libevent based echo server got stuck - c

Question

Here is an libevent based on echoServer with a little bit of my tweak (very minor).
The question is, when running a client simulation again, it appears to be stuck. Here is how the client does: it open a TCP connection to this server, send a small data (about 20B) and wait for a reply, then it close the connection with TCP RST and then repeat.
After thousands (sometimes ~20000) iterations, the client stopped.
Wireshark listening on loopback interface showed that when it stopped, the last TCP session has data sent from client, but the server was not echoing/sending it back to client, causing the client to hang.
Any ideas? Thanks in advance!
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <netinet/tcp.h>
#include <event.h>
#include <event2/listener.h>
#include <event2/bufferevent_ssl.h>
struct event_base *base;
static void echo_read_cb(struct bufferevent *bev, void *ctx) {
/* This callback is invoked when there is data to read on bev. */
struct evbuffer *input = bufferevent_get_input(bev);
struct evbuffer *output = bufferevent_get_output(bev);
/* Copy all the data from the input buffer to the output buffer. */
int ret = evbuffer_add_buffer(output, input);
if (ret) {
printf("error happened when adding buf\n");
}
}
static void echo_event_cb(struct bufferevent *bev, short events, void *ctx) {
if (events & (BEV_EVENT_EOF|BEV_EVENT_ERROR)) {
int fd = bufferevent_getfd(bev);
evutil_closesocket(fd);
bufferevent_free(bev);
return;
}
}
static void accept_error_cb(struct evconnlistener *listener, void *ctx) {
struct event_base *base = evconnlistener_get_base(listener);
int err = EVUTIL_SOCKET_ERROR();
fprintf(stderr, "Got an error %d (%s) on the listener. "
"Shutting down.\n", err, evutil_socket_error_to_string(err));
}
static void accept_conn_cb(struct evconnlistener *serv, int sock, struct sockaddr *sa,
int sa_len, void *arg) {
struct bufferevent *bev = bufferevent_socket_new(
base, sock, BEV_OPT_CLOSE_ON_FREE);
int flag = 1;
setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (char *) &flag, sizeof(int));
bufferevent_setcb(bev, echo_read_cb, NULL, echo_event_cb, NULL);
bufferevent_enable(bev, EV_READ|EV_WRITE);
}
int main(int argc, char **argv) {
struct evconnlistener *listener;
struct sockaddr_in sin;
memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(9999);
sin.sin_addr.s_addr = htonl(0x7f000001); /* 127.0.0.1 */
base = event_base_new();
listener = evconnlistener_new_bind(base, accept_conn_cb, NULL,
LEV_OPT_CLOSE_ON_FREE|LEV_OPT_REUSEABLE, -1,
(struct sockaddr*)&sin, sizeof(sin));
if (!listener) {
perror("Couldn't create listener");
return 1;
}
evconnlistener_set_error_cb(listener, accept_error_cb);
event_base_loop(base, 0);
evconnlistener_free(listener);
return 0;
}

Answer 1

Figured out the cause of the problem: in the function echo_event_cb, there is a call evutil_closesocket(fd); This is not only unnecessary, it's harmful! After the call to close socket is removed, it works perfect.
It's unnecessary because the bufferedevent was created with BEV_OPT_CLOSE_ON_FREE.