Subject: Re: [PATCH v3 02/12] netlink: spec: add shaper YAML spec

From: Donald Hunter <[email-masked]>
Date: Wed, 31 Jul 2024 22:13:22 +0100

Paolo Abeni <[email-masked]> writes:

> diff --git a/Documentation/netlink/specs/shaper.yaml b/Documentation/netlink/specs/shaper.yaml
> new file mode 100644
> index 000000000000..7327f5596fdb
> --- /dev/null
> +++ b/Documentation/netlink/specs/shaper.yaml

It's probably more user-friendly to use the same filename as the spec
name, so net-shaper.yaml

> @@ -0,0 +1,262 @@
> +# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
> +
> +name: net-shaper
> +
> +doc: Network device HW Rate Limiting offload
> +
> +definitions:
> +  -
> +    type: enum
> +    name: scope
> +    doc: the different scopes where a shaper can be attached

Nit: upper case 'The' to be consistent with rest of docs.

> +    render-max: true
> +    entries:
> +      - name: unspec
> +        doc: The scope is not specified

What are the semantics of 'unspec' ? When can it be used?

> +      -
> +        name: port
> +        doc: The root for the whole H/W
> +      -
> +        name: netdev
> +        doc: The main shaper for the given network device.

What are the semantic differences between netdev and port?

> +      -
> +        name: queue
> +        doc: The shaper is attached to the given device queue.
> +      -
> +        name: detached
> +        doc: |
> +             The shaper is not attached to any user-visible network
> +             device component and allows nesting and grouping of
> +             queues or others detached shapers.

I assume that shapers are always owned by the netdev regardless of
attach status?

> +  -
> +    type: enum
> +    name: metric
> +    doc: different metric each shaper can support

Nit: upper case here as well.

> +    entries:
> +      -
> +        name: bps
> +        doc: Shaper operates on a bits per second basis
> +      -
> +        name: pps
> +        doc: Shaper operates on a packets per second basis
> +
> +attribute-sets:
> +  -
> +    name: net-shaper
> +    attributes:
> +      -
> +        name: ifindex
> +        type: u32
> +        doc: Interface index owing the specified shaper[s]

Typo: this should be 'owning' ?

> +      -
> +        name: handle
> +        type: nest
> +        nested-attributes: handle
> +        doc: Unique identifier for the given shaper
> +      -
> +        name: metric
> +        type: u32
> +        enum: metric
> +        doc: Metric used by the given shaper for bw-min, bw-max and burst
> +      -
> +        name: bw-min
> +        type: uint
> +        doc: Minimum guaranteed B/W for the given shaper
> +      -
> +        name: bw-max
> +        type: uint
> +        doc: Shaping B/W for the given shaper or 0 when unlimited
> +      -
> +        name: burst
> +        type: uint
> +        doc: Maximum burst-size for bw-min and bw-max
> +      -
> +        name: priority
> +        type: u32
> +        doc: Scheduling priority for the given shaper
> +      -
> +        name: weight
> +        type: u32
> +        doc: |
> +          Weighted round robin weight for given shaper.
> +          The scheduling is applied to all the sibling
> +          shapers with the same priority
> +      -
> +        name: scope
> +        type: u32
> +        enum: scope
> +        doc: The given handle scope
> +      -
> +        name: id
> +        type: u32
> +        doc: |
> +          The given handle id. The id semantic depends on the actual
> +          scope, e.g. for 'queue' scope it's the queue id, for
> +          'detached' scope it's the shaper group identifier.

If scope and id are only ever used as attributes of a handle then they
would be better specified as a separate attribute-set, instead of
mixing them in here and using a subset.

You use 'quoted' references here and @refs elsewhere. It would be good
to be consistent. See note below about @ in htmldocs.

> +      -
> +        name: parent
> +        type: nest
> +        nested-attributes: handle
> +        doc: |
> +          Identifier for the parent of the affected shaper,
> +          The parent handle value is implied by the shaper handle itself,
> +          except for the output shaper in the 'group' operation.

Nit: quoted ref again here

> +      -
> +        name: inputs
> +        type: nest
> +        multi-attr: true
> +        nested-attributes: ns-info
> +        doc: |
> +           Describes a set of inputs shapers for a @group operation

The @group renders exactly as-is in the generated htmldocs. There may be
a more .rst friendly markup you can use that will render better.

> +      -
> +        name: output
> +        type: nest
> +        nested-attributes: ns-output-info
> +        doc: |
> +           Describes the output shaper for a @group operation
> +           Differently from @inputs and @shaper allow specifying
> +           the shaper parent handle, too.
> +

Nit: remove the extra blank line here

> +      -
> +        name: shaper
> +        type: nest
> +        nested-attributes: ns-info
> +        doc: |
> +           Describes a single shaper for a @set operation
> +  -
> +    name: handle
> +    subset-of: net-shaper
> +    attributes:
> +      -
> +        name: scope
> +      -
> +        name: id
> +  -
> +    name: ns-info
> +    subset-of: net-shaper
> +    attributes:
> +      -
> +        name: handle
> +      -
> +        name: metric
> +      -
> +        name: bw-min
> +      -
> +        name: bw-max
> +      -
> +        name: burst
> +      -
> +        name: priority
> +      -
> +        name: weight
> +  -
> +    name: ns-output-info
> +    subset-of: net-shaper
> +    attributes:
> +      -
> +        name: parent
> +      -
> +        name: handle
> +      -
> +        name: metric
> +      -
> +        name: bw-min
> +      -
> +        name: bw-max
> +      -
> +        name: burst
> +      -
> +        name: priority
> +      -
> +        name: weight
> +
> +operations:
> +  list:
> +    -
> +      name: get
> +      doc: |
> +        Get / Dump information about a/all the shaper for a given device
> +      attribute-set: net-shaper
> +
> +      do:
> +        request:
> +          attributes:
> +            - ifindex
> +            - handle
> +        reply:
> +          attributes: &ns-attrs
> +            - parent
> +            - handle
> +            - metric
> +            - bw-min
> +            - bw-max
> +            - burst
> +            - priority
> +            - weight
> +
> +      dump:
> +        request:
> +          attributes:
> +            - ifindex
> +        reply:
> +          attributes: *ns-attrs
> +    -
> +      name: set
> +      doc: |
> +        Create or configures the specified shaper.
> +        On failures the extack is set accordingly.
> +        Can't create @detached scope shaper, use
> +        the @group operation instead.
> +      attribute-set: net-shaper
> +      flags: [ admin-perm ]
> +
> +      do:
> +        request:
> +          attributes:
> +            - ifindex
> +            - shaper
> +
> +    -
> +      name: delete
> +      doc: |
> +        Clear (remove) the specified shaper. If after the removal
> +        the parent shaper has no more children and the parent
> +        shaper scope is @detached, even the parent is deleted,
> +        recursively.
> +        On failures the extack is set accordingly.
> +      attribute-set: net-shaper
> +      flags: [ admin-perm ]
> +
> +      do:
> +        request:
> +          attributes:
> +            - ifindex
> +            - handle
> +
> +    -
> +      name: group
> +      doc: |
> +        Group the specified input shapers under the specified
> +        output shaper, eventually creating the latter, if needed.
> +        Input shapers scope must be either @queue or @detached.

It says above that you cannot create a detached shaper, so how do you
create one to use as an input shaper here? Is this group op more like a
multi-create op?

> +        Output shaper scope must be either @detached or @netdev.
> +        When using an output @detached scope shaper, if the
> +        @handle @id is not specified, a new shaper of such scope
> +        is created and, otherwise the specified output shaper
> +        must be already existing.
> +        The operation is atomic, on failures the extack is set
> +        accordingly and no change is applied to the device
> +        shaping configuration, otherwise the output shaper
> +        handle is provided as reply.
> +      attribute-set: net-shaper
> +      flags: [ admin-perm ]

Does there need to be a reciprocal 'ungroup' operation? Without it,
create / group / delete seems like they will have ambiguous semantics.

> +      do:
> +        request:
> +          attributes:
> +            - ifindex
> +            - inputs
> +            - output
> +        reply:
> +          attributes:
> +            - handle