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be130bc880
Summary: Whilst chatting with simpkins we realized that we lost the handshake portion of the takeover protocol during a refactor. The handshake is important for a couple of reasons: 1. It prevents unmounting and loosing all the mounts in the case that sometime decides to netcat or otherwise connect to the socket 2. It gives us an opportunity to short circuit any heavy lifting if we know that it will be impossible to succeed. 3. It allows us to rollback to earlier builds with older versions of the takeover protocol. This diff adds a little bit of machinery to enable passing a set of supported takeover protocol version numbers. The intent is to retain support for the two of these at a time; any time we change the encoding/protocol for takeover we'll bump the version number and add supporting code to handle the new format, retaining support for the prior version. Retaining the ability to handle the prior version allows us to downgrade to an earlier build gracefully if/when the need arises. I opted to do this here rather than by bumping the `kProtocolID` constant in `UnixSocket.h` becase we're not really changing the lowest level of the protocol; just the takeover specific portions. I haven't actually changed the takeover serialization in this diff, but do have some work on that happening in D6733406; that diff will be amended to take advantage and demonstrate how this versioning scheme works. A key thing to note about the implementation of this diff is that the client sends the version number to the server, but doesn't add any explicit version encoding in the response we receive. This is deliberate and allows us to upgrade prior builds to this new scheme. I'll add a more definitive check for this situation when I actually rev the format in the following diff. Reviewed By: simpkins Differential Revision: D6743065 fbshipit-source-id: c991cebfee918daad098105ca6bcfef76374c0ff
32 lines
929 B
C++
32 lines
929 B
C++
/*
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* Copyright (c) 2004-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*
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*/
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#pragma once
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#include "eden/fs/takeover/TakeoverData.h"
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#include "eden/fs/utils/PathFuncs.h"
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namespace facebook {
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namespace eden {
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/**
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* Request to take over mount points from an existing edenfs process.
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*
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* Returns a TakeoverData object on success, or throws an exception on error.
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*/
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TakeoverData takeoverMounts(
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AbsolutePathPiece socketPath,
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// this parameter is present for testing purposes and should not normally
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// be used in the production build.
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const std::set<int32_t>& supportedTakeoverVersions =
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kSupportedTakeoverVersions);
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} // namespace eden
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} // namespace facebook
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