tools/net/ynl: Add support for encoding sub-messages

Add sub-message encoding to ynl. This makes it possible to create
tc qdiscs and other polymorphic netlink objects.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240129223458.52046-6-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/lib/ynl.py

@@ -469,7 +469,7 @@ def ntf_subscribe(self, mcast_name):
         self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_ADD_MEMBERSHIP,
                              mcast_id)
 
-    def _add_attr(self, space, name, value):
+    def _add_attr(self, space, name, value, search_attrs):
         try:
             attr = self.attr_sets[space][name]
         except KeyError:
@@ -478,8 +478,10 @@ def _add_attr(self, space, name, value):
         if attr["type"] == 'nest':
             nl_type |= Netlink.NLA_F_NESTED
             attr_payload = b''
+            sub_attrs = SpaceAttrs(self.attr_sets[space], value, search_attrs)
             for subname, subvalue in value.items():
-                attr_payload += self._add_attr(attr['nested-attributes'], subname, subvalue)
+                attr_payload += self._add_attr(attr['nested-attributes'],
+                                               subname, subvalue, sub_attrs)
         elif attr["type"] == 'flag':
             attr_payload = b''
         elif attr["type"] == 'string':
@@ -489,6 +491,8 @@ def _add_attr(self, space, name, value):
                 attr_payload = value
             elif isinstance(value, str):
                 attr_payload = bytes.fromhex(value)
+            elif isinstance(value, dict) and attr.struct_name:
+                attr_payload = self._encode_struct(attr.struct_name, value)
             else:
                 raise Exception(f'Unknown type for binary attribute, value: {value}')
         elif attr.is_auto_scalar:
@@ -501,6 +505,20 @@ def _add_attr(self, space, name, value):
             attr_payload = format.pack(int(value))
         elif attr['type'] in "bitfield32":
             attr_payload = struct.pack("II", int(value["value"]), int(value["selector"]))
+        elif attr['type'] == 'sub-message':
+            msg_format = self._resolve_selector(attr, search_attrs)
+            attr_payload = b''
+            if msg_format.fixed_header:
+                attr_payload += self._encode_struct(msg_format.fixed_header, value)
+            if msg_format.attr_set:
+                if msg_format.attr_set in self.attr_sets:
+                    nl_type |= Netlink.NLA_F_NESTED
+                    sub_attrs = SpaceAttrs(msg_format.attr_set, value, search_attrs)
+                    for subname, subvalue in value.items():
+                        attr_payload += self._add_attr(msg_format.attr_set,
+                                                       subname, subvalue, sub_attrs)
+                else:
+                    raise Exception(f"Unknown attribute-set '{msg_format.attr_set}'")
         else:
             raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')
 
@@ -637,7 +655,7 @@ def _decode(self, attrs, space, outer_attrs = None):
                     selector = self._decode_enum(selector, attr_spec)
                 decoded = {"value": value, "selector": selector}
             elif attr_spec["type"] == 'sub-message':
-                decoded = self._decode_sub_msg(attr, attr_spec, vals)
+                decoded = self._decode_sub_msg(attr, attr_spec, search_attrs)
             else:
                 if not self.process_unknown:
                     raise Exception(f'Unknown {attr_spec["type"]} with name {attr_spec["name"]}')
@@ -795,8 +813,9 @@ def _op(self, method, vals, flags=None, dump=False):
         msg = self.nlproto.message(nl_flags, op.req_value, 1, req_seq)
         if op.fixed_header:
             msg += self._encode_struct(op.fixed_header, vals)
+        search_attrs = SpaceAttrs(op.attr_set, vals)
         for name, value in vals.items():
-            msg += self._add_attr(op.attr_set.name, name, value)
+            msg += self._add_attr(op.attr_set.name, name, value, search_attrs)
         msg = _genl_msg_finalize(msg)
 
         self.sock.send(msg, 0)