networking/arping.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * arping.c - Ping hosts by ARP requests/replies
   4  *
   5  * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   6  *
   7  * Author:      Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   8  * Busybox port: Nick Fedchik <nick@fedchik.org.ua>
   9  */
  10
  11 #include <sys/ioctl.h>
  12 #include <signal.h>
  13
  14 #include <errno.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <unistd.h>
  18
  19 #include <arpa/inet.h>
  20 #include <net/if.h>
  21 #include <netinet/ether.h>
  22 #include <netpacket/packet.h>
  23
  24 #include "busybox.h"
  25
  26 static struct in_addr src;
  27 static struct in_addr dst;
  28 static struct sockaddr_ll me;
  29 static struct sockaddr_ll he;
  30 static struct timeval last;
  31
  32 enum cfg_e {
  33         dad = 1,
  34         unsolicited = 2,
  35         advert = 4,
  36         quiet = 8,
  37         quit_on_reply = 16,
  38         broadcast_only = 32,
  39         unicasting = 64
  40 };
  41 static int cfg;
  42
  43 static int s;
  44 static unsigned count = UINT_MAX;
  45 static unsigned timeout;
  46 static int sent;
  47 static int brd_sent;
  48 static int received;
  49 static int brd_recv;
  50 static int req_recv;
  51
  52
  53 #define MS_TDIFF(tv1,tv2) ( ((tv1).tv_sec-(tv2).tv_sec)*1000 + \
  54                            ((tv1).tv_usec-(tv2).tv_usec)/1000 )
  55 static int send_pack(int sock, struct in_addr *src_addr,
  56                                          struct in_addr *dst_addr, struct sockaddr_ll *ME,
  57                                          struct sockaddr_ll *HE)
  58 {
  59         int err;
  60         struct timeval now;
  61         RESERVE_CONFIG_UBUFFER(buf, 256);
  62         struct arphdr *ah = (struct arphdr *) buf;
  63         unsigned char *p = (unsigned char *) (ah + 1);
  64
  65         ah->ar_hrd = htons(ME->sll_hatype);
  66         ah->ar_hrd = htons(ARPHRD_ETHER);
  67         ah->ar_pro = htons(ETH_P_IP);
  68         ah->ar_hln = ME->sll_halen;
  69         ah->ar_pln = 4;
  70         ah->ar_op = cfg&advert ? htons(ARPOP_REPLY) : htons(ARPOP_REQUEST);
  71
  72         memcpy(p, &ME->sll_addr, ah->ar_hln);
  73         p += ME->sll_halen;
  74
  75         memcpy(p, src_addr, 4);
  76         p += 4;
  77
  78         if (cfg&advert)
  79                 memcpy(p, &ME->sll_addr, ah->ar_hln);
  80         else
  81                 memcpy(p, &HE->sll_addr, ah->ar_hln);
  82         p += ah->ar_hln;
  83
  84         memcpy(p, dst_addr, 4);
  85         p += 4;
  86
  87         gettimeofday(&now, NULL);
  88         err = sendto(sock, buf, p - buf, 0, (struct sockaddr *) HE, sizeof(*HE));
  89         if (err == p - buf) {
  90                 last = now;
  91                 sent++;
  92                 if (!(cfg&unicasting))
  93                         brd_sent++;
  94         }
  95         RELEASE_CONFIG_BUFFER(buf);
  96         return err;
  97 }
  98
  99 static void finish(void)
 100 {
 101         if (!(cfg&quiet)) {
 102                 printf("Sent %d probes (%d broadcast(s))\n"
 103                         "Received %d repl%s",
 104                         sent, brd_sent,
 105                         received, (received > 1) ? "ies" : "y");
 106                 if (brd_recv || req_recv) {
 107                         printf(" (");
 108                         if (req_recv)
 109                                 printf("%d request(s)", req_recv);
 110                         if (brd_recv)
 111                                 printf("%s%d broadcast(s)", req_recv ? ", " : "", brd_recv);
 112                         putchar(')');
 113                 }
 114                 putchar('\n');
 115                 fflush(stdout);
 116         }
 117         if (cfg&dad)
 118                 exit(!!received);
 119         if (cfg&unsolicited)
 120                 exit(0);
 121         exit(!received);
 122 }
 123
 124 static void catcher(void)
 125 {
 126         struct timeval tv;
 127         static struct timeval start;
 128
 129         gettimeofday(&tv, NULL);
 130
 131         if (start.tv_sec == 0)
 132                 start = tv;
 133
 134         if (count-- == 0
 135                 || (timeout && MS_TDIFF(tv, start) > timeout * 1000 + 500))
 136                 finish();
 137
 138         if (last.tv_sec == 0 || MS_TDIFF(tv, last) > 500) {
 139                 send_pack(s, &src, &dst, &me, &he);
 140                 if (count == 0 && cfg&unsolicited)
 141                         finish();
 142         }
 143         alarm(1);
 144 }
 145
 146 static int recv_pack(unsigned char *buf, int len, struct sockaddr_ll *FROM)
 147 {
 148         struct arphdr *ah = (struct arphdr *) buf;
 149         unsigned char *p = (unsigned char *) (ah + 1);
 150         struct in_addr src_ip, dst_ip;
 151
 152         /* Filter out wild packets */
 153         if (FROM->sll_pkttype != PACKET_HOST &&
 154                 FROM->sll_pkttype != PACKET_BROADCAST &&
 155                 FROM->sll_pkttype != PACKET_MULTICAST)
 156                 return 0;
 157
 158         /* Only these types are recognised */
 159         if (ah->ar_op != htons(ARPOP_REQUEST) && ah->ar_op != htons(ARPOP_REPLY))
 160                 return 0;
 161
 162         /* ARPHRD check and this darned FDDI hack here :-( */
 163         if (ah->ar_hrd != htons(FROM->sll_hatype) &&
 164                 (FROM->sll_hatype != ARPHRD_FDDI
 165                  || ah->ar_hrd != htons(ARPHRD_ETHER)))
 166                 return 0;
 167
 168         /* Protocol must be IP. */
 169         if (ah->ar_pro != htons(ETH_P_IP))
 170                 return 0;
 171         if (ah->ar_pln != 4)
 172                 return 0;
 173         if (ah->ar_hln != me.sll_halen)
 174                 return 0;
 175         if (len < sizeof(*ah) + 2 * (4 + ah->ar_hln))
 176                 return 0;
 177         memcpy(&src_ip, p + ah->ar_hln, 4);
 178         memcpy(&dst_ip, p + ah->ar_hln + 4 + ah->ar_hln, 4);
 179         if (!(cfg&dad)) {
 180                 if (src_ip.s_addr != dst.s_addr)
 181                         return 0;
 182                 if (src.s_addr != dst_ip.s_addr)
 183                         return 0;
 184                 if (memcmp(p + ah->ar_hln + 4, &me.sll_addr, ah->ar_hln))
 185                         return 0;
 186         } else {
 187                 /* DAD packet was:
 188                    src_ip = 0 (or some src)
 189                    src_hw = ME
 190                    dst_ip = tested address
 191                    dst_hw = <unspec>
 192
 193                    We fail, if receive request/reply with:
 194                    src_ip = tested_address
 195                    src_hw != ME
 196                    if src_ip in request was not zero, check
 197                    also that it matches to dst_ip, otherwise
 198                    dst_ip/dst_hw do not matter.
 199                  */
 200                 if (src_ip.s_addr != dst.s_addr)
 201                         return 0;
 202                 if (memcmp(p, &me.sll_addr, me.sll_halen) == 0)
 203                         return 0;
 204                 if (src.s_addr && src.s_addr != dst_ip.s_addr)
 205                         return 0;
 206         }
 207         if (!(cfg&quiet)) {
 208                 int s_printed = 0;
 209                 struct timeval tv;
 210
 211                 gettimeofday(&tv, NULL);
 212
 213                 printf("%s %s from %s [%s]",
 214                         FROM->sll_pkttype == PACKET_HOST ? "Unicast" : "Broadcast",
 215                         ah->ar_op == htons(ARPOP_REPLY) ? "reply" : "request",
 216                         inet_ntoa(src_ip),
 217                         ether_ntoa((struct ether_addr *) p));
 218                 if (dst_ip.s_addr != src.s_addr) {
 219                         printf("for %s ", inet_ntoa(dst_ip));
 220                         s_printed = 1;
 221                 }
 222                 if (memcmp(p + ah->ar_hln + 4, me.sll_addr, ah->ar_hln)) {
 223                         if (!s_printed)
 224                                 printf("for ");
 225                         printf("[%s]",
 226                                    ether_ntoa((struct ether_addr *) p + ah->ar_hln + 4));
 227                 }
 228
 229                 if (last.tv_sec) {
 230                         long usecs = (tv.tv_sec - last.tv_sec) * 1000000 +
 231                                 tv.tv_usec - last.tv_usec;
 232                         long msecs = (usecs + 500) / 1000;
 233
 234                         usecs -= msecs * 1000 - 500;
 235                         printf(" %ld.%03ldms\n", msecs, usecs);
 236                 } else {
 237                         printf(" UNSOLICITED?\n");
 238                 }
 239                 fflush(stdout);
 240         }
 241         received++;
 242         if (FROM->sll_pkttype != PACKET_HOST)
 243                 brd_recv++;
 244         if (ah->ar_op == htons(ARPOP_REQUEST))
 245                 req_recv++;
 246         if (cfg&quit_on_reply)
 247                 finish();
 248         if (!(cfg&broadcast_only)) {
 249                 memcpy(he.sll_addr, p, me.sll_halen);
 250                 cfg |= unicasting;
 251         }
 252         return 1;
 253 }
 254
 255 int arping_main(int argc, char **argv)
 256 {
 257         char *device = "eth0";
 258         int ifindex;
 259         char *source = NULL;
 260         char *target;
 261
 262         s = xsocket(PF_PACKET, SOCK_DGRAM, 0);
 263
 264         // Drop suid root privileges
 265         xsetuid(getuid());
 266
 267         {
 268                 unsigned opt;
 269                 char *_count, *_timeout;
 270
 271                 /* Dad also sets quit_on_reply.
 272                  * Advert also sets unsolicited.
 273                  */
 274                 opt_complementary = "Df:AU";
 275                 opt = getopt32(argc, argv, "DUAqfbc:w:i:s:",
 276                                         &_count, &_timeout, &device, &source);
 277                 cfg |= opt & 0x3f; /* set respective flags */
 278                 if (opt & 0x40) /* -c: count */
 279                         count = xatou(_count);
 280                 if (opt & 0x80) /* -w: timeout */
 281                         timeout = xatoul_range(_timeout, 0, INT_MAX/2000);
 282                 if (opt & 0x100) { /* -i: interface */
 283                         if (strlen(device) > IF_NAMESIZE) {
 284                                 bb_error_msg_and_die("interface name '%s' is too long",
 285                                                                 device);
 286                         }
 287                 }
 288                 //if (opt & 0x200) /* -s: source */
 289         }
 290         argc -= optind;
 291         argv += optind;
 292
 293         if (argc != 1)
 294                 bb_show_usage();
 295
 296         target = *argv;
 297
 298         xfunc_error_retval = 2;
 299
 300         {
 301                 struct ifreq ifr;
 302
 303                 memset(&ifr, 0, sizeof(ifr));
 304                 strncpy(ifr.ifr_name, device, IFNAMSIZ - 1);
 305                 if (ioctl(s, SIOCGIFINDEX, &ifr) < 0) {
 306                         bb_error_msg_and_die("interface %s not found", device);
 307                 }
 308                 ifindex = ifr.ifr_ifindex;
 309
 310                 if (ioctl(s, SIOCGIFFLAGS, (char *) &ifr)) {
 311                         bb_error_msg_and_die("SIOCGIFFLAGS");
 312                 }
 313                 if (!(ifr.ifr_flags & IFF_UP)) {
 314                         bb_error_msg_and_die("interface %s is down", device);
 315                 }
 316                 if (ifr.ifr_flags & (IFF_NOARP | IFF_LOOPBACK)) {
 317                         bb_error_msg("interface %s is not ARPable", device);
 318                         exit(cfg&dad ? 0 : 2);
 319                 }
 320         }
 321
 322         if (!inet_aton(target, &dst)) {
 323                 struct hostent *hp;
 324
 325                 hp = gethostbyname2(target, AF_INET);
 326                 if (!hp) {
 327                         bb_error_msg_and_die("invalid or unknown target %s", target);
 328                 }
 329                 memcpy(&dst, hp->h_addr, 4);
 330         }
 331
 332         if (source && !inet_aton(source, &src)) {
 333                 bb_error_msg_and_die("invalid source address %s", source);
 334         }
 335
 336         if (!(cfg&dad) && cfg&unsolicited && src.s_addr == 0)
 337                 src = dst;
 338
 339         if (!(cfg&dad) || src.s_addr) {
 340                 struct sockaddr_in saddr;
 341                 int probe_fd = xsocket(AF_INET, SOCK_DGRAM, 0);
 342
 343                 if (device) {
 344                         if (setsockopt
 345                                 (probe_fd, SOL_SOCKET, SO_BINDTODEVICE, device,
 346                                  strlen(device) + 1) == -1)
 347                                 bb_error_msg("warning: interface %s is ignored", device);
 348                 }
 349                 memset(&saddr, 0, sizeof(saddr));
 350                 saddr.sin_family = AF_INET;
 351                 if (src.s_addr) {
 352                         saddr.sin_addr = src;
 353                         if (bind(probe_fd, (struct sockaddr *) &saddr, sizeof(saddr)) == -1) {
 354                                 bb_error_msg_and_die("bind");
 355                         }
 356                 } else if (!(cfg&dad)) {
 357                         int on = 1;
 358                         socklen_t alen = sizeof(saddr);
 359
 360                         saddr.sin_port = htons(1025);
 361                         saddr.sin_addr = dst;
 362
 363                         if (setsockopt
 364                                 (probe_fd, SOL_SOCKET, SO_DONTROUTE, (char *) &on,
 365                                  sizeof(on)) == -1)
 366                                 bb_perror_msg("warning: setsockopt(SO_DONTROUTE)");
 367                         if (connect(probe_fd, (struct sockaddr *) &saddr, sizeof(saddr))
 368                                 == -1) {
 369                                 bb_error_msg_and_die("connect");
 370                         }
 371                         if (getsockname(probe_fd, (struct sockaddr *) &saddr, &alen) ==
 372                                 -1) {
 373                                 bb_error_msg_and_die("getsockname");
 374                         }
 375                         src = saddr.sin_addr;
 376                 }
 377                 close(probe_fd);
 378         };
 379
 380         me.sll_family = AF_PACKET;
 381         me.sll_ifindex = ifindex;
 382         me.sll_protocol = htons(ETH_P_ARP);
 383         if (bind(s, (struct sockaddr *) &me, sizeof(me)) == -1) {
 384                 bb_error_msg_and_die("bind");
 385         }
 386
 387         {
 388                 socklen_t alen = sizeof(me);
 389
 390                 if (getsockname(s, (struct sockaddr *) &me, &alen) == -1) {
 391                         bb_error_msg_and_die("getsockname");
 392                 }
 393         }
 394         if (me.sll_halen == 0) {
 395                 bb_error_msg("Interface \"%s\" is not ARPable (no ll address)", device);
 396                 exit(cfg&dad ? 0 : 2);
 397         }
 398         he = me;
 399         memset(he.sll_addr, -1, he.sll_halen);
 400
 401         if (!(cfg&quiet)) {
 402                 printf("ARPING to %s from %s via %s\n",
 403                         inet_ntoa(dst), inet_ntoa(src),
 404                         device ? device : "unknown");
 405         }
 406
 407         if (!src.s_addr && !(cfg&dad)) {
 408                 bb_error_msg_and_die("no src address in the non-DAD mode");
 409         }
 410
 411         {
 412                 struct sigaction sa;
 413
 414                 memset(&sa, 0, sizeof(sa));
 415                 sa.sa_flags = SA_RESTART;
 416
 417                 sa.sa_handler = (void (*)(int)) finish;
 418                 sigaction(SIGINT, &sa, NULL);
 419
 420                 sa.sa_handler = (void (*)(int)) catcher;
 421                 sigaction(SIGALRM, &sa, NULL);
 422         }
 423
 424         catcher();
 425
 426         while (1) {
 427                 sigset_t sset, osset;
 428                 RESERVE_CONFIG_UBUFFER(packet, 4096);
 429                 struct sockaddr_ll from;
 430                 socklen_t alen = sizeof(from);
 431                 int cc;
 432
 433                 if ((cc = recvfrom(s, packet, 4096, 0,
 434                                                    (struct sockaddr *) &from, &alen)) < 0) {
 435                         bb_perror_msg("recvfrom");
 436                         continue;
 437                 }
 438                 sigemptyset(&sset);
 439                 sigaddset(&sset, SIGALRM);
 440                 sigaddset(&sset, SIGINT);
 441                 sigprocmask(SIG_BLOCK, &sset, &osset);
 442                 recv_pack(packet, cc, &from);
 443                 sigprocmask(SIG_SETMASK, &osset, NULL);
 444                 RELEASE_CONFIG_BUFFER(packet);
 445         }
 446 }