the backend memory is tied to the single device
  and traffic goes through a paired device.

* For the use-case of AF_XDP, the control plane needs to use netkit in the
  single device mode. The single device mode currently enforces only a
  pass policy when no BPF is attached, and does not yet support BPF link
  attachments for AF_XDP. skbs sent to that device get dropped at the
  moment. Given AF_XDP operates at a lower layer of the stack tying this
  to the netkit pair did not make sense. In future, the plan is to allow
  BPF at the XDP layer which can: i) process traffic coming from the AF_XDP
  application (e.g. QEMU with AF_XDP backend) to filter egress traffic or
  to push selected egress traffic up to the single netkit device to the
  local stack (e.g. DHCP requests), and ii) vice-versa skbs sent to the
  single netkit into the AF_XDP application (e.g. DHCP replies). Also,
  the control-plane can dynamically add/remove rxq bindings for the single
  netkit device without having to interrupt (e.g. down/up cycle) the main
  netkit pair for the Pod which has traffic going in and out.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Jordan Rife <jordan@jrife.io>
Link: https://docs.cilium.io/en/stable/operations/performance/tuning/#netkit-device-mode [0]
---
 drivers/net/netkit.c         | 108 ++++++++++++++++++++++-------------
 include/uapi/linux/if_link.h |   6 ++
 2 files changed, 74 insertions(+), 40 deletions(-)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index 492be60f2e70..e3a2445d83fc 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -25,6 +25,7 @@ struct netkit {
 
 	/* Needed in slow-path */
 	enum netkit_mode mode;
+	enum netkit_pairing pair;
 	bool primary;
 	u32 headroom;
 };
@@ -133,6 +134,10 @@ static int netkit_open(struct net_device *dev)
 	struct netkit *nk = netkit_priv(dev);
 	struct net_device *peer = rtnl_dereference(nk->peer);
 
+	if (nk->pair == NETKIT_DEVICE_SINGLE) {
+		netif_carrier_on(dev);
+		return 0;
+	}
 	if (!peer)
 		return -ENOTCONN;
 	if (peer->flags & IFF_UP) {
@@ -333,6 +338,7 @@ static int netkit_new_link(struct net_device *dev,
 	enum netkit_scrub scrub_prim = NETKIT_SCRUB_DEFAULT;
 	enum netkit_scrub scrub_peer = NETKIT_SCRUB_DEFAULT;
 	struct nlattr *peer_tb[IFLA_MAX + 1], **tbp, *attr;
+	enum netkit_pairing pair = NETKIT_DEVICE_PAIR;
 	enum netkit_action policy_prim = NETKIT_PASS;
 	enum netkit_action policy_peer = NETKIT_PASS;
 	struct nlattr **data = params->data;
@@ -341,7 +347,7 @@ static int netkit_new_link(struct net_device *dev,
 	struct nlattr **tb = params->tb;
 	u16 headroom = 0, tailroom = 0;
 	struct ifinfomsg *ifmp = NULL;
-	struct net_device *peer;
+	struct net_device *peer = NULL;
 	char ifname[IFNAMSIZ];
 	struct netkit *nk;
 	int err;
@@ -378,6 +384,8 @@ static int netkit_new_link(struct net_device *dev,
 			headroom = nla_get_u16(data[IFLA_NETKIT_HEADROOM]);
 		if (data[IFLA_NETKIT_TAILROOM])
 			tailroom = nla_get_u16(data[IFLA_NETKIT_TAILROOM]);
+		if (data[IFLA_NETKIT_PAIRING])
+			pair = nla_get_u32(data[IFLA_NETKIT_PAIRING]);
 	}
 
 	if (ifmp && tbp[IFLA_IFNAME]) {
@@ -390,45 +398,49 @@ static int netkit_new_link(struct net_device *dev,
 	if (mode != NETKIT_L2 &&
 	    (tb[IFLA_ADDRESS] || tbp[IFLA_ADDRESS]))
 		return -EOPNOTSUPP;
+	if (pair == NETKIT_DEVICE_SINGLE &&
+	    (tb != tbp ||
+	     tb[IFLA_NETKIT_PEER_POLICY] ||
+	     tb[IFLA_NETKIT_PEER_SCRUB] ||
+	     policy_prim != NETKIT_PASS))
+		return -EOPNOTSUPP;
 
-	peer = rtnl_create_link(peer_net, ifname, ifname_assign_type,
-				&netkit_link_ops, tbp, extack);
-	if (IS_ERR(peer))
-		return PTR_ERR(peer);
-
-	netif_inherit_tso_max(peer, dev);
-	if (headroom) {
-		peer->needed_headroom = headroom;
-		dev->needed_headroom = headroom;
-	}
-	if (tailroom) {
-		peer->needed_tailroom = tailroom;
-		dev->needed_tailroom = tailroom;
-	}
-
-	if (mode == NETKIT_L2 && !(ifmp && tbp[IFLA_ADDRESS]))
-		eth_hw_addr_random(peer);
-	if (ifmp && dev->ifindex)
-		peer->ifindex = ifmp->ifi_index;
-
-	nk = netkit_priv(peer);
-	nk->primary = false;
-	nk->policy = policy_peer;
-	nk->scrub = scrub_peer;
-	nk->mode = mode;
-	nk->headroom = headroom;
-	bpf_mprog_bundle_init(&nk->bundle);
+	if (pair == NETKIT_DEVICE_PAIR) {
+		peer = rtnl_create_link(peer_net, ifname, ifname_assign_type,
+					&netkit_link_ops, tbp, extack);
+		if (IS_ERR(peer))
+			return PTR_ERR(peer);
+
+		netif_inherit_tso_max(peer, dev);
+		if (headroom)
+			peer->needed_headroom = headroom;
+		if (tailroom)
+			peer->needed_tailroom = tailroom;
+		if (mode == NETKIT_L2 && !(ifmp && tbp[IFLA_ADDRESS]))
+			eth_hw_addr_random(peer);
+		if (ifmp && dev->ifindex)
+			peer->ifindex = ifmp->ifi_index;
 
-	err = register_netdevice(peer);
-	if (err < 0)
-		goto err_register_peer;
-	netif_carrier_off(peer);
-	if (mode == NETKIT_L2)
-		dev_change_flags(peer, peer->flags & ~IFF_NOARP, NULL);
+		nk = netkit_priv(peer);
+		nk->primary = false;
+		nk->policy = policy_peer;
+		nk->scrub = scrub_peer;
+		nk->mode = mode;
+		nk->pair = pair;
+		nk->headroom = headroom;
+		bpf_mprog_bundle_init(&nk->bundle);
+
+		err = register_netdevice(peer);
+		if (err < 0)
+			goto err_register_peer;
+		netif_carrier_off(peer);
+		if (mode == NETKIT_L2)
+			dev_change_flags(peer, peer->flags & ~IFF_NOARP, NULL);
 
-	err = rtnl_configure_link(peer, NULL, 0, NULL);
-	if (err < 0)
-		goto err_configure_peer;
+		err = rtnl_configure_link(peer, NULL, 0, NULL);
+		if (err < 0)
+			goto err_configure_peer;
+	}
 
 	if (mode == NETKIT_L2 && !tb[IFLA_ADDRESS])
 		eth_hw_addr_random(dev);
@@ -436,12 +448,17 @@ static int netkit_new_link(struct net_device *dev,
 		nla_strscpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
 	else
 		strscpy(dev->name, "nk%d", IFNAMSIZ);
+	if (headroom)
+		dev->needed_headroom = headroom;
+	if (tailroom)
+		dev->needed_tailroom = tailroom;
 
 	nk = netkit_priv(dev);
 	nk->primary = true;
 	nk->policy = policy_prim;
 	nk->scrub = scrub_prim;
 	nk->mode = mode;
+	nk->pair = pair;
 	nk->headroom = headroom;
 	bpf_mprog_bundle_init(&nk->bundle);
 
@@ -453,10 +470,12 @@ static int netkit_new_link(struct net_device *dev,
 		dev_change_flags(dev, dev->flags & ~IFF_NOARP, NULL);
 
 	rcu_assign_pointer(netkit_priv(dev)->peer, peer);
-	rcu_assign_pointer(netkit_priv(peer)->peer, dev);
+	if (peer)
+		rcu_assign_pointer(netkit_priv(peer)->peer, dev);
 	return 0;
 err_configure_peer:
-	unregister_netdevice(peer);
+	if (peer)
+		unregister_netdevice(peer);
 	return err;
 err_register_peer:
 	free_netdev(peer);
@@ -516,6 +535,8 @@ static struct net_device *netkit_dev_fetch(struct net *net, u32 ifindex, u32 whi
 	nk = netkit_priv(dev);
 	if (!nk->primary)
 		return ERR_PTR(-EACCES);
+	if (nk->pair == NETKIT_DEVICE_SINGLE)
+		return ERR_PTR(-EOPNOTSUPP);
 	if (which == BPF_NETKIT_PEER) {
 		dev = rcu_dereference_rtnl(nk->peer);
 		if (!dev)
@@ -877,6 +898,7 @@ static int netkit_change_link(struct net_device *dev, struct nlattr *tb[],
 		{ IFLA_NETKIT_PEER_INFO,  "peer info" },
 		{ IFLA_NETKIT_HEADROOM,   "headroom" },
 		{ IFLA_NETKIT_TAILROOM,   "tailroom" },
+		{ IFLA_NETKIT_PAIRING,    "pairing" },
 	};
 
 	if (!nk->primary) {
@@ -896,9 +918,11 @@ static int netkit_change_link(struct net_device *dev, struct nlattr *tb[],
 	}
 
 	if (data[IFLA_NETKIT_POLICY]) {
+		err = -EOPNOTSUPP;
 		attr = data[IFLA_NETKIT_POLICY];
 		policy = nla_get_u32(attr);
-		err = netkit_check_policy(policy, attr, extack);
+		if (nk->pair == NETKIT_DEVICE_PAIR)
+			err = netkit_check_policy(policy, attr, extack);
 		if (err)
 			return err;
 		WRITE_ONCE(nk->policy, policy);
@@ -929,6 +953,7 @@ static size_t netkit_get_size(const struct net_device *dev)
 	       nla_total_size(sizeof(u8))  + /* IFLA_NETKIT_PRIMARY */
 	       nla_total_size(sizeof(u16)) + /* IFLA_NETKIT_HEADROOM */
 	       nla_total_size(sizeof(u16)) + /* IFLA_NETKIT_TAILROOM */
+	       nla_total_size(sizeof(u32)) + /* IFLA_NETKIT_PAIRING */
 	       0;
 }
 
@@ -949,6 +974,8 @@ static int netkit_fill_info(struct sk_buff *skb, const struct net_device *dev)
 		return -EMSGSIZE;
 	if (nla_put_u16(skb, IFLA_NETKIT_TAILROOM, dev->needed_tailroom))
 		return -EMSGSIZE;
+	if (nla_put_u32(skb, IFLA_NETKIT_PAIRING, nk->pair))
+		return -EMSGSIZE;
 
 	if (peer) {
 		nk = netkit_priv(peer);
@@ -970,6 +997,7 @@ static const struct nla_policy netkit_policy[IFLA_NETKIT_MAX + 1] = {
 	[IFLA_NETKIT_TAILROOM]		= { .type = NLA_U16 },
 	[IFLA_NETKIT_SCRUB]		= NLA_POLICY_MAX(NLA_U32, NETKIT_SCRUB_DEFAULT),
 	[IFLA_NETKIT_PEER_SCRUB]	= NLA_POLICY_MAX(NLA_U32, NETKIT_SCRUB_DEFAULT),
+	[IFLA_NETKIT_PAIRING]		= NLA_POLICY_MAX(NLA_U32, NETKIT_DEVICE_SINGLE),
 	[IFLA_NETKIT_PRIMARY]		= { .type = NLA_REJECT,
 					    .reject_message = "Primary attribute is read-only" },
 };
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 3b491d96e52e..bbd565757298 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -1296,6 +1296,11 @@ enum netkit_mode {
 	NETKIT_L3,
 };
 
+enum netkit_pairing {
+	NETKIT_DEVICE_PAIR,
+	NETKIT_DEVICE_SINGLE,
+};
+
 /* NETKIT_SCRUB_NONE leaves clearing skb->{mark,priority} up to
  * the BPF program if attached. This also means the latter can
  * consume the two fields if they were populated earlier.
@@ -1320,6 +1325,7 @@ enum {
 	IFLA_NETKIT_PEER_SCRUB,
 	IFLA_NETKIT_HEADROOM,
 	IFLA_NETKIT_TAILROOM,
+	IFLA_NETKIT_PAIRING,
 	__IFLA_NETKIT_MAX,
 };
 #define IFLA_NETKIT_MAX	(__IFLA_NETKIT_MAX - 1)
-- 
2.43.0

Instead of a comment, just use two cachline groups to document the intent
for members often accessed in fast or slow path.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 drivers/net/netkit.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index e3a2445d83fc..96734828bfb8 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -16,18 +16,20 @@
 #define DRV_NAME "netkit"
 
 struct netkit {
-	/* Needed in fast-path */
+	__cacheline_group_begin(netkit_fastpath);
 	struct net_device __rcu *peer;
 	struct bpf_mprog_entry __rcu *active;
 	enum netkit_action policy;
 	enum netkit_scrub scrub;
 	struct bpf_mprog_bundle	bundle;
+	__cacheline_group_end(netkit_fastpath);
 
-	/* Needed in slow-path */
+	__cacheline_group_begin(netkit_slowpath);
 	enum netkit_mode mode;
 	enum netkit_pairing pair;
 	bool primary;
 	u32 headroom;
+	__cacheline_group_end(netkit_slowpath);
 };
 
 struct netkit_link {
-- 
2.43.0

From: David Wei <dw@davidwei.uk>

Implement rtnl_link_ops->alloc that allows the number of rx queues to be
set when netkit is created. By default, netkit has only a single rxq (and
single txq). The number of queues is deliberately not allowed to be changed
via ethtool -L and is fixed for the lifetime of a netkit instance.

For netkit device creation, numrxqueues with larger than one rxq can be
specified. These rxqs are then mappable to real rxqs in physical netdevs:

  ip link add type netkit peer numrxqueues 64      # for device pair
  ip link add numrxqueues 64 type netkit single    # for single device

The limit of numrxqueues for netkit is currently set to 256, which allows
binding multiple real rxqs from physical netdevs.

The implementation of ndo_queue_create() adds a new rxq during the bind
queue operation. We allow to create queues either in single device mode or
for the case of dual device mode for the netkit peer device which gets
placed into the target network namespace. For dual device mode the bind
against the primary device does not make sense for the targeted use cases,
and therefore gets rejected.

We also need to add a lockdep class for netkit, such that lockdep does
not trip over us, similarly done as in commit 0bef512012b1 ("net: add
netdev_lockdep_set_classes() to virtual drivers").

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 drivers/net/netkit.c | 129 +++++++++++++++++++++++++++++++++++++++----
 1 file changed, 117 insertions(+), 12 deletions(-)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index 96734828bfb8..75b57496b72e 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -9,11 +9,20 @@
 #include <linux/bpf_mprog.h>
 #include <linux/indirect_call_wrapper.h>
 
+#include <net/netdev_lock.h>
+#include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
 #include <net/netkit.h>
 #include <net/dst.h>
 #include <net/tcx.h>
 
-#define DRV_NAME "netkit"
+#define NETKIT_DRV_NAME	"netkit"
+
+#define NETKIT_NUM_RX_QUEUES_MAX  256
+#define NETKIT_NUM_TX_QUEUES_MAX  1
+
+#define NETKIT_NUM_RX_QUEUES_REAL 1
+#define NETKIT_NUM_TX_QUEUES_REAL 1
 
 struct netkit {
 	__cacheline_group_begin(netkit_fastpath);
@@ -37,6 +46,8 @@ struct netkit_link {
 	struct net_device *dev;
 };
 
+static struct rtnl_link_ops netkit_link_ops;
+
 static __always_inline int
 netkit_run(const struct bpf_mprog_entry *entry, struct sk_buff *skb,
 	   enum netkit_action ret)
@@ -224,9 +235,16 @@ static void netkit_get_stats(struct net_device *dev,
 	stats->tx_dropped = DEV_STATS_READ(dev, tx_dropped);
 }
 
+static int netkit_init(struct net_device *dev)
+{
+	netdev_lockdep_set_classes(dev);
+	return 0;
+}
+
 static void netkit_uninit(struct net_device *dev);
 
 static const struct net_device_ops netkit_netdev_ops = {
+	.ndo_init		= netkit_init,
 	.ndo_open		= netkit_open,
 	.ndo_stop		= netkit_close,
 	.ndo_start_xmit		= netkit_xmit,
@@ -243,13 +261,99 @@ static const struct net_device_ops netkit_netdev_ops = {
 static void netkit_get_drvinfo(struct net_device *dev,
 			       struct ethtool_drvinfo *info)
 {
-	strscpy(info->driver, DRV_NAME, sizeof(info->driver));
+	strscpy(info->driver, NETKIT_DRV_NAME, sizeof(info->driver));
+}
+
+static void netkit_get_channels(struct net_device *dev,
+				struct ethtool_channels *channels)
+{
+	channels->max_rx = dev->num_rx_queues;
+	channels->max_tx = dev->num_tx_queues;
+	channels->max_other = 0;
+	channels->max_combined = 1;
+	channels->rx_count = dev->real_num_rx_queues;
+	channels->tx_count = dev->real_num_tx_queues;
+	channels->other_count = 0;
+	channels->combined_count = 0;
 }
 
 static const struct ethtool_ops netkit_ethtool_ops = {
 	.get_drvinfo		= netkit_get_drvinfo,
+	.get_channels		= netkit_get_channels,
 };
 
+static int netkit_queue_create(struct net_device *dev)
+{
+	struct netkit *nk = netkit_priv(dev);
+	u32 rxq_count_old, rxq_count_new;
+	int err;
+
+	rxq_count_old = dev->real_num_rx_queues;
+	rxq_count_new = rxq_count_old + 1;
+
+	/* Only allow to bind in single device mode or to bind against
+	 * the peer device which then ends up in the target netns.
+	 */
+	if (nk->pair == NETKIT_DEVICE_PAIR && nk->primary)
+		return -EOPNOTSUPP;
+
+	if (netif_running(dev))
+		netif_carrier_off(dev);
+	err = netif_set_real_num_rx_queues(dev, rxq_count_new);
+	if (netif_running(dev))
+		netif_carrier_on(dev);
+
+	return err ? err : rxq_count_new;
+}
+
+static const struct netdev_queue_mgmt_ops netkit_queue_mgmt_ops = {
+	.ndo_queue_create = netkit_queue_create,
+};
+
+static struct net_device *netkit_alloc(struct nlattr *tb[],
+				       const char *ifname,
+				       unsigned char name_assign_type,
+				       unsigned int num_tx_queues,
+				       unsigned int num_rx_queues)
+{
+	const struct rtnl_link_ops *ops = &netkit_link_ops;
+	struct net_device *dev;
+
+	if (num_tx_queues > NETKIT_NUM_TX_QUEUES_MAX ||
+	    num_rx_queues > NETKIT_NUM_RX_QUEUES_MAX)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	dev = alloc_netdev_mqs(ops->priv_size, ifname,
+			       name_assign_type, ops->setup,
+			       num_tx_queues, num_rx_queues);
+	if (dev) {
+		dev->real_num_tx_queues = NETKIT_NUM_TX_QUEUES_REAL;
+		dev->real_num_rx_queues = NETKIT_NUM_RX_QUEUES_REAL;
+	}
+	return dev;
+}
+
+static void netkit_queue_unpeer(struct net_device *dev)
+{
+	struct netdev_rx_queue *src_rxq, *dst_rxq;
+	struct net_device *src_dev;
+	int i;
+
+	if (dev->real_num_rx_queues == 1)
+		return;
+	netdev_lock(dev);
+	for (i = 1; i < dev->real_num_rx_queues; i++) {
+		dst_rxq = __netif_get_rx_queue(dev, i);
+		src_rxq = dst_rxq->peer;
+		src_dev = src_rxq->dev;
+
+		netdev_lock(src_dev);
+		netdev_rx_queue_unpeer(src_dev, src_rxq, dst_rxq);
+		netdev_unlock(src_dev);
+	}
+	netdev_unlock(dev);
+}
+
 static void netkit_setup(struct net_device *dev)
 {
 	static const netdev_features_t netkit_features_hw_vlan =
@@ -280,8 +384,9 @@ static void netkit_setup(struct net_device *dev)
 	dev->priv_flags |= IFF_DISABLE_NETPOLL;
 	dev->lltx = true;
 
-	dev->ethtool_ops = &netkit_ethtool_ops;
-	dev->netdev_ops  = &netkit_netdev_ops;
+	dev->netdev_ops     = &netkit_netdev_ops;
+	dev->ethtool_ops    = &netkit_ethtool_ops;
+	dev->queue_mgmt_ops = &netkit_queue_mgmt_ops;
 
 	dev->features |= netkit_features;
 	dev->hw_features = netkit_features;
@@ -330,8 +435,6 @@ static int netkit_validate(struct nlattr *tb[], struct nlattr *data[],
 	return 0;
 }
 
-static struct rtnl_link_ops netkit_link_ops;
-
 static int netkit_new_link(struct net_device *dev,
 			   struct rtnl_newlink_params *params,
 			   struct netlink_ext_ack *extack)
@@ -865,6 +968,7 @@ static void netkit_release_all(struct net_device *dev)
 static void netkit_uninit(struct net_device *dev)
 {
 	netkit_release_all(dev);
+	netkit_queue_unpeer(dev);
 }
 
 static void netkit_del_link(struct net_device *dev, struct list_head *head)
@@ -1005,8 +1109,9 @@ static const struct nla_policy netkit_policy[IFLA_NETKIT_MAX + 1] = {
 };
 
 static struct rtnl_link_ops netkit_link_ops = {
-	.kind		= DRV_NAME,
+	.kind		= NETKIT_DRV_NAME,
 	.priv_size	= sizeof(struct netkit),
+	.alloc		= netkit_alloc,
 	.setup		= netkit_setup,
 	.newlink	= netkit_new_link,
 	.dellink	= netkit_del_link,
@@ -1020,7 +1125,7 @@ static struct rtnl_link_ops netkit_link_ops = {
 	.maxtype	= IFLA_NETKIT_MAX,
 };
 
-static __init int netkit_init(void)
+static __init int netkit_mod_init(void)
 {
 	BUILD_BUG_ON((int)NETKIT_NEXT != (int)TCX_NEXT ||
 		     (int)NETKIT_PASS != (int)TCX_PASS ||
@@ -1030,16 +1135,16 @@ static __init int netkit_init(void)
 	return rtnl_link_register(&netkit_link_ops);
 }
 
-static __exit void netkit_exit(void)
+static __exit void netkit_mod_exit(void)
 {
 	rtnl_link_unregister(&netkit_link_ops);
 }
 
-module_init(netkit_init);
-module_exit(netkit_exit);
+module_init(netkit_mod_init);
+module_exit(netkit_mod_exit);
 
 MODULE_DESCRIPTION("BPF-programmable network device");
 MODULE_AUTHOR("Daniel Borkmann <daniel@iogearbox.net>");
 MODULE_AUTHOR("Nikolay Aleksandrov <razor@blackwall.org>");
 MODULE_LICENSE("GPL");
-MODULE_ALIAS_RTNL_LINK(DRV_NAME);
+MODULE_ALIAS_RTNL_LINK(NETKIT_DRV_NAME);
-- 
2.43.0

From: David Wei <dw@davidwei.uk>

This adds the last missing bit to netkit for supporting io_uring with
zero-copy mode [0]. Up until this point it was not possible to consume
the latter out of containers or Kubernetes Pods where applications are
in their own network namespace.

Thus, as a last missing bit, implement ndo_queue_get_dma_dev() in netkit
to return the physical device of the real rxq for DMA. This allows memory
providers like io_uring zero-copy or devmem to bind to the physically
mapped rxq in netkit.

io_uring example with eth0 being a physical device with 16 queues where
netkit is bound to the last queue, iou-zcrx.c is binary from selftests.
Flow steering to that queue is based on the service VIP:port of the
server utilizing io_uring:

  # ethtool -X eth0 start 0 equal 15
  # ethtool -X eth0 start 15 equal 1 context new
  # ethtool --config-ntuple eth0 flow-type tcp4 dst-ip 1.2.3.4 dst-port 5000 action 15
  # ip netns add foo
  # ip link add type netkit peer numrxqueues 2
  # ./pyynl/cli.py --spec ~/netlink/specs/netdev.yaml \
                   --do bind-queue \
                   --json "{"src-ifindex": $(ifindex eth0), "src-queue-id": 15, \
                            "dst-ifindex": $(ifindex nk0), "queue-type": "rx"}"
  {'dst-queue-id': 1}
  # ip link set nk0 netns foo
  # ip link set nk1 up
  # ip netns exec foo ip link set lo up
  # ip netns exec foo ip link set nk0 up
  # ip netns exec foo ip addr add 1.2.3.4/32 dev nk0
  [ ... setup routing etc to get external traffic into the netns ... ]
  # ip netns exec foo ./iou-zcrx -s -p 5000 -i nk0 -q 1

Remote io_uring client:

  # ./iou-zcrx -c -h 1.2.3.4 -p 5000 -l 12840 -z 65536

We have tested the above against a Broadcom BCM957504 (bnxt_en)
100G NIC, supporting TCP header/data split.

Similarly, this also works for devmem which we tested using ncdevmem:

  # ip netns exec foo ./ncdevmem -s 1.2.3.4 -l -p 5000 -f nk0 -t 1 -q 1

And on the remote client:

  # ./ncdevmem -s 1.2.3.4 -p 5000 -f eth0

For Cilium, the plan is to open up support for the various memory providers
for regular Kubernetes Pods when Cilium is configured with netkit datapath
mode.

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://kernel-recipes.org/en/2024/schedule/efficient-zero-copy-networking-using-io_uring [0]
---
 drivers/net/netkit.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index 75b57496b72e..a281b39a1047 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -282,6 +282,21 @@ static const struct ethtool_ops netkit_ethtool_ops = {
 	.get_channels		= netkit_get_channels,
 };
 
+static struct device *netkit_queue_get_dma_dev(struct net_device *dev, int idx)
+{
+	struct netdev_rx_queue *rxq, *peer_rxq;
+	unsigned int peer_idx;
+
+	rxq = __netif_get_rx_queue(dev, idx);
+	if (!rxq->peer)
+		return NULL;
+
+	peer_rxq = rxq->peer;
+	peer_idx = get_netdev_rx_queue_index(peer_rxq);
+
+	return netdev_queue_get_dma_dev(peer_rxq->dev, peer_idx);
+}
+
 static int netkit_queue_create(struct net_device *dev)
 {
 	struct netkit *nk = netkit_priv(dev);
@@ -307,7 +322,8 @@ static int netkit_queue_create(struct net_device *dev)
 }
 
 static const struct netdev_queue_mgmt_ops netkit_queue_mgmt_ops = {
-	.ndo_queue_create = netkit_queue_create,
+	.ndo_queue_get_dma_dev		= netkit_queue_get_dma_dev,
+	.ndo_queue_create		= netkit_queue_create,
 };
 
 static struct net_device *netkit_alloc(struct nlattr *tb[],
-- 
2.43.0

Enable support for AF_XDP applications to operate on a netkit device.
The goal is that AF_XDP applications can natively consume AF_XDP
from network namespaces. The use-case from Cilium side is to support
Kubernetes KubeVirt VMs through QEMU's AF_XDP backend. KubeVirt is a
virtual machine management add-on for Kubernetes which aims to provide
a common ground for virtualization. KubeVirt spawns the VMs inside
Kubernetes Pods which reside in their own network namespace just like
regular Pods.

Raw QEMU AF_XDP backend example with eth0 being a physical device with
16 queues where netkit is bound to the last queue (for multi-queue RSS
context can be used if supported by the driver):

  # ethtool -X eth0 start 0 equal 15
  # ethtool -X eth0 start 15 equal 1 context new
  # ethtool --config-ntuple eth0 flow-type ether \
            src 00:00:00:00:00:00 \
            src-mask ff:ff:ff:ff:ff:ff \
            dst $mac dst-mask 00:00:00:00:00:00 \
            proto 0 proto-mask 0xffff action 15
  [ ... setup BPF/XDP prog on eth0 to steer into shared xsk map ... ]
  # ip netns add foo
  # ip link add numrxqueues 2 nk type netkit single
  # ./pyynl/cli.py --spec ~/netlink/specs/netdev.yaml \
                   --do bind-queue \
                   --json "{"src-ifindex": $(ifindex eth0), "src-queue-id": 15, \
                            "dst-ifindex": $(ifindex nk), "queue-type": "rx"}"
  {'dst-queue-id': 1}
  # ip link set nk netns foo
  # ip netns exec foo ip link set lo up
  # ip netns exec foo ip link set nk up
  # ip netns exec foo qemu-system-x86_64 \
          -kernel $kernel \
          -drive file=${image_name},index=0,media=disk,format=raw \
          -append "root=/dev/sda rw console=ttyS0" \
          -cpu host \
          -m $memory \
          -enable-kvm \
          -device virtio-net-pci,netdev=net0,mac=$mac \
          -netdev af-xdp,ifname=nk,id=net0,mode=native,queues=1,start-queue=1,inhibit=on,map-path=$dir/xsks_map \
          -nographic

We have tested the above against a dual-port Nvidia ConnectX-6 (mlx5)
100G NIC with successful network connectivity out of QEMU. An earlier
iteration of this work was presented at LSF/MM/BPF [0].

For getting to a first starting point to connect all things with
KubeVirt, bind mounting the xsk map from Cilium into the VM launcher
Pod which acts as a regular Kubernetes Pod while not perfect, is not
a big problem given its out of reach from the application sitting
inside the VM (and some of the control plane aspects are baked in
the launcher Pod already), so the isolation barrier is still the VM.
Eventually the goal is to have a XDP/XSK redirect extension where
there is no need to have the xsk map, and the BPF program can just
derive the target xsk through the queue where traffic was received
on.

The exposure through netkit is because Cilium should not act as a
proxy handing out xsk sockets. Existing applications expect a netdev
from kernel side and should not need to rewrite just to implement
against a CNI's protocol. Also, all the memory should not be accounted
against Cilium but rather the application Pod itself which is consuming
AF_XDP. Further, on up/downgrades we expect the data plane to being
completely decoupled from the control plane; if Cilium would own the
sockets that would be disruptive. Another use-case which opens up and
is regularly asked from users would be to have DPDK applications on
top of AF_XDP in regular Kubernetes Pods.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Co-developed-by: David Wei <dw@davidwei.uk>
Signed-off-by: David Wei <dw@davidwei.uk>
Link: https://bpfconf.ebpf.io/bpfconf2025/bpfconf2025_material/lsfmmbpf_2025_netkit_borkmann.pdf [0]
---
 drivers/net/netkit.c | 71 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 1 deletion(-)

diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c
index a281b39a1047..f69abe5ec4cd 100644
--- a/drivers/net/netkit.c
+++ b/drivers/net/netkit.c
@@ -12,6 +12,7 @@
 #include <net/netdev_lock.h>
 #include <net/netdev_queues.h>
 #include <net/netdev_rx_queue.h>
+#include <net/xdp_sock_drv.h>
 #include <net/netkit.h>
 #include <net/dst.h>
 #include <net/tcx.h>
@@ -235,6 +236,71 @@ static void netkit_get_stats(struct net_device *dev,
 	stats->tx_dropped = DEV_STATS_READ(dev, tx_dropped);
 }
 
+static bool netkit_xsk_supported_at_phys(const struct net_device *dev)
+{
+	if (!dev->netdev_ops->ndo_bpf ||
+	    !dev->netdev_ops->ndo_xdp_xmit ||
+	    !dev->netdev_ops->ndo_xsk_wakeup)
+		return false;
+	if ((dev->xdp_features & NETDEV_XDP_ACT_XSK) != NETDEV_XDP_ACT_XSK)
+		return false;
+	return true;
+}
+
+static int netkit_xsk(struct net_device *dev, struct netdev_bpf *xdp)
+{
+	struct netkit *nk = netkit_priv(dev);
+	struct netdev_bpf xdp_lower;
+	struct netdev_rx_queue *rxq;
+	struct net_device *phys;
+
+	switch (xdp->command) {
+	case XDP_SETUP_XSK_POOL:
+		if (nk->pair == NETKIT_DEVICE_PAIR)
+			return -EOPNOTSUPP;
+		if (xdp->xsk.queue_id >= dev->real_num_rx_queues)
+			return -EINVAL;
+
+		rxq = __netif_get_rx_queue(dev, xdp->xsk.queue_id);
+		if (!rxq->peer)
+			return -EOPNOTSUPP;
+
+		phys = rxq->peer->dev;
+		if (!netkit_xsk_supported_at_phys(phys))
+			return -EOPNOTSUPP;
+
+		memcpy(&xdp_lower, xdp, sizeof(xdp_lower));
+		xdp_lower.xsk.queue_id = get_netdev_rx_queue_index(rxq->peer);
+		break;
+	case XDP_SETUP_PROG:
+		return -EPERM;
+	default:
+		return -EINVAL;
+	}
+
+	return phys->netdev_ops->ndo_bpf(phys, &xdp_lower);
+}
+
+static int netkit_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags)
+{
+	struct netdev_rx_queue *rxq;
+	struct net_device *phys;
+
+	if (queue_id >= dev->real_num_rx_queues)
+		return -EINVAL;
+
+	rxq = __netif_get_rx_queue(dev, queue_id);
+	if (!rxq->peer)
+		return -EOPNOTSUPP;
+
+	phys = rxq->peer->dev;
+	if (!netkit_xsk_supported_at_phys(phys))
+		return -EOPNOTSUPP;
+
+	return phys->netdev_ops->ndo_xsk_wakeup(phys,
+			get_netdev_rx_queue_index(rxq->peer), flags);
+}
+
 static int netkit_init(struct net_device *dev)
 {
 	netdev_lockdep_set_classes(dev);
@@ -255,6 +321,8 @@ static const struct net_device_ops netkit_netdev_ops = {
 	.ndo_get_peer_dev	= netkit_peer_dev,
 	.ndo_get_stats64	= netkit_get_stats,
 	.ndo_uninit		= netkit_uninit,
+	.ndo_bpf		= netkit_xsk,
+	.ndo_xsk_wakeup		= netkit_xsk_wakeup,
 	.ndo_features_check	= passthru_features_check,
 };
 
@@ -409,10 +477,11 @@ static void netkit_setup(struct net_device *dev)
 	dev->hw_enc_features = netkit_features;
 	dev->mpls_features = NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE;
 	dev->vlan_features = dev->features & ~netkit_features_hw_vlan;
-
 	dev->needs_free_netdev = true;
 
 	netif_set_tso_max_size(dev, GSO_MAX_SIZE);
+
+	xdp_set_features_flag(dev, NETDEV_XDP_ACT_XSK);
 }
 
 static struct net *netkit_get_link_net(const struct net_device *dev)
-- 
2.43.0