mirror of
https://github.com/GNS3/gns3-server.git
synced 2026-10-12 13:35:31 +03:00
116 lines
3.4 KiB
Python
116 lines
3.4 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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Optional optimistic concurrency (ETag / If-Match) for controller resources.
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"""
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import asyncio
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import contextlib
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import hashlib
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import json
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from typing import Any, AsyncIterator, Optional
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from fastapi import Header, HTTPException, Response, status
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from fastapi.encoders import jsonable_encoder
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from gns3server import schemas
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ETAG_RESPONSE_HEADERS: dict[str, Any] = {
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"ETag": {
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"description": "Entity tag of the current representation of the resource",
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"schema": {"type": "string"},
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}
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}
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PRECONDITION_FAILED_RESPONSE: dict[int | str, dict[str, Any]] = {
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status.HTTP_412_PRECONDITION_FAILED: {
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"model": schemas.ErrorMessage,
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"description": "The If-Match header does not match the current ETag of the resource",
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}
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}
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GET_RESPONSES: dict[int | str, dict[str, Any]] = {status.HTTP_200_OK: {"headers": ETAG_RESPONSE_HEADERS}}
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PUT_RESPONSES: dict[int | str, dict[str, Any]] = {**GET_RESPONSES, **PRECONDITION_FAILED_RESPONSE}
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_locks: dict[str, list[Any]] = {}
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def compute_etag(resource: Any) -> str:
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"""
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Compute a strong entity tag from the serialized resource.
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"""
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payload = json.dumps(jsonable_encoder(resource), sort_keys=True, separators=(",", ":"), default=str)
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return f'"{hashlib.sha256(payload.encode()).hexdigest()[:32]}"'
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def set_etag(response: Response, resource: Any) -> None:
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"""
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Add the ETag header of the resource to the response.
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"""
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response.headers["ETag"] = compute_etag(resource)
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def if_match_header(
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if_match: Optional[str] = Header(
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None,
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alias="If-Match",
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description="Only apply the update if this entity tag matches the current resource",
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),
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) -> Optional[str]:
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"""
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Dependency returning the raw If-Match request header.
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"""
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return if_match
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def check_if_match(if_match: Optional[str], resource: Any) -> None:
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"""
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Raise a 412 error if If-Match is present and does not match the resource.
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"""
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if if_match is None:
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return
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candidates = [tag.strip() for tag in if_match.split(",")]
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if "*" in candidates:
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return
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if compute_etag(resource) not in candidates:
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raise HTTPException(
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status_code=status.HTTP_412_PRECONDITION_FAILED,
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detail="The resource was modified since it was last retrieved (If-Match does not match the current ETag)",
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)
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@contextlib.asynccontextmanager
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async def serialize_updates(key: str) -> AsyncIterator[None]:
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"""
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Serialize updates of the same resource so that the If-Match check and the update are atomic.
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"""
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entry = _locks.setdefault(key, [asyncio.Lock(), 0])
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entry[1] += 1
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try:
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async with entry[0]:
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yield
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finally:
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entry[1] -= 1
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if entry[1] <= 0:
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_locks.pop(key, None)
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