/* 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>
 */
//config:config BB_SYSCTL
//config:       bool "sysctl (7.4 kb)"
//config:       default y
//config:       help
//config:       Configure kernel parameters at runtime.

//applet:IF_BB_SYSCTL(APPLET_NOEXEC(sysctl, sysctl, BB_DIR_SBIN, BB_SUID_DROP, sysctl))

//kbuild:lib-$(CONFIG_BB_SYSCTL) += sysctl.o

//usage:#define sysctl_trivial_usage
//usage:       "[-enq] { -a | -p [FILE]... | [-w] [KEY[=VALUE]]... }"
//usage:#define sysctl_full_usage "\n\n"
//usage:       "Show/set kernel parameters\n"
//usage:     "\n        -e      Don't warn about unknown keys"
//usage:     "\n        -n      Don't show key names"
//usage:     "\n        -q      Quiet"
//usage:     "\n        -a      Show all values"
/* Same as -a, no need to show it */
/* //usage:     "\n     -A      Show all values in table form" */
//usage:     "\n        -p      Set values from FILEs (default /etc/sysctl.conf)"
//usage:     "\n        -w      Set values"
//usage:
//usage:#define sysctl_example_usage
//usage:       "sysctl [-n] [-e] variable...\n"
//usage:       "sysctl [-n] [-e] [-q] -w variable=value...\n"
//usage:       "sysctl [-n] [-e] -a\n"
//usage:       "sysctl [-n] [-e] [-q] -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,
        /* NB: procps 3.2.8 does not require -w for KEY=VAL to work, it only rejects non-KEY=VAL form */
        FLAG_WRITE           = 1 << 5,
        FLAG_QUIET           = 1 << 6,
};
#define OPTION_STR "neAapwq"

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

        end = strchrnul(name, '=');

        slash = strchrnul(name, '/');
        if (slash < end
         && strchrnul(name, '.') < slash
        ) {
                /* There are both dots and slashes, and 1st dot is
                 * before 1st slash.
                 * (IOW: not raw, unmangled a/b/c.d format)
                 *
                 * procps supports this syntax for names with dots:
                 *  net.ipv4.conf.eth0/100.mc_forwarding
                 * (dots and slashes are simply swapped)
                 */
                while (end != name) {
                        end--;
                        if (*end == '.') *end = '/';
                        else if (*end == '/') *end = '.';
                }
                return;
        }
        /* else: use our old behavior: */

        /* 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_ch = *end;
        *end = '.'; /* trick the loop into trying full name too */

        last_good = name - 1;
 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 = end_ch;
}

static int sysctl_act_on_setting(char *setting)
{
        int fd, retval = EXIT_SUCCESS;
        char *cptr, *outname;
        char *value = value; /* for compiler */
        bool writing = (option_mask32 & FLAG_WRITE);

        outname = xstrdup(setting);

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

        cptr = strchr(setting, '=');
        if (cptr)
                writing = 1;
        if (writing) {
                if (!cptr) {
                        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 /* "name" can't be empty */
                 /* || !*value - WRONG: "sysctl net.ipv4.ip_local_reserved_ports=" is a valid syntax (clears the 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;
                case EACCES:
                        /* Happens for write-only settings, e.g. net.ipv6.route.flush */
                        if (!writing)
                                goto end;
                        /* fall through */
                default:
                        bb_perror_msg("error %sing key '%s'",
                                        writing ?
                                                "sett" : "read",
                                        outname);
                        break;
                }
                retval = EXIT_FAILURE;
                goto end;
        }

        if (writing) {
//TODO: procps 3.2.7 writes "value\n", note trailing "\n"
                xwrite_str(fd, value);
                close(fd);
                if (!(option_mask32 & FLAG_QUIET)) {
                        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);
                        retval = EXIT_FAILURE;
                        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)
{
        struct stat buf;
        int retval = 0;

        if (!(option_mask32 & FLAG_WRITE)
         && !strchr(path, '=')  /* do not try to resurse on "var=val" */
         && stat(path, &buf) == 0
         && S_ISDIR(buf.st_mode)
        ) {
                struct dirent *entry;
                DIR *dirp;

                dirp = opendir(path);
                if (dirp == NULL)
                        return -1;
                while ((entry = readdir(dirp)) != NULL) {
                        char *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;
        int parse_flags;

        parser = config_open(filename);
        /* Must do it _after_ config_open(): */
        xchdir("/proc/sys");

        parse_flags = 0;
        parse_flags &= ~PARSE_COLLAPSE;   // NO (var==val is not var=val) - treat consecutive delimiters as one
        parse_flags &= ~PARSE_TRIM;       // NO - trim leading and trailing delimiters
        parse_flags |= PARSE_GREEDY;      // YES - last token takes entire remainder of the line
        parse_flags &= ~PARSE_MIN_DIE;    // NO - die if < min tokens found
        parse_flags &= ~PARSE_EOL_COMMENTS; // NO (only first char) - comments are recognized even if not first char
        parse_flags |= PARSE_ALT_COMMENTS;// YES - two comment chars: ';' and '#'
        /* <space><tab><space>#comment is also comment, not strictly 1st char only */
        parse_flags |= PARSE_WS_COMMENTS; // YES - comments are recognized even if there is whitespace before
        while (config_read(parser, token, 2, 2, ";#=", parse_flags)) {
                char *tp;

                trim(token[1]);
                tp = trim(token[0]);
                sysctl_dots_to_slashes(token[0]);
                /* ^^^converted in-place. tp still points to NUL */
                /* now, add "=TOKEN1" */
                *tp++ = '=';
                overlapping_strcpy(tp, token[1]);

                sysctl_act_on_setting(token[0]);
        }
        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) {
                int cur_dir_fd;
                option_mask32 |= FLAG_WRITE;
                if (!*argv)
                        *--argv = (char*)"/etc/sysctl.conf";
                cur_dir_fd = xopen(".", O_RDONLY | O_DIRECTORY);
                do {
                        /* xchdir("/proc/sys") is inside */
                        sysctl_handle_preload_file(*argv);
                        xfchdir(cur_dir_fd); /* files can be relative, must restore cwd */
                } while (*++argv);
                return 0; /* procps-ng 3.3.10 does not flag parse errors */
        }
        xchdir("/proc/sys");
        if (opt & (FLAG_TABLE_FORMAT | FLAG_SHOW_ALL)) {
                return sysctl_act_recursive(".");
        }

//TODO: if(!argv[0]) bb_show_usage() ?

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

        return retval;
}