networking/arp.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * arp.c - Manipulate the system ARP cache
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version
   8  * 2 of the License, or (at your option) any later version.
   9  *
  10  * Author: Fred N. van Kempen, <waltje at uwalt.nl.mugnet.org>
  11  * Busybox port: Paul van Gool <pvangool at mimotech.com>
  12  *
  13  * modified for getopt32 by Arne Bernin <arne [at] alamut.de>
  14  */
  15
  16 #include "libbb.h"
  17 #include "inet_common.h"
  18
  19 #include <arpa/inet.h>
  20 #include <net/if.h>
  21 #include <net/if_arp.h>
  22 #include <netinet/ether.h>
  23 #include <netpacket/packet.h>
  24
  25 #define DEBUG 0
  26
  27 #define DFLT_AF "inet"
  28 #define DFLT_HW "ether"
  29
  30 #define ARP_OPT_A (0x1)
  31 #define ARP_OPT_p (0x2)
  32 #define ARP_OPT_H (0x4)
  33 #define ARP_OPT_t (0x8)
  34 #define ARP_OPT_i (0x10)
  35 #define ARP_OPT_a (0x20)
  36 #define ARP_OPT_d (0x40)
  37 #define ARP_OPT_n (0x80)        /* do not resolve addresses     */
  38 #define ARP_OPT_D (0x100)       /* HW-address is devicename     */
  39 #define ARP_OPT_s (0x200)
  40 #define ARP_OPT_v (0x400 * DEBUG)       /* debugging output flag        */
  41
  42
  43 static const struct aftype *ap; /* current address family       */
  44 static const struct hwtype *hw; /* current hardware type        */
  45 static int sockfd;              /* active socket descriptor     */
  46 static smallint hw_set;         /* flag if hw-type was set (-H) */
  47 static const char *device = ""; /* current device               */
  48
  49 static const char options[] ALIGN1 =
  50         "pub\0"
  51         "priv\0"
  52         "temp\0"
  53         "trail\0"
  54         "dontpub\0"
  55         "auto\0"
  56         "dev\0"
  57         "netmask\0";
  58
  59 /* Delete an entry from the ARP cache. */
  60 /* Called only from main, once */
  61 static int arp_del(char **args)
  62 {
  63         char *host;
  64         struct arpreq req;
  65         struct sockaddr sa;
  66         int flags = 0;
  67         int err;
  68
  69         memset(&req, 0, sizeof(req));
  70
  71         /* Resolve the host name. */
  72         host = *args;
  73         if (ap->input(host, &sa) < 0) {
  74                 bb_herror_msg_and_die("%s", host);
  75         }
  76
  77         /* If a host has more than one address, use the correct one! */
  78         memcpy(&req.arp_pa, &sa, sizeof(struct sockaddr));
  79
  80         if (hw_set)
  81                 req.arp_ha.sa_family = hw->type;
  82
  83         req.arp_flags = ATF_PERM;
  84         args++;
  85         while (*args != NULL) {
  86                 switch (index_in_strings(options, *args)) {
  87                 case 0: /* "pub" */
  88                         flags |= 1;
  89                         args++;
  90                         break;
  91                 case 1: /* "priv" */
  92                         flags |= 2;
  93                         args++;
  94                         break;
  95                 case 2: /* "temp" */
  96                         req.arp_flags &= ~ATF_PERM;
  97                         args++;
  98                         break;
  99                 case 3: /* "trail" */
 100                         req.arp_flags |= ATF_USETRAILERS;
 101                         args++;
 102                         break;
 103                 case 4: /* "dontpub" */
 104 #ifdef HAVE_ATF_DONTPUB
 105                         req.arp_flags |= ATF_DONTPUB;
 106 #else
 107                         bb_error_msg("feature ATF_DONTPUB is not supported");
 108 #endif
 109                         args++;
 110                         break;
 111                 case 5: /* "auto" */
 112 #ifdef HAVE_ATF_MAGIC
 113                         req.arp_flags |= ATF_MAGIC;
 114 #else
 115                         bb_error_msg("feature ATF_MAGIC is not supported");
 116 #endif
 117                         args++;
 118                         break;
 119                 case 6: /* "dev" */
 120                         if (*++args == NULL)
 121                                 bb_show_usage();
 122                         device = *args;
 123                         args++;
 124                         break;
 125                 case 7: /* "netmask" */
 126                         if (*++args == NULL)
 127                                 bb_show_usage();
 128                         if (strcmp(*args, "255.255.255.255") != 0) {
 129                                 host = *args;
 130                                 if (ap->input(host, &sa) < 0) {
 131                                         bb_herror_msg_and_die("%s", host);
 132                                 }
 133                                 memcpy(&req.arp_netmask, &sa, sizeof(struct sockaddr));
 134                                 req.arp_flags |= ATF_NETMASK;
 135                         }
 136                         args++;
 137                         break;
 138                 default:
 139                         bb_show_usage();
 140                         break;
 141                 }
 142         }
 143         if (flags == 0)
 144                 flags = 3;
 145
 146         strncpy(req.arp_dev, device, sizeof(req.arp_dev));
 147
 148         err = -1;
 149
 150         /* Call the kernel. */
 151         if (flags & 2) {
 152                 if (option_mask32 & ARP_OPT_v)
 153                         bb_error_msg("SIOCDARP(nopub)");
 154                 err = ioctl(sockfd, SIOCDARP, &req);
 155                 if (err < 0) {
 156                         if (errno == ENXIO) {
 157                                 if (flags & 1)
 158                                         goto nopub;
 159                                 printf("No ARP entry for %s\n", host);
 160                                 return -1;
 161                         }
 162                         bb_perror_msg_and_die("SIOCDARP(priv)");
 163                 }
 164         }
 165         if ((flags & 1) && err) {
 166  nopub:
 167                 req.arp_flags |= ATF_PUBL;
 168                 if (option_mask32 & ARP_OPT_v)
 169                         bb_error_msg("SIOCDARP(pub)");
 170                 if (ioctl(sockfd, SIOCDARP, &req) < 0) {
 171                         if (errno == ENXIO) {
 172                                 printf("No ARP entry for %s\n", host);
 173                                 return -1;
 174                         }
 175                         bb_perror_msg_and_die("SIOCDARP(pub)");
 176                 }
 177         }
 178         return 0;
 179 }
 180
 181 /* Get the hardware address to a specified interface name */
 182 static void arp_getdevhw(char *ifname, struct sockaddr *sa,
 183                                                  const struct hwtype *hwt)
 184 {
 185         struct ifreq ifr;
 186         const struct hwtype *xhw;
 187
 188         strcpy(ifr.ifr_name, ifname);
 189         ioctl_or_perror_and_die(sockfd, SIOCGIFHWADDR, &ifr,
 190                                         "cant get HW-Address for '%s'", ifname);
 191         if (hwt && (ifr.ifr_hwaddr.sa_family != hw->type)) {
 192                 bb_error_msg_and_die("protocol type mismatch");
 193         }
 194         memcpy(sa, &(ifr.ifr_hwaddr), sizeof(struct sockaddr));
 195
 196         if (option_mask32 & ARP_OPT_v) {
 197                 xhw = get_hwntype(ifr.ifr_hwaddr.sa_family);
 198                 if (!xhw || !xhw->print) {
 199                         xhw = get_hwntype(-1);
 200                 }
 201                 bb_error_msg("device '%s' has HW address %s '%s'",
 202                                          ifname, xhw->name,
 203                                          xhw->print((char *) &ifr.ifr_hwaddr.sa_data));
 204         }
 205 }
 206
 207 /* Set an entry in the ARP cache. */
 208 /* Called only from main, once */
 209 static int arp_set(char **args)
 210 {
 211         char *host;
 212         struct arpreq req;
 213         struct sockaddr sa;
 214         int flags;
 215
 216         memset(&req, 0, sizeof(req));
 217
 218         host = *args++;
 219         if (ap->input(host, &sa) < 0) {
 220                 bb_herror_msg_and_die("%s", host);
 221         }
 222         /* If a host has more than one address, use the correct one! */
 223         memcpy(&req.arp_pa, &sa, sizeof(struct sockaddr));
 224
 225         /* Fetch the hardware address. */
 226         if (*args == NULL) {
 227                 bb_error_msg_and_die("need hardware address");
 228         }
 229         if (option_mask32 & ARP_OPT_D) {
 230                 arp_getdevhw(*args++, &req.arp_ha, hw_set ? hw : NULL);
 231         } else {
 232                 if (hw->input(*args++, &req.arp_ha) < 0) {
 233                         bb_error_msg_and_die("invalid hardware address");
 234                 }
 235         }
 236
 237         /* Check out any modifiers. */
 238         flags = ATF_PERM | ATF_COM;
 239         while (*args != NULL) {
 240                 switch (index_in_strings(options, *args)) {
 241                 case 0: /* "pub" */
 242                         flags |= ATF_PUBL;
 243                         args++;
 244                         break;
 245                 case 1: /* "priv" */
 246                         flags &= ~ATF_PUBL;
 247                         args++;
 248                         break;
 249                 case 2: /* "temp" */
 250                         flags &= ~ATF_PERM;
 251                         args++;
 252                         break;
 253                 case 3: /* "trail" */
 254                         flags |= ATF_USETRAILERS;
 255                         args++;
 256                         break;
 257                 case 4: /* "dontpub" */
 258 #ifdef HAVE_ATF_DONTPUB
 259                         flags |= ATF_DONTPUB;
 260 #else
 261                         bb_error_msg("feature ATF_DONTPUB is not supported");
 262 #endif
 263                         args++;
 264                         break;
 265                 case 5: /* "auto" */
 266 #ifdef HAVE_ATF_MAGIC
 267                         flags |= ATF_MAGIC;
 268 #else
 269                         bb_error_msg("feature ATF_MAGIC is not supported");
 270 #endif
 271                         args++;
 272                         break;
 273                 case 6: /* "dev" */
 274                         if (*++args == NULL)
 275                                 bb_show_usage();
 276                         device = *args;
 277                         args++;
 278                         break;
 279                 case 7: /* "netmask" */
 280                         if (*++args == NULL)
 281                                 bb_show_usage();
 282                         if (strcmp(*args, "255.255.255.255") != 0) {
 283                                 host = *args;
 284                                 if (ap->input(host, &sa) < 0) {
 285                                         bb_herror_msg_and_die("%s", host);
 286                                 }
 287                                 memcpy(&req.arp_netmask, &sa, sizeof(struct sockaddr));
 288                                 flags |= ATF_NETMASK;
 289                         }
 290                         args++;
 291                         break;
 292                 default:
 293                         bb_show_usage();
 294                         break;
 295                 }
 296         }
 297
 298         /* Fill in the remainder of the request. */
 299         req.arp_flags = flags;
 300
 301         strncpy(req.arp_dev, device, sizeof(req.arp_dev));
 302
 303         /* Call the kernel. */
 304         if (option_mask32 & ARP_OPT_v)
 305                 bb_error_msg("SIOCSARP()");
 306         xioctl(sockfd, SIOCSARP, &req);
 307         return 0;
 308 }
 309
 310
 311 /* Print the contents of an ARP request block. */
 312 static void
 313 arp_disp(const char *name, char *ip, int type, int arp_flags,
 314                  char *hwa, char *mask, char *dev)
 315 {
 316         const struct hwtype *xhw;
 317
 318         xhw = get_hwntype(type);
 319         if (xhw == NULL)
 320                 xhw = get_hwtype(DFLT_HW);
 321
 322         printf("%s (%s) at ", name, ip);
 323
 324         if (!(arp_flags & ATF_COM)) {
 325                 if (arp_flags & ATF_PUBL)
 326                         printf("* ");
 327                 else
 328                         printf("<incomplete> ");
 329         } else {
 330                 printf("%s [%s] ", hwa, xhw->name);
 331         }
 332
 333         if (arp_flags & ATF_NETMASK)
 334                 printf("netmask %s ", mask);
 335
 336         if (arp_flags & ATF_PERM)
 337                 printf("PERM ");
 338         if (arp_flags & ATF_PUBL)
 339                 printf("PUP ");
 340 #ifdef HAVE_ATF_MAGIC
 341         if (arp_flags & ATF_MAGIC)
 342                 printf("AUTO ");
 343 #endif
 344 #ifdef HAVE_ATF_DONTPUB
 345         if (arp_flags & ATF_DONTPUB)
 346                 printf("DONTPUB ");
 347 #endif
 348         if (arp_flags & ATF_USETRAILERS)
 349                 printf("TRAIL ");
 350
 351         printf("on %s\n", dev);
 352 }
 353
 354 /* Display the contents of the ARP cache in the kernel. */
 355 /* Called only from main, once */
 356 static int arp_show(char *name)
 357 {
 358         const char *host;
 359         const char *hostname;
 360         FILE *fp;
 361         struct sockaddr sa;
 362         int type, flags;
 363         int num;
 364         unsigned entries = 0, shown = 0;
 365         char ip[128];
 366         char hwa[128];
 367         char mask[128];
 368         char line[128];
 369         char dev[128];
 370
 371         host = NULL;
 372         if (name != NULL) {
 373                 /* Resolve the host name. */
 374                 if (ap->input(name, &sa) < 0) {
 375                         bb_herror_msg_and_die("%s", name);
 376                 }
 377                 host = xstrdup(ap->sprint(&sa, 1));
 378         }
 379         fp = xfopen("/proc/net/arp", "r");
 380         /* Bypass header -- read one line */
 381         fgets(line, sizeof(line), fp);
 382
 383         /* Read the ARP cache entries. */
 384         while (fgets(line, sizeof(line), fp)) {
 385
 386                 mask[0] = '-'; mask[1] = '\0';
 387                 dev[0] = '-'; dev[1] = '\0';
 388                 /* All these strings can't overflow
 389                  * because fgets above reads limited amount of data */
 390                 num = sscanf(line, "%s 0x%x 0x%x %s %s %s\n",
 391                                          ip, &type, &flags, hwa, mask, dev);
 392                 if (num < 4)
 393                         break;
 394
 395                 entries++;
 396                 /* if the user specified hw-type differs, skip it */
 397                 if (hw_set && (type != hw->type))
 398                         continue;
 399
 400                 /* if the user specified address differs, skip it */
 401                 if (host && strcmp(ip, host) != 0)
 402                         continue;
 403
 404                 /* if the user specified device differs, skip it */
 405                 if (device[0] && strcmp(dev, device) != 0)
 406                         continue;
 407
 408                 shown++;
 409                 /* This IS ugly but it works -be */
 410                 hostname = "?";
 411                 if (!(option_mask32 & ARP_OPT_n)) {
 412                         if (ap->input(ip, &sa) < 0)
 413                                 hostname = ip;
 414                         else
 415                                 hostname = ap->sprint(&sa, (option_mask32 & ARP_OPT_n) | 0x8000);
 416                         if (strcmp(hostname, ip) == 0)
 417                                 hostname = "?";
 418                 }
 419
 420                 arp_disp(hostname, ip, type, flags, hwa, mask, dev);
 421         }
 422         if (option_mask32 & ARP_OPT_v)
 423                 printf("Entries: %d\tSkipped: %d\tFound: %d\n",
 424                            entries, entries - shown, shown);
 425
 426         if (!shown) {
 427                 if (hw_set || host || device[0])
 428                         printf("No match found in %d entries\n", entries);
 429         }
 430         if (ENABLE_FEATURE_CLEAN_UP) {
 431                 free((char*)host);
 432                 fclose(fp);
 433         }
 434         return 0;
 435 }
 436
 437 int arp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 438 int arp_main(int argc, char **argv)
 439 {
 440         char *hw_type;
 441         char *protocol;
 442
 443         /* Initialize variables... */
 444         ap = get_aftype(DFLT_AF);
 445         if (!ap)
 446                 bb_error_msg_and_die("%s: %s not supported", DFLT_AF, "address family");
 447
 448         getopt32(argv, "A:p:H:t:i:adnDsv", &protocol, &protocol,
 449                                  &hw_type, &hw_type, &device);
 450         argv += optind;
 451         if (option_mask32 & ARP_OPT_A || option_mask32 & ARP_OPT_p) {
 452                 ap = get_aftype(protocol);
 453                 if (ap == NULL)
 454                         bb_error_msg_and_die("%s: unknown %s", protocol, "address family");
 455         }
 456         if (option_mask32 & ARP_OPT_A || option_mask32 & ARP_OPT_p) {
 457                 hw = get_hwtype(hw_type);
 458                 if (hw == NULL)
 459                         bb_error_msg_and_die("%s: unknown %s", hw_type, "hardware type");
 460                 hw_set = 1;
 461         }
 462         //if (option_mask32 & ARP_OPT_i)... -i
 463
 464         if (ap->af != AF_INET) {
 465                 bb_error_msg_and_die("%s: kernel only supports 'inet'", ap->name);
 466         }
 467
 468         /* If no hw type specified get default */
 469         if (!hw) {
 470                 hw = get_hwtype(DFLT_HW);
 471                 if (!hw)
 472                         bb_error_msg_and_die("%s: %s not supported", DFLT_HW, "hardware type");
 473         }
 474
 475         if (hw->alen <= 0) {
 476                 bb_error_msg_and_die("%s: %s without ARP support",
 477                                                          hw->name, "hardware type");
 478         }
 479         sockfd = xsocket(AF_INET, SOCK_DGRAM, 0);
 480
 481         /* Now see what we have to do here... */
 482         if (option_mask32 & (ARP_OPT_d|ARP_OPT_s)) {
 483                 if (argv[0] == NULL)
 484                         bb_error_msg_and_die("need host name");
 485                 if (option_mask32 & ARP_OPT_s)
 486                         return arp_set(argv);
 487                 return arp_del(argv);
 488         }
 489         //if (option_mask32 & ARP_OPT_a) - default
 490         return arp_show(argv[0]);
 491 }