Merge branch 'tools-ynl-fill-in-some-gaps-of-ethtool-spec'

Stanislav Fomichev says:

====================
tools: ynl: fill in some gaps of ethtool spec

I was trying to fill in the spec while exploring ethtool API for some
related work. I don't think I'll have the patience to fill in the rest,
so decided to share whatever I currently have.

Patches 1-2 add the be16 + spec.
Patches 3-4 implement an ethtool-like python tool to test the spec.

Patches 3-4 are there because it felt more fun do the tool instead
of writing the actual tests; feel free to drop it; sharing mostly
to show that the spec is not a complete nonsense.

The spec is not 100% complete, see patch 2 for what's missing.
I was hoping to finish the stats-get message, but I'm too dump
to implement bitmask marshaling (multi-attr).
====================

Link: https://lore.kernel.org/r/20230329221655.708489-1-sdf@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/net/ynl/lib/nlspec.py

@@ -163,6 +163,7 @@ class SpecAttr(SpecElement):
         self.is_multi = yaml.get('multi-attr', False)
         self.struct_name = yaml.get('struct')
         self.sub_type = yaml.get('sub-type')
+        self.byte_order = yaml.get('byte-order')
 
 
 class SpecAttrSet(SpecElement):
@@ -443,6 +444,15 @@ class SpecFamily(SpecElement):
 
             self.msgs[op.name] = op
 
+    def find_operation(self, name):
+      """
+      For a given operation name, find and return operation spec.
+      """
+      for op in self.yaml['operations']['list']:
+        if name == op['name']:
+          return op
+      return None
+
     def resolve(self):
         self.resolve_up(super())
 

tools/net/ynl/lib/ynl.py

@@ -67,6 +67,14 @@ class Netlink:
     NLMSGERR_ATTR_MISS_NEST = 6
 
 
+class NlError(Exception):
+  def __init__(self, nl_msg):
+    self.nl_msg = nl_msg
+
+  def __str__(self):
+    return f"Netlink error: {os.strerror(-self.nl_msg.error)}\n{self.nl_msg}"
+
+
 class NlAttr:
     type_formats = { 'u8' : ('B', 1), 's8' : ('b', 1),
                      'u16': ('H', 2), 's16': ('h', 2),
@@ -80,17 +88,25 @@ class NlAttr:
         self.full_len = (self.payload_len + 3) & ~3
         self.raw = raw[offset + 4:offset + self.payload_len]
 
+    def format_byte_order(byte_order):
+        if byte_order:
+            return ">" if byte_order == "big-endian" else "<"
+        return ""
+
     def as_u8(self):
         return struct.unpack("B", self.raw)[0]
 
-    def as_u16(self):
-        return struct.unpack("H", self.raw)[0]
+    def as_u16(self, byte_order=None):
+        endian = NlAttr.format_byte_order(byte_order)
+        return struct.unpack(f"{endian}H", self.raw)[0]
 
-    def as_u32(self):
-        return struct.unpack("I", self.raw)[0]
+    def as_u32(self, byte_order=None):
+        endian = NlAttr.format_byte_order(byte_order)
+        return struct.unpack(f"{endian}I", self.raw)[0]
 
-    def as_u64(self):
-        return struct.unpack("Q", self.raw)[0]
+    def as_u64(self, byte_order=None):
+        endian = NlAttr.format_byte_order(byte_order)
+        return struct.unpack(f"{endian}Q", self.raw)[0]
 
     def as_strz(self):
         return self.raw.decode('ascii')[:-1]
@@ -365,11 +381,14 @@ class YnlFamily(SpecFamily):
         elif attr["type"] == 'u8':
             attr_payload = struct.pack("B", int(value))
         elif attr["type"] == 'u16':
-            attr_payload = struct.pack("H", int(value))
+            endian = NlAttr.format_byte_order(attr.byte_order)
+            attr_payload = struct.pack(f"{endian}H", int(value))
         elif attr["type"] == 'u32':
-            attr_payload = struct.pack("I", int(value))
+            endian = NlAttr.format_byte_order(attr.byte_order)
+            attr_payload = struct.pack(f"{endian}I", int(value))
         elif attr["type"] == 'u64':
-            attr_payload = struct.pack("Q", int(value))
+            endian = NlAttr.format_byte_order(attr.byte_order)
+            attr_payload = struct.pack(f"{endian}Q", int(value))
         elif attr["type"] == 'string':
             attr_payload = str(value).encode('ascii') + b'\x00'
         elif attr["type"] == 'binary':
@@ -415,11 +434,11 @@ class YnlFamily(SpecFamily):
             elif attr_spec['type'] == 'u8':
                 decoded = attr.as_u8()
             elif attr_spec['type'] == 'u16':
-                decoded = attr.as_u16()
+                decoded = attr.as_u16(attr_spec.byte_order)
             elif attr_spec['type'] == 'u32':
-                decoded = attr.as_u32()
+                decoded = attr.as_u32(attr_spec.byte_order)
             elif attr_spec['type'] == 'u64':
-                decoded = attr.as_u64()
+                decoded = attr.as_u64(attr_spec.byte_order)
             elif attr_spec["type"] == 'string':
                 decoded = attr.as_strz()
             elif attr_spec["type"] == 'binary':
@@ -508,6 +527,17 @@ class YnlFamily(SpecFamily):
 
                 self.handle_ntf(nl_msg, gm)
 
+    def operation_do_attributes(self, name):
+      """
+      For a given operation name, find and return a supported
+      set of attributes (as a dict).
+      """
+      op = self.find_operation(name)
+      if not op:
+        return None
+
+      return op['do']['request']['attributes'].copy()
+
     def _op(self, method, vals, dump=False):
         op = self.ops[method]
 
@@ -540,9 +570,7 @@ class YnlFamily(SpecFamily):
                     self._decode_extack(msg, op.attr_set, nl_msg.extack)
 
                 if nl_msg.error:
-                    print("Netlink error:", os.strerror(-nl_msg.error))
-                    print(nl_msg)
-                    return
+                    raise NlError(nl_msg)
                 if nl_msg.done:
                     if nl_msg.extack:
                         print("Netlink warning:")