busybox/procps/sysctl.c

/* 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:       "-p [-enq] [FILE...] / [-enqaw] [KEY[=VALUE]]..."
//usage:#define sysctl_full_usage "\n\n"
//usage:       "Show/set kernel parameters\n"
//usage:     "\n	-p	Set values from FILEs (default /etc/sysctl.conf)"
//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	-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 EACCES:
			/* Happens for write-only settings, e.g. net.ipv6.route.flush */
			goto end;
		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'",
					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)
	 && 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;
}