procps/sysctl.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Sysctl 1.01 - A utility to read and manipulate the sysctl parameters
   4  *
   5  * Copyright 1999 George Staikos
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  *
   9  * Changelog:
  10  * v1.01   - added -p <preload> to preload values from a file
  11  * v1.01.1 - busybox applet aware by <solar@gentoo.org>
  12  */
  13 //config:config BB_SYSCTL
  14 //config:       bool "sysctl (6.9 kb)"
  15 //config:       default y
  16 //config:       help
  17 //config:       Configure kernel parameters at runtime.
  18
  19 //applet:IF_BB_SYSCTL(APPLET(sysctl, BB_DIR_SBIN, BB_SUID_DROP))
  20
  21 //kbuild:lib-$(CONFIG_BB_SYSCTL) += sysctl.o
  22
  23 //usage:#define sysctl_trivial_usage
  24 //usage:       "-p [-enq] [FILE...] / [-enqaw] [KEY[=VALUE]]..."
  25 //usage:#define sysctl_full_usage "\n\n"
  26 //usage:       "Show/set kernel parameters\n"
  27 //usage:     "\n        -p      Set values from FILEs (default /etc/sysctl.conf)"
  28 //usage:     "\n        -e      Don't warn about unknown keys"
  29 //usage:     "\n        -n      Don't show key names"
  30 //usage:     "\n        -q      Quiet"
  31 //usage:     "\n        -a      Show all values"
  32 /* Same as -a, no need to show it */
  33 /* //usage:     "\n     -A      Show all values in table form" */
  34 //usage:     "\n        -w      Set values"
  35 //usage:
  36 //usage:#define sysctl_example_usage
  37 //usage:       "sysctl [-n] [-e] variable...\n"
  38 //usage:       "sysctl [-n] [-e] [-q] -w variable=value...\n"
  39 //usage:       "sysctl [-n] [-e] -a\n"
  40 //usage:       "sysctl [-n] [-e] [-q] -p file   (default /etc/sysctl.conf)\n"
  41 //usage:       "sysctl [-n] [-e] -A\n"
  42
  43 #include "libbb.h"
  44
  45 enum {
  46         FLAG_SHOW_KEYS       = 1 << 0,
  47         FLAG_SHOW_KEY_ERRORS = 1 << 1,
  48         FLAG_TABLE_FORMAT    = 1 << 2, /* not implemented */
  49         FLAG_SHOW_ALL        = 1 << 3,
  50         FLAG_PRELOAD_FILE    = 1 << 4,
  51         /* NB: procps 3.2.8 does not require -w for KEY=VAL to work, it only rejects non-KEY=VAL form */
  52         FLAG_WRITE           = 1 << 5,
  53         FLAG_QUIET           = 1 << 6,
  54 };
  55 #define OPTION_STR "neAapwq"
  56
  57 static void sysctl_dots_to_slashes(char *name)
  58 {
  59         char *cptr, *last_good, *end;
  60
  61         /* Convert minimum number of '.' to '/' so that
  62          * we end up with existing file's name.
  63          *
  64          * Example from bug 3894:
  65          * net.ipv4.conf.eth0.100.mc_forwarding ->
  66          * net/ipv4/conf/eth0.100/mc_forwarding
  67          * NB: net/ipv4/conf/eth0/mc_forwarding *also exists*,
  68          * therefore we must start from the end, and if
  69          * we replaced even one . -> /, start over again,
  70          * but never replace dots before the position
  71          * where last replacement occurred.
  72          *
  73          * Another bug we later had is that
  74          * net.ipv4.conf.eth0.100
  75          * (without .mc_forwarding) was mishandled.
  76          *
  77          * To set up testing: modprobe 8021q; vconfig add eth0 100
  78          */
  79         end = name + strlen(name);
  80         last_good = name - 1;
  81         *end = '.'; /* trick the loop into trying full name too */
  82
  83  again:
  84         cptr = end;
  85         while (cptr > last_good) {
  86                 if (*cptr == '.') {
  87                         *cptr = '\0';
  88                         //bb_error_msg("trying:'%s'", name);
  89                         if (access(name, F_OK) == 0) {
  90                                 *cptr = '/';
  91                                 //bb_error_msg("replaced:'%s'", name);
  92                                 last_good = cptr;
  93                                 goto again;
  94                         }
  95                         *cptr = '.';
  96                 }
  97                 cptr--;
  98         }
  99         *end = '\0';
 100 }
 101
 102 static int sysctl_act_on_setting(char *setting)
 103 {
 104         int fd, retval = EXIT_SUCCESS;
 105         char *cptr, *outname;
 106         char *value = value; /* for compiler */
 107         bool writing = (option_mask32 & FLAG_WRITE);
 108
 109         outname = xstrdup(setting);
 110
 111         cptr = outname;
 112         while (*cptr) {
 113                 if (*cptr == '/')
 114                         *cptr = '.';
 115                 cptr++;
 116         }
 117
 118         cptr = strchr(setting, '=');
 119         if (cptr)
 120                 writing = 1;
 121         if (writing) {
 122                 if (cptr == NULL) {
 123                         bb_error_msg("error: '%s' must be of the form name=value",
 124                                 outname);
 125                         retval = EXIT_FAILURE;
 126                         goto end;
 127                 }
 128                 value = cptr + 1;  /* point to the value in name=value */
 129                 if (setting == cptr || !*value) {
 130                         bb_error_msg("error: malformed setting '%s'", outname);
 131                         retval = EXIT_FAILURE;
 132                         goto end;
 133                 }
 134                 *cptr = '\0';
 135                 outname[cptr - setting] = '\0';
 136                 /* procps 3.2.7 actually uses these flags */
 137                 fd = open(setting, O_WRONLY|O_CREAT|O_TRUNC, 0666);
 138         } else {
 139                 fd = open(setting, O_RDONLY);
 140         }
 141
 142         if (fd < 0) {
 143                 switch (errno) {
 144                 case EACCES:
 145                         /* Happens for write-only settings, e.g. net.ipv6.route.flush */
 146                         goto end;
 147                 case ENOENT:
 148                         if (option_mask32 & FLAG_SHOW_KEY_ERRORS)
 149                                 bb_error_msg("error: '%s' is an unknown key", outname);
 150                         break;
 151                 default:
 152                         bb_perror_msg("error %sing key '%s'",
 153                                         writing ?
 154                                                 "sett" : "read",
 155                                         outname);
 156                         break;
 157                 }
 158                 retval = EXIT_FAILURE;
 159                 goto end;
 160         }
 161
 162         if (writing) {
 163 //TODO: procps 3.2.7 writes "value\n", note trailing "\n"
 164                 xwrite_str(fd, value);
 165                 close(fd);
 166                 if (!(option_mask32 & FLAG_QUIET)) {
 167                         if (option_mask32 & FLAG_SHOW_KEYS)
 168                                 printf("%s = ", outname);
 169                         puts(value);
 170                 }
 171         } else {
 172                 char c;
 173
 174                 value = cptr = xmalloc_read(fd, NULL);
 175                 close(fd);
 176                 if (value == NULL) {
 177                         bb_perror_msg("error reading key '%s'", outname);
 178                         goto end;
 179                 }
 180
 181                 /* dev.cdrom.info and sunrpc.transports, for example,
 182                  * are multi-line. Try "sysctl sunrpc.transports"
 183                  */
 184                 while ((c = *cptr) != '\0') {
 185                         if (option_mask32 & FLAG_SHOW_KEYS)
 186                                 printf("%s = ", outname);
 187                         while (1) {
 188                                 fputc(c, stdout);
 189                                 cptr++;
 190                                 if (c == '\n')
 191                                         break;
 192                                 c = *cptr;
 193                                 if (c == '\0')
 194                                         break;
 195                         }
 196                 }
 197                 free(value);
 198         }
 199  end:
 200         free(outname);
 201         return retval;
 202 }
 203
 204 static int sysctl_act_recursive(const char *path)
 205 {
 206         DIR *dirp;
 207         struct stat buf;
 208         struct dirent *entry;
 209         char *next;
 210         int retval = 0;
 211
 212         stat(path, &buf);
 213         if (S_ISDIR(buf.st_mode) && !(option_mask32 & FLAG_WRITE)) {
 214                 dirp = opendir(path);
 215                 if (dirp == NULL)
 216                         return -1;
 217                 while ((entry = readdir(dirp)) != NULL) {
 218                         next = concat_subpath_file(path, entry->d_name);
 219                         if (next == NULL)
 220                                 continue; /* d_name is "." or ".." */
 221                         /* if path was ".", drop "./" prefix: */
 222                         retval |= sysctl_act_recursive((next[0] == '.' && next[1] == '/') ?
 223                                         next + 2 : next);
 224                         free(next);
 225                 }
 226                 closedir(dirp);
 227         } else {
 228                 char *name = xstrdup(path);
 229                 retval |= sysctl_act_on_setting(name);
 230                 free(name);
 231         }
 232
 233         return retval;
 234 }
 235
 236 /* Set sysctl's from a conf file. Format example:
 237  * # Controls IP packet forwarding
 238  * net.ipv4.ip_forward = 0
 239  */
 240 static int sysctl_handle_preload_file(const char *filename)
 241 {
 242         char *token[2];
 243         parser_t *parser;
 244         int parse_flags;
 245
 246         parser = config_open(filename);
 247         /* Must do it _after_ config_open(): */
 248         xchdir("/proc/sys");
 249
 250         parse_flags = 0;
 251         parse_flags &= ~PARSE_COLLAPSE;   // NO (var==val is not var=val) - treat consecutive delimiters as one
 252         parse_flags &= ~PARSE_TRIM;       // NO - trim leading and trailing delimiters
 253         parse_flags |= PARSE_GREEDY;      // YES - last token takes entire remainder of the line
 254         parse_flags &= ~PARSE_MIN_DIE;    // NO - die if < min tokens found
 255         parse_flags &= ~PARSE_EOL_COMMENTS; // NO (only first char) - comments are recognized even if not first char
 256         parse_flags |= PARSE_ALT_COMMENTS;// YES - two comment chars: ';' and '#'
 257         /* <space><tab><space>#comment is also comment, not strictly 1st char only */
 258         parse_flags |= PARSE_WS_COMMENTS; // YES - comments are recognized even if there is whitespace before
 259         while (config_read(parser, token, 2, 2, ";#=", parse_flags)) {
 260                 char *tp;
 261
 262                 trim(token[1]);
 263                 tp = trim(token[0]);
 264                 sysctl_dots_to_slashes(token[0]);
 265                 /* ^^^converted in-place. tp still points to NUL */
 266                 /* now, add "=TOKEN1" */
 267                 *tp++ = '=';
 268                 overlapping_strcpy(tp, token[1]);
 269
 270                 sysctl_act_on_setting(token[0]);
 271         }
 272         if (ENABLE_FEATURE_CLEAN_UP)
 273                 config_close(parser);
 274         return 0;
 275 }
 276
 277 int sysctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 278 int sysctl_main(int argc UNUSED_PARAM, char **argv)
 279 {
 280         int retval;
 281         int opt;
 282
 283         opt = getopt32(argv, "+" OPTION_STR); /* '+' - stop on first non-option */
 284         argv += optind;
 285         opt ^= (FLAG_SHOW_KEYS | FLAG_SHOW_KEY_ERRORS);
 286         option_mask32 = opt;
 287
 288         if (opt & FLAG_PRELOAD_FILE) {
 289                 int cur_dir_fd;
 290                 option_mask32 |= FLAG_WRITE;
 291                 if (!*argv)
 292                         *--argv = (char*)"/etc/sysctl.conf";
 293                 cur_dir_fd = xopen(".", O_RDONLY | O_DIRECTORY);
 294                 do {
 295                         /* xchdir("/proc/sys") is inside */
 296                         sysctl_handle_preload_file(*argv);
 297                         xfchdir(cur_dir_fd); /* files can be relative, must restore cwd */
 298                 } while (*++argv);
 299                 return 0; /* procps-ng 3.3.10 does not flag parse errors */
 300         }
 301         xchdir("/proc/sys");
 302         if (opt & (FLAG_TABLE_FORMAT | FLAG_SHOW_ALL)) {
 303                 return sysctl_act_recursive(".");
 304         }
 305
 306         retval = 0;
 307         while (*argv) {
 308                 sysctl_dots_to_slashes(*argv);
 309                 retval |= sysctl_act_recursive(*argv);
 310                 argv++;
 311         }
 312
 313         return retval;
 314 }