Re: [Libevent-users] Bug in win32_dispatch?

[Mark Ellzey <mthomas@xxxxxxxxxx>]

On Wed, May 13, 2015 at 05:32:51PM +0300, Alexey Simak wrote:
> Hi,
> 
> We are using libevent in the next scenario:
> 
> 1) Create nonblocking socket.
> 2) Call "connect()" on it.
> 3) Create an event for socket and wait in event_base_dispatch() for
> socket events.
> 4) Check for EV_TIMEOUT, EV_READ or EV_WRITE passed to callback.
> 
> There is a problem on win32:
> 
> When we are connecting to a destination that is not listening on the
> socket, we receive
> EV_WRITE event, which is not correct from my point of view.
> 
> The problem is in win32_dispatch from win32select.c:
> 
> 
>    res = select(fd_count,
>             (struct fd_set*)win32op->readset_out,
>             (struct fd_set*)win32op->writeset_out,
>             (struct fd_set*)win32op->exset_out, tv);
> 
>    EVBASE_ACQUIRE_LOCK(base, th_base_lock);
> 
>    event_debug(("%s: select returned %d", __func__, res));
> 
>    if (res <= 0) {
>        return res;
>    }
> 
>    if (win32op->readset_out->fd_count) {
>        i = rand() % win32op->readset_out->fd_count;
>        for (j=0; j<win32op->readset_out->fd_count; ++j) {
>            if (++i >= win32op->readset_out->fd_count)
>                i = 0;
>            s = win32op->readset_out->fd_array[i];
>            evmap_io_active(base, s, EV_READ);
>        }
>    }
>    if (win32op->exset_out->fd_count) {
>        i = rand() % win32op->exset_out->fd_count;
>        for (j=0; j<win32op->exset_out->fd_count; ++j) {
>            if (++i >= win32op->exset_out->fd_count)
>                i = 0;
>            s = win32op->exset_out->fd_array[i];
>            evmap_io_active(base, s, EV_WRITE);
>        }
>    }
>    if (win32op->writeset_out->fd_count) {
>        SOCKET s;
>        i = rand() % win32op->writeset_out->fd_count;
>        for (j=0; j<win32op->writeset_out->fd_count; ++j) {
>            if (++i >= win32op->writeset_out->fd_count)
>                i = 0;
>            s = win32op->writeset_out->fd_array[i];
>            evmap_io_active(base, s, EV_WRITE);
>        }
>    }
>    return (0);
> 
> 
> As you see, EV_WRITE is returned if there is some socket error.
> 
> Is this behaviour a bug or "as designed"?



What version are you using?


(I created a ticket for this here: https://github.com/libevent/libevent/issues/248)


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