static int
rcv_kern(int sock, void *buf, int len, struct sockaddr *addr,
     socklen_t *addrlen)
{
    struct timeval timeout = {1, 0};
    fd_set set;
    int status;

    FD_SET(sock, &set);
    if ((status = select(sock + 1, &set, NULL, NULL, &timeout)) == 0) {
    	FD_ZERO(&set);
    	fprintf(stderr,
    		"timeout while receiving answer from kerneln");
    	exit(1);
    } else if (status == -1) {
    	FD_ZERO(&set);
    	perror("recvfrom failed");
    	exit(1);
    }
    FD_ZERO(&set);
    return recvfrom(sock, buf, len, 0, addr, addrlen);
}

static int
rcv_kern(int sock, void *buf, int len, struct sockaddr *addr,
     socklen_t *addrlen)
{
    struct timeval timeout = {1, 0};
    fd_set set;
    int status;

    FD_ZERO(&set);
    FD_SET(sock, &set);
    if ((status = select(sock + 1, &set, NULL, NULL, &timeout)) == 0) {
        fprintf(stderr,
                "timeout while receiving answer from kerneln");
        exit(1);
    } else if (status < 0) {
        perror("recvfrom failed");
        exit(1);
    }
    if ((status = recvfrom(sock, buf, len, 0, addr, addrlen)) < 0) {
        perror("recvfrom error");
        exit(1);
    }
    if (status == 0) {
        fprintf(stderr, "kernel closed socketn");
        exit(1);
    }
    return status;
}