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linux-stable/tools/net/ynl/lib/ynl.py
Jakub Kicinski ebe3bdc435 tools: ynl: throw a more meaningful exception if family not supported 
cli.py currently throws a pure KeyError if kernel doesn't support
a netlink family. Users who did not write ynl (hah) may waste
their time investigating what's wrong with the Python code.
Improve the error message:

Traceback (most recent call last):
  File "/home/kicinski/devel/linux/tools/net/ynl/lib/ynl.py", line 362, in __init__
    self.family = GenlFamily(self.yaml['name'])
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/kicinski/devel/linux/tools/net/ynl/lib/ynl.py", line 331, in __init__
    self.genl_family = genl_family_name_to_id[family_name]
                       ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
KeyError: 'netdev'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/kicinski/devel/linux/./tools/net/ynl/cli.py", line 52, in <module>
    main()
  File "/home/kicinski/devel/linux/./tools/net/ynl/cli.py", line 31, in main
    ynl = YnlFamily(args.spec, args.schema)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/kicinski/devel/linux/tools/net/ynl/lib/ynl.py", line 364, in __init__
    raise Exception(f"Family '{self.yaml['name']}' not supported by the kernel")
Exception: Family 'netdev' not supported by the kernel

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230407145609.297525-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2023-04-11 15:33:46 +02:00

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# SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
import functools
import os
import random
import socket
import struct
import yaml
from .nlspec import SpecFamily
#
# Generic Netlink code which should really be in some library, but I can't quickly find one.
#
class Netlink:
# Netlink socket
SOL_NETLINK = 270
NETLINK_ADD_MEMBERSHIP = 1
NETLINK_CAP_ACK = 10
NETLINK_EXT_ACK = 11
# Netlink message
NLMSG_ERROR = 2
NLMSG_DONE = 3
NLM_F_REQUEST = 1
NLM_F_ACK = 4
NLM_F_ROOT = 0x100
NLM_F_MATCH = 0x200
NLM_F_APPEND = 0x800
NLM_F_CAPPED = 0x100
NLM_F_ACK_TLVS = 0x200
NLM_F_DUMP = NLM_F_ROOT | NLM_F_MATCH
NLA_F_NESTED = 0x8000
NLA_F_NET_BYTEORDER = 0x4000
NLA_TYPE_MASK = NLA_F_NESTED | NLA_F_NET_BYTEORDER
# Genetlink defines
NETLINK_GENERIC = 16
GENL_ID_CTRL = 0x10
# nlctrl
CTRL_CMD_GETFAMILY = 3
CTRL_ATTR_FAMILY_ID = 1
CTRL_ATTR_FAMILY_NAME = 2
CTRL_ATTR_MAXATTR = 5
CTRL_ATTR_MCAST_GROUPS = 7
CTRL_ATTR_MCAST_GRP_NAME = 1
CTRL_ATTR_MCAST_GRP_ID = 2
# Extack types
NLMSGERR_ATTR_MSG = 1
NLMSGERR_ATTR_OFFS = 2
NLMSGERR_ATTR_COOKIE = 3
NLMSGERR_ATTR_POLICY = 4
NLMSGERR_ATTR_MISS_TYPE = 5
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),
'u32': ('I', 4), 's32': ('i', 4),
'u64': ('Q', 8), 's64': ('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
self.payload_len = self._len
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, 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_strz(self):
return self.raw.decode('ascii')[:-1]
def as_bin(self):
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) })
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
value[m.name] = decoded[0]
return value
def __repr__(self):
return f"[type:{self.type} len:{self._len}] {self.raw}"
class NlAttrs:
def __init__(self, msg):
self.attrs = []
offset = 0
while offset < len(msg):
attr = NlAttr(msg, offset)
offset += attr.full_len
self.attrs.append(attr)
def __iter__(self):
yield from self.attrs
def __repr__(self):
msg = ''
for a in self.attrs:
if msg:
msg += '\n'
msg += repr(a)
return msg
class NlMsg:
def __init__(self, msg, offset, attr_space=None):
self.hdr = msg[offset:offset + 16]
self.nl_len, self.nl_type, self.nl_flags, self.nl_seq, self.nl_portid = \
struct.unpack("IHHII", self.hdr)
self.raw = msg[offset + 16:offset + self.nl_len]
self.error = 0
self.done = 0
extack_off = None
if self.nl_type == Netlink.NLMSG_ERROR:
self.error = struct.unpack("i", self.raw[0:4])[0]
self.done = 1
extack_off = 20
elif self.nl_type == Netlink.NLMSG_DONE:
self.done = 1
extack_off = 4
self.extack = None
if self.nl_flags & Netlink.NLM_F_ACK_TLVS and extack_off:
self.extack = dict()
extack_attrs = NlAttrs(self.raw[extack_off:])
for extack in extack_attrs:
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()
elif extack.type == Netlink.NLMSGERR_ATTR_MISS_NEST:
self.extack['miss-nest'] = extack.as_u32()
elif extack.type == Netlink.NLMSGERR_ATTR_OFFS:
self.extack['bad-attr-offs'] = extack.as_u32()
else:
if 'unknown' not in self.extack:
self.extack['unknown'] = []
self.extack['unknown'].append(extack)
if attr_space:
# We don't have the ability to parse nests yet, so only do global
if 'miss-type' in self.extack and 'miss-nest' not in self.extack:
miss_type = self.extack['miss-type']
if miss_type in attr_space.attrs_by_val:
spec = attr_space.attrs_by_val[miss_type]
desc = spec['name']
if 'doc' in spec:
desc += f" ({spec['doc']})"
self.extack['miss-type'] = desc
def __repr__(self):
msg = f"nl_len = {self.nl_len} ({len(self.raw)}) nl_flags = 0x{self.nl_flags:x} nl_type = {self.nl_type}\n"
if self.error:
msg += '\terror: ' + str(self.error)
if self.extack:
msg += '\textack: ' + repr(self.extack)
return msg
class NlMsgs:
def __init__(self, data, attr_space=None):
self.msgs = []
offset = 0
while offset < len(data):
msg = NlMsg(data, offset, attr_space=attr_space)
offset += msg.nl_len
self.msgs.append(msg)
def __iter__(self):
yield from self.msgs
genl_family_name_to_id = None
def _genl_msg(nl_type, nl_flags, genl_cmd, genl_version, seq=None):
# we prepend length in _genl_msg_finalize()
if seq is None:
seq = random.randint(1, 1024)
nlmsg = struct.pack("HHII", nl_type, nl_flags, seq, 0)
genlmsg = struct.pack("BBH", genl_cmd, genl_version, 0)
return nlmsg + genlmsg
def _genl_msg_finalize(msg):
return struct.pack("I", len(msg) + 4) + msg
def _genl_load_families():
with socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, Netlink.NETLINK_GENERIC) as sock:
sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_CAP_ACK, 1)
msg = _genl_msg(Netlink.GENL_ID_CTRL,
Netlink.NLM_F_REQUEST | Netlink.NLM_F_ACK | Netlink.NLM_F_DUMP,
Netlink.CTRL_CMD_GETFAMILY, 1)
msg = _genl_msg_finalize(msg)
sock.send(msg, 0)
global genl_family_name_to_id
genl_family_name_to_id = dict()
while True:
reply = sock.recv(128 * 1024)
nms = NlMsgs(reply)
for nl_msg in nms:
if nl_msg.error:
print("Netlink error:", nl_msg.error)
return
if nl_msg.done:
return
gm = GenlMsg(nl_msg)
fam = dict()
for attr in gm.raw_attrs:
if attr.type == Netlink.CTRL_ATTR_FAMILY_ID:
fam['id'] = attr.as_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()
elif attr.type == Netlink.CTRL_ATTR_MCAST_GROUPS:
fam['mcast'] = dict()
for entry in NlAttrs(attr.raw):
mcast_name = None
mcast_id = None
for entry_attr in NlAttrs(entry.raw):
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()
if mcast_name and mcast_id is not None:
fam['mcast'][mcast_name] = mcast_id
if 'name' in fam and 'id' in fam:
genl_family_name_to_id[fam['name']] = fam
class GenlMsg:
def __init__(self, nl_msg, fixed_header_members=[]):
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, size = NlAttr.type_formats[m.type]
decoded = struct.unpack_from(format, nl_msg.raw, offset)
offset += size
self.fixed_header_attrs[m.name] = decoded[0]
self.raw = nl_msg.raw[offset:]
self.raw_attrs = NlAttrs(self.raw)
def __repr__(self):
msg = repr(self.nl)
msg += f"\tgenl_cmd = {self.genl_cmd} genl_ver = {self.genl_version}\n"
for a in self.raw_attrs:
msg += '\t\t' + repr(a) + '\n'
return msg
class GenlFamily:
def __init__(self, family_name):
self.family_name = family_name
global genl_family_name_to_id
if genl_family_name_to_id is None:
_genl_load_families()
self.genl_family = genl_family_name_to_id[family_name]
self.family_id = genl_family_name_to_id[family_name]['id']
#
# YNL implementation details.
#
class YnlFamily(SpecFamily):
def __init__(self, def_path, schema=None):
super().__init__(def_path, schema)
self.include_raw = False
self.sock = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, Netlink.NETLINK_GENERIC)
self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_CAP_ACK, 1)
self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_EXT_ACK, 1)
self.async_msg_ids = set()
self.async_msg_queue = []
for msg in self.msgs.values():
if msg.is_async:
self.async_msg_ids.add(msg.rsp_value)
for op_name, op in self.ops.items():
bound_f = functools.partial(self._op, op_name)
setattr(self, op.ident_name, bound_f)
try:
self.family = GenlFamily(self.yaml['name'])
except KeyError:
raise Exception(f"Family '{self.yaml['name']}' not supported by the kernel")
def ntf_subscribe(self, mcast_name):
if mcast_name not in self.family.genl_family['mcast']:
raise Exception(f'Multicast group "{mcast_name}" not present in the family')
self.sock.bind((0, 0))
self.sock.setsockopt(Netlink.SOL_NETLINK, Netlink.NETLINK_ADD_MEMBERSHIP,
self.family.genl_family['mcast'][mcast_name])
def _add_attr(self, space, name, value):
attr = self.attr_sets[space][name]
nl_type = attr.value
if attr["type"] == 'nest':
nl_type |= Netlink.NLA_F_NESTED
attr_payload = b''
for subname, subvalue in value.items():
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"]}')
pad = b'\x00' * ((4 - len(attr_payload) % 4) % 4)
return struct.pack('HH', len(attr_payload) + 4, nl_type) + attr_payload + pad
def _decode_enum(self, rsp, attr_spec):
raw = rsp[attr_spec['name']]
enum = self.consts[attr_spec['enum']]
i = attr_spec.get('value-start', 0)
if 'enum-as-flags' in attr_spec and attr_spec['enum-as-flags']:
value = set()
while raw:
if raw & 1:
value.add(enum.entries_by_val[i].name)
raw >>= 1
i += 1
else:
value = enum.entries_by_val[raw - i].name
rsp[attr_spec['name']] = value
def _decode_binary(self, attr, attr_spec):
if attr_spec.struct_name:
decoded = attr.as_struct(self.consts[attr_spec.struct_name])
elif attr_spec.sub_type:
decoded = attr.as_c_array(attr_spec.sub_type)
else:
decoded = attr.as_bin()
return decoded
def _decode(self, attrs, space):
attr_space = self.attr_sets[space]
rsp = dict()
for attr in attrs:
attr_spec = attr_space.attrs_by_val[attr.type]
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"]}')
if not attr_spec.is_multi:
rsp[attr_spec['name']] = decoded
elif attr_spec.name in rsp:
rsp[attr_spec.name].append(decoded)
else:
rsp[attr_spec.name] = [decoded]
if 'enum' in attr_spec:
self._decode_enum(rsp, attr_spec)
return rsp
def _decode_extack_path(self, attrs, attr_set, offset, target):
for attr in attrs:
attr_spec = attr_set.attrs_by_val[attr.type]
if offset > target:
break
if offset == target:
return '.' + attr_spec.name
if offset + attr.full_len <= target:
offset += attr.full_len
continue
if attr_spec['type'] != 'nest':
raise Exception(f"Can't dive into {attr.type} ({attr_spec['name']}) for extack")
offset += 4
subpath = self._decode_extack_path(NlAttrs(attr.raw),
self.attr_sets[attr_spec['nested-attributes']],
offset, target)
if subpath is None:
return None
return '.' + attr_spec.name + subpath
return None
def _decode_extack(self, request, attr_space, 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'])
if path:
del extack['bad-attr-offs']
extack['bad-attr'] = path
def handle_ntf(self, nl_msg, genl_msg):
msg = dict()
if self.include_raw:
msg['nlmsg'] = nl_msg
msg['genlmsg'] = genl_msg
op = self.rsp_by_value[genl_msg.genl_cmd]
msg['name'] = op['name']
msg['msg'] = self._decode(genl_msg.raw_attrs, op.attr_set.name)
self.async_msg_queue.append(msg)
def check_ntf(self):
while True:
try:
reply = self.sock.recv(128 * 1024, socket.MSG_DONTWAIT)
except BlockingIOError:
return
nms = NlMsgs(reply)
for nl_msg in nms:
if nl_msg.error:
print("Netlink error in ntf!?", os.strerror(-nl_msg.error))
print(nl_msg)
continue
if nl_msg.done:
print("Netlink done while checking for ntf!?")
continue
gm = GenlMsg(nl_msg)
if gm.genl_cmd not in self.async_msg_ids:
print("Unexpected msg id done while checking for ntf", gm)
continue
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]
nl_flags = Netlink.NLM_F_REQUEST | Netlink.NLM_F_ACK
if dump:
nl_flags |= Netlink.NLM_F_DUMP
req_seq = random.randint(1024, 65535)
msg = _genl_msg(self.family.family_id, nl_flags, op.req_value, 1, req_seq)
fixed_header_members = []
if op.fixed_header:
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)
for name, value in vals.items():
msg += self._add_attr(op.attr_set.name, name, value)
msg = _genl_msg_finalize(msg)
self.sock.send(msg, 0)
done = False
rsp = []
while not done:
reply = self.sock.recv(128 * 1024)
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)
if nl_msg.error:
raise NlError(nl_msg)
if nl_msg.done:
if nl_msg.extack:
print("Netlink warning:")
print(nl_msg)
done = True
break
gm = GenlMsg(nl_msg, fixed_header_members)
# 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:
self.handle_ntf(nl_msg, gm)
continue
else:
print('Unexpected message: ' + repr(gm))
continue
rsp.append(self._decode(gm.raw_attrs, op.attr_set.name)
| gm.fixed_header_attrs)
if not rsp:
return None
if not dump and len(rsp) == 1:
return rsp[0]
return rsp
def do(self, method, vals):
return self._op(method, vals)
def dump(self, method, vals):
return self._op(method, vals, dump=True)
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