"""Netlink Socket (lib/socket.c).
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c
Representation of a Netlink socket.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation version 2.1
of the License.
"""
import contextlib
import logging
import os
import socket
import time
from libnl.errno_ import NLE_BAD_SOCK, NLE_INVAL
from libnl.error import nl_syserr2nlerr
from libnl.handlers import nl_cb_alloc, NL_CB_DEBUG, NL_CB_DEFAULT, nl_cb_err, nl_cb_set, NL_CB_VERBOSE
from libnl.linux_private.netlink import NETLINK_ADD_MEMBERSHIP, NETLINK_DROP_MEMBERSHIP
from libnl.misc import __init
from libnl.netlink_private.netlink import BUG
from libnl.netlink_private.types import NL_OWN_PORT, nl_sock, NL_SOCK_BUFSIZE_SET
_LOGGER = logging.getLogger(__name__)
_PREVIOUS_LOCAL_PORT = None
default_cb = NL_CB_DEFAULT # https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L40
SOL_NETLINK = 270
@__init
def init_default_cb():
"""https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L42."""
global default_cb
nlcb = os.environ.get('NLCB', '').lower()
if not nlcb:
return
if nlcb == 'default':
default_cb = NL_CB_DEFAULT
elif nlcb == 'verbose':
default_cb = NL_CB_VERBOSE
elif nlcb == 'debug':
default_cb = NL_CB_DEBUG
else:
_LOGGER.warning('Unknown value for NLCB, valid values: {default | verbose | debug}')
def generate_local_port():
"""https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L63."""
global _PREVIOUS_LOCAL_PORT
if _PREVIOUS_LOCAL_PORT is None:
try:
with contextlib.closing(socket.socket(getattr(socket, 'AF_NETLINK', -1), socket.SOCK_RAW)) as s:
s.bind((0, 0))
_PREVIOUS_LOCAL_PORT = int(s.getsockname()[0])
except OSError:
_PREVIOUS_LOCAL_PORT = 4294967295 # UINT32_MAX
return int(_PREVIOUS_LOCAL_PORT)
def nl_socket_alloc(cb=None):
"""Allocate new Netlink socket. Does not yet actually open a socket.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L206
Also has code for generating local port once.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/nl.c#L123
Keyword arguments:
cb -- custom callback handler.
Returns:
Newly allocated Netlink socket (nl_sock class instance) or None.
"""
# Allocate the callback.
cb = cb or nl_cb_alloc(default_cb)
if not cb:
return None
# Allocate the socket.
sk = nl_sock()
sk.s_cb = cb
sk.s_local.nl_family = getattr(socket, 'AF_NETLINK', -1)
sk.s_peer.nl_family = getattr(socket, 'AF_NETLINK', -1)
sk.s_seq_expect = sk.s_seq_next = int(time.time())
sk.s_flags = NL_OWN_PORT # The port is 0 (unspecified), meaning NL_OWN_PORT.
# Generate local port.
nl_socket_get_local_port(sk) # I didn't find this in the C source, but during testing I saw this behavior.
return sk
def nl_socket_free(sk):
"""Free a Netlink socket (closes the socket).
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L244
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
"""
if sk and sk.socket_instance:
sk.socket_instance.close()
def nl_socket_get_local_port(sk):
"""https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L357.
Also https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L338
"""
if not sk.s_local.nl_pid:
port = generate_local_port()
sk.s_flags &= ~NL_OWN_PORT
sk.s_local.nl_pid = port
return port
return sk.s_local.nl_pid
def nl_socket_add_memberships(sk, *group):
"""Join groups.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L417
Joins the specified groups using the modern socket option. The list of groups has to be terminated by 0.
Make sure to use the correct group definitions as the older bitmask definitions for nl_join_groups() are likely to
still be present for backward compatibility reasons.
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
group -- group identifier (integer).
Returns:
0 on success or a negative error code.
"""
if sk.s_fd == -1:
return -NLE_BAD_SOCK
for grp in group:
if not grp:
break
if grp < 0:
return -NLE_INVAL
try:
sk.socket_instance.setsockopt(SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, grp)
except OSError as exc:
return -nl_syserr2nlerr(exc.errno)
return 0
def nl_socket_add_membership(sk, group):
"""Join a group.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L448
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
group -- group identifier (integer).
Returns:
0 on success or a negative error code.
"""
return nl_socket_add_memberships(sk, group, 0)
def nl_socket_drop_memberships(sk, *group):
"""Leave groups.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L465
Leaves the specified groups using the modern socket option. The list of groups has to terminated by 0.
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
group -- group identifier (integer).
Returns:
0 on success or a negative error code.
"""
if sk.s_fd == -1:
return -NLE_BAD_SOCK
for grp in group:
if not grp:
break
if grp < 0:
return -NLE_INVAL
try:
sk.socket_instance.setsockopt(SOL_NETLINK, NETLINK_DROP_MEMBERSHIP, grp)
except OSError as exc:
return -nl_syserr2nlerr(exc.errno)
return 0
def nl_socket_drop_membership(sk, group):
"""Leave a group.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L496
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
group -- group identifier (integer).
Returns:
0 on success or a negative error code.
"""
return nl_socket_drop_memberships(sk, group, 0)
def nl_socket_get_cb(sk):
"""Get the current nl_cb callback handler stored in the nl_sock socket.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L609
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
Returns:
nl_cb class instance.
"""
return sk.s_cb
def nl_socket_set_cb(sk, cb):
"""Store nl_cb callback handler in the nl_sock socket, overwriting the previous callbacks.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L614
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
cb -- callbacks (nl_cb class instance).
"""
if cb is None:
raise BUG
sk.s_cb = cb
def nl_socket_modify_cb(sk, type_, kind, func, arg):
"""Modify the callback handler associated with the socket.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L633
Sets specific callback functions in the existing nl_cb class instance stored in the nl_sock socket.
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
type_ -- which type callback to set (integer).
kind -- kind of callback (integer).
func -- callback function.
arg -- argument to be passed to callback function.
Returns:
0 on success or a negative error code.
"""
return int(nl_cb_set(sk.s_cb, type_, kind, func, arg))
def nl_socket_modify_err_cb(sk, kind, func, arg):
"""Modify the error callback handler associated with the socket.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L649
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
kind -- kind of callback (integer).
func -- callback function.
arg -- argument to be passed to callback function.
Returns:
0 on success or a negative error code.
"""
return int(nl_cb_err(sk.s_cb, kind, func, arg))
def nl_socket_set_buffer_size(sk, rxbuf, txbuf):
"""Set socket buffer size of Netlink socket.
https://github.com/thom311/libnl/blob/libnl3_2_25/lib/socket.c#L675
Sets the socket buffer size of a Netlink socket to the specified values `rxbuf` and `txbuf`. Providing a value of 0
assumes a good default value.
Positional arguments:
sk -- Netlink socket (nl_sock class instance).
rxbuf -- new receive socket buffer size in bytes (integer).
txbuf -- new transmit socket buffer size in bytes (integer).
Returns:
0 on success or a negative error code.
"""
rxbuf = 32768 if rxbuf <= 0 else rxbuf
txbuf = 32768 if txbuf <= 0 else txbuf
if sk.s_fd == -1:
return -NLE_BAD_SOCK
try:
sk.socket_instance.setsockopt(socket.SOL_SOCKET, socket.SO_SNDBUF, txbuf)
except OSError as exc:
return -nl_syserr2nlerr(exc.errno)
try:
sk.socket_instance.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, rxbuf)
except OSError as exc:
return -nl_syserr2nlerr(exc.errno)
sk.s_flags |= NL_SOCK_BUFSIZE_SET
return 0
