[RFC net-next 0/4] tools/net/ynl: Add batch operations for nftables

[Donald Hunter <donald.hunter@gmail.com>]

The nftables netlink families use batch operations for create update and
delete operations. This is a first cut at extending the netlink-raw
schema so that operations can wrapped with begin-batch and end-batch
messages.

The begin/end messages themselves are defined as ordinary ops, but there
are new attributes that describe the op name and parameters for the
begin/end messages.

The section of yaml spec that defines the begin/end ops looks like this;
the newtable op is marked 'is-batch: true' so the message needs to be
wrapped with 'batch-begin(res-id: 10)' and batch-end(res-id: 10) messages:

operations:
  enum-model: directional
  begin-batch:                # Define how to begin a batch
    operation: batch-begin
    parameters:
      res-id: 10
  end-batch:                  # Define how to end a batch
    operation: batch-end
    parameters:
      res-id: 10
  list:
    -
      name: batch-begin
      doc: Start a batch of operations
      attribute-set: batch-attrs
      fixed-header: nfgenmsg
      do:
        request:
          value: 0x10
          attributes:
            - genid
        reply:
          value: 0x10
          attributes:
            - genid
    -
      name: batch-end
      doc: Finish a batch of operations
      attribute-set: batch-attrs
      fixed-header: nfgenmsg
      do:
        request:
          value: 0x11
          attributes:
            - genid
    -
      name: newtable
      doc: Create a new table.
      attribute-set: table-attrs
      fixed-header: nfgenmsg
      do:
        request:
          value: 0xa00
          is-batch: True      # This message must be in a batch
          attributes:
            - name

The code in ynl.py is sufficient to test the idea but I haven't extended
nlspec.py nor have I added any support for multiple messages to ynl.

This can be tested with e.g.:

./tools/net/ynl/cli.py --spec Documentation/netlink/specs/nftables.yaml \
     --do newtable --json '{"name": "table", "nfgen-family": 1}'

If the approach is acceptable, then I would do the following:

 - Extend nlspec.py to support the new schema properties.
 - Extend cli.py to include a --batch option, then only allow
   'is-batch' ops. Also fail 'is-batch' ops when --batch is not used.
 - Extend ynl to support a heterogeneous list of ops to be sent
   in a batch.
 - Update documentation.

I'm thinking that usage would be '--do <op> | --dump <op> | --batch' and
when '--batch' is used, the '--json' parameter would be a list of op /
param pairs like this:

[ { "newtable": { "name": "x", "nfgen-family": 1 },
  { "newchain": { "table": "x", "name": "y", "nfgen-family": 1 } ]

Alternatively, usage could be '--batch <ops>' where <ops> is the json
above.

Thoughts?

Donald Hunter (4):
  doc/netlink: Add batch op definitions to netlink-raw schema
  tools/net/ynl: Extract message encoding into _encode_message()
  tools/net/ynl: Add batch message encoding for nftables
  doc/netlink/specs: Add draft nftables spec

 Documentation/netlink/netlink-raw.yaml    |   21 +
 Documentation/netlink/specs/nftables.yaml | 1292 +++++++++++++++++++++
 tools/net/ynl/lib/ynl.py                  |   33 +-
 3 files changed, 1339 insertions(+), 7 deletions(-)
 create mode 100644 Documentation/netlink/specs/nftables.yaml

-- 
2.42.0