[PATCH net-next v2 4/6] tools: ynl: Add struct attr decoding to ynl

[Donald Hunter <donald.hunter@gmail.com>]

Add support for decoding attributes that contain C structs.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
---
 Documentation/netlink/genetlink-legacy.yaml |  7 ++++++-
 tools/net/ynl/lib/ynl.py                    | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Documentation/netlink/genetlink-legacy.yaml b/Documentation/netlink/genetlink-legacy.yaml
index 5dc6f1c07a97..654f40b26beb 100644
--- a/Documentation/netlink/genetlink-legacy.yaml
+++ b/Documentation/netlink/genetlink-legacy.yaml
@@ -172,7 +172,7 @@ properties:
                 type: string
               type: &attr-type
                 enum: [ unused, pad, flag, binary, u8, u16, u32, u64, s32, s64,
-                        string, nest, array-nest, nest-type-value ]
+                        string, nest, array-nest, nest-type-value, struct ]
               doc:
                 description: Documentation of the attribute.
                 type: string
@@ -218,6 +218,11 @@ properties:
                     description: Max length for a string or a binary attribute.
                     $ref: '#/$defs/len-or-define'
               sub-type: *attr-type
+              # Start genetlink-legacy
+              struct:
+                description: Name of the struct type used for the attribute.
+                type: string
+              # End genetlink-legacy
 
       # Make sure name-prefix does not appear in subsets (subsets inherit naming)
       dependencies:
diff --git a/tools/net/ynl/lib/ynl.py b/tools/net/ynl/lib/ynl.py
index 077ba9e8dc98..24f8af3c2b38 100644
--- a/tools/net/ynl/lib/ynl.py
+++ b/tools/net/ynl/lib/ynl.py
@@ -68,6 +68,11 @@ class Netlink:
 
 
 class NlAttr:
+    type_formats = { 'u8' : ('B', 1),
+                     'u16': ('H', 2),
+                     'u32': ('I', 4),
+                     'u64': ('Q', 8) }
+
     def __init__(self, raw, offset):
         self._len, self._type = struct.unpack("HH", raw[offset:offset + 4])
         self.type = self._type & ~Netlink.NLA_TYPE_MASK
@@ -97,6 +102,16 @@ class NlAttr:
         format, _ = self.type_formats[type]
         return list({ x[0] for x in struct.iter_unpack(format, self.raw) })
 
+    def as_struct(self, members):
+        value = dict()
+        offset = 0
+        for m in members:
+            format, size = self.type_formats[m.type]
+            decoded = struct.unpack_from(format, self.raw, offset)
+            offset += size
+            value[m.name] = decoded[0]
+        return value
+
     def __repr__(self):
         return f"[type:{self.type} len:{self._len}] {self.raw}"
 
@@ -385,6 +400,9 @@ class YnlFamily(SpecFamily):
                 decoded = attr.as_bin()
             elif attr_spec["type"] == 'flag':
                 decoded = True
+            elif attr_spec["type"] == 'struct':
+                s = attr_spec['struct']
+                decoded = attr.as_struct(self.consts[s])
             elif attr_spec["type"] == 'array-nest':
                 decoded = attr.as_array(attr_spec["sub-type"])
             else:
-- 
2.39.0