libstore: move daemon protocol struct out of Settings

we'll use this to create a registry of protocols the system understands.
also use this struct during connection setup to make that simpler later.

Change-Id: Ifa481fea7ea2efa2a1f1be4d81076a9e022d24f9

lix/libstore/globals.hh

@@ -10,6 +10,13 @@
 
 namespace nix {
 
+namespace daemon {
+struct Protocol
+{
+    Path path;
+};
+}
+
 typedef enum { smEnabled, smRelaxed, smDisabled } SandboxMode;
 
 void to_json(JSON & j, const SandboxMode & e);
@@ -63,14 +70,7 @@ const uint32_t maxIdsPerBuild =
 
 class Settings : public Config
 {
-public:
-    struct DaemonSocketPath
-    {
-        Path path;
-    };
-
-private:
-    std::list<DaemonSocketPath> nixDaemonSockets_;
+    std::list<daemon::Protocol> nixDaemonSockets_;
 
     unsigned int getDefaultCores();
 
@@ -128,7 +128,7 @@ public:
     /**
      * Socket paths a client should connect to, in order of decreasing preference.
      */
-    const std::list<DaemonSocketPath> & nixDaemonSockets() const
+    const std::list<daemon::Protocol> & nixDaemonSockets() const
     {
         return nixDaemonSockets_;
     }

lix/libstore/uds-remote-store.cc

@@ -59,23 +59,26 @@ std::string UDSRemoteStore::getUri()
     }
 }
 
-static void connectToFirstAvailableSocket(AutoCloseFD & sockFD, const std::list<Path> & paths)
+static void connectToFirstAvailableSocket(AutoCloseFD & sockFD, const std::list<daemon::Protocol> & paths)
 {
     for (const auto & socket : paths) {
         try {
-            nix::connect(sockFD.get(), socket);
+            nix::connect(sockFD.get(), socket.path);
             return;
         } catch (SysError & e) {
             if (e.errNo == EACCES || e.errNo == EPERM || e.errNo == ECONNREFUSED || e.errNo == ENOENT
                 || e.errNo == ENOTDIR || e.errNo == ENOTSOCK)
             {
-                debug("skipping socket %s: %s", socket, strerror(e.errNo));
+                debug("skipping socket %s: %s", socket.path, strerror(e.errNo));
             } else {
                 throw;
             }
         }
     }
-    throw Error("could not connect to any lix socket (tried %s)", concatStringsSep(", ", paths));
+    throw Error(
+        "could not connect to any lix socket (tried %s)",
+        concatMapStringsSep(", ", paths, [](auto & s) { return s.path; })
+    );
 }
 
 kj::Promise<Result<ref<RemoteStore::Connection>>> UDSRemoteStore::openConnection()
@@ -85,24 +88,22 @@ try {
     /* Connect to a daemon that does the privileged work for us. */
     conn->fd = createUnixDomainSocket();
 
-    std::list<Path> candidates;
+    std::list<daemon::Protocol> candidates;
 
     if (path) {
         if (config().protocol == "any") {
-            candidates.emplace_back(*path + LEGACY_SOCKET_COMBINED);
+            candidates.push_back(daemon::Protocol{*path + LEGACY_SOCKET_COMBINED});
         } else {
             for (const auto & proto : tokenizeString<std::list<std::string>>(config().protocol.get(), " ,")) {
                 if (proto == "legacy-combined") {
-                    candidates.emplace_back(*path);
+                    candidates.push_back(daemon::Protocol{*path});
                 } else {
                     throw Error("can't connect to %s with unknown daemon protocol %s", *path, proto);
                 }
             }
         }
     } else {
-        candidates = settings.nixDaemonSockets()
-            | std::views::transform([](auto & socket) { return socket.path; })
-            | std::ranges::to<std::list<Path>>();
+        candidates = settings.nixDaemonSockets();
     }
 
     connectToFirstAvailableSocket(conn->fd, candidates);

lix/nix/daemon.cc

@@ -340,7 +340,7 @@ static std::pair<TrustedFlag, std::string> authPeer(const PeerInfo & peer)
 
 static kj::Promise<Result<void>> daemonLoopForSocket(
     const Path & self,
-    const Settings::DaemonSocketPath & socket,
+    const daemon::Protocol & socket,
     AutoCloseFD & fdSocket,
     std::optional<TrustedFlag> forceTrustClientOpt
 )
@@ -437,7 +437,7 @@ try {
         return *tmp;
     }();
 
-    std::list<std::pair<Settings::DaemonSocketPath, AutoCloseFD>> sockets;
+    std::list<std::pair<daemon::Protocol, AutoCloseFD>> sockets;
     for (auto & socket : settings.nixDaemonSockets()) {
         createDirs(dirOf(socket.path));
         sockets.emplace_back(socket, createUnixDomainSocket(socket.path, 0666));