Fix race condition when creating socket folder

If two processes call `mkdir` at the same time, the second one will fail
and wrongly assume the folder wasn't created properly.

We now first check if the folder really doesn't exist and we also catch
any IPC initialization errors and disable IPC instead of crashing the
whole bar.

src/ipc/util.cpp

@@ -20,8 +20,11 @@ namespace ipc {
   string ensure_runtime_path() {
     string runtime_path = get_runtime_path();
     if (!file_util::exists(runtime_path) && mkdir(runtime_path.c_str(), 0700) == -1) {
+      // It's possible the folder was created in the meantime, we have to check again.
+      if (!file_util::exists(runtime_path)) {
         throw system_error("Failed to create ipc socket folders");
       }
+    }
 
     return runtime_path;
   }

src/main.cpp

@@ -148,7 +148,12 @@ int main(int argc, char** argv) {
     unique_ptr<ipc::ipc> ipc{};
 
     if (conf.get(conf.section(), "enable-ipc", false)) {
+      try {
         ipc = ipc::ipc::make(loop);
+      } catch (const std::exception& e) {
+        ipc.reset();
+        logger.err("Disabling IPC channels due to error: %s", e.what());
+      }
     }
 
     auto ctrl = controller::make((bool)ipc, loop);