config.c

/*
 *	Process Isolator -- Configuration File
 *
 *	(c) 2016 Martin Mares <mj@ucw.cz>
 *
 *	(c) 2020-2021 Vasiluta Mihai-Alexandru <alexv@siluta.ro>
 */

#include "isolate.h"

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_LINE_LEN 1024

char *cf_box_root;
char *cf_cg_root;
char *cf_cg_parent;
int cf_first_uid;
int cf_first_gid;
int cf_num_boxes;

static int line_number;
static struct cf_per_box *per_box_configs;

static void NONRET cf_err(char *msg)
{
    die("Error in config file, line %d: %s", line_number, msg);
}

static char *cf_string(char *val)
{
    return xstrdup(val);
}

static int cf_int(char *val)
{
    char *end;
    errno = 0;
    long int x = strtol(val, &end, 10);
    if (errno || end == val || end && *end)
        cf_err("Invalid number");
    if ((long int)(int)x != x)
        cf_err("Number out of range");
    return x;
}

static void cf_entry_toplevel(char *key, char *val)
{
    if (!strcmp(key, "box_root"))
        cf_box_root = cf_string(val);
    else if (!strcmp(key, "cg_root"))
        cf_cg_root = cf_string(val);
    else if (!strcmp(key, "cg_parent"))
        cf_cg_parent = cf_string(val);
    else if (!strcmp(key, "first_uid"))
        cf_first_uid = cf_int(val);
    else if (!strcmp(key, "first_gid"))
        cf_first_gid = cf_int(val);
    else if (!strcmp(key, "num_boxes"))
        cf_num_boxes = cf_int(val);
    else
        cf_err("Unknown configuration item");
}

static void cf_entry_compound(char *key, char *subkey, char *val)
{
    if (strncmp(key, "box", 3))
        cf_err("Unknown configuration section");
    int box_id = cf_int(key + 3);
    struct cf_per_box *c = cf_per_box(box_id);

    if (!strcmp(subkey, "cpus"))
        c->cpus = cf_string(val);
    else if (!strcmp(subkey, "mems"))
        c->mems = cf_string(val);
    else
        cf_err("Unknown per-box configuration item");
}

static void cf_entry(char *key, char *val)
{
    char *dot = strchr(key, '.');
    if (!dot)
        cf_entry_toplevel(key, val);
    else
    {
        *dot++ = 0;
        cf_entry_compound(key, dot, val);
    }
}

static void cf_check(void)
{
    if (!cf_box_root ||
        !cf_cg_root ||
        !cf_first_uid ||
        !cf_first_gid ||
        !cf_num_boxes)
        cf_err("Configuration is not complete");
}

void cf_parse(void)
{
    FILE *f = fopen(CONFIG_FILE, "r");
    if (!f)
        die("Cannot open %s: %m", CONFIG_FILE);

    char line[MAX_LINE_LEN];
    while (fgets(line, sizeof(line), f))
    {
        line_number++;
        char *nl = strchr(line, '\n');
        if (!nl)
            cf_err("Line not terminated or too long");
        *nl = 0;

        if (!line[0] || line[0] == '#')
            continue;

        char *s = line;
        while (*s && *s != ' ' && *s != '\t' && *s != '=')
            s++;
        while (*s == ' ' || *s == '\t')
            *s++ = 0;
        if (*s != '=')
            cf_err("Syntax error, expecting key=value");
        *s++ = 0;
        while (*s == ' ' || *s == '\t')
            *s++ = 0;

        cf_entry(line, s);
    }

    fclose(f);
    cf_check();
}

struct cf_per_box *cf_per_box(int box_id)
{
    struct cf_per_box *c;

    for (c = per_box_configs; c; c = c->next)
        if (c->box_id == box_id)
            return c;

    c = xmalloc(sizeof(*c));
    memset(c, 0, sizeof(*c));
    c->next = per_box_configs;
    per_box_configs = c;
    c->box_id = box_id;
    return c;
}

struct cf_per_box *cf_current_box(void)
{
    return cf_per_box(box_id);
}