/*

 * udev-kvm-check.c

 *

 * Copyright 2018 Red Hat, Inc.

 *

 * This is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

#include <ctype.h>

#include <syslog.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define DEFAULT 0

#define FACILITY "kvm"

#define SYSCONFIG_KVM "/etc/sysconfig/kvm"

#define COUNT_MSG \

    "%d %s now active"

#define SUBSCRIPTION_MSG \

    "%d %s now active; your Red Hat Enterprise Linux subscription" \

    " limit is %d guests. Please review your Red Hat Enterprise Linux" \

    " subscription agreement or contact your Red Hat" \

    " support representative for more information. You" \

    " may review the Red Hat Enterprise subscription" \

    " limits at http://www.redhat.com/rhel-virt-limits"

int get_threshold_from_file(FILE *fp)

{

    static const char key[] = "THRESHOLD=";

    int pos = 0;

    int thres;

    int ch;

start:

    /* State START - at beginning of line, search for beginning of "THRESHOLD="

     * string.

     */

    ch = getc(fp);

    if (ch == EOF) {

        return DEFAULT;

    }

    if (isspace(ch)) {

        goto start;

    }

    if (ch == 'T') {

        pos = 1;

        goto key;

    }

    goto eol;

eol:

    /* State EOL - loop until end of line */

    ch = getc(fp);

    if (ch == EOF) {

        return DEFAULT;

    }

    if (ch == '\n') {

        goto start;

    }

    goto eol;

key:

    /* State KEY - match "THRESHOLD=" string, go to THRESHOLD if found */

    ch = getc(fp);

    if (ch == EOF) {

        return DEFAULT;

    }

    if (ch == key[pos]) {

        pos++;

        if (key[pos] == 0) {

            goto threshold;

        } else {

            goto key;

        }

    }

    goto eol;

threshold:

    /* State THRESHOLD - parse number using fscanf, expect comment or space

     * or EOL.

     */

    ch = getc(fp);

    if (ch == EOF) {

        return DEFAULT;

    }

    if (!isdigit(ch)) {

        goto eol;

    }

    ungetc(ch, fp);

    if (fscanf(fp, "%d", &thres) != 1) {

        return DEFAULT;

    }

    ch = getc(fp);

    if (ch == '#' || ch == EOF || ch == '\n' || isspace(ch)) {

        return thres;

    }

    goto eol;

}

int get_threshold()

{

    FILE *fp = fopen(SYSCONFIG_KVM, "r");

    int val;

    if (!fp) {

        return DEFAULT;

    }

    val = get_threshold_from_file(fp);

    fclose (fp);

    return val;

}

const char *guest(int count)

{

    return (count == 1 ? "guest" : "guests");

}

void emit_count_message(int count)

{

    openlog(FACILITY, LOG_CONS, LOG_USER);

    syslog(LOG_INFO, COUNT_MSG, count, guest(count));

    closelog();

}

void emit_subscription_message(int count, int threshold)

{

    openlog(FACILITY, LOG_CONS, LOG_USER);

    syslog(LOG_WARNING, SUBSCRIPTION_MSG, count, guest(count), threshold);

    closelog();

}

int main(int argc, char **argv)

{

    int count, threshold;

    if (argc < 3)

        exit(1);

    count = atoi(argv[1]);

    threshold = get_threshold();

    if (!strcmp(argv[2], "create")) {

        if (threshold == 0) {

            emit_count_message(count);

        } else if (count > threshold) {

            emit_subscription_message(count, threshold);

        }

    } else {

        if (count >= threshold) {

            emit_count_message(count);

        }

    }

    return 0;

}