Re: [PATCH net-next 01/20] net, ynl: Add bind-queue operation

[Stanislav Fomichev <stfomichev@gmail.com>]

On 09/19, Daniel Borkmann wrote:
> From: David Wei <dw@davidwei.uk>
> 
> Add a ynl netdev family operation called bind-queue that _binds_ an
> rxq from a real netdev to a virtual netdev i.e. netkit or veth. This
> bound or _mapped_ rxq in the virtual netdev acts as a proxy for the
> parent real rxq, and can be used by processes running in a container
> to use memory providers (io_uring zero-copy rx or devmem) or 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 rxq respectively.
> dst-ifindex is the virtual netdev. Note that this op doesn't take
> dst-queue-id, because the expectation is that the op will _create_ a
> new rxq in the virtual netdev. The virtual netdev must have
> real_num_rx_queues less than num_rx_queues at the time of calling
> bind-queue.
> 
> 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 | 37 +++++++++++++++++++++++++
>  include/uapi/linux/netdev.h             | 11 ++++++++
>  net/core/netdev-genl-gen.c              | 14 ++++++++++
>  net/core/netdev-genl-gen.h              |  1 +
>  net/core/netdev-genl.c                  |  4 +++
>  tools/include/uapi/linux/netdev.h       | 11 ++++++++
>  6 files changed, 78 insertions(+)
> 
> diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
> index e00d3fa1c152..99a430ea8a9a 100644
> --- a/Documentation/netlink/specs/netdev.yaml
> +++ b/Documentation/netlink/specs/netdev.yaml
> @@ -561,6 +561,29 @@ attribute-sets:
>          type: u32
>          checks:
>            min: 1
> +  -
> +    name: queue-pair
> +    attributes:
> +      -
> +        name: src-ifindex
> +        doc: netdev ifindex of the physical device
> +        type: u32
> +        checks:
> +          min: 1
> +      -
> +        name: src-queue-id
> +        doc: netdev queue id of the physical device
> +        type: u32
> +      -
> +        name: dst-ifindex
> +        doc: netdev ifindex of the virtual device
> +        type: u32
> +        checks:
> +          min: 1
> +      -
> +        name: dst-queue-id
> +        doc: netdev queue id of the virtual device
> +        type: u32
>  
>  operations:
>    list:
> @@ -772,6 +795,20 @@ operations:
>            attributes:
>              - id
>  
> +    -
> +      name: bind-queue
> +      doc: Bind a physical netdev queue to a virtual one
> +      attribute-set: queue-pair
> +      do:
> +        request:
> +          attributes:
> +            - 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..05e17765a39d 100644
> --- a/include/uapi/linux/netdev.h
> +++ b/include/uapi/linux/netdev.h
> @@ -210,6 +210,16 @@ enum {
>  	NETDEV_A_DMABUF_MAX = (__NETDEV_A_DMABUF_MAX - 1)
>  };
>  
> +enum {
> +	NETDEV_A_QUEUE_PAIR_SRC_IFINDEX = 1,
> +	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 +236,7 @@ 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..10b2ab4dd500 100644
> --- a/net/core/netdev-genl-gen.c
> +++ b/net/core/netdev-genl-gen.c
> @@ -106,6 +106,13 @@ 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_SRC_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
> +	[NETDEV_A_QUEUE_PAIR_SRC_QUEUE_ID] = { .type = NLA_U32, },
> +	[NETDEV_A_QUEUE_PAIR_DST_IFINDEX] = NLA_POLICY_MIN(NLA_U32, 1),
> +};
> +
>  /* Ops table for netdev */
>  static const struct genl_split_ops netdev_nl_ops[] = {
>  	{
> @@ -204,6 +211,13 @@ 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..b0aea27bf84e 100644
> --- a/net/core/netdev-genl.c
> +++ b/net/core/netdev-genl.c
> @@ -1120,6 +1120,10 @@ 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)
> +{

nit: return 'not supported' for now or something similar?