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WorkerProto: Support fine-grained protocol feature negotiation

Browse source 
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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51
src/libstore/worker-protocol-connection.cc
View file

@ -5,6 +5,8 @@
namespace nix {
const std::set<WorkerProto::Feature> WorkerProto::allFeatures{};
WorkerProto::BasicClientConnection::~BasicClientConnection()
{
try {
@ -137,8 +139,21 @@ void WorkerProto::BasicClientConnection::processStderr(bool * daemonException, S
}
}
WorkerProto::Version
WorkerProto::BasicClientConnection::handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion)
static std::set<WorkerProto::Feature>
intersectFeatures(const std::set<WorkerProto::Feature> & a, const std::set<WorkerProto::Feature> & b)
{
std::set<WorkerProto::Feature> res;
for (auto & x : a)
if (b.contains(x))
res.insert(x);
return res;
}
std::tuple<WorkerProto::Version, std::set<WorkerProto::Feature>> WorkerProto::BasicClientConnection::handshake(
BufferedSink & to,
Source & from,
WorkerProto::Version localVersion,
const std::set<WorkerProto::Feature> & supportedFeatures)
{
to << WORKER_MAGIC_1 << localVersion;
to.flush();
@ -153,11 +168,24 @@ WorkerProto::BasicClientConnection::handshake(BufferedSink & to, Source & from,
if (GET_PROTOCOL_MINOR(daemonVersion) < 10)
throw Error("the Nix daemon version is too old");
return std::min(daemonVersion, localVersion);
auto protoVersion = std::min(daemonVersion, localVersion);
/* Exchange features. */
std::set<WorkerProto::Feature> daemonFeatures;
if (GET_PROTOCOL_MINOR(protoVersion) >= 38) {
to << supportedFeatures;
to.flush();
daemonFeatures = readStrings<std::set<WorkerProto::Feature>>(from);
}
return {protoVersion, intersectFeatures(daemonFeatures, supportedFeatures)};
}
WorkerProto::Version
WorkerProto::BasicServerConnection::handshake(BufferedSink & to, Source & from, WorkerProto::Version localVersion)
std::tuple<WorkerProto::Version, std::set<WorkerProto::Feature>> WorkerProto::BasicServerConnection::handshake(
BufferedSink & to,
Source & from,
WorkerProto::Version localVersion,
const std::set<WorkerProto::Feature> & supportedFeatures)
{
unsigned int magic = readInt(from);
if (magic != WORKER_MAGIC_1)
@ -165,7 +193,18 @@ WorkerProto::BasicServerConnection::handshake(BufferedSink & to, Source & from,
to << WORKER_MAGIC_2 << localVersion;
to.flush();
auto clientVersion = readInt(from);
return std::min(clientVersion, localVersion);
auto protoVersion = std::min(clientVersion, localVersion);
/* Exchange features. */
std::set<WorkerProto::Feature> clientFeatures;
if (GET_PROTOCOL_MINOR(protoVersion) >= 38) {
clientFeatures = readStrings<std::set<WorkerProto::Feature>>(from);
to << supportedFeatures;
to.flush();
}
return {protoVersion, intersectFeatures(clientFeatures, supportedFeatures)};
}
WorkerProto::ClientHandshakeInfo WorkerProto::BasicClientConnection::postHandshake(const StoreDirConfig & store)