[Libevent-users] Re: recv() event not triggering

[Salman Ahmed <salman.isd@xxxxxxxxx>]

Nevermind... what dumb mistakes.... I should be creating events ev,ev1,ev2 AFTER creating  a socket and making it nonblock not before. All events are working fine after rearranging those lines.

On Wed, Feb 12, 2020 at 10:44 PM Salman Ahmed <salman.isd@xxxxxxxxx> wrote:

Pleas ignore the exit(0) in the fail connect() condition. I have removed it since non blocking connect will return <0 anyways. still the output I get is

connecting failed
DISPATCHING
IN CB CONNECT
IN CB CHECKSTATUS
ADDED READ EVENT

On Wed, Feb 12, 2020 at 10:34 PM Salman Ahmed <salman.isd@xxxxxxxxx> wrote:

Hello,

I am trying to connect to the local openvpn client over its managment socket and query its state/status.

I have implemented the follow program with libevent support.

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <event2/event.h>
#include <fcntl.h>
#include <string.h>

char message[1000], server_reply[2000];
struct event *ev, *ev1, *ev2;

void cb_func_hold_release(evutil_socket_t fd, short what, void *arg)
{
    int sock = *(int *)arg;
    struct timeval one_seconds = {1,0};
    printf("IN CB CONNECT\n");
    sprintf (message, "hold release\n");
    if (send (sock, message, strlen (message), 0) < 0) {
        printf("send failed\n");
    }
    event_add(ev1, NULL);
}

void cb_func_write(evutil_socket_t fd, short what, void *arg)
{
    int sock = *(int *)arg;
    printf("IN CB CHECKSTATUS\n");
    sprintf (message, "status\n");
    if (send (sock, message, strlen (message), 0) < 0) {
        printf("send failed\n");
    }
    /*
        int reclen = recv (sock, server_reply, 2000, 0);
        if (reclen < 0) {
            printf("recving failed");
        } else {
            if (reclen > 1) {
                server_reply[reclen-1] = '\0';
            }
            printf("SERVER REPLT< %s\n", server_reply);
        }
        if (strstr(message, "CONNECTED")) {
            printf("VPN CONNECTED");
        }
    */
    event_add(ev2, NULL);
    if (event_pending(ev2,EV_READ|EV_PERSIST, NULL)) {
        printf("ADDED READ EVENT\n");

    }
}

void cb_func_read(evutil_socket_t fd, short what, void *arg)
{
    int sock = *(int *)arg;
    printf("IN CB READ\n");
    int reclen = recv (sock, server_reply, 2000, 0);
    if (reclen < 0) {
        printf("recving failed");
    } else {
        if (reclen > 1) {
            server_reply[reclen-1] = '\0';
        }
        printf("SERVER REPLY %s\n", server_reply);
    }
    if (strstr(message, "CONNECTED")) {
        printf("VPN CONNECTED");
    }

}

int main(void)
{
    int flags;
    int mgmretry = 0;
    int sock = 0;
    struct sockaddr_in server;

    struct timeval five_seconds = {1,0};
    struct event_base *base = event_base_new();


    ev = event_new(base, sock, EV_TIMEOUT, cb_func_hold_release, &sock);
    ev1 = event_new(base, sock, EV_WRITE, cb_func_write, &sock);
    ev2 = event_new(base, sock, EV_READ, cb_func_read, &sock);

    sock = socket (AF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        printf("COUILD NOT CREATE SOCKET\n");
        exit(0);
    }

    evutil_make_socket_nonblocking(sock);

    server.sin_addr.s_addr = inet_addr("127.0.0.1");
    server.sin_family = AF_INET;
    server.sin_port = htons (12345);

    if (connect (sock, (struct sockaddr *)&server, sizeof (server)) < 0) {
        printf("connecting failed\n");
        exit(0);
    }



    event_add(ev, &five_seconds);
    printf("DISPATCHING\n");
    event_base_dispatch(base);

}

The issue is the the read callback "cb_func_read" is not being triggered. My expectation is that after I send the "status" message to the vpn from cb_func_write(), there is some data sent back which should trigger the read callback but that's not happening.

If I recv() directly after send() in the write callback(the commented portion) I can print the response sent from openvpn so the communication between these two are working.