Fixed SIGPIPE problem (#2411, #2312)

lib/core/ogs-epoll.c

@@ -227,7 +227,22 @@ static int epoll_process(ogs_pollset_t *pollset, ogs_time_t timeout)
 
         received = context->event_list[i].events;
         if (received & EPOLLERR) {
+        /*
+         * The libevent library has OGS_POLLOUT turned on in EPOLLERR.
+         *
+         * However, SIGPIPE can occur if write() is called
+         * when the peer connection is closed.
+         *
+         * Therefore, Open5GS turns off OGS_POLLOUT
+         * so that write() cannot be called in case of EPOLLERR.
+         *
+         * See also #2411 and #2312
+         */
+#if 0
             when = OGS_POLLIN|OGS_POLLOUT;
+#else
+            when = OGS_POLLIN;
+#endif
         } else if ((received & EPOLLHUP) && !(received & EPOLLRDHUP)) {
             when = OGS_POLLIN|OGS_POLLOUT;
         } else {