# octavia.amphorae.backends.utils.network_namespace

# Source code for octavia.amphorae.backends.utils.network_namespace

    # Copyright 2020 Red Hat, Inc. All rights reserved.
    #
    # Licensed under the Apache License, Version 2.0 (the "License"); you may
    # not use this file except in compliance with the License. You may obtain
    # a copy of the License at
    #
    # http://www.apache.org/licenses/LICENSE-2.0
    #
    # Unless required by applicable law or agreed to in writing, software
    # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
    # License for the specific language governing permissions and limitations
    # under the License.
    import ctypes
    import os

    class NetworkNamespace:
        """A network namespace context manager.

        Runs wrapped code inside the specified network namespace.

        :param netns: The network namespace name to enter.
        """
        # from linux/sched.h - We want to enter a network namespace
        CLONE_NEWNET = 0x40000000

        @staticmethod
        def _error_handler(result, func, arguments):
            if result == -1:
                errno = ctypes.get_errno()
                raise OSError(errno, os.strerror(errno))

        def __init__(self, netns):
            self.current_netns = f'/proc/{os.getpid()}/ns/net'
            self.target_netns = f'/var/run/netns/{netns}'
            # reference: man setns(2)
            self.set_netns = ctypes.CDLL('libc.so.6', use_errno=True).setns
            self.set_netns.errcheck = self._error_handler

        def __enter__(self):
            # Save the current network namespace
            self.current_netns_fd = open(self.current_netns, encoding='utf-8')
            with open(self.target_netns, encoding='utf-8') as fd:
                self.set_netns(fd.fileno(), self.CLONE_NEWNET)

        def __exit__(self, *args):
            # Return to the previous network namespace
            self.set_netns(self.current_netns_fd.fileno(), self.CLONE_NEWNET)
            self.current_netns_fd.close()

this page last updated: 2025-10-06 11:22:08

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