[patch net-next v1 0/2] tools: ynl: Add byte-order support for struct members

[patch net-next v1 0/2] tools: ynl: Add byte-order support for struct members

[Donald Hunter]

This patchset adds support to ynl for handling byte-order in struct
members. The first patch is a refactor to use predefined Struct() objects
instead of generating byte-order specific formats on the fly. The second
patch adds byte-order handling for struct members.

Donald Hunter (2):
  tools: ynl: Use dict of predefined Structs to decode scalar types
  tools: ynl: Handle byte-order in struct members

 Documentation/netlink/genetlink-legacy.yaml |   2 +
 tools/net/ynl/lib/nlspec.py                 |   4 +-
 tools/net/ynl/lib/ynl.py                    | 107 +++++++++-----------
 3 files changed, 53 insertions(+), 60 deletions(-)

-- 
2.39.0

[patch net-next v1 1/2] tools: ynl: Use dict of predefined Structs to decode scalar types

[Donald Hunter]

Use a dict of predefined Struct() objects to decode scalar types in native,
big or little endian format. This removes the repetitive code for the
scalar variants and ensures all the signed variants are supported.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
---
 tools/net/ynl/lib/ynl.py | 107 ++++++++++++++++++---------------------
 1 file changed, 48 insertions(+), 59 deletions(-)

diff --git a/tools/net/ynl/lib/ynl.py b/tools/net/ynl/lib/ynl.py
index aa77bcae4807..62e31db07c1f 100644
--- a/tools/net/ynl/lib/ynl.py
+++ b/tools/net/ynl/lib/ynl.py
@@ -1,10 +1,12 @@
 # SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
 
+from collections import namedtuple
 import functools
 import os
 import random
 import socket
 import struct
+from struct import Struct
 import yaml
 
 from .nlspec import SpecFamily
@@ -76,10 +78,17 @@ class NlError(Exception):
 
 
 class NlAttr:
-    type_formats = { 'u8' : ('B', 1), 's8' : ('b', 1),
-                     'u16': ('H', 2), 's16': ('h', 2),
-                     'u32': ('I', 4), 's32': ('i', 4),
-                     'u64': ('Q', 8), 's64': ('q', 8) }
+    ScalarFormat = namedtuple('ScalarFormat', ['native', 'big', 'little'])
+    type_formats = {
+        'u8' : ScalarFormat(Struct('B'), Struct("B"),  Struct("B")),
+        's8' : ScalarFormat(Struct('b'), Struct("b"),  Struct("b")),
+        'u16': ScalarFormat(Struct('H'), Struct(">H"), Struct("<H")),
+        's16': ScalarFormat(Struct('h'), Struct(">h"), Struct("<h")),
+        'u32': ScalarFormat(Struct('I'), Struct(">I"), Struct("<I")),
+        's32': ScalarFormat(Struct('i'), Struct(">i"), Struct("<i")),
+        'u64': ScalarFormat(Struct('Q'), Struct(">Q"), Struct("<Q")),
+        's64': ScalarFormat(Struct('q'), Struct(">q"), Struct("<q"))
+    }
 
     def __init__(self, raw, offset):
         self._len, self._type = struct.unpack("HH", raw[offset:offset + 4])
@@ -88,25 +97,17 @@ 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):
+    @classmethod
+    def get_format(cls, attr_type, byte_order=None):
+        format = cls.type_formats[attr_type]
         if byte_order:
-            return ">" if byte_order == "big-endian" else "<"
-        return ""
+            return format.big if byte_order == "big-endian" \
+                else format.little
+        return format.native
 
-    def as_u8(self):
-        return struct.unpack("B", 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, byte_order=None):
-        endian = NlAttr.format_byte_order(byte_order)
-        return struct.unpack(f"{endian}I", 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_scalar(self, attr_type, byte_order=None):
+        format = self.get_format(attr_type, byte_order)
+        return format.unpack(self.raw)[0]
 
     def as_strz(self):
         return self.raw.decode('ascii')[:-1]
@@ -115,17 +116,17 @@ class NlAttr:
         return self.raw
 
     def as_c_array(self, type):
-        format, _ = self.type_formats[type]
-        return list({ x[0] for x in struct.iter_unpack(format, self.raw) })
+        format = self.get_format(type)
+        return list({ x[0] for x in format.iter_unpack(self.raw) })
 
     def as_struct(self, members):
         value = dict()
         offset = 0
         for m in members:
             # TODO: handle non-scalar members
-            format, size = self.type_formats[m.type]
-            decoded = struct.unpack_from(format, self.raw, offset)
-            offset += size
+            format = self.get_format(m.type)
+            decoded = format.unpack_from(self.raw, offset)
+            offset += format.size
             value[m.name] = decoded[0]
         return value
 
@@ -184,11 +185,11 @@ class NlMsg:
                 if extack.type == Netlink.NLMSGERR_ATTR_MSG:
                     self.extack['msg'] = extack.as_strz()
                 elif extack.type == Netlink.NLMSGERR_ATTR_MISS_TYPE:
-                    self.extack['miss-type'] = extack.as_u32()
+                    self.extack['miss-type'] = extack.as_scalar('u32')
                 elif extack.type == Netlink.NLMSGERR_ATTR_MISS_NEST:
-                    self.extack['miss-nest'] = extack.as_u32()
+                    self.extack['miss-nest'] = extack.as_scalar('u32')
                 elif extack.type == Netlink.NLMSGERR_ATTR_OFFS:
-                    self.extack['bad-attr-offs'] = extack.as_u32()
+                    self.extack['bad-attr-offs'] = extack.as_scalar('u32')
                 else:
                     if 'unknown' not in self.extack:
                         self.extack['unknown'] = []
@@ -272,11 +273,11 @@ def _genl_load_families():
                 fam = dict()
                 for attr in gm.raw_attrs:
                     if attr.type == Netlink.CTRL_ATTR_FAMILY_ID:
-                        fam['id'] = attr.as_u16()
+                        fam['id'] = attr.as_scalar('u16')
                     elif attr.type == Netlink.CTRL_ATTR_FAMILY_NAME:
                         fam['name'] = attr.as_strz()
                     elif attr.type == Netlink.CTRL_ATTR_MAXATTR:
-                        fam['maxattr'] = attr.as_u32()
+                        fam['maxattr'] = attr.as_scalar('u32')
                     elif attr.type == Netlink.CTRL_ATTR_MCAST_GROUPS:
                         fam['mcast'] = dict()
                         for entry in NlAttrs(attr.raw):
@@ -286,7 +287,7 @@ def _genl_load_families():
                                 if entry_attr.type == Netlink.CTRL_ATTR_MCAST_GRP_NAME:
                                     mcast_name = entry_attr.as_strz()
                                 elif entry_attr.type == Netlink.CTRL_ATTR_MCAST_GRP_ID:
-                                    mcast_id = entry_attr.as_u32()
+                                    mcast_id = entry_attr.as_scalar('u32')
                             if mcast_name and mcast_id is not None:
                                 fam['mcast'][mcast_name] = mcast_id
                 if 'name' in fam and 'id' in fam:
@@ -304,9 +305,9 @@ class GenlMsg:
 
         self.fixed_header_attrs = dict()
         for m in fixed_header_members:
-            format, size = NlAttr.type_formats[m.type]
-            decoded = struct.unpack_from(format, nl_msg.raw, offset)
-            offset += size
+            format = NlAttr.get_format(m.type)
+            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:]
@@ -381,23 +382,16 @@ class YnlFamily(SpecFamily):
                 attr_payload += self._add_attr(attr['nested-attributes'], subname, subvalue)
         elif attr["type"] == 'flag':
             attr_payload = b''
-        elif attr["type"] == 'u8':
-            attr_payload = struct.pack("B", int(value))
-        elif attr["type"] == 'u16':
-            endian = NlAttr.format_byte_order(attr.byte_order)
-            attr_payload = struct.pack(f"{endian}H", int(value))
-        elif attr["type"] == 'u32':
-            endian = NlAttr.format_byte_order(attr.byte_order)
-            attr_payload = struct.pack(f"{endian}I", int(value))
-        elif attr["type"] == 'u64':
-            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':
             attr_payload = value
         else:
-            raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')
+            try:
+                format = NlAttr.get_format(attr['type'], attr.byte_order)
+                attr_payload = format.pack(int(value))
+            except:
+                raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')
 
         pad = b'\x00' * ((4 - len(attr_payload) % 4) % 4)
         return struct.pack('HH', len(attr_payload) + 4, nl_type) + attr_payload + pad
@@ -434,22 +428,17 @@ class YnlFamily(SpecFamily):
             if attr_spec["type"] == 'nest':
                 subdict = self._decode(NlAttrs(attr.raw), attr_spec['nested-attributes'])
                 decoded = subdict
-            elif attr_spec['type'] == 'u8':
-                decoded = attr.as_u8()
-            elif attr_spec['type'] == 'u16':
-                decoded = attr.as_u16(attr_spec.byte_order)
-            elif attr_spec['type'] == 'u32':
-                decoded = attr.as_u32(attr_spec.byte_order)
-            elif attr_spec['type'] == 'u64':
-                decoded = attr.as_u64(attr_spec.byte_order)
             elif attr_spec["type"] == 'string':
                 decoded = attr.as_strz()
             elif attr_spec["type"] == 'binary':
                 decoded = self._decode_binary(attr, attr_spec)
             elif attr_spec["type"] == 'flag':
                 decoded = True
-            else:
-                raise Exception(f'Unknown {attr.type} {attr_spec["name"]} {attr_spec["type"]}')
+            elif attr_spec["type"]:
+                try:
+                    decoded = attr.as_scalar(attr_spec['type'], attr_spec.byte_order)
+                except:
+                    raise Exception(f'Unknown {attr_spec["type"]} with name {attr_spec["name"]}')
 
             if not attr_spec.is_multi:
                 rsp[attr_spec['name']] = decoded
@@ -555,8 +544,8 @@ class YnlFamily(SpecFamily):
             fixed_header_members = self.consts[op.fixed_header].members
             for m in fixed_header_members:
                 value = vals.pop(m.name)
-                format, _ = NlAttr.type_formats[m.type]
-                msg += struct.pack(format, value)
+                format = NlAttr.get_format(m.type)
+                msg += format.pack(value)
         for name, value in vals.items():
             msg += self._add_attr(op.attr_set.name, name, value)
         msg = _genl_msg_finalize(msg)
-- 
2.39.0

[patch net-next v1 2/2] tools: ynl: Handle byte-order in struct members

[Donald Hunter]

Add support for byte-order in struct members in the genetlink-legacy
spec.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
---
 Documentation/netlink/genetlink-legacy.yaml | 2 ++
 tools/net/ynl/lib/nlspec.py                 | 4 +++-
 tools/net/ynl/lib/ynl.py                    | 6 +++---
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Documentation/netlink/genetlink-legacy.yaml b/Documentation/netlink/genetlink-legacy.yaml
index b33541a51d6b..b5319cde9e17 100644
--- a/Documentation/netlink/genetlink-legacy.yaml
+++ b/Documentation/netlink/genetlink-legacy.yaml
@@ -122,6 +122,8 @@ properties:
                 enum: [ u8, u16, u32, u64, s8, s16, s32, s64, string ]
               len:
                 $ref: '#/$defs/len-or-define'
+              byte-order:
+                enum: [ little-endian, big-endian ]
         # End genetlink-legacy
 
   attribute-sets:
diff --git a/tools/net/ynl/lib/nlspec.py b/tools/net/ynl/lib/nlspec.py
index a0241add3839..c624cdfde223 100644
--- a/tools/net/ynl/lib/nlspec.py
+++ b/tools/net/ynl/lib/nlspec.py
@@ -226,11 +226,13 @@ class SpecStructMember(SpecElement):
     Represents a single struct member attribute.
 
     Attributes:
-        type    string, type of the member attribute
+        type        string, type of the member attribute
+        byte_order  string or None for native byte order
     """
     def __init__(self, family, yaml):
         super().__init__(family, yaml)
         self.type = yaml['type']
+        self.byte_order = yaml.get('byte-order')
 
 
 class SpecStruct(SpecElement):
diff --git a/tools/net/ynl/lib/ynl.py b/tools/net/ynl/lib/ynl.py
index 62e31db07c1f..41a4f8de7e17 100644
--- a/tools/net/ynl/lib/ynl.py
+++ b/tools/net/ynl/lib/ynl.py
@@ -124,7 +124,7 @@ class NlAttr:
         offset = 0
         for m in members:
             # TODO: handle non-scalar members
-            format = self.get_format(m.type)
+            format = self.get_format(m.type, m.byte_order)
             decoded = format.unpack_from(self.raw, offset)
             offset += format.size
             value[m.name] = decoded[0]
@@ -305,7 +305,7 @@ class GenlMsg:
 
         self.fixed_header_attrs = dict()
         for m in fixed_header_members:
-            format = NlAttr.get_format(m.type)
+            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]
@@ -544,7 +544,7 @@ class YnlFamily(SpecFamily):
             fixed_header_members = self.consts[op.fixed_header].members
             for m in fixed_header_members:
                 value = vals.pop(m.name)
-                format = NlAttr.get_format(m.type)
+                format = NlAttr.get_format(m.type, m.byte_order)
                 msg += format.pack(value)
         for name, value in vals.items():
             msg += self._add_attr(op.attr_set.name, name, value)
-- 
2.39.0

Re: [patch net-next v1 1/2] tools: ynl: Use dict of predefined Structs to decode scalar types

[Jakub Kicinski]

On Sun, 21 May 2023 18:07:32 +0100 Donald Hunter wrote:
> Use a dict of predefined Struct() objects to decode scalar types in native,
> big or little endian format. This removes the repetitive code for the
> scalar variants and ensures all the signed variants are supported.

> @@ -115,17 +116,17 @@ class NlAttr:
>          return self.raw
>  
>      def as_c_array(self, type):
> -        format, _ = self.type_formats[type]
> -        return list({ x[0] for x in struct.iter_unpack(format, self.raw) })
> +        format = self.get_format(type)
> +        return list({ x[0] for x in format.iter_unpack(self.raw) })

I probably asked about this before, and maybe not the question 
for this series but - why list({ ... }) and not [...]?

>          else:
> -            raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')
> +            try:
> +                format = NlAttr.get_format(attr['type'], attr.byte_order)
> +                attr_payload = format.pack(int(value))
> +            except:
> +                raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')

Could we do:

	elif attr["type"] in NlAttr.type_formats:

instead? Maybe my C brain treats exceptions as too exceptional..

> +            elif attr_spec["type"]:
> +                try:
> +                    decoded = attr.as_scalar(attr_spec['type'], attr_spec.byte_order)
> +                except:
> +                    raise Exception(f'Unknown {attr_spec["type"]} with name {attr_spec["name"]}')

Same here.

Nice cleanup!

Re: [patch net-next v1 2/2] tools: ynl: Handle byte-order in struct members

[Jakub Kicinski]

On Sun, 21 May 2023 18:07:33 +0100 Donald Hunter wrote:
> Add support for byte-order in struct members in the genetlink-legacy
> spec.

Acked-by: Jakub Kicinski <kuba@kernel.org>

Which spec is this for? 

Re: [patch net-next v1 1/2] tools: ynl: Use dict of predefined Structs to decode scalar types

[Donald Hunter]

Jakub Kicinski <kuba@kernel.org> writes:

> On Sun, 21 May 2023 18:07:32 +0100 Donald Hunter wrote:
>> Use a dict of predefined Struct() objects to decode scalar types in native,
>> big or little endian format. This removes the repetitive code for the
>> scalar variants and ensures all the signed variants are supported.
>
>> @@ -115,17 +116,17 @@ class NlAttr:
>>          return self.raw
>>  
>>      def as_c_array(self, type):
>> -        format, _ = self.type_formats[type]
>> -        return list({ x[0] for x in struct.iter_unpack(format, self.raw) })
>> +        format = self.get_format(type)
>> +        return list({ x[0] for x in format.iter_unpack(self.raw) })
>
> I probably asked about this before, and maybe not the question 
> for this series but - why list({ ... }) and not [...]?

It looks like I cargo-culted something there, and it's just plain
wrong. Reading it now, it's clearly a set comprehension coerced into a
list, which could well change ordering.

I'll fix this in the next version.

>>          else:
>> -            raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')
>> +            try:
>> +                format = NlAttr.get_format(attr['type'], attr.byte_order)
>> +                attr_payload = format.pack(int(value))
>> +            except:
>> +                raise Exception(f'Unknown type at {space} {name} {value} {attr["type"]}')
>
> Could we do:
>
> 	elif attr["type"] in NlAttr.type_formats:
>
> instead? Maybe my C brain treats exceptions as too exceptional..

Good suggestion, that's much cleaner.

>> +            elif attr_spec["type"]:
>> +                try:
>> +                    decoded = attr.as_scalar(attr_spec['type'], attr_spec.byte_order)
>> +                except:
>> +                    raise Exception(f'Unknown {attr_spec["type"]} with name {attr_spec["name"]}')
>
> Same here.

Ack.

> Nice cleanup!

Re: [patch net-next v1 2/2] tools: ynl: Handle byte-order in struct members

[Donald Hunter]

Jakub Kicinski <kuba@kernel.org> writes:

> On Sun, 21 May 2023 18:07:33 +0100 Donald Hunter wrote:
>> Add support for byte-order in struct members in the genetlink-legacy
>> spec.
>
> Acked-by: Jakub Kicinski <kuba@kernel.org>
>
> Which spec is this for? 

ovs_flow needs it and some rtnetlink specs I am working towards will
also need it.