tools: ynl: Add fixed-header support to ynl

Add support for netlink families that add an optional fixed header structure
after the genetlink header and before any attributes. The fixed-header can be
specified on a per op basis, or once for all operations, which serves as a
default value that can be overridden.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/genetlink-legacy.yaml

@@ -261,6 +261,14 @@ properties:
  async-enum:
  description: Name for the enum type with notifications/events.
  type: string
+ # Start genetlink-legacy
+ fixed-header: &fixed-header
+ description: |
+ Name of the structure defining the optional fixed-length protocol
+ header. This header is placed in a message after the netlink and
+ genetlink headers and before any attributes.
+ type: string
+ # End genetlink-legacy
  list:
  description: List of commands
  type: array
@@ -293,6 +301,9 @@ properties:
  type: array
  items:
  enum: [ strict, dump ]
+ # Start genetlink-legacy
+ fixed-header: *fixed-header
+ # End genetlink-legacy
  do: &subop-type
  description: Main command handler.
  type: object

tools/net/ynl/lib/nlspec.py

@@ -263,16 +263,17 @@ class SpecOperation(SpecElement):
  Information about a single Netlink operation.
 
  Attributes:
- value numerical ID when serialized, None if req/rsp values differ
+ value  numerical ID when serialized, None if req/rsp values differ
 
- req_value numerical ID when serialized, user -> kernel
- rsp_value numerical ID when serialized, user <- kernel
- is_call bool, whether the operation is a call
- is_async bool, whether the operation is a notification
- is_resv bool, whether the operation does not exist (it's just a reserved ID)
- attr_set attribute set name
+ req_value numerical ID when serialized, user -> kernel
+ rsp_value numerical ID when serialized, user <- kernel
+ is_call bool, whether the operation is a call
+ is_async bool, whether the operation is a notification
+ is_resv bool, whether the operation does not exist (it's just a reserved ID)
+ attr_set attribute set name
+ fixed_header string, optional name of fixed header struct
 
- yaml raw spec as loaded from the spec file
+ yaml  raw spec as loaded from the spec file
  """
  def __init__(self, family, yaml, req_value, rsp_value):
  super().__init__(family, yaml)
@@ -284,6 +285,7 @@ def __init__(self, family, yaml, req_value, rsp_value):
  self.is_call = 'do' in yaml or 'dump' in yaml
  self.is_async = 'notify' in yaml or 'event' in yaml
  self.is_resv = not self.is_async and not self.is_call
+ self.fixed_header = self.yaml.get('fixed-header', family.fixed_header)
 
  # Added by resolve:
  self.attr_set = None
@@ -324,6 +326,7 @@ class SpecFamily(SpecElement):
  msgs_by_value dict of all messages (indexed by name)
  ops dict of all valid requests / responses
  consts dict of all constants/enums
+ fixed_header string, optional name of family default fixed header struct
  """
  def __init__(self, spec_path, schema_path=None):
  with open(spec_path, "r") as stream:
@@ -397,6 +400,7 @@ def add_unresolved(self, elem):
  self._resolution_list.append(elem)
 
  def _dictify_ops_unified(self):
+ self.fixed_header = self.yaml['operations'].get('fixed-header')
  val = 1
  for elem in self.yaml['operations']['list']:
  if 'value' in elem:
@@ -408,6 +412,7 @@ def _dictify_ops_unified(self):
  self.msgs[op.name] = op
 
  def _dictify_ops_directional(self):
+ self.fixed_header = self.yaml['operations'].get('fixed-header')
  req_val = rsp_val = 1
  for elem in self.yaml['operations']['list']:
  if 'notify' in elem:

tools/net/ynl/lib/ynl.py

@@ -278,14 +278,22 @@ def _genl_load_families():
 
 
 class GenlMsg:
- def __init__(self, nl_msg):
+ def __init__(self, nl_msg, fixed_header_members=[]):
  self.nl = nl_msg
 
  self.hdr = nl_msg.raw[0:4]
- self.raw = nl_msg.raw[4:]
+ offset = 4
 
  self.genl_cmd, self.genl_version, _ = struct.unpack("BBH", self.hdr)
 
+ self.fixed_header_attrs = dict()
+ for m in fixed_header_members:
+ format, size = NlAttr.type_formats[m.type]
+ decoded = struct.unpack_from(format, nl_msg.raw, offset)
+ offset += size
+ self.fixed_header_attrs[m.name] = decoded[0]
+
+ self.raw = nl_msg.raw[offset:]
  self.raw_attrs = NlAttrs(self.raw)
 
  def __repr__(self):
@@ -509,6 +517,13 @@ def _op(self, method, vals, dump=False):
 
  req_seq = random.randint(1024, 65535)
  msg = _genl_msg(self.family.family_id, nl_flags, op.req_value, 1, req_seq)
+ fixed_header_members = []
+ if op.fixed_header:
+ fixed_header_members = self.consts[op.fixed_header].members
+ for m in fixed_header_members:
+ value = vals.pop(m.name)
+ format, _ = NlAttr.type_formats[m.type]
+ msg += struct.pack(format, value)
  for name, value in vals.items():
  msg += self._add_attr(op.attr_set.name, name, value)
  msg = _genl_msg_finalize(msg)
@@ -535,7 +550,7 @@ def _op(self, method, vals, dump=False):
  done = True
  break
 
- gm = GenlMsg(nl_msg)
+ gm = GenlMsg(nl_msg, fixed_header_members)
  # Check if this is a reply to our request
  if nl_msg.nl_seq != req_seq or gm.genl_cmd != op.rsp_value:
  if gm.genl_cmd in self.async_msg_ids:
@@ -545,7 +560,8 @@ def _op(self, method, vals, dump=False):
  print('Unexpected message: ' + repr(gm))
  continue
 
- rsp.append(self._decode(gm.raw_attrs, op.attr_set.name))
+ rsp.append(self._decode(gm.raw_attrs, op.attr_set.name)
+ | gm.fixed_header_attrs)
 
  if not rsp:
  return None