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WorkerProto: Support fine-grained protocol feature negotiation

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Currently, the worker protocol has a version number that we increment
whenever we change something in the protocol. However, this can cause
a collision between Nix PRs / forks that make protocol changes
(e.g. PR #9857 increments the version, which could collide with
another PR). So instead, the client and daemon now exchange a set of
protocol features (such as `auth-forwarding`). They will use the
intersection of the sets of features, i.e. the features they both
support.

Note that protocol features are completely distinct from
`ExperimentalFeature`s.
This commit is contained in:
Eelco Dolstra 2024-07-19 15:48:19 +02:00
parent b13ba7490c
commit 3be7c0037e
6 changed files with 127 additions and 29 deletions
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27
src/libstore/worker-protocol-connection.hh
View file

@ -23,6 +23,11 @@ struct WorkerProto::BasicConnection
*/
WorkerProto::Version protoVersion;
/**
* The set of features that both sides support.
*/
std::set<Feature> features;
/**
* Coercion to `WorkerProto::ReadConn`. This makes it easy to use the
* factored out serve protocol serializers with a
@ -72,8 +77,8 @@ struct WorkerProto::BasicClientConnection : WorkerProto::BasicConnection
/**
* Establishes connection, negotiating version.
*
* @return the version provided by the other side of the
* connection.
* @return the minimum version supported by both sides and the set
* of protocol features supported by both sides.
*
* @param to Taken by reference to allow for various error handling
* mechanisms.
@ -82,8 +87,15 @@ struct WorkerProto::BasicClientConnection : WorkerProto::BasicConnection
* handling mechanisms.
*
* @param localVersion Our version which is sent over
*
* @param features The protocol features that we support
*/
static Version handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion);
// FIXME: this should probably be a constructor.
static std::tuple<Version, std::set<Feature>> handshake(
BufferedSink & to,
Source & from,
WorkerProto::Version localVersion,
const std::set<Feature> & supportedFeatures);
/**
* After calling handshake, must call this to exchange some basic
@ -138,8 +150,15 @@ struct WorkerProto::BasicServerConnection : WorkerProto::BasicConnection
* handling mechanisms.
*
* @param localVersion Our version which is sent over
*
* @param features The protocol features that we support
*/
static WorkerProto::Version handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion);
// FIXME: this should probably be a constructor.
static std::tuple<Version, std::set<Feature>> handshake(
BufferedSink & to,
Source & from,
WorkerProto::Version localVersion,
const std::set<Feature> & supportedFeatures);
/**
* After calling handshake, must call this to exchange some basic