tools/net/ynl: Add 'sub-message' attribute decoding to ynl

Implement the 'sub-message' attribute type in ynl.

Encode support is not yet implemented. Support for sub-message selectors
at a different nest level from the key attribute is not yet supported.

Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20231215093720.18774-5-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 40 insertions, 8 deletions

diff --git a/tools/net/ynl/lib/ynl.py b/tools/net/ynl/lib/ynl.py
index df7b1547de1f..a8db71441634 100644
--- a/tools/net/ynl/lib/ynl.py
+++ b/tools/net/ynl/lib/ynl.py
@@ -170,10 +170,9 @@ class NlAttr:
 
 
 class NlAttrs:
-    def __init__(self, msg):
+    def __init__(self, msg, offset=0):
         self.attrs = []
 
-        offset = 0
         while offset < len(msg):
             attr = NlAttr(msg, offset)
             offset += attr.full_len
@@ -371,8 +370,8 @@ class NetlinkProtocol:
         fixed_header_size = 0
         if ynl:
             op = ynl.rsp_by_value[msg.cmd()]
-            fixed_header_size = ynl._fixed_header_size(op)
-        msg.raw_attrs = NlAttrs(msg.raw[fixed_header_size:])
+            fixed_header_size = ynl._fixed_header_size(op.fixed_header)
+        msg.raw_attrs = NlAttrs(msg.raw, fixed_header_size)
         return msg
 
     def get_mcast_id(self, mcast_name, mcast_groups):
@@ -549,6 +548,37 @@ class YnlFamily(SpecFamily):
         else:
             rsp[name] = [decoded]
 
+    def _resolve_selector(self, attr_spec, vals):
+        sub_msg = attr_spec.sub_message
+        if sub_msg not in self.sub_msgs:
+            raise Exception(f"No sub-message spec named {sub_msg} for {attr_spec.name}")
+        sub_msg_spec = self.sub_msgs[sub_msg]
+
+        selector = attr_spec.selector
+        if selector not in vals:
+            raise Exception(f"There is no value for {selector} to resolve '{attr_spec.name}'")
+        value = vals[selector]
+        if value not in sub_msg_spec.formats:
+            raise Exception(f"No message format for '{value}' in sub-message spec '{sub_msg}'")
+
+        spec = sub_msg_spec.formats[value]
+        return spec
+
+    def _decode_sub_msg(self, attr, attr_spec, rsp):
+        msg_format = self._resolve_selector(attr_spec, rsp)
+        decoded = {}
+        offset = 0
+        if msg_format.fixed_header:
+            decoded.update(self._decode_fixed_header(attr, msg_format.fixed_header));
+            offset = self._fixed_header_size(msg_format.fixed_header)
+        if msg_format.attr_set:
+            if msg_format.attr_set in self.attr_sets:
+                subdict = self._decode(NlAttrs(attr.raw, offset), msg_format.attr_set)
+                decoded.update(subdict)
+            else:
+                raise Exception(f"Unknown attribute-set '{attr_space}' when decoding '{attr_spec.name}'")
+        return decoded
+
     def _decode(self, attrs, space):
         if space:
             attr_space = self.attr_sets[space]
@@ -586,6 +616,8 @@ class YnlFamily(SpecFamily):
                     value = self._decode_enum(value, attr_spec)
                     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, rsp)
             else:
                 if not self.process_unknown:
                     raise Exception(f'Unknown {attr_spec["type"]} with name {attr_spec["name"]}')
@@ -626,16 +658,16 @@ class YnlFamily(SpecFamily):
             return
 
         msg = self.nlproto.decode(self, NlMsg(request, 0, op.attr_set))
-        offset = 20 + self._fixed_header_size(op)
+        offset = 20 + self._fixed_header_size(op.fixed_header)
         path = self._decode_extack_path(msg.raw_attrs, 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
+    def _fixed_header_size(self, name):
+        if name:
+            fixed_header_members = self.consts[name].members
             size = 0
             for m in fixed_header_members:
                 format = NlAttr.get_format(m.type, m.byte_order)