nix store ping: Report Nix daemon version

Fixes #5952.

doc/manual/src/release-notes/rl-next.md

@@ -1,2 +1,3 @@
 # Release X.Y (202?-??-??)
 
+* `nix store ping` now reports the version of the remote Nix daemon.

src/libstore/daemon.cc

@@ -981,7 +981,11 @@ void processConnection(
         readInt(from);
     }
 
-    readInt(from); // obsolete reserveSpace
+    if (GET_PROTOCOL_MINOR(clientVersion) >= 11)
+        readInt(from); // obsolete reserveSpace
+
+    if (GET_PROTOCOL_MINOR(clientVersion) >= 33)
+        to << nixVersion;
 
     /* Send startup error messages to the client. */
     tunnelLogger->startWork();

src/libstore/local-store.cc

@@ -1919,4 +1919,10 @@ void LocalStore::addBuildLog(const StorePath & drvPath, std::string_view log)
         throw SysError("renaming '%1%' to '%2%'", tmpFile, logPath);
 }
 
+std::optional<std::string> LocalStore::getVersion()
+{
+    return nixVersion;
+}
+
+
 }  // namespace nix

src/libstore/local-store.hh

@@ -211,6 +211,8 @@ public:
     void queryRealisationUncached(const DrvOutput&,
         Callback<std::shared_ptr<const Realisation>> callback) noexcept override;
 
+    std::optional<std::string> getVersion() override;
+
 private:
 
     int getSchema();

src/libstore/remote-store.cc

@@ -188,7 +188,12 @@ void RemoteStore::initConnection(Connection & conn)
         }
 
         if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 11)
-            conn.to << false;
+            conn.to << false; // obsolete reserveSpace
+
+        if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 33) {
+            conn.to.flush();
+            conn.daemonNixVersion = readString(conn.from);
+        }
 
         auto ex = conn.processStderr();
         if (ex) std::rethrow_exception(ex);
@@ -920,6 +925,13 @@ void RemoteStore::addBuildLog(const StorePath & drvPath, std::string_view log)
 }
 
 
+std::optional<std::string> RemoteStore::getVersion()
+{
+    auto conn(getConnection());
+    return conn->daemonNixVersion;
+}
+
+
 void RemoteStore::connect()
 {
     auto conn(getConnection());

src/libstore/remote-store.hh

@@ -118,6 +118,8 @@ public:
 
     void addBuildLog(const StorePath & drvPath, std::string_view log) override;
 
+    std::optional<std::string> getVersion() override;
+
     void connect() override;
 
     unsigned int getProtocol() override;
@@ -129,6 +131,7 @@ public:
         FdSink to;
         FdSource from;
         unsigned int daemonVersion;
+        std::optional<std::string> daemonNixVersion;
         std::chrono::time_point<std::chrono::steady_clock> startTime;
 
         virtual ~Connection();

src/libstore/store-api.hh

@@ -765,6 +765,9 @@ public:
      * (a no-op when there’s no daemon)
      */
     virtual void setOptions() { }
+
+    virtual std::optional<std::string> getVersion() { return {}; }
+
 protected:
 
     Stats stats;

src/libstore/worker-protocol.hh

@@ -9,7 +9,7 @@ namespace nix {
 #define WORKER_MAGIC_1 0x6e697863
 #define WORKER_MAGIC_2 0x6478696f
 
-#define PROTOCOL_VERSION (1 << 8 | 32)
+#define PROTOCOL_VERSION (1 << 8 | 33)
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 

src/nix/ping-store.cc

@@ -20,7 +20,10 @@ struct CmdPingStore : StoreCommand
 
     void run(ref<Store> store) override
     {
+        notice("Store URL: %s", store->getUri());
         store->connect();
+        if (auto version = store->getVersion())
+            notice("Version: %s", *version);
     }
 };