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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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10
src/libstore/remote-store.cc
View file

@ -73,8 +73,11 @@ void RemoteStore::initConnection(Connection & conn)
StringSink saved;
TeeSource tee(conn.from, saved);
try {
conn.protoVersion = WorkerProto::BasicClientConnection::handshake(
conn.to, tee, PROTOCOL_VERSION);
auto [protoVersion, features] = WorkerProto::BasicClientConnection::handshake(
conn.to, tee, PROTOCOL_VERSION,
WorkerProto::allFeatures);
conn.protoVersion = protoVersion;
conn.features = features;
} catch (SerialisationError & e) {
/* In case the other side is waiting for our input, close
it. */
@ -88,6 +91,9 @@ void RemoteStore::initConnection(Connection & conn)
static_cast<WorkerProto::ClientHandshakeInfo &>(conn) = conn.postHandshake(*this);
for (auto & feature : conn.features)
debug("negotiated feature '%s'", feature);
auto ex = conn.processStderrReturn();
if (ex) std::rethrow_exception(ex);
}