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import json
from ctypes import *
import sys
class Nftables:
"""A class representing libnftables interface"""
debug_flags = {
"scanner": 0x1,
"parser": 0x2,
"eval": 0x4,
"netlink": 0x8,
"mnl": 0x10,
"proto-ctx": 0x20,
"segtree": 0x40,
}
numeric_levels = {
"none": 0,
"addr": 1,
"port": 2,
"all": 3,
}
def __init__(self, sofile="libnftables.so"):
"""Instantiate a new Nftables class object.
Accepts a shared object file to open, by default standard search path
is searched for a file named 'libnftables.so'.
After loading the library using ctypes module, a new nftables context
is requested from the library and buffering of output and error streams
is turned on.
"""
lib = cdll.LoadLibrary(sofile)
### API function definitions
self.nft_ctx_new = lib.nft_ctx_new
self.nft_ctx_new.restype = c_void_p
self.nft_ctx_new.argtypes = [c_int]
self.nft_ctx_output_get_handle = lib.nft_ctx_output_get_handle
self.nft_ctx_output_get_handle.restype = c_bool
self.nft_ctx_output_get_handle.argtypes = [c_void_p]
self.nft_ctx_output_set_handle = lib.nft_ctx_output_set_handle
self.nft_ctx_output_set_handle.argtypes = [c_void_p, c_bool]
self.nft_ctx_output_get_numeric = lib.nft_ctx_output_get_numeric
self.nft_ctx_output_get_numeric.restype = c_int
self.nft_ctx_output_get_numeric.argtypes = [c_void_p]
self.nft_ctx_output_set_numeric = lib.nft_ctx_output_set_numeric
self.nft_ctx_output_set_numeric.argtypes = [c_void_p, c_int]
self.nft_ctx_output_get_stateless = lib.nft_ctx_output_get_stateless
self.nft_ctx_output_get_stateless.restype = c_bool
self.nft_ctx_output_get_stateless.argtypes = [c_void_p]
self.nft_ctx_output_set_stateless = lib.nft_ctx_output_set_stateless
self.nft_ctx_output_set_stateless.argtypes = [c_void_p, c_bool]
self.nft_ctx_output_get_debug = lib.nft_ctx_output_get_debug
self.nft_ctx_output_get_debug.restype = c_int
self.nft_ctx_output_get_debug.argtypes = [c_void_p]
self.nft_ctx_output_set_debug = lib.nft_ctx_output_set_debug
self.nft_ctx_output_set_debug.argtypes = [c_void_p, c_int]
self.nft_ctx_buffer_output = lib.nft_ctx_buffer_output
self.nft_ctx_buffer_output.restype = c_int
self.nft_ctx_buffer_output.argtypes = [c_void_p]
self.nft_ctx_get_output_buffer = lib.nft_ctx_get_output_buffer
self.nft_ctx_get_output_buffer.restype = c_char_p
self.nft_ctx_get_output_buffer.argtypes = [c_void_p]
self.nft_ctx_buffer_error = lib.nft_ctx_buffer_error
self.nft_ctx_buffer_error.restype = c_int
self.nft_ctx_buffer_error.argtypes = [c_void_p]
self.nft_ctx_get_error_buffer = lib.nft_ctx_get_error_buffer
self.nft_ctx_get_error_buffer.restype = c_char_p
self.nft_ctx_get_error_buffer.argtypes = [c_void_p]
self.nft_run_cmd_from_buffer = lib.nft_run_cmd_from_buffer
self.nft_run_cmd_from_buffer.restype = c_int
self.nft_run_cmd_from_buffer.argtypes = [c_void_p, c_char_p, c_int]
self.nft_ctx_free = lib.nft_ctx_free
lib.nft_ctx_free.argtypes = [c_void_p]
# initialize libnftables context
self.__ctx = self.nft_ctx_new(0)
self.nft_ctx_buffer_output(self.__ctx)
self.nft_ctx_buffer_error(self.__ctx)
def get_handle_output(self):
"""Get the current state of handle output.
Returns a boolean indicating whether handle output is active or not.
"""
return self.nft_ctx_output_get_handle(self.__ctx)
def set_handle_output(self, val):
"""Enable or disable handle output.
Accepts a boolean turning handle output on or off.
Returns the previous value.
"""
old = self.get_handle_output()
self.nft_ctx_output_set_handle(self.__ctx, val)
return old
def get_numeric_output(self):
"""Get the current state of numeric output.
Returns a boolean indicating whether boolean output is active or not.
"""
return self.nft_ctx_output_get_numeric(self.__ctx)
def set_numeric_output(self, val):
"""Enable or disable numeric output.
Accepts a boolean turning numeric output on or off.
Returns the previous value.
"""
old = self.get_numeric_output()
if type(val) is str:
val = self.numeric_levels[val]
self.nft_ctx_output_set_numeric(self.__ctx, val)
return old
def get_stateless_output(self):
"""Get the current state of stateless output.
Returns a boolean indicating whether stateless output is active or not.
"""
return self.nft_ctx_output_get_stateless(self.__ctx)
def set_stateless_output(self, val):
"""Enable or Disable stateless output.
Accepts a boolean turning stateless output either on or off.
Returns the previous value.
"""
old = self.get_stateless_output()
self.nft_ctx_output_set_stateless(self.__ctx, val)
return old
def get_debug(self):
"""Get currently active debug flags.
Returns a set of flag names. See set_debug() for details.
"""
val = self.nft_ctx_output_get_debug(self.__ctx)
names = []
for n,v in self.debug_flags.items():
if val & v:
names.append(n)
val &= ~v
if val:
names.append(val)
return names
def set_debug(self, values):
"""Set debug output flags.
Accepts either a single flag or a set of flags. Each flag might be
given either as string or integer value as shown in the following
table:
Name | Value (hex)
-----------------------
scanner | 0x1
parser | 0x2
eval | 0x4
netlink | 0x8
mnl | 0x10
proto-ctx | 0x20
segtree | 0x40
Returns a set of previously active debug flags, as returned by
get_debug() method.
"""
old = self.get_debug()
if type(values) in [str, int]:
values = [values]
val = 0
for v in values:
if type(v) is str:
v = self.debug_flags[v]
val |= v
self.nft_ctx_output_set_debug(self.__ctx, val)
return old
def cmd(self, cmdline):
"""Run a simple nftables command via libnftables.
Accepts a string containing an nftables command just like what one
would enter into an interactive nftables (nft -i) session.
Returns a tuple (rc, output, error):
rc -- return code as returned by nft_run_cmd_from_buffer() fuction
output -- a string containing output written to stdout
error -- a string containing output written to stderr
"""
rc = self.nft_run_cmd_from_buffer(self.__ctx, cmdline, len(cmdline))
output = self.nft_ctx_get_output_buffer(self.__ctx)
error = self.nft_ctx_get_error_buffer(self.__ctx)
return (rc, output, error)
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