tools/net/ynl: Fix extack parsing with fixed header genlmsg

Move decode_fixed_header into YnlFamily and add a _fixed_header_size
method to allow extack decoding to skip the fixed header.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20230825122756.7603-7-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: donaldh

tools/net/ynl/lib/ynl.py

@@ -293,7 +293,7 @@ def _genl_load_families():
 
                 gm = GenlMsg(nl_msg)
                 fam = dict()
-                for attr in gm.raw_attrs:
+                for attr in NlAttrs(gm.raw):
                     if attr.type == Netlink.CTRL_ATTR_FAMILY_ID:
                         fam['id'] = attr.as_scalar('u16')
                     elif attr.type == Netlink.CTRL_ATTR_FAMILY_NAME:
@@ -317,23 +317,10 @@ def _genl_load_families():
 
 
 class GenlMsg:
-    def __init__(self, nl_msg, fixed_header_members=[]):
+    def __init__(self, nl_msg):
         self.nl = nl_msg
-
-        self.hdr = nl_msg.raw[0:4]
-        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 = NlAttr.get_format(m.type, m.byte_order)
-            decoded = format.unpack_from(nl_msg.raw, offset)
-            offset += format.size
-            self.fixed_header_attrs[m.name] = decoded[0]
-
-        self.raw = nl_msg.raw[offset:]
-        self.raw_attrs = NlAttrs(self.raw)
+        self.genl_cmd, self.genl_version, _ = struct.unpack_from("BBH", nl_msg.raw, 0)
+        self.raw = nl_msg.raw[4:]
 
     def __repr__(self):
         msg = repr(self.nl)
@@ -514,17 +501,44 @@ def _decode_extack_path(self, attrs, attr_set, offset, target):
 
         return None
 
-    def _decode_extack(self, request, attr_space, extack):
+    def _decode_extack(self, request, op, extack):
         if 'bad-attr-offs' not in extack:
             return
 
-        genl_req = GenlMsg(NlMsg(request, 0, attr_space=attr_space))
-        path = self._decode_extack_path(genl_req.raw_attrs, attr_space,
-                                        20, extack['bad-attr-offs'])
+        genl_req = GenlMsg(NlMsg(request, 0, op.attr_set))
+        fixed_header_size = self._fixed_header_size(op)
+        offset = 20 + fixed_header_size
+        path = self._decode_extack_path(NlAttrs(genl_req.raw[fixed_header_size:]),
+                                        op.attr_set, offset,
+                                        extack['bad-attr-offs'])
         if path:
             del extack['bad-attr-offs']
             extack['bad-attr'] = path
 
+    def _fixed_header_size(self, op):
+        if op.fixed_header:
+            fixed_header_members = self.consts[op.fixed_header].members
+            size = 0
+            for m in fixed_header_members:
+                format = NlAttr.get_format(m.type, m.byte_order)
+                size += format.size
+            return size
+        else:
+            return 0
+
+    def _decode_fixed_header(self, msg, name):
+        fixed_header_members = self.consts[name].members
+        fixed_header_attrs = dict()
+        offset = 0
+        for m in fixed_header_members:
+            format = NlAttr.get_format(m.type, m.byte_order)
+            [ value ] = format.unpack_from(msg.raw, offset)
+            offset += format.size
+            if m.enum:
+                value = self._decode_enum(value, m)
+            fixed_header_attrs[m.name] = value
+        return fixed_header_attrs
+
     def handle_ntf(self, nl_msg, genl_msg):
         msg = dict()
         if self.include_raw:
@@ -599,7 +613,7 @@ def _op(self, method, vals, dump=False):
             nms = NlMsgs(reply, attr_space=op.attr_set)
             for nl_msg in nms:
                 if nl_msg.extack:
-                    self._decode_extack(msg, op.attr_set, nl_msg.extack)
+                    self._decode_extack(msg, op, nl_msg.extack)
 
                 if nl_msg.error:
                     raise NlError(nl_msg)
@@ -610,7 +624,7 @@ def _op(self, method, vals, dump=False):
                     done = True
                     break
 
-                gm = GenlMsg(nl_msg, fixed_header_members)
+                gm = GenlMsg(nl_msg)
                 # 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:
@@ -620,8 +634,9 @@ def _op(self, method, vals, dump=False):
                         print('Unexpected message: ' + repr(gm))
                         continue
 
-                rsp_msg = self._decode(gm.raw_attrs, op.attr_set.name)
-                rsp_msg.update(gm.fixed_header_attrs)
+                rsp_msg = self._decode(NlAttrs(gm.raw), op.attr_set.name)
+                if op.fixed_header:
+                    rsp_msg.update(self._decode_fixed_header(gm, op.fixed_header))
                 rsp.append(rsp_msg)
 
         if not rsp: