[PATCH net-next v2 3/3] tools: ynl-gen: support struct for binary attributes

[Jakub Kicinski <kuba@kernel.org>]

Support using a struct pointer for binary attrs. Len field is maintained
because the structs may grow with newer kernel versions. Or, which matters
more, be shorter if the binary is built against newer uAPI than kernel
against which it's executed. Since we are storing a pointer to a struct
type - always allocate at least the amount of memory needed by the struct
per current uAPI headers (unused mem is zeroed). Technically users should
check the length field but per modern ASAN checks storing a short object
under a pointer seems like a bad idea.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
  - create a separate class
v1: https://lore.kernel.org/20250508022839.1256059-4-kuba@kernel.org
---
 tools/net/ynl/pyynl/ynl_gen_c.py | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/tools/net/ynl/pyynl/ynl_gen_c.py b/tools/net/ynl/pyynl/ynl_gen_c.py
index 9a5c65966e9d..3b064c61a374 100755
--- a/tools/net/ynl/pyynl/ynl_gen_c.py
+++ b/tools/net/ynl/pyynl/ynl_gen_c.py
@@ -566,6 +566,23 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
                 f'memcpy({member}, {self.c_name}, {presence});']
 
 
+class TypeBinaryStruct(TypeBinary):
+    def struct_member(self, ri):
+        ri.cw.p(f'struct {c_lower(self.get("struct"))} *{self.c_name};')
+
+    def _attr_get(self, ri, var):
+        struct_sz = 'sizeof(struct ' + c_lower(self.get("struct")) + ')'
+        len_mem = var + '->_' + self.presence_type() + '.' + self.c_name
+        return [f"{len_mem} = len;",
+                f"if (len < {struct_sz})",
+                f"{var}->{self.c_name} = calloc(1, {struct_sz});",
+                "else",
+                f"{var}->{self.c_name} = malloc(len);",
+                f"memcpy({var}->{self.c_name}, ynl_attr_data(attr), len);"], \
+               ['len = ynl_attr_data_len(attr);'], \
+               ['unsigned int len;']
+
+
 class TypeBinaryScalarArray(TypeBinary):
     def arg_member(self, ri):
         return [f'__{self.get("sub-type")} *{self.c_name}', 'size_t count']
@@ -1010,7 +1027,9 @@ from lib import SpecFamily, SpecAttrSet, SpecAttr, SpecOperation, SpecEnumSet, S
         elif elem['type'] == 'string':
             t = TypeString(self.family, self, elem, value)
         elif elem['type'] == 'binary':
-            if elem.get('sub-type') in scalars:
+            if 'struct' in elem:
+                t = TypeBinaryStruct(self.family, self, elem, value)
+            elif elem.get('sub-type') in scalars:
                 t = TypeBinaryScalarArray(self.family, self, elem, value)
             else:
                 t = TypeBinary(self.family, self, elem, value)
-- 
2.49.0