fix: Handle errors when calling fcntl

src/net/tcp_client.cpp

@@ -126,7 +126,13 @@ tcp_client::tcp_client(
             if (connect(socket_candidate.get(), socket_identifier.ptr(), socket_identifier.size()) == 0) {
                 status = 0;
                 this->net_socket = std::forward<auto_fd>(socket_candidate);
-                fcntl(this->net_socket.get(), F_SETFL, fcntl(this->net_socket.get(), F_GETFL, 0) | O_NONBLOCK);
+
+                if (
+                    const auto existing_fd_flags = fcntl(this->net_socket.get(), F_GETFL, 0);
+                    existing_fd_flags == -1 || fcntl(this->net_socket.get(), F_SETFL, existing_fd_flags | O_NONBLOCK) == -1
+                ) {
+                    throw netio_exception("Failed to set socket mode. fcntl resulted in error:" + std::to_string(errno));
+                }
 
                 // Hier bin ich mir nicht sicher, wie ich das am besten mache. Auch mit socketaddr und type cast ist das irgendwie doof.
                 // Das Problem besteht darin, dass erst nach erfolgreichem connect der Port auf dieser Seite bekannt ist.

src/net/tcp_server_socket.cpp

@@ -105,7 +105,13 @@ void tcp_server_socket::await_raw_socket_incomming(
         throw netio_exception("Unable to bind incoming client");
     }
 
-    fcntl(client_fd_raw, F_SETFL, fcntl(client_fd_raw, F_GETFL, 0) | O_NONBLOCK);
+    auto flags = O_NONBLOCK;
+    if (
+        const auto existing_fd_flags = fcntl(client_fd_raw, F_GETFL, 0);
+        existing_fd_flags == -1 || fcntl(client_fd_raw, F_SETFL, existing_fd_flags | flags) == -1
+    ) {
+        throw netio_exception("Failed to set socket mode. fcntl resulted in error:" + std::to_string(errno));
+    }
 
     const std::string address = inet_ntoa(client_addr.sin_addr);
     const uint16_t port = ntohs(client_addr.sin_port);