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process.py
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# Copyright 2023 VyOS maintainers and contributors <maintainers@vyos.io>
#
# 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; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <http://www.gnu.org/licenses/>.
import os
import shlex
from subprocess import Popen
from subprocess import PIPE
from subprocess import STDOUT
from subprocess import DEVNULL
def get_wrapper(vrf, netns):
wrapper = None
if vrf:
wrapper = ['ip', 'vrf', 'exec', vrf]
elif netns:
wrapper = ['ip', 'netns', 'exec', netns]
return wrapper
def popen(command, flag='', shell=None, input=None, timeout=None, env=None,
stdout=PIPE, stderr=PIPE, decode='utf-8', vrf=None, netns=None):
"""
popen is a wrapper helper around subprocess.Popen
with it default setting it will return a tuple (out, err)
out: the output of the program run
err: the error code returned by the program
it can be affected by the following flags:
shell: do not try to auto-detect if a shell is required
for example if a pipe (|) or redirection (>, >>) is used
input: data to sent to the child process via STDIN
the data should be bytes but string will be converted
timeout: time after which the command will be considered to have failed
env: mapping that defines the environment variables for the new process
stdout: define how the output of the program should be handled
- PIPE (default), sends stdout to the output
- DEVNULL, discard the output
stderr: define how the output of the program should be handled
- None (default), send/merge the data to/with stderr
- PIPE, popen will append it to output
- STDOUT, send the data to be merged with stdout
- DEVNULL, discard the output
decode: specify the expected text encoding (utf-8, ascii, ...)
the default is explicitely utf-8 which is python's own default
vrf: run command in a VRF context
netns: run command in the named network namespace
usage:
get both stdout and stderr: popen('command', stdout=PIPE, stderr=STDOUT)
discard stdout and get stderr: popen('command', stdout=DEVNUL, stderr=PIPE)
"""
# airbag must be left as an import in the function as otherwise we have a
# a circual import dependency
from vyos import debug
from vyos import airbag
# log if the flag is set, otherwise log if command is set
if not debug.enabled(flag):
flag = 'command'
use_shell = shell
stdin = None
if shell is None:
use_shell = False
if ' ' in command:
use_shell = True
if env:
use_shell = True
# Must be run as root to execute command in VRF or network namespace
wrapper = get_wrapper(vrf, netns)
if vrf or netns:
if os.getuid() != 0:
raise OSError(
'Permission denied: cannot execute commands in VRF and netns contexts as an unprivileged user'
)
if use_shell:
command = f'{shlex.join(wrapper)} {command}'
else:
if type(command) is not list:
command = [command]
command = wrapper + command
cmd_msg = f"cmd '{command}'" if use_shell else f"cmd '{shlex.join(command)}'"
debug.message(cmd_msg, flag)
if input:
stdin = PIPE
input = input.encode() if type(input) is str else input
p = Popen(command, stdin=stdin, stdout=stdout, stderr=stderr,
env=env, shell=use_shell)
pipe = p.communicate(input, timeout)
pipe_out = b''
if stdout == PIPE:
pipe_out = pipe[0]
pipe_err = b''
if stderr == PIPE:
pipe_err = pipe[1]
str_out = pipe_out.decode(decode).replace('\r\n', '\n').strip()
str_err = pipe_err.decode(decode).replace('\r\n', '\n').strip()
out_msg = f"returned (out):\n{str_out}"
if str_out:
debug.message(out_msg, flag)
if str_err:
from sys import stderr
err_msg = f"returned (err):\n{str_err}"
# this message will also be send to syslog via airbag
debug.message(err_msg, flag, destination=stderr)
# should something go wrong, report this too via airbag
airbag.noteworthy(cmd_msg)
airbag.noteworthy(out_msg)
airbag.noteworthy(err_msg)
return str_out, p.returncode
def run(command, flag='', shell=None, input=None, timeout=None, env=None,
stdout=DEVNULL, stderr=PIPE, decode='utf-8', vrf=None, netns=None):
"""
A wrapper around popen, which discard the stdout and
will return the error code of a command
"""
_, code = popen(
command, flag,
stdout=stdout, stderr=stderr,
input=input, timeout=timeout,
env=env, shell=shell,
decode=decode,
vrf=vrf,
netns=netns,
)
return code
def cmd(command, flag='', shell=None, input=None, timeout=None, env=None,
stdout=PIPE, stderr=PIPE, decode='utf-8', raising=None, message='',
expect=[0], vrf=None, netns=None):
"""
A wrapper around popen, which returns the stdout and
will raise the error code of a command
raising: specify which call should be used when raising
the class should only require a string as parameter
(default is OSError) with the error code
expect: a list of error codes to consider as normal
"""
decoded, code = popen(
command, flag,
stdout=stdout, stderr=stderr,
input=input, timeout=timeout,
env=env, shell=shell,
decode=decode,
vrf=vrf,
netns=netns,
)
if code not in expect:
wrapper = get_wrapper(vrf, netns)
command = f'{wrapper} {command}'
feedback = message + '\n' if message else ''
feedback += f'failed to run command: {command}\n'
feedback += f'returned: {decoded}\n'
feedback += f'exit code: {code}'
if raising is None:
# error code can be recovered with .errno
raise OSError(code, feedback)
else:
raise raising(feedback)
return decoded
def rc_cmd(command, flag='', shell=None, input=None, timeout=None, env=None,
stdout=PIPE, stderr=STDOUT, decode='utf-8', vrf=None, netns=None):
"""
A wrapper around popen, which returns the return code
of a command and stdout
% rc_cmd('uname')
(0, 'Linux')
% rc_cmd('ip link show dev eth99')
(1, 'Device "eth99" does not exist.')
"""
out, code = popen(
command, flag,
stdout=stdout, stderr=stderr,
input=input, timeout=timeout,
env=env, shell=shell,
decode=decode,
vrf=vrf,
netns=netns,
)
return code, out
def call(command, flag='', shell=None, input=None, timeout=None, env=None,
stdout=None, stderr=None, decode='utf-8', vrf=None, netns=None):
"""
A wrapper around popen, which print the stdout and
will return the error code of a command
"""
out, code = popen(
command, flag,
stdout=stdout, stderr=stderr,
input=input, timeout=timeout,
env=env, shell=shell,
decode=decode,
vrf=vrf,
netns=netns,
)
if out:
print(out)
return code
def process_running(pid_file):
""" Checks if a process with PID in pid_file is running """
from psutil import pid_exists
if not os.path.isfile(pid_file):
return False
with open(pid_file, 'r') as f:
pid = f.read().strip()
return pid_exists(int(pid))
def process_named_running(name: str, cmdline: str=None, timeout: int=0):
""" Checks if process with given name is running and returns its PID.
If Process is not running, return None
"""
from psutil import process_iter
def check_process(name, cmdline):
for p in process_iter(['name', 'pid', 'cmdline']):
if cmdline:
if name in p.info['name'] and cmdline in p.info['cmdline']:
return p.info['pid']
elif name in p.info['name']:
return p.info['pid']
return None
if timeout:
import time
time_expire = time.time() + timeout
while True:
tmp = check_process(name, cmdline)
if not tmp:
if time.time() > time_expire:
break
time.sleep(0.100) # wait 100ms
continue
return tmp
else:
return check_process(name, cmdline)
return None
def is_systemd_service_active(service):
""" Test is a specified systemd service is activated.
Returns True if service is active, false otherwise.
Copied from: https://unix.stackexchange.com/a/435317 """
tmp = cmd(f'systemctl show --value -p ActiveState {service}')
return bool((tmp == 'active'))
def is_systemd_service_running(service):
""" Test is a specified systemd service is actually running.
Returns True if service is running, false otherwise.
Copied from: https://unix.stackexchange.com/a/435317 """
tmp = cmd(f'systemctl show --value -p SubState {service}')
return bool((tmp == 'running'))
def ip_cmd(args, json=True):
""" A helper for easily calling iproute2 commands """
if json:
from json import loads
res = cmd(f"ip --json {args}").strip()
if res:
return loads(res)
else:
# Many mutation commands like "ip link set"
# return an empty string
return None
else:
res = cmd(f"ip {args}")
return res

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