/* vi: set sw=4 ts=4: */
/*
 * Sysctl 1.01 - A utility to read and manipulate the sysctl parameters
 *
 * Copyright 1999 George Staikos
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 *
 * Changelog:
 * v1.01   - added -p <preload> to preload values from a file
 * v1.01.1 - busybox applet aware by <solar@gentoo.org>
 */

//usage:#define sysctl_trivial_usage
//usage:       "[OPTIONS] [VALUE]..."
//usage:#define sysctl_full_usage "\n\n"
//usage:       "Configure kernel parameters at runtime\n"
//usage:     "\n        -n      Don't print key names"
//usage:     "\n        -e      Don't warn about unknown keys"
//usage:     "\n        -w      Change sysctl setting"
//usage:     "\n        -p FILE Load sysctl settings from FILE (default /etc/sysctl.conf)"
//usage:     "\n        -a      Display all values"
//usage:     "\n        -A      Display all values in table form"
//usage:
//usage:#define sysctl_example_usage
//usage:       "sysctl [-n] [-e] variable...\n"
//usage:       "sysctl [-n] [-e] -w variable=value...\n"
//usage:       "sysctl [-n] [-e] -a\n"
//usage:       "sysctl [-n] [-e] -p file        (default /etc/sysctl.conf)\n"
//usage:       "sysctl [-n] [-e] -A\n"

#include "libbb.h"

enum {
        FLAG_SHOW_KEYS       = 1 << 0,
        FLAG_SHOW_KEY_ERRORS = 1 << 1,
        FLAG_TABLE_FORMAT    = 1 << 2, /* not implemented */
        FLAG_SHOW_ALL        = 1 << 3,
        FLAG_PRELOAD_FILE    = 1 << 4,
        FLAG_WRITE           = 1 << 5,
};
#define OPTION_STR "neAapw"

static void sysctl_dots_to_slashes(char *name)
{
        char *cptr, *last_good, *end;

        /* Convert minimum number of '.' to '/' so that
         * we end up with existing file's name.
         *
         * Example from bug 3894:
         * net.ipv4.conf.eth0.100.mc_forwarding ->
         * net/ipv4/conf/eth0.100/mc_forwarding
         * NB: net/ipv4/conf/eth0/mc_forwarding *also exists*,
         * therefore we must start from the end, and if
         * we replaced even one . -> /, start over again,
         * but never replace dots before the position
         * where last replacement occurred.
         *
         * Another bug we later had is that
         * net.ipv4.conf.eth0.100
         * (without .mc_forwarding) was mishandled.
         *
         * To set up testing: modprobe 8021q; vconfig add eth0 100
         */
        end = name + strlen(name);
        last_good = name - 1;
        *end = '.'; /* trick the loop into trying full name too */

 again:
        cptr = end;
        while (cptr > last_good) {
                if (*cptr == '.') {
                        *cptr = '\0';
                        //bb_error_msg("trying:'%s'", name);
                        if (access(name, F_OK) == 0) {
                                *cptr = '/';
                                //bb_error_msg("replaced:'%s'", name);
                                last_good = cptr;
                                goto again;
                        }
                        *cptr = '.';
                }
                cptr--;
        }
        *end = '\0';
}

static int sysctl_act_on_setting(char *setting)
{
        int fd, retval = EXIT_SUCCESS;
        char *cptr, *outname;
        char *value = value; /* for compiler */

        outname = xstrdup(setting);

        cptr = outname;
        while (*cptr) {
                if (*cptr == '/')
                        *cptr = '.';
                cptr++;
        }

        if (option_mask32 & FLAG_WRITE) {
                cptr = strchr(setting, '=');
                if (cptr == NULL) {
                        bb_error_msg("error: '%s' must be of the form name=value",
                                outname);
                        retval = EXIT_FAILURE;
                        goto end;
                }
                value = cptr + 1;  /* point to the value in name=value */
                if (setting == cptr || !*value) {
                        bb_error_msg("error: malformed setting '%s'", outname);
                        retval = EXIT_FAILURE;
                        goto end;
                }
                *cptr = '\0';
                outname[cptr - setting] = '\0';
                /* procps 3.2.7 actually uses these flags */
                fd = open(setting, O_WRONLY|O_CREAT|O_TRUNC, 0666);
        } else {
                fd = open(setting, O_RDONLY);
        }

        if (fd < 0) {
                switch (errno) {
                case ENOENT:
                        if (option_mask32 & FLAG_SHOW_KEY_ERRORS)
                                bb_error_msg("error: '%s' is an unknown key", outname);
                        break;
                default:
                        bb_perror_msg("error %sing key '%s'",
                                        option_mask32 & FLAG_WRITE ?
                                                "sett" : "read",
                                        outname);
                        break;
                }
                retval = EXIT_FAILURE;
                goto end;
        }

        if (option_mask32 & FLAG_WRITE) {
//TODO: procps 3.2.7 writes "value\n", note trailing "\n"
                xwrite_str(fd, value);
                close(fd);
                if (option_mask32 & FLAG_SHOW_KEYS)
                        printf("%s = ", outname);
                puts(value);
        } else {
                char c;

                value = cptr = xmalloc_read(fd, NULL);
                close(fd);
                if (value == NULL) {
                        bb_perror_msg("error reading key '%s'", outname);
                        goto end;
                }

                /* dev.cdrom.info and sunrpc.transports, for example,
                 * are multi-line. Try "sysctl sunrpc.transports"
                 */
                while ((c = *cptr) != '\0') {
                        if (option_mask32 & FLAG_SHOW_KEYS)
                                printf("%s = ", outname);
                        while (1) {
                                fputc(c, stdout);
                                cptr++;
                                if (c == '\n')
                                        break;
                                c = *cptr;
                                if (c == '\0')
                                        break;
                        }
                }
                free(value);
        }
 end:
        free(outname);
        return retval;
}

static int sysctl_act_recursive(const char *path)
{
        DIR *dirp;
        struct stat buf;
        struct dirent *entry;
        char *next;
        int retval = 0;

        stat(path, &buf);
        if (S_ISDIR(buf.st_mode) && !(option_mask32 & FLAG_WRITE)) {
                dirp = opendir(path);
                if (dirp == NULL)
                        return -1;
                while ((entry = readdir(dirp)) != NULL) {
                        next = concat_subpath_file(path, entry->d_name);
                        if (next == NULL)
                                continue; /* d_name is "." or ".." */
                        /* if path was ".", drop "./" prefix: */
                        retval |= sysctl_act_recursive((next[0] == '.' && next[1] == '/') ?
                                            next + 2 : next);
                        free(next);
                }
                closedir(dirp);
        } else {
                char *name = xstrdup(path);
                retval |= sysctl_act_on_setting(name);
                free(name);
        }

        return retval;
}

/* Set sysctl's from a conf file. Format example:
 * # Controls IP packet forwarding
 * net.ipv4.ip_forward = 0
 */
static int sysctl_handle_preload_file(const char *filename)
{
        char *token[2];
        parser_t *parser;

        parser = config_open(filename);
        /* Must do it _after_ config_open(): */
        xchdir("/proc/sys");
        /* xchroot("/proc/sys") - if you are paranoid */

//TODO: ';' is comment char too
//TODO: comment may be only at line start. "var=1 #abc" - "1 #abc" is the value
// (but _whitespace_ from ends should be trimmed first (and we do it right))
//TODO: "var==1" is mishandled (must use "=1" as a value, but uses "1")
// can it be fixed by removing PARSE_COLLAPSE bit?
        while (config_read(parser, token, 2, 2, "# \t=", PARSE_NORMAL)) {
                char *tp;
                sysctl_dots_to_slashes(token[0]);
                tp = xasprintf("%s=%s", token[0], token[1]);
                sysctl_act_recursive(tp);
                free(tp);
        }
        if (ENABLE_FEATURE_CLEAN_UP)
                config_close(parser);
        return 0;
}

int sysctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int sysctl_main(int argc UNUSED_PARAM, char **argv)
{
        int retval;
        int opt;

        opt = getopt32(argv, "+" OPTION_STR); /* '+' - stop on first non-option */
        argv += optind;
        opt ^= (FLAG_SHOW_KEYS | FLAG_SHOW_KEY_ERRORS);
        option_mask32 = opt;

        if (opt & FLAG_PRELOAD_FILE) {
                option_mask32 |= FLAG_WRITE;
                /* xchdir("/proc/sys") is inside */
                return sysctl_handle_preload_file(*argv ? *argv : "/etc/sysctl.conf");
        }
        xchdir("/proc/sys");
        /* xchroot("/proc/sys") - if you are paranoid */
        if (opt & (FLAG_TABLE_FORMAT | FLAG_SHOW_ALL)) {
                return sysctl_act_recursive(".");
        }

        retval = 0;
        while (*argv) {
                sysctl_dots_to_slashes(*argv);
                retval |= sysctl_act_recursive(*argv);
                argv++;
        }

        return retval;
}