static int udp_read(URLContext *h, uint8_t *buf, int size)
{
    UDPContext *s = h->priv_data;
    struct pollfd p = {s->udp_fd, POLLIN, 0};
    int len;
    int ret;

    for(;;) {
        if (url_interrupt_cb())
            return AVERROR_EXIT;
        ret = poll(&p, 1, 100);
        if (ret < 0) {
            if (ff_neterrno() == AVERROR(EINTR))
                continue;
            return AVERROR(EIO);
        }
        if (!(ret == 1 && p.revents & POLLIN))
            continue;
        len = recv(s->udp_fd, buf, size, 0);
        if (len < 0) {
            if (ff_neterrno() != AVERROR(EAGAIN) &&
                ff_neterrno() != AVERROR(EINTR))
                return AVERROR(EIO);
        } else {
            break;
        }
    }
    return len;
}