LXR busybox/networking/arping.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   4 *
   5 * Author: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
   6 * Busybox port: Nick Fedchik <nick@fedchik.org.ua>
   7 */
   8//config:config ARPING
   9//config:       bool "arping (9 kb)"
  10//config:       default y
  11//config:       select PLATFORM_LINUX
  12//config:       help
  13//config:       Ping hosts by ARP packets.
  14
  15//applet:IF_ARPING(APPLET(arping, BB_DIR_USR_SBIN, BB_SUID_DROP))
  16
  17//kbuild:lib-$(CONFIG_ARPING) += arping.o
  18
  19//usage:#define arping_trivial_usage
  20//usage:       "[-fqbDUA] [-c CNT] [-w TIMEOUT] [-I IFACE] [-s SRC_IP] DST_IP"
  21//usage:#define arping_full_usage "\n\n"
  22//usage:       "Send ARP requests/replies\n"
  23//usage:     "\n        -f              Quit on first ARP reply"
  24//usage:     "\n        -q              Quiet"
  25//usage:     "\n        -b              Keep broadcasting, don't go unicast"
  26//usage:     "\n        -D              Exit with 1 if DST_IP replies"
  27//usage:     "\n        -U              Unsolicited ARP mode, update your neighbors"
  28//usage:     "\n        -A              ARP answer mode, update your neighbors"
  29//usage:     "\n        -c N            Stop after sending N ARP requests"
  30//usage:     "\n        -w TIMEOUT      Seconds to wait for ARP reply"
  31//NB: in iputils-s20160308, iface is mandatory, no default
  32//usage:     "\n        -I IFACE        Interface to use (default eth0)"
  33//usage:     "\n        -s SRC_IP       Sender IP address"
  34//usage:     "\n        DST_IP          Target IP address"
  35
  36#include <arpa/inet.h>
  37#include <net/if.h>
  38#include <netinet/ether.h>
  39#include <netpacket/packet.h>
  40
  41#include "libbb.h"
  42#include "common_bufsiz.h"
  43
  44/* We don't expect to see 1000+ seconds delay, unsigned is enough */
  45#define MONOTONIC_US() ((unsigned)monotonic_us())
  46
  47enum {
  48        UNSOLICITED   = 1 << 0,
  49        DAD           = 1 << 1,
  50        ADVERT        = 1 << 2,
  51        QUIET         = 1 << 3,
  52        QUIT_ON_REPLY = 1 << 4,
  53        BCAST_ONLY    = 1 << 5,
  54        UNICASTING    = 1 << 6,
  55        TIMEOUT       = 1 << 7,
  56};
  57#define GETOPT32(str_timeout, device, source) \
  58        getopt32(argv, "^" \
  59                "UDAqfbc:+w:I:s:" \
  60                /* DAD also sets quit_on_reply, */ \
  61                /* advert also sets unsolicited: */ \
  62                "\0" "=1:Df:AU", \
  63                &count, &str_timeout, &device, &source \
  64        );
  65
  66struct globals {
  67        struct in_addr src;
  68        struct in_addr dst;
  69        struct sockaddr_ll me;
  70        struct sockaddr_ll he;
  71
  72        int count; // = -1;
  73        unsigned last;
  74        unsigned timeout_us;
  75        unsigned start;
  76
  77        unsigned sent;
  78        unsigned brd_sent;
  79        unsigned received;
  80        unsigned brd_recv;
  81        unsigned req_recv;
  82
  83        /* should be in main(), but are here to reduce stack use: */
  84        struct ifreq ifr;
  85        struct sockaddr_in probe_saddr;
  86        sigset_t sset;
  87        unsigned char packet[4096];
  88} FIX_ALIASING;
  89#define src        (G.src       )
  90#define dst        (G.dst       )
  91#define me         (G.me        )
  92#define he         (G.he        )
  93#define count      (G.count     )
  94#define last       (G.last      )
  95#define timeout_us (G.timeout_us)
  96#define start      (G.start     )
  97#define sent       (G.sent      )
  98#define brd_sent   (G.brd_sent  )
  99#define received   (G.received  )
 100#define brd_recv   (G.brd_recv  )
 101#define req_recv   (G.req_recv  )
 102//#define G (*(struct globals*)bb_common_bufsiz1)
 103#define G (*ptr_to_globals)
 104#define INIT_G() do { \
 105        /*setup_common_bufsiz();*/ \
 106        SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
 107        count = -1; \
 108} while (0)
 109
 110#define sock_fd 3
 111
 112static int send_pack(struct in_addr *src_addr,
 113                        struct in_addr *dst_addr,
 114                        struct sockaddr_ll *ME,
 115                        struct sockaddr_ll *HE)
 116{
 117        int err;
 118        unsigned char buf[256];
 119        struct arphdr *ah = (struct arphdr *) buf;
 120        unsigned char *p;
 121
 122        ah->ar_hrd = htons(ARPHRD_ETHER);
 123        ah->ar_pro = htons(ETH_P_IP);
 124        ah->ar_hln = ME->sll_halen;
 125        ah->ar_pln = 4;
 126        ah->ar_op = option_mask32 & ADVERT ? htons(ARPOP_REPLY) : htons(ARPOP_REQUEST);
 127
 128        p = (unsigned char *) (ah + 1);
 129        p = mempcpy(p, &ME->sll_addr, ah->ar_hln);
 130        p = mempcpy(p, src_addr, 4);
 131
 132        if (option_mask32 & ADVERT)
 133                p = mempcpy(p, &ME->sll_addr, ah->ar_hln);
 134        else
 135                p = mempcpy(p, &HE->sll_addr, ah->ar_hln);
 136
 137        p = mempcpy(p, dst_addr, 4);
 138
 139        err = sendto(sock_fd, buf, p - buf, 0, (struct sockaddr *) HE, sizeof(*HE));
 140        if (err == p - buf) {
 141                last = MONOTONIC_US();
 142                sent++;
 143                if (!(option_mask32 & UNICASTING))
 144                        brd_sent++;
 145        }
 146        return err;
 147}
 148
 149static void finish(void) NORETURN;
 150static void finish(void)
 151{
 152        if (!(option_mask32 & QUIET)) {
 153                printf("Sent %u probe(s) (%u broadcast(s))\n"
 154                        "Received %u response(s)"
 155                        " (%u request(s), %u broadcast(s))\n",
 156                        sent, brd_sent,
 157                        received,
 158                        req_recv, brd_recv);
 159        }
 160        if (option_mask32 & DAD)
 161                exit(!!received);
 162        if (option_mask32 & UNSOLICITED)
 163                exit(EXIT_SUCCESS);
 164        exit(!received);
 165}
 166
 167static void catcher(void)
 168{
 169        unsigned now;
 170
 171        now = MONOTONIC_US();
 172        if (start == 0)
 173                start = now;
 174
 175        if (count == 0 || (timeout_us && (now - start) > timeout_us))
 176                finish();
 177
 178        /* count < 0 means "infinite count" */
 179        if (count > 0)
 180                count--;
 181
 182        if (last == 0 || (now - last) > 500000) {
 183                send_pack(&src, &dst, &me, &he);
 184                if (count == 0 && (option_mask32 & UNSOLICITED))
 185                        finish();
 186        }
 187        alarm(1);
 188}
 189
 190static void recv_pack(unsigned char *buf, int len, struct sockaddr_ll *FROM)
 191{
 192        struct arphdr *ah = (struct arphdr *) buf;
 193        unsigned char *p = (unsigned char *) (ah + 1);
 194        struct in_addr src_ip, dst_ip;
 195
 196        /* moves below assume in_addr is 4 bytes big, ensure that */
 197        BUILD_BUG_ON(sizeof(struct in_addr) != 4);
 198        BUILD_BUG_ON(sizeof(src_ip.s_addr) != 4);
 199
 200        /* Filter out wild packets */
 201        if (FROM->sll_pkttype != PACKET_HOST
 202         && FROM->sll_pkttype != PACKET_BROADCAST
 203         && FROM->sll_pkttype != PACKET_MULTICAST)
 204                return;
 205
 206        /* Only these types are recognized */
 207        if (ah->ar_op != htons(ARPOP_REQUEST) && ah->ar_op != htons(ARPOP_REPLY))
 208                return;
 209
 210        /* ARPHRD check and this darned FDDI hack here :-( */
 211        if (ah->ar_hrd != htons(FROM->sll_hatype)
 212         && (FROM->sll_hatype != ARPHRD_FDDI || ah->ar_hrd != htons(ARPHRD_ETHER)))
 213                return;
 214
 215        /* Protocol must be IP. */
 216        if (ah->ar_pro != htons(ETH_P_IP)
 217         || (ah->ar_pln != 4)
 218         || (ah->ar_hln != me.sll_halen)
 219         || (len < (int)(sizeof(*ah) + 2 * (4 + ah->ar_hln)))
 220        ) {
 221                return;
 222        }
 223
 224        move_from_unaligned32(src_ip.s_addr, p + ah->ar_hln);
 225        move_from_unaligned32(dst_ip.s_addr, p + ah->ar_hln + 4 + ah->ar_hln);
 226
 227        if (dst.s_addr != src_ip.s_addr)
 228                return;
 229        if (!(option_mask32 & DAD)) {
 230                if ((src.s_addr != dst_ip.s_addr)
 231                 || (memcmp(p + ah->ar_hln + 4, &me.sll_addr, ah->ar_hln)))
 232                        return;
 233        } else {
 234                /* DAD packet was:
 235                   src_ip = 0 (or some src)
 236                   src_hw = ME
 237                   dst_ip = tested address
 238                   dst_hw = <unspec>
 239
 240                   We fail, if receive request/reply with:
 241                   src_ip = tested_address
 242                   src_hw != ME
 243                   if src_ip in request was not zero, check
 244                   also that it matches to dst_ip, otherwise
 245                   dst_ip/dst_hw do not matter.
 246                 */
 247                if ((memcmp(p, &me.sll_addr, me.sll_halen) == 0)
 248                 || (src.s_addr && src.s_addr != dst_ip.s_addr))
 249                        return;
 250        }
 251        if (!(option_mask32 & QUIET)) {
 252                int s_printed = 0;
 253
 254//TODO: arping from iputils-s20160308 print upprcase hex in MAC, follow them?
 255                printf("%scast re%s from %s [%02x:%02x:%02x:%02x:%02x:%02x]",
 256                        FROM->sll_pkttype == PACKET_HOST ? "Uni" : "Broad",
 257                        ah->ar_op == htons(ARPOP_REPLY) ? "ply" : "quest",
 258                        inet_ntoa(src_ip),
 259                        p[0], p[1], p[2], p[3], p[4], p[5]
 260                );
 261                if (dst_ip.s_addr != src.s_addr) {
 262                        printf("for %s", inet_ntoa(dst_ip));
 263                        s_printed = 1;
 264                }
 265                if (memcmp(p + ah->ar_hln + 4, me.sll_addr, ah->ar_hln)) {
 266                        unsigned char *pp = p + ah->ar_hln + 4;
 267                        if (!s_printed)
 268                                printf(" for");
 269                        printf(" [%02x:%02x:%02x:%02x:%02x:%02x]",
 270                                pp[0], pp[1], pp[2], pp[3], pp[4], pp[5]
 271                        );
 272                }
 273
 274                if (last) {
 275                        unsigned diff = MONOTONIC_US() - last;
 276                        printf(" %u.%03ums\n", diff / 1000, diff % 1000);
 277                } else {
 278                        puts(" UNSOLICITED?");
 279                }
 280                fflush_all();
 281        }
 282        received++;
 283        if (FROM->sll_pkttype != PACKET_HOST)
 284                brd_recv++;
 285        if (ah->ar_op == htons(ARPOP_REQUEST))
 286                req_recv++;
 287        if (option_mask32 & QUIT_ON_REPLY)
 288                finish();
 289        if (!(option_mask32 & BCAST_ONLY)) {
 290                memcpy(he.sll_addr, p, me.sll_halen);
 291                option_mask32 |= UNICASTING;
 292        }
 293}
 294
 295int arping_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 296int arping_main(int argc UNUSED_PARAM, char **argv)
 297{
 298        const char *device = "eth0";
 299        char *source = NULL;
 300        char *target;
 301        char *err_str;
 302
 303        INIT_G();
 304
 305        xmove_fd(xsocket(AF_PACKET, SOCK_DGRAM, 0), sock_fd);
 306
 307        // If you ever change BB_SUID_DROP to BB_SUID_REQUIRE,
 308        // drop suid root privileges here:
 309        //xsetuid(getuid());
 310
 311        {
 312                unsigned opt;
 313                char *str_timeout;
 314
 315                opt = GETOPT32(str_timeout, device, source);
 316                if (opt & TIMEOUT)
 317                        timeout_us = xatou_range(str_timeout, 0, INT_MAX/2000000) * 1000000 + 500000;
 318        }
 319
 320        target = argv[optind];
 321        err_str = xasprintf("interface %s %%s", device);
 322        xfunc_error_retval = 2;
 323
 324        /*memset(&G.ifr, 0, sizeof(G.ifr)); - zeroed by INIT_G */
 325        strncpy_IFNAMSIZ(G.ifr.ifr_name, device);
 326        ioctl_or_perror_and_die(sock_fd, SIOCGIFINDEX, &G.ifr, err_str, "not found");
 327        me.sll_ifindex = G.ifr.ifr_ifindex;
 328
 329        xioctl(sock_fd, SIOCGIFFLAGS, (char *) &G.ifr);
 330
 331        if (!(G.ifr.ifr_flags & IFF_UP)) {
 332                bb_error_msg_and_die(err_str, "is down");
 333        }
 334        if (G.ifr.ifr_flags & (IFF_NOARP | IFF_LOOPBACK)) {
 335                bb_error_msg(err_str, "is not ARPable");
 336                BUILD_BUG_ON(DAD != 2);
 337                /* exit 0 if DAD, else exit 2 */
 338                return (~option_mask32 & DAD);
 339        }
 340
 341        /* if (!inet_aton(target, &dst)) - not needed */ {
 342                len_and_sockaddr *lsa;
 343                lsa = xhost_and_af2sockaddr(target, 0, AF_INET);
 344                dst = lsa->u.sin.sin_addr;
 345                if (ENABLE_FEATURE_CLEAN_UP)
 346                        free(lsa);
 347        }
 348
 349        if (source && !inet_aton(source, &src)) {
 350                bb_error_msg_and_die("invalid source address %s", source);
 351        }
 352
 353        if ((option_mask32 & (DAD|UNSOLICITED)) == UNSOLICITED && src.s_addr == 0)
 354                src = dst;
 355
 356        if (!(option_mask32 & DAD) || src.s_addr) {
 357                /*struct sockaddr_in probe_saddr;*/
 358                int probe_fd = xsocket(AF_INET, SOCK_DGRAM, 0);
 359
 360                setsockopt_bindtodevice(probe_fd, device);
 361
 362                /*memset(&G.probe_saddr, 0, sizeof(G.probe_saddr)); - zeroed by INIT_G */
 363                G.probe_saddr.sin_family = AF_INET;
 364                if (src.s_addr) {
 365                        /* Check that this is indeed our IP */
 366                        G.probe_saddr.sin_addr = src;
 367                        xbind(probe_fd, (struct sockaddr *) &G.probe_saddr, sizeof(G.probe_saddr));
 368                } else { /* !(option_mask32 & DAD) case */
 369                        /* Find IP address on this iface */
 370                        G.probe_saddr.sin_port = htons(1025);
 371                        G.probe_saddr.sin_addr = dst;
 372
 373                        if (setsockopt_SOL_SOCKET_1(probe_fd, SO_DONTROUTE) != 0)
 374                                bb_perror_msg("setsockopt(%s)", "SO_DONTROUTE");
 375                        xconnect(probe_fd, (struct sockaddr *) &G.probe_saddr, sizeof(G.probe_saddr));
 376                        bb_getsockname(probe_fd, (struct sockaddr *) &G.probe_saddr, sizeof(G.probe_saddr));
 377                        if (G.probe_saddr.sin_family != AF_INET)
 378                                bb_error_msg_and_die("no IP address configured");
 379                        src = G.probe_saddr.sin_addr;
 380                }
 381                close(probe_fd);
 382        }
 383
 384        me.sll_family = AF_PACKET;
 385        //me.sll_ifindex = ifindex; - done before
 386        me.sll_protocol = htons(ETH_P_ARP);
 387        xbind(sock_fd, (struct sockaddr *) &me, sizeof(me));
 388
 389        bb_getsockname(sock_fd, (struct sockaddr *) &me, sizeof(me));
 390        //never happens:
 391        //if (getsockname(sock_fd, (struct sockaddr *) &me, &alen) == -1)
 392        //      bb_perror_msg_and_die("getsockname");
 393        if (me.sll_halen == 0) {
 394                bb_error_msg(err_str, "is not ARPable (no ll address)");
 395                BUILD_BUG_ON(DAD != 2);
 396                /* exit 0 if DAD, else exit 2 */
 397                return (~option_mask32 & DAD);
 398        }
 399        he = me;
 400        memset(he.sll_addr, -1, he.sll_halen);
 401
 402        if (!(option_mask32 & QUIET)) {
 403                /* inet_ntoa uses static storage, can't use in same printf */
 404                printf("ARPING %s", inet_ntoa(dst));
 405                printf(" from %s %s\n", inet_ntoa(src), device);
 406        }
 407
 408        /*sigemptyset(&G.sset); - zeroed by INIT_G */
 409        sigaddset(&G.sset, SIGALRM);
 410        sigaddset(&G.sset, SIGINT);
 411        signal_SA_RESTART_empty_mask(SIGINT,  (void (*)(int))finish);
 412        signal_SA_RESTART_empty_mask(SIGALRM, (void (*)(int))catcher);
 413
 414        /* Send the first packet, arm ALRM */
 415        catcher();
 416
 417        while (1) {
 418                struct sockaddr_ll from;
 419                socklen_t alen = sizeof(from);
 420                int cc;
 421
 422                /* Unblock SIGALRM so that the previously called alarm()
 423                 * can prevent recvfrom from blocking forever in case the
 424                 * inherited procmask is blocking SIGALRM.
 425                 */
 426                sigprocmask(SIG_UNBLOCK, &G.sset, NULL);
 427
 428                cc = recvfrom(sock_fd, G.packet, sizeof(G.packet), 0, (struct sockaddr *) &from, &alen);
 429
 430                /* Don't allow SIGALRMs while we process the reply */
 431                sigprocmask(SIG_BLOCK, &G.sset, NULL);
 432                if (cc < 0) {
 433                        bb_perror_msg("recvfrom");
 434                        continue;
 435                }
 436                recv_pack(G.packet, cc, &from);
 437        }
 438}
 439