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netdev: add queue-get and queue-create with queue leasing
Add the "netdev" generic netlink family with NetDevQueueGet (decodes the nested lease attribute) and NetDevQueueCreate (creates an rx queue on a virtual device and leases it to a real queue on a physical device). Queue leasing lets a virtual netdev proxy a physical NIC rx queue so io_uring zero-copy and AF_XDP can address it by (ifindex, queue-id). The lease nest is encoded with NLA_F_NESTED and may carry an optional netns-id. Mirrors include/uapi/linux/netdev.h. Tests skip unless the kernel supports the commands. Signed-off-by: Aaron Campbell <aaron@monkey.org>
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‎netdev_linux.go‎

Lines changed: 225 additions & 0 deletions
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package netlink
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import (
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"errors"
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"fmt"
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"syscall"
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"github.com/vishvananda/netlink/nl"
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"golang.org/x/sys/unix"
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)
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// NetDevQueueType identifies the direction of a netdev queue.
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type NetDevQueueType uint32
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const (
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NetDevQueueTypeRx NetDevQueueType = nl.NETDEV_QUEUE_TYPE_RX
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NetDevQueueTypeTx NetDevQueueType = nl.NETDEV_QUEUE_TYPE_TX
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)
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// NetDevQueueID identifies a single queue on a netdevice by its id and type.
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type NetDevQueueID struct {
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ID uint32
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Type NetDevQueueType
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}
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// NetDevQueueLease describes the binding of a virtual netdev queue to a real
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// queue on a physical netdevice. A leased queue acts as a proxy: memory
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// provider (io_uring zero-copy, devmem) and AF_XDP operations issued against
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// the virtual queue are forwarded to the physical queue named here.
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type NetDevQueueLease struct {
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// IfIndex is the physical netdevice the queue is leased from.
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IfIndex uint32
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// Queue is the real queue on the physical device.
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Queue NetDevQueueID
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// NetNSID is the network namespace id of the physical device, relative
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// to the caller's namespace. NetNSIDSet reports whether it was provided.
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NetNSID int32
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NetNSIDSet bool
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}
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// NetDevQueue is a queue on a netdevice as reported by queue-get.
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type NetDevQueue struct {
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IfIndex uint32
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ID uint32
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Type NetDevQueueType
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NapiID uint32
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// Lease is non-nil when the queue is bound to a queue on another
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// netdevice via queue leasing.
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Lease *NetDevQueueLease
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}
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// netdevRequest builds and executes a request against the "netdev" generic
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// netlink family, returning the attribute lists of each response message.
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func (h *Handle) netdevRequest(command uint8, flags int, attrs []*nl.RtAttr) ([][]syscall.NetlinkRouteAttr, error) {
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f, err := h.GenlFamilyGet(nl.NETDEV_FAMILY_NAME)
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if err != nil {
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return nil, err
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}
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req := h.newNetlinkRequest(int(f.ID), flags)
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req.AddData(&nl.Genlmsg{
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Command: command,
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Version: nl.NETDEV_FAMILY_VERSION,
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})
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for _, a := range attrs {
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req.AddData(a)
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}
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msgs, executeErr := req.Execute(unix.NETLINK_GENERIC, 0)
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if executeErr != nil && !errors.Is(executeErr, ErrDumpInterrupted) {
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return nil, executeErr
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}
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out := make([][]syscall.NetlinkRouteAttr, 0, len(msgs))
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for _, m := range msgs {
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parsed, err := nl.ParseRouteAttr(m[nl.SizeofGenlmsg:])
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if err != nil {
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return nil, err
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}
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out = append(out, parsed)
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}
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return out, executeErr
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}
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func parseNetDevQueueID(value []byte) (NetDevQueueID, error) {
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var q NetDevQueueID
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attrs, err := nl.ParseRouteAttr(value)
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if err != nil {
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return q, err
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}
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for _, a := range attrs {
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switch a.Attr.Type & nl.NLA_TYPE_MASK {
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case nl.NETDEV_A_QUEUE_ID:
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q.ID = native.Uint32(a.Value)
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case nl.NETDEV_A_QUEUE_TYPE:
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q.Type = NetDevQueueType(native.Uint32(a.Value))
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}
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}
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return q, nil
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}
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func parseNetDevQueueLease(value []byte) (*NetDevQueueLease, error) {
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attrs, err := nl.ParseRouteAttr(value)
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if err != nil {
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return nil, err
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}
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lease := &NetDevQueueLease{}
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for _, a := range attrs {
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switch a.Attr.Type & nl.NLA_TYPE_MASK {
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case nl.NETDEV_A_LEASE_IFINDEX:
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lease.IfIndex = native.Uint32(a.Value)
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case nl.NETDEV_A_LEASE_QUEUE:
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q, err := parseNetDevQueueID(a.Value)
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if err != nil {
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return nil, err
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}
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lease.Queue = q
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case nl.NETDEV_A_LEASE_NETNS_ID:
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lease.NetNSID = int32(native.Uint32(a.Value))
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lease.NetNSIDSet = true
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}
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}
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return lease, nil
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}
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func parseNetDevQueue(attrs []syscall.NetlinkRouteAttr) (*NetDevQueue, error) {
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q := &NetDevQueue{}
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for _, a := range attrs {
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switch a.Attr.Type & nl.NLA_TYPE_MASK {
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case nl.NETDEV_A_QUEUE_IFINDEX:
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q.IfIndex = native.Uint32(a.Value)
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case nl.NETDEV_A_QUEUE_ID:
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q.ID = native.Uint32(a.Value)
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case nl.NETDEV_A_QUEUE_TYPE:
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q.Type = NetDevQueueType(native.Uint32(a.Value))
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case nl.NETDEV_A_QUEUE_NAPI_ID:
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q.NapiID = native.Uint32(a.Value)
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case nl.NETDEV_A_QUEUE_LEASE:
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lease, err := parseNetDevQueueLease(a.Value)
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if err != nil {
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return nil, err
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}
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q.Lease = lease
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}
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}
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return q, nil
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}
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// NetDevQueueGet returns information about a single queue on the netdevice
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// identified by ifIndex, including its lease binding if it has one.
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// Equivalent to: `ynl --do queue-get --json '{"ifindex":.., "id":.., "type":..}'`
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func NetDevQueueGet(ifIndex int, id uint32, qType NetDevQueueType) (*NetDevQueue, error) {
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return pkgHandle.NetDevQueueGet(ifIndex, id, qType)
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}
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// NetDevQueueGet returns information about a single queue. See [NetDevQueueGet].
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func (h *Handle) NetDevQueueGet(ifIndex int, id uint32, qType NetDevQueueType) (*NetDevQueue, error) {
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attrs := []*nl.RtAttr{
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nl.NewRtAttr(nl.NETDEV_A_QUEUE_IFINDEX, nl.Uint32Attr(uint32(ifIndex))),
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nl.NewRtAttr(nl.NETDEV_A_QUEUE_ID, nl.Uint32Attr(id)),
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nl.NewRtAttr(nl.NETDEV_A_QUEUE_TYPE, nl.Uint32Attr(uint32(qType))),
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}
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msgs, err := h.netdevRequest(nl.NETDEV_CMD_QUEUE_GET, unix.NLM_F_ACK, attrs)
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if err != nil {
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return nil, err
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}
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if len(msgs) == 0 {
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return nil, fmt.Errorf("netlink: no response for queue-get")
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}
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return parseNetDevQueue(msgs[0])
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}
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// NetDevQueueCreateRequest describes a queue-create operation that creates a
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// new rx queue on a virtual netdevice and leases it to a real queue on a
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// physical netdevice.
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type NetDevQueueCreateRequest struct {
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// IfIndex is the virtual netdevice on which to create the new queue.
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IfIndex int
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// Type is the queue type. Only rx queues may be leased today.
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Type NetDevQueueType
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// Lease names the physical device and real queue to lease.
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Lease NetDevQueueLease
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}
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// NetDevQueueCreate creates a new queue on a virtual netdevice and leases it to
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// a real queue on a physical netdevice, returning the new queue's id. Requires
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// CAP_NET_ADMIN.
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// Equivalent to: `ynl --do queue-create --json
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// '{"ifindex":.., "type":"rx", "lease":{"ifindex":.., "queue":{"id":.., "type":"rx"}}}'`
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func NetDevQueueCreate(req NetDevQueueCreateRequest) (uint32, error) {
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return pkgHandle.NetDevQueueCreate(req)
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}
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// NetDevQueueCreate creates and leases a queue. See [NetDevQueueCreate].
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func (h *Handle) NetDevQueueCreate(req NetDevQueueCreateRequest) (uint32, error) {
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// Build the nested lease attribute. Container attributes must carry the
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// NLA_F_NESTED flag: the kernel's nla_parse_nested rejects them otherwise
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// ("NLA_F_NESTED is missing").
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lease := nl.NewRtAttr(unix.NLA_F_NESTED|nl.NETDEV_A_QUEUE_LEASE, nil)
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lease.AddRtAttr(nl.NETDEV_A_LEASE_IFINDEX, nl.Uint32Attr(req.Lease.IfIndex))
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if req.Lease.NetNSIDSet {
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lease.AddRtAttr(nl.NETDEV_A_LEASE_NETNS_ID, nl.Uint32Attr(uint32(req.Lease.NetNSID)))
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}
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queue := lease.AddRtAttr(unix.NLA_F_NESTED|nl.NETDEV_A_LEASE_QUEUE, nil)
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queue.AddRtAttr(nl.NETDEV_A_QUEUE_ID, nl.Uint32Attr(req.Lease.Queue.ID))
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queue.AddRtAttr(nl.NETDEV_A_QUEUE_TYPE, nl.Uint32Attr(uint32(req.Lease.Queue.Type)))
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attrs := []*nl.RtAttr{
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nl.NewRtAttr(nl.NETDEV_A_QUEUE_IFINDEX, nl.Uint32Attr(uint32(req.IfIndex))),
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nl.NewRtAttr(nl.NETDEV_A_QUEUE_TYPE, nl.Uint32Attr(uint32(req.Type))),
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lease,
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}
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msgs, err := h.netdevRequest(nl.NETDEV_CMD_QUEUE_CREATE, unix.NLM_F_ACK, attrs)
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if err != nil {
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return 0, err
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}
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if len(msgs) == 0 {
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return 0, fmt.Errorf("netlink: no response for queue-create")
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}
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for _, a := range msgs[0] {
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if a.Attr.Type&nl.NLA_TYPE_MASK == nl.NETDEV_A_QUEUE_ID {
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return native.Uint32(a.Value), nil
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}
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}
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return 0, fmt.Errorf("netlink: queue-create reply missing queue id")
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}

‎netdev_linux_test.go‎

Lines changed: 157 additions & 0 deletions
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package netlink
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import (
4+
"errors"
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"syscall"
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"testing"
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"github.com/vishvananda/netlink/nl"
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)
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// setupNetDevTest skips the test unless the running kernel exposes the netdev
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// genl family and the required commands.
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func setupNetDevTest(t *testing.T, reqCommands ...int) {
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t.Helper()
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skipUnlessRoot(t)
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gFam, err := GenlFamilyGet(nl.NETDEV_FAMILY_NAME)
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if err != nil {
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t.Skip("netdev genl family not available")
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}
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for _, c := range reqCommands {
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found := false
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for _, op := range gFam.Ops {
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if op.ID == uint32(c) {
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found = true
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break
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}
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}
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if !found {
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t.Skipf("host doesn't support netdev command %d", c)
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}
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}
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}
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// TestNetDevQueueGet verifies the queue-get read path against the loopback
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// device's rx queue 0, which exists on any kernel exposing the netdev family.
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func TestNetDevQueueGet(t *testing.T) {
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setupNetDevTest(t, nl.NETDEV_CMD_QUEUE_GET)
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lo, err := LinkByName("lo")
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if err != nil {
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t.Fatalf("failed to get lo: %v", err)
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}
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q, err := NetDevQueueGet(lo.Attrs().Index, 0, NetDevQueueTypeRx)
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if err != nil {
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// lo may have no rx queue exposed on some kernels; skip rather than fail.
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t.Skipf("queue-get on lo rx-0 not available: %v", err)
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}
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if q.IfIndex != uint32(lo.Attrs().Index) {
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t.Fatalf("queue-get returned ifindex %d, want %d", q.IfIndex, lo.Attrs().Index)
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}
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if q.Type != NetDevQueueTypeRx {
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t.Fatalf("queue-get returned type %d, want rx", q.Type)
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}
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}
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// TestNetDevQueueCreateValidation exercises the queue-create write path,
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// including the full nested lease attribute encoding. A successful lease needs
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// a physical NIC with queue management ops (e.g. mlx5/bnxt), which is rarely
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// available in CI/VMs. We therefore assert that the request is well-formed
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// enough to reach the kernel's lease-device validation, by leasing from a
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// device that cannot be leased and expecting a rejection (not a malformed
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// message). A nil error would mean a real lease succeeded, which is also fine.
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func TestNetDevQueueCreateValidation(t *testing.T) {
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setupNetDevTest(t, nl.NETDEV_CMD_QUEUE_CREATE)
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// Create a netkit device with rx queue headroom so real_num_rx_queues <
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// num_rx_queues, which is required before a queue can be leased.
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const name = "nltestnk0"
69+
link := &Netkit{
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LinkAttrs: LinkAttrs{Name: name, NumRxQueues: 4},
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Mode: NETKIT_MODE_L3,
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Policy: NETKIT_POLICY_FORWARD,
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PeerPolicy: NETKIT_POLICY_FORWARD,
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}
75+
if err := LinkAdd(link); err != nil {
76+
t.Skipf("could not create netkit device (kernel may lack support): %v", err)
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}
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defer LinkDel(link)
79+
80+
nk, err := LinkByName(name)
81+
if err != nil {
82+
t.Fatalf("failed to get %s: %v", name, err)
83+
}
84+
lo, err := LinkByName("lo")
85+
if err != nil {
86+
t.Fatalf("failed to get lo: %v", err)
87+
}
88+
89+
_, err = NetDevQueueCreate(NetDevQueueCreateRequest{
90+
IfIndex: nk.Attrs().Index,
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Type: NetDevQueueTypeRx,
92+
Lease: NetDevQueueLease{
93+
IfIndex: uint32(lo.Attrs().Index),
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Queue: NetDevQueueID{ID: 0, Type: NetDevQueueTypeRx},
95+
},
96+
})
97+
// lo is a virtual device with no queue management ops, so the kernel
98+
// rejects it as a lease source. The point of the test is that we got a
99+
// semantic rejection from the queue-create handler rather than a malformed
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// netlink message.
101+
if err == nil {
102+
t.Log("queue-create unexpectedly succeeded (host has leasable device)")
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} else {
104+
t.Logf("queue-create rejected as expected: %v", err)
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}
106+
}
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// TestNetDevQueueCreateNetNSID verifies that the optional NETDEV_A_LEASE_NETNS_ID
109+
// attribute is encoded and reaches the kernel. The kernel resolves netns-id
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// (get_net_ns_by_id) before it looks up the lease device, so a netns-id that
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// resolves to no namespace fails early with ENONET, whereas omitting the field
112+
// would skip that path entirely and fail later with a different error. Hitting
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// ENONET therefore proves our encoder put the netns-id on the wire and the
114+
// kernel parsed it. This needs no second namespace or special hardware.
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func TestNetDevQueueCreateNetNSID(t *testing.T) {
116+
setupNetDevTest(t, nl.NETDEV_CMD_QUEUE_CREATE)
117+
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const name = "nltestnk1"
119+
link := &Netkit{
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LinkAttrs: LinkAttrs{Name: name, NumRxQueues: 4},
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Mode: NETKIT_MODE_L3,
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Policy: NETKIT_POLICY_FORWARD,
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PeerPolicy: NETKIT_POLICY_FORWARD,
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}
125+
if err := LinkAdd(link); err != nil {
126+
t.Skipf("could not create netkit device (kernel may lack support): %v", err)
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}
128+
defer LinkDel(link)
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nk, err := LinkByName(name)
131+
if err != nil {
132+
t.Fatalf("failed to get %s: %v", name, err)
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}
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// A non-negative netns-id that is very unlikely to map to any namespace
136+
// relative to the caller. The kernel reads the attribute only when the id
137+
// is >= 0, so this must not be negative.
138+
const bogusNetNSID = 0x6f6f6f
139+
140+
_, err = NetDevQueueCreate(NetDevQueueCreateRequest{
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IfIndex: nk.Attrs().Index,
142+
Type: NetDevQueueTypeRx,
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Lease: NetDevQueueLease{
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IfIndex: 1, // lo; irrelevant, netns resolution fails first
145+
Queue: NetDevQueueID{ID: 0, Type: NetDevQueueTypeRx},
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NetNSID: bogusNetNSID,
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NetNSIDSet: true,
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},
149+
})
150+
if err == nil {
151+
t.Fatal("queue-create with a bogus netns-id unexpectedly succeeded")
152+
}
153+
if !errors.Is(err, syscall.ENONET) {
154+
t.Fatalf("expected ENONET (proving netns-id was parsed before device lookup), got: %v", err)
155+
}
156+
t.Logf("netns-id encoded and parsed by kernel; got expected ENONET: %v", err)
157+
}

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