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 (7.4 kb)"
  15 //config:       default y
  16 //config:       help
  17 //config:       Configure kernel parameters at runtime.
  18
  19 //applet:IF_BB_SYSCTL(APPLET_NOEXEC(sysctl, sysctl, BB_DIR_SBIN, BB_SUID_DROP, sysctl))
  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         char end_ch;
  61
  62         /* Convert minimum number of '.' to '/' so that
  63          * we end up with existing file's name.
  64          *
  65          * Example from bug 3894:
  66          * net.ipv4.conf.eth0.100.mc_forwarding ->
  67          * net/ipv4/conf/eth0.100/mc_forwarding
  68          * NB: net/ipv4/conf/eth0/mc_forwarding *also exists*,
  69          * therefore we must start from the end, and if
  70          * we replaced even one . -> /, start over again,
  71          * but never replace dots before the position
  72          * where last replacement occurred.
  73          *
  74          * Another bug we later had is that
  75          * net.ipv4.conf.eth0.100
  76          * (without .mc_forwarding) was mishandled.
  77          *
  78          * To set up testing: modprobe 8021q; vconfig add eth0 100
  79          */
  80         end = strchrnul(name, '=');
  81         end_ch = *end;
  82         *end = '.'; /* trick the loop into trying full name too */
  83
  84         last_good = name - 1;
  85  again:
  86         cptr = end;
  87         while (cptr > last_good) {
  88                 if (*cptr == '.') {
  89                         *cptr = '\0';
  90                         //bb_error_msg("trying:'%s'", name);
  91                         if (access(name, F_OK) == 0) {
  92                                 *cptr = '/';
  93                                 //bb_error_msg("replaced:'%s'", name);
  94                                 last_good = cptr;
  95                                 goto again;
  96                         }
  97                         *cptr = '.';
  98                 }
  99                 cptr--;
 100         }
 101         *end = end_ch;
 102 }
 103
 104 static int sysctl_act_on_setting(char *setting)
 105 {
 106         int fd, retval = EXIT_SUCCESS;
 107         char *cptr, *outname;
 108         char *value = value; /* for compiler */
 109         bool writing = (option_mask32 & FLAG_WRITE);
 110
 111         outname = xstrdup(setting);
 112
 113         cptr = outname;
 114         while (*cptr) {
 115                 if (*cptr == '/')
 116                         *cptr = '.';
 117                 cptr++;
 118         }
 119
 120         cptr = strchr(setting, '=');
 121         if (cptr)
 122                 writing = 1;
 123         if (writing) {
 124                 if (!cptr) {
 125                         bb_error_msg("error: '%s' must be of the form name=value",
 126                                 outname);
 127                         retval = EXIT_FAILURE;
 128                         goto end;
 129                 }
 130                 value = cptr + 1;  /* point to the value in name=value */
 131                 if (setting == cptr /* "name" can't be empty */
 132                  /* || !*value - WRONG: "sysctl net.ipv4.ip_local_reserved_ports=" is a valid syntax (clears the value) */
 133                 ) {
 134                         bb_error_msg("error: malformed setting '%s'", outname);
 135                         retval = EXIT_FAILURE;
 136                         goto end;
 137                 }
 138                 *cptr = '\0';
 139                 outname[cptr - setting] = '\0';
 140                 /* procps 3.2.7 actually uses these flags */
 141                 fd = open(setting, O_WRONLY|O_CREAT|O_TRUNC, 0666);
 142         } else {
 143                 fd = open(setting, O_RDONLY);
 144         }
 145
 146         if (fd < 0) {
 147                 switch (errno) {
 148                 case EACCES:
 149                         /* Happens for write-only settings, e.g. net.ipv6.route.flush */
 150                         goto end;
 151                 case ENOENT:
 152                         if (option_mask32 & FLAG_SHOW_KEY_ERRORS)
 153                                 bb_error_msg("error: '%s' is an unknown key", outname);
 154                         break;
 155                 default:
 156                         bb_perror_msg("error %sing key '%s'",
 157                                         writing ?
 158                                                 "sett" : "read",
 159                                         outname);
 160                         break;
 161                 }
 162                 retval = EXIT_FAILURE;
 163                 goto end;
 164         }
 165
 166         if (writing) {
 167 //TODO: procps 3.2.7 writes "value\n", note trailing "\n"
 168                 xwrite_str(fd, value);
 169                 close(fd);
 170                 if (!(option_mask32 & FLAG_QUIET)) {
 171                         if (option_mask32 & FLAG_SHOW_KEYS)
 172                                 printf("%s = ", outname);
 173                         puts(value);
 174                 }
 175         } else {
 176                 char c;
 177
 178                 value = cptr = xmalloc_read(fd, NULL);
 179                 close(fd);
 180                 if (value == NULL) {
 181                         bb_perror_msg("error reading key '%s'", outname);
 182                         retval = EXIT_FAILURE;
 183                         goto end;
 184                 }
 185
 186                 /* dev.cdrom.info and sunrpc.transports, for example,
 187                  * are multi-line. Try "sysctl sunrpc.transports"
 188                  */
 189                 while ((c = *cptr) != '\0') {
 190                         if (option_mask32 & FLAG_SHOW_KEYS)
 191                                 printf("%s = ", outname);
 192                         while (1) {
 193                                 fputc(c, stdout);
 194                                 cptr++;
 195                                 if (c == '\n')
 196                                         break;
 197                                 c = *cptr;
 198                                 if (c == '\0')
 199                                         break;
 200                         }
 201                 }
 202                 free(value);
 203         }
 204  end:
 205         free(outname);
 206         return retval;
 207 }
 208
 209 static int sysctl_act_recursive(const char *path)
 210 {
 211         struct stat buf;
 212         int retval = 0;
 213
 214         if (!(option_mask32 & FLAG_WRITE)
 215          && stat(path, &buf) == 0
 216          && S_ISDIR(buf.st_mode)
 217         ) {
 218                 struct dirent *entry;
 219                 DIR *dirp;
 220
 221                 dirp = opendir(path);
 222                 if (dirp == NULL)
 223                         return -1;
 224                 while ((entry = readdir(dirp)) != NULL) {
 225                         char *next = concat_subpath_file(path, entry->d_name);
 226                         if (next == NULL)
 227                                 continue; /* d_name is "." or ".." */
 228                         /* if path was ".", drop "./" prefix: */
 229                         retval |= sysctl_act_recursive((next[0] == '.' && next[1] == '/') ?
 230                                         next + 2 : next);
 231                         free(next);
 232                 }
 233                 closedir(dirp);
 234         } else {
 235                 char *name = xstrdup(path);
 236                 retval |= sysctl_act_on_setting(name);
 237                 free(name);
 238         }
 239
 240         return retval;
 241 }
 242
 243 /* Set sysctl's from a conf file. Format example:
 244  * # Controls IP packet forwarding
 245  * net.ipv4.ip_forward = 0
 246  */
 247 static int sysctl_handle_preload_file(const char *filename)
 248 {
 249         char *token[2];
 250         parser_t *parser;
 251         int parse_flags;
 252
 253         parser = config_open(filename);
 254         /* Must do it _after_ config_open(): */
 255         xchdir("/proc/sys");
 256
 257         parse_flags = 0;
 258         parse_flags &= ~PARSE_COLLAPSE;   // NO (var==val is not var=val) - treat consecutive delimiters as one
 259         parse_flags &= ~PARSE_TRIM;       // NO - trim leading and trailing delimiters
 260         parse_flags |= PARSE_GREEDY;      // YES - last token takes entire remainder of the line
 261         parse_flags &= ~PARSE_MIN_DIE;    // NO - die if < min tokens found
 262         parse_flags &= ~PARSE_EOL_COMMENTS; // NO (only first char) - comments are recognized even if not first char
 263         parse_flags |= PARSE_ALT_COMMENTS;// YES - two comment chars: ';' and '#'
 264         /* <space><tab><space>#comment is also comment, not strictly 1st char only */
 265         parse_flags |= PARSE_WS_COMMENTS; // YES - comments are recognized even if there is whitespace before
 266         while (config_read(parser, token, 2, 2, ";#=", parse_flags)) {
 267                 char *tp;
 268
 269                 trim(token[1]);
 270                 tp = trim(token[0]);
 271                 sysctl_dots_to_slashes(token[0]);
 272                 /* ^^^converted in-place. tp still points to NUL */
 273                 /* now, add "=TOKEN1" */
 274                 *tp++ = '=';
 275                 overlapping_strcpy(tp, token[1]);
 276
 277                 sysctl_act_on_setting(token[0]);
 278         }
 279         if (ENABLE_FEATURE_CLEAN_UP)
 280                 config_close(parser);
 281         return 0;
 282 }
 283
 284 int sysctl_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 285 int sysctl_main(int argc UNUSED_PARAM, char **argv)
 286 {
 287         int retval;
 288         int opt;
 289
 290         opt = getopt32(argv, "+" OPTION_STR); /* '+' - stop on first non-option */
 291         argv += optind;
 292         opt ^= (FLAG_SHOW_KEYS | FLAG_SHOW_KEY_ERRORS);
 293         option_mask32 = opt;
 294
 295         if (opt & FLAG_PRELOAD_FILE) {
 296                 int cur_dir_fd;
 297                 option_mask32 |= FLAG_WRITE;
 298                 if (!*argv)
 299                         *--argv = (char*)"/etc/sysctl.conf";
 300                 cur_dir_fd = xopen(".", O_RDONLY | O_DIRECTORY);
 301                 do {
 302                         /* xchdir("/proc/sys") is inside */
 303                         sysctl_handle_preload_file(*argv);
 304                         xfchdir(cur_dir_fd); /* files can be relative, must restore cwd */
 305                 } while (*++argv);
 306                 return 0; /* procps-ng 3.3.10 does not flag parse errors */
 307         }
 308         xchdir("/proc/sys");
 309         if (opt & (FLAG_TABLE_FORMAT | FLAG_SHOW_ALL)) {
 310                 return sysctl_act_recursive(".");
 311         }
 312
 313 //TODO: if(!argv[0]) bb_show_usage() ?
 314
 315         retval = 0;
 316         while (*argv) {
 317                 sysctl_dots_to_slashes(*argv);
 318                 retval |= sysctl_act_recursive(*argv);
 319                 argv++;
 320         }
 321
 322         return retval;
 323 }