[Backport 2.32-maintenance] Restore ServeProto::Command::ImportPaths

src/libstore/include/nix/store/serve-protocol-connection.hh

@@ -82,6 +82,8 @@ struct ServeProto::BasicClientConnection
     BuildResult getBuildDerivationResponse(const StoreDirConfig & store);
 
     void narFromPath(const StoreDirConfig & store, const StorePath & path, std::function<void(Source &)> fun);
+
+    void importPaths(const StoreDirConfig & store, std::function<void(Sink &)> fun);
 };
 
 struct ServeProto::BasicServerConnection

src/libstore/include/nix/store/serve-protocol.hh

@@ -108,6 +108,13 @@ enum struct ServeProto::Command : uint64_t {
     QueryValidPaths = 1,
     QueryPathInfos = 2,
     DumpStorePath = 3,
+    /**
+     * @note This is no longer used by Nix (as a client), but it is used
+     * by Hydra. We should therefore not remove it until Hydra no longer
+     * uses it either.
+     */
+    ImportPaths = 4,
+    // ExportPaths = 5,
     BuildPaths = 6,
     QueryClosure = 7,
     BuildDerivation = 8,

src/libstore/serve-protocol-connection.cc

@@ -93,4 +93,14 @@ void ServeProto::BasicClientConnection::narFromPath(
     fun(from);
 }
 
+void ServeProto::BasicClientConnection::importPaths(const StoreDirConfig & store, std::function<void(Sink &)> fun)
+{
+    to << ServeProto::Command::ImportPaths;
+    fun(to);
+    to.flush();
+
+    if (readInt(from) != 1)
+        throw Error("remote machine failed to import closure");
+}
+
 } // namespace nix

src/nix/nix-store/nix-store.cc

@@ -986,6 +986,16 @@ static void opServe(Strings opFlags, Strings opArgs)
             store->narFromPath(store->parseStorePath(readString(in)), out);
             break;
 
+        case ServeProto::Command::ImportPaths: {
+            if (!writeAllowed)
+                throw Error("importing paths is not allowed");
+            // FIXME: should we skip sig checking?
+            importPaths(*store, in, NoCheckSigs);
+            // indicate success
+            out << 1;
+            break;
+        }
+
         case ServeProto::Command::BuildPaths: {
 
             if (!writeAllowed)