285 lines
8.1 KiB
Python
285 lines
8.1 KiB
Python
# tractor: structured concurrent "actors".
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# Copyright 2018-eternity Tyler Goodlet.
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU Affero General Public License for more details.
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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'''
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Linux network-namespace actor-bootstrap primitives.
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'''
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from __future__ import annotations
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from collections.abc import (
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Callable,
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Iterator,
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)
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from contextlib import contextmanager as cm
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import errno
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from pathlib import Path
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import os
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import sys
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from typing import TYPE_CHECKING
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if TYPE_CHECKING:
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from ..net._bindspace import Bindspace
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# `setns(2)` mutates only the calling thread's namespace:
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# https://man7.org/linux/man-pages/man2/setns.2.html
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# `/proc/thread-self` addresses the caller's current task:
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# https://man7.org/linux/man-pages/man5/proc_pid_task.5.html
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# Do not use `/proc/self` because it resolves through the process
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# leader.
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_SELF_NETNS: Path = Path('/proc/thread-self/ns/net')
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def enter_netns(
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namespace_fd: int,
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expected_inode: int,
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) -> int:
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'''
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Enter and verify one inherited Linux network namespace.
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The caller owns and closes `namespace_fd`.
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'''
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if sys.platform != 'linux':
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raise RuntimeError(
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'Network namespace entry is Linux-only!'
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)
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if (
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type(namespace_fd) is not int
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or
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namespace_fd < 0
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):
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raise ValueError(
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'`namespace_fd` must be a non-negative `int`!'
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)
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if (
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type(expected_inode) is not int
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or
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expected_inode <= 0
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):
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raise ValueError(
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'`expected_inode` must be a positive `int`!'
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)
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setns: Callable[[int, int], None]|None = getattr(
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os,
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'setns',
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None,
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)
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clone_newnet: int|None = getattr(
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os,
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'CLONE_NEWNET',
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None,
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)
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if (
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setns is None
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or
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clone_newnet is None
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):
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raise RuntimeError(
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'Python has no Linux network namespace entry support!'
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)
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inherited_inode: int = os.fstat(namespace_fd).st_ino
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if inherited_inode != expected_inode:
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raise ValueError(
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f'Inherited namespace FD inode {inherited_inode} does not '
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f'match expected inode {expected_inode}!'
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)
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try:
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setns(namespace_fd, clone_newnet)
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except OSError as exc:
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raise RuntimeError(
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f'Could not enter network namespace inode '
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f'{expected_inode}!'
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) from exc
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entered_inode: int = _SELF_NETNS.stat().st_ino
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if entered_inode != expected_inode:
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raise RuntimeError(
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f'Entered network namespace inode {entered_inode} does not '
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f'match expected inode {expected_inode}!'
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)
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return entered_inode
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@cm
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def close_fd(
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owned_fd: int,
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fd_name: str,
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) -> Iterator[None]:
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'''
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Close one owned netns FD without masking a prior error.
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'''
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operation: str = (
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f'close owned {fd_name} netns FD {owned_fd}'
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)
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try:
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yield
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except BaseException as primary_error:
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try:
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os.close(owned_fd)
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except BaseException as close_error:
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primary_error.add_note(
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f'Also failed to {operation}: {close_error!r}'
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)
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raise primary_error
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else:
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try:
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os.close(owned_fd)
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except BaseException as close_error:
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close_error.add_note(
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f'Failed to {operation} during root netns cleanup.'
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)
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raise close_error
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@cm
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def dup_fd(
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source_fd: int,
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) -> Iterator[int]:
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'''
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Duplicate and own the target netns FD for this context.
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'''
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try:
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owned_fd: int = os.dup(source_fd)
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except OSError as dup_error:
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if dup_error.errno != errno.EBADF:
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raise dup_error
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raise ValueError(
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'`bindspace.namespace_fd` does not reference '
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'a live FD!'
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) from dup_error
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with close_fd(owned_fd, 'target'):
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yield owned_fd
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@cm
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def _enter_netns_temporarily(
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bindspace: Bindspace|None,
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) -> Iterator[int|None]:
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'''
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Enter a root bindspace and restore the caller thread's netns.
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`_root._enter_root_bindspace()` adapts this synchronous scope to
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the root actor's async lifecycle.
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Only descriptors opened or duplicated by this context are used
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for validation, entry and restoration. Since `setns()` is
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thread-local, this synchronous context performs no checkpoints
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around either transition.
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'''
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if bindspace is None:
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yield None
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return
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if sys.platform != 'linux':
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raise RuntimeError(
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'Network namespace entry is Linux-only!'
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)
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namespace_fd: int|None = bindspace.namespace_fd
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if namespace_fd is None:
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raise ValueError(
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'`bindspace.namespace_fd` must be a live netns FD for '
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'root actor entry!'
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)
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if (
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type(namespace_fd) is not int
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or
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namespace_fd < 0
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):
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raise ValueError(
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'`bindspace.namespace_fd` must be a live '
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'non-negative FD!'
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)
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# Borrow `Bindspace.namespace_fd`; duplicate it so this context
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# owns target cleanup and cannot close the caller's capability.
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# Nested FD scopes aggregate later close failures as notes on the
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# first body, restoration or cleanup error.
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with dup_fd(namespace_fd) as tgt_fd:
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tgt_stat: os.stat_result = os.fstat(tgt_fd)
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tgt_inode: int = bindspace.ref.inode
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if tgt_stat.st_ino != tgt_inode:
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raise ValueError(
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f'Target namespace FD inode '
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f'{tgt_stat.st_ino} does '
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f'not match bindspace inode {tgt_inode}!'
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)
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# Capture the calling thread's current netns before any
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# transition. It need not be the process's initial netns. This
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# context owns the snapshot FD even when no transition is
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# needed, so keep it live through restoration and always close
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# it afterward.
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orig_fd = os.open(
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_SELF_NETNS,
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os.O_RDONLY | os.O_CLOEXEC,
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)
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with close_fd(orig_fd, 'original'):
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orig_stat: os.stat_result = os.fstat(orig_fd)
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orig_inode: int = orig_stat.st_ino
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restore_needed: bool = (
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tgt_stat.st_dev != orig_stat.st_dev
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or
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tgt_inode != orig_inode
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)
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try:
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if restore_needed:
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enter_netns(
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tgt_fd,
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tgt_inode,
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)
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yield tgt_inode
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except BaseException as primary_error:
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if restore_needed:
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try:
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enter_netns(
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orig_fd,
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orig_inode,
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)
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except BaseException as restore_error:
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primary_error.add_note(
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'Also failed to restore the original '
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'network namespace: '
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f'{restore_error!r}'
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)
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raise primary_error
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if restore_needed:
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try:
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enter_netns(
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orig_fd,
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orig_inode,
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)
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except BaseException as restore_error:
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restore_error.add_note(
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'Failed to restore the original network '
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'namespace during root netns cleanup.'
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)
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raise restore_error
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