initial commit with a working nsenter program

Author: hjacobs

.gitignore

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+build
+dist
+*.egg*

README.rst

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+=======
+NSEnter
+=======

nsenter/__init__.py

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+#!/usr/bin/env python3
+
+'''
+nsenter - run program with namespaces of other processes
+'''
+
+import argparse
+import ctypes
+import os
+import shlex
+import subprocess
+import logging
+from pathlib import Path
+from contextlib import ExitStack
+
+NAMESPACE_NAMES = frozenset('mnt ipc net pid user uts'.split())
+
+log = logging.getLogger('nsenter')
+
+libc = ctypes.CDLL('libc.so.6')
+
+def nsfd(process:str, ns_type:str) -> Path:
+    """
+    Returns the namespace file descriptor for process (self or PID) and namespace type
+    """
+    return Path('/proc') / process / 'ns' / ns_type
+
+
+class Namespace:
+    def __init__(self, pid: str, ns_type: str):
+        self.pid = pid
+        self.ns_type = ns_type
+        self.parent_fd = nsfd('self', ns_type).open()
+        self.parent_fileno =self.parent_fd.fileno()
+        self.target_fd = nsfd(pid, ns_type).open()
+        self.target_fileno =self.target_fd.fileno()
+
+    def __enter__(self):
+        log.debug('Entering %s namespace %s', self.ns_type, self.pid)
+        libc.setns(self.target_fileno, 0)
+
+    def __exit__(self, type, value, tb):
+        log.debug('Leaving %s namespace %s', self.ns_type, self.pid)
+        libc.setns(self.parent_fileno, 0)
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--target', metavar='PID', help='Specify a target process to get contexts from.')
+    for ns in NAMESPACE_NAMES:
+        parser.add_argument('--{}'.format(ns), action='store_true', help='Enter the {} namespace'.format(ns))
+    parser.add_argument('--all', action='store_true', help='Enter all namespaces')
+    parser.add_argument('command')
+
+    args = parser.parse_args()
+
+    with ExitStack() as stack:
+        namespaces = []
+        for ns in NAMESPACE_NAMES:
+            if getattr(args, ns) or args.all:
+                namespaces.append(Namespace(args.target, ns))
+        for ns in namespaces:
+            stack.enter_context(ns)
+        os.execl(args.command, args.command)
+
+
+if __name__ == '__main__':
+    main()

requirements.txt

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+# empty

setup.py

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+#!/usr/bin/env python3
+
+import inspect
+import os
+import setuptools
+
+__location__ = os.path.join(os.getcwd(), os.path.dirname(inspect.getfile(inspect.currentframe())))
+
+def get_install_requirements(path):
+    content = open(os.path.join(__location__, path)).read()
+    return [req for req in content.split('\\n') if req != '']
+
+def read(fname):
+    return open(os.path.join(__location__, fname)).read()
+
+def setup_package():
+    install_reqs = get_install_requirements('requirements.txt')
+    setuptools.setup(
+        name='nsenter',
+        version='0.1',
+        url='https://github.com/zalando/python-nsenter',
+        description='',
+        author='Henning Jacobs',
+        author_email='[email protected]',
+        long_description=read('README.rst'),
+        classifiers=['Development Status :: 4 - Beta', 'Programming Language :: Python'],
+        test_suite='tests',
+        packages=setuptools.find_packages(exclude=['tests', 'tests.*']),
+        install_requires=install_reqs,
+        entry_points={'console_scripts': ['nsenter = nsenter:main']}
+    )
+
+if __name__ == '__main__':
+    setup_package()