mirror of
https://github.com/GNS3/gns3-server.git
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93 lines
3.5 KiB
Python
93 lines
3.5 KiB
Python
#
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# Copyright (C) 2026 GNS3 Technologies Inc.
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#
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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 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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#
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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 General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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"""
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Standalone VPCS tap-mode probe.
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A VPCS node anchors a kernel-datapath link on a persistent TAP the vpcs
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process attaches to by name (``-e -d <anchor>``). That shape needs a vpcs
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build that also refuses to auto-configure the host side of the TAP (``-n``):
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without the flag every ``ip`` command inside the guest runs
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``ifconfig <tap> … up`` on the anchor — the server owns the anchor's
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addresses and bridge membership, so a vpcs touching them ranges from noise
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(an ifconfig on a name that cannot resolve) to sabotage (reconfiguring an
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interface that does exist).
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The probe asks the configured binary for its usage (``vpcs -h``) and looks
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for the ``-n`` line, caching the answer by binary identity (path, mtime,
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size, ctime) exactly like the uBridge probes — the same binary never
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answers differently, but replacing it must re-probe. This feeds the compute
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``/capabilities`` payload (``vpcs_tap``) so the controller can gate VPCS
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kernel links on it. Never raises: any failure (missing binary, timeout)
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means unknown, reported as None and cached as such — the safe answer keeps
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the node on the relay datapath.
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"""
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import asyncio
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import logging
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import os
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import shutil
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from gns3server.config import Config
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from gns3server.utils.asyncio import subprocess_check_output
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log = logging.getLogger(__name__)
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# binary identity (path, mtime, size, ctime) -> whether -n is available
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# (None = probed and unknown)
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_cache: dict[tuple[str, int, int, int], bool | None] = {}
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_lock = asyncio.Lock()
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# The stable tail of the -n usage line (the flag itself is wrapped in ANSI
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# escapes, the description is not).
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_NO_HOSTCONF_NEEDLE = "do not auto-configure"
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async def probe_vpcs_tap(timeout: float = 5.0) -> bool | None:
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"""
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Whether this host's VPCS binary can anchor a kernel link (tap mode with
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``-n``), probed once per binary identity.
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:returns: True when the usage advertises ``-n``, False when it does not
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(an upstream build), None when the probe failed (unknown binary).
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"""
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config = Config.instance()
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vpcs_path = config.settings.VPCS.vpcs_path
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if not os.path.isabs(vpcs_path):
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vpcs_path = shutil.which(vpcs_path)
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if not vpcs_path or not os.path.isfile(vpcs_path):
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return None
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try:
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stat = os.stat(vpcs_path)
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key = (vpcs_path, stat.st_mtime_ns, stat.st_size, stat.st_ctime_ns)
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except OSError:
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return None
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async with _lock:
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if key in _cache:
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return _cache[key]
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try:
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output = await asyncio.wait_for(subprocess_check_output(vpcs_path, "-h"), timeout=timeout)
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except (TimeoutError, OSError, ValueError) as e:
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log.debug("VPCS tap-mode probe failed: %s", e)
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supported = None
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else:
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supported = _NO_HOSTCONF_NEEDLE in output
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_cache[key] = supported
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return supported
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