networking/ipcalc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Mini ipcalc implementation for busybox
   4  *
   5  * By Jordan Crouse <jordan@cosmicpenguin.net>
   6  *    Stephan Linz  <linz@li-pro.net>
   7  *
   8  * This is a complete reimplementation of the ipcalc program
   9  * from Red Hat.  I didn't look at their source code, but there
  10  * is no denying that this is a loving reimplementation
  11  *
  12  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  13  */
  14
  15 //usage:#define ipcalc_trivial_usage
  16 //usage:       "[OPTIONS] ADDRESS"
  17 //usage:       IF_FEATURE_IPCALC_FANCY("[/PREFIX]") " [NETMASK]"
  18 //usage:#define ipcalc_full_usage "\n\n"
  19 //usage:       "Calculate IP network settings from a IP address\n"
  20 //usage:        IF_FEATURE_IPCALC_LONG_OPTIONS(
  21 //usage:     "\n        -b,--broadcast  Display calculated broadcast address"
  22 //usage:     "\n        -n,--network    Display calculated network address"
  23 //usage:     "\n        -m,--netmask    Display default netmask for IP"
  24 //usage:        IF_FEATURE_IPCALC_FANCY(
  25 //usage:     "\n        -p,--prefix     Display the prefix for IP/NETMASK"
  26 //usage:     "\n        -h,--hostname   Display first resolved host name"
  27 //usage:     "\n        -s,--silent     Don't ever display error messages"
  28 //usage:        )
  29 //usage:        )
  30 //usage:        IF_NOT_FEATURE_IPCALC_LONG_OPTIONS(
  31 //usage:     "\n        -b      Display calculated broadcast address"
  32 //usage:     "\n        -n      Display calculated network address"
  33 //usage:     "\n        -m      Display default netmask for IP"
  34 //usage:        IF_FEATURE_IPCALC_FANCY(
  35 //usage:     "\n        -p      Display the prefix for IP/NETMASK"
  36 //usage:     "\n        -h      Display first resolved host name"
  37 //usage:     "\n        -s      Don't ever display error messages"
  38 //usage:        )
  39 //usage:        )
  40
  41 #include "libbb.h"
  42 /* After libbb.h, because on some systems it needs other includes */
  43 #include <arpa/inet.h>
  44
  45 #define CLASS_A_NETMASK ntohl(0xFF000000)
  46 #define CLASS_B_NETMASK ntohl(0xFFFF0000)
  47 #define CLASS_C_NETMASK ntohl(0xFFFFFF00)
  48
  49 static unsigned long get_netmask(unsigned long ipaddr)
  50 {
  51         ipaddr = htonl(ipaddr);
  52
  53         if ((ipaddr & 0xC0000000) == 0xC0000000)
  54                 return CLASS_C_NETMASK;
  55         else if ((ipaddr & 0x80000000) == 0x80000000)
  56                 return CLASS_B_NETMASK;
  57         else if ((ipaddr & 0x80000000) == 0)
  58                 return CLASS_A_NETMASK;
  59         else
  60                 return 0;
  61 }
  62
  63 #if ENABLE_FEATURE_IPCALC_FANCY
  64 static int get_prefix(unsigned long netmask)
  65 {
  66         unsigned long msk = 0x80000000;
  67         int ret = 0;
  68
  69         netmask = htonl(netmask);
  70         while (msk) {
  71                 if (netmask & msk)
  72                         ret++;
  73                 msk >>= 1;
  74         }
  75         return ret;
  76 }
  77 #else
  78 int get_prefix(unsigned long netmask);
  79 #endif
  80
  81
  82 #define NETMASK   0x01
  83 #define BROADCAST 0x02
  84 #define NETWORK   0x04
  85 #define NETPREFIX 0x08
  86 #define HOSTNAME  0x10
  87 #define SILENT    0x20
  88
  89 #if ENABLE_FEATURE_IPCALC_LONG_OPTIONS
  90         static const char ipcalc_longopts[] ALIGN1 =
  91                 "netmask\0"   No_argument "m" // netmask from IP (assuming complete class A, B, or C network)
  92                 "broadcast\0" No_argument "b" // broadcast from IP [netmask]
  93                 "network\0"   No_argument "n" // network from IP [netmask]
  94 # if ENABLE_FEATURE_IPCALC_FANCY
  95                 "prefix\0"    No_argument "p" // prefix from IP[/prefix] [netmask]
  96                 "hostname\0"  No_argument "h" // hostname from IP
  97                 "silent\0"    No_argument "s" // don’t ever display error messages
  98 # endif
  99                 ;
 100 #endif
 101
 102 int ipcalc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 103 int ipcalc_main(int argc UNUSED_PARAM, char **argv)
 104 {
 105         unsigned opt;
 106         bool have_netmask = 0;
 107         struct in_addr s_netmask, s_broadcast, s_network, s_ipaddr;
 108         /* struct in_addr { in_addr_t s_addr; }  and  in_addr_t
 109          * (which in turn is just a typedef to uint32_t)
 110          * are essentially the same type. A few macros for less verbosity: */
 111 #define netmask   (s_netmask.s_addr)
 112 #define broadcast (s_broadcast.s_addr)
 113 #define network   (s_network.s_addr)
 114 #define ipaddr    (s_ipaddr.s_addr)
 115         char *ipstr;
 116
 117 #if ENABLE_FEATURE_IPCALC_LONG_OPTIONS
 118         applet_long_options = ipcalc_longopts;
 119 #endif
 120         opt_complementary = "-1:?2"; /* minimum 1 arg, maximum 2 args */
 121         opt = getopt32(argv, "mbn" IF_FEATURE_IPCALC_FANCY("phs"));
 122         argv += optind;
 123         if (opt & SILENT)
 124                 logmode = LOGMODE_NONE; /* suppress error_msg() output */
 125         opt &= ~SILENT;
 126         if (!(opt & (BROADCAST | NETWORK | NETPREFIX))) {
 127                 /* if no options at all or
 128                  * (no broadcast,network,prefix) and (two args)... */
 129                 if (!opt || argv[1])
 130                         bb_show_usage();
 131         }
 132
 133         ipstr = argv[0];
 134         if (ENABLE_FEATURE_IPCALC_FANCY) {
 135                 unsigned long netprefix = 0;
 136                 char *prefixstr;
 137
 138                 prefixstr = ipstr;
 139
 140                 while (*prefixstr) {
 141                         if (*prefixstr == '/') {
 142                                 *prefixstr++ = '\0';
 143                                 if (*prefixstr) {
 144                                         unsigned msk;
 145                                         netprefix = xatoul_range(prefixstr, 0, 32);
 146                                         netmask = 0;
 147                                         msk = 0x80000000;
 148                                         while (netprefix > 0) {
 149                                                 netmask |= msk;
 150                                                 msk >>= 1;
 151                                                 netprefix--;
 152                                         }
 153                                         netmask = htonl(netmask);
 154                                         /* Even if it was 0, we will signify that we have a netmask. This allows */
 155                                         /* for specification of default routes, etc which have a 0 netmask/prefix */
 156                                         have_netmask = 1;
 157                                 }
 158                                 break;
 159                         }
 160                         prefixstr++;
 161                 }
 162         }
 163
 164         if (inet_aton(ipstr, &s_ipaddr) == 0) {
 165                 bb_error_msg_and_die("bad IP address: %s", argv[0]);
 166         }
 167
 168         if (argv[1]) {
 169                 if (ENABLE_FEATURE_IPCALC_FANCY && have_netmask) {
 170                         bb_error_msg_and_die("use prefix or netmask, not both");
 171                 }
 172                 if (inet_aton(argv[1], &s_netmask) == 0) {
 173                         bb_error_msg_and_die("bad netmask: %s", argv[1]);
 174                 }
 175         } else {
 176                 /* JHC - If the netmask wasn't provided then calculate it */
 177                 if (!ENABLE_FEATURE_IPCALC_FANCY || !have_netmask)
 178                         netmask = get_netmask(ipaddr);
 179         }
 180
 181         if (opt & NETMASK) {
 182                 printf("NETMASK=%s\n", inet_ntoa(s_netmask));
 183         }
 184
 185         if (opt & BROADCAST) {
 186                 broadcast = (ipaddr & netmask) | ~netmask;
 187                 printf("BROADCAST=%s\n", inet_ntoa(s_broadcast));
 188         }
 189
 190         if (opt & NETWORK) {
 191                 network = ipaddr & netmask;
 192                 printf("NETWORK=%s\n", inet_ntoa(s_network));
 193         }
 194
 195         if (ENABLE_FEATURE_IPCALC_FANCY) {
 196                 if (opt & NETPREFIX) {
 197                         printf("PREFIX=%i\n", get_prefix(netmask));
 198                 }
 199
 200                 if (opt & HOSTNAME) {
 201                         struct hostent *hostinfo;
 202
 203                         hostinfo = gethostbyaddr((char *) &ipaddr, sizeof(ipaddr), AF_INET);
 204                         if (!hostinfo) {
 205                                 bb_herror_msg_and_die("can't find hostname for %s", argv[0]);
 206                         }
 207                         str_tolower(hostinfo->h_name);
 208
 209                         printf("HOSTNAME=%s\n", hostinfo->h_name);
 210                 }
 211         }
 212
 213         return EXIT_SUCCESS;
 214 }