Re: [PATCH net-next] tools: ynl-gen-c: keep the type values of a nest in spec order

Family._load_nested_set_nest() collects the type-value names of a
nest-type-value attribute into a set and Struct.set_inherited() renders
them sorted, while TypeNestTypeValue._attr_get() passes them to the
parse helper in the order the spec lists them.  For nlctrl's

  type-value: [policy-id, attr-id]

that makes the generated helper take (attr_id, policy_id) and the caller
pass (policy_id, attr_id).  Both are __u32 so nothing complains, and
every C YNL user of the nlctrl policy dump gets the two swapped.

Two attributes nesting the same attribute set with the type values in
a different order now fail set_inherited() instead of comparing equal.
No spec does that today, but better safe than sorry.

Nesting an attribute set which is also used as a sub-message gets its own
check: it used to be caught by the list-versus-set type mismatch, which
the ordering fix removes, and without it the generator emits a call
to the sub-message parser with the selector argument missing.
Again, no spec does this today.

nlctrl is the only spec affected, discovered by an LLM scan of the spec.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
Doesn't affect kernel code, just tooling, so not a fix.

CC: donald.hunter@gmail.com
---
 tools/net/ynl/pyynl/ynl_gen_c.py | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index 2b3483db1b60..15c79849c609 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py

@@ -986,7 +986,8 @@ from lib import SpecSubMessage
         self.family = family
         self.space_name = space_name
         self.attr_set = family.attr_sets[space_name]
-        # Use list to catch comparisons with empty sets
+        # Stored by reference, _load_nested_set_nest() fills the list in
+        # after constructing us.
         self._inherited = inherited if inherited is not None else []
         self.inherited = []
         self.fixed_header = None

@@ -1038,9 +1039,11 @@ from lib import SpecSubMessage
         return self.attr_list

     def set_inherited(self, new_inherited):
+        if self.submsg:
+            raise Exception("Nesting a sub-message as an attribute set not supported")
         if self._inherited != new_inherited:
-            raise Exception("Inheriting different members not supported")
-        self.inherited = [c_lower(x) for x in sorted(self._inherited)]
+            raise Exception("Inheriting different members, or a different order, not supported")
+        self.inherited = [c_lower(x) for x in self._inherited]

     def external_selectors(self):
         sels = []

@@ -1394,7 +1397,7 @@ from lib import SpecSubMessage
                 pns_key_list.append(name)

     def _load_nested_set_nest(self, spec):
-        inherit = set()
+        inherit = []
         nested = spec['nested-attributes']
         if nested not in self.root_sets:
             if nested not in self.pure_nested_structs:

@@ -1407,9 +1410,9 @@ from lib import SpecSubMessage
         if 'type-value' in spec:
             if nested in self.root_sets:
                 raise Exception("Inheriting members to a space used as root not supported")
-            inherit.update(set(spec['type-value']))
+            inherit.extend(spec['type-value'])
         elif spec['type'] == 'indexed-array':
-            inherit.add('idx')
+            inherit.append('idx')
         self.pure_nested_structs[nested].set_inherited(inherit)

         return nested