source: MondoRescue/branches/stable/mindi-busybox/networking/arping.c

/* vi: set sw=4 ts=4: */
/*
 * arping.c - Ping hosts by ARP requests/replies
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 *
 * Author:  Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
 * Busybox port: Nick Fedchik <nick@fedchik.org.ua>
 */

#include <arpa/inet.h>
#include <net/if.h>
#include <netinet/ether.h>
#include <netpacket/packet.h>

#include "libbb.h"

/* We don't expect to see 1000+ seconds delay, unsigned is enough */
#define MONOTONIC_US() ((unsigned)monotonic_us())

static struct in_addr src;
static struct in_addr dst;
static struct sockaddr_ll me;
static struct sockaddr_ll he;
static unsigned last;

enum {
    DAD = 1,
    UNSOLICITED = 2,
    ADVERT = 4,
    QUIET = 8,
    QUIT_ON_REPLY = 16,
    BCAST_ONLY = 32,
    UNICASTING = 64
};

static int sock;
static unsigned count = UINT_MAX;
static unsigned timeout_us;
static unsigned sent;
static unsigned brd_sent;
static unsigned received;
static unsigned brd_recv;
static unsigned req_recv;

static int send_pack(struct in_addr *src_addr,
            struct in_addr *dst_addr, struct sockaddr_ll *ME,
            struct sockaddr_ll *HE)
{
    int err;
    unsigned now;
    unsigned char buf[256];
    struct arphdr *ah = (struct arphdr *) buf;
    unsigned char *p = (unsigned char *) (ah + 1);

    ah->ar_hrd = htons(ME->sll_hatype);
    ah->ar_hrd = htons(ARPHRD_ETHER);
    ah->ar_pro = htons(ETH_P_IP);
    ah->ar_hln = ME->sll_halen;
    ah->ar_pln = 4;
    ah->ar_op = option_mask32 & ADVERT ? htons(ARPOP_REPLY) : htons(ARPOP_REQUEST);

    memcpy(p, &ME->sll_addr, ah->ar_hln);
    p += ME->sll_halen;

    memcpy(p, src_addr, 4);
    p += 4;

    if (option_mask32 & ADVERT)
        memcpy(p, &ME->sll_addr, ah->ar_hln);
    else
        memcpy(p, &HE->sll_addr, ah->ar_hln);
    p += ah->ar_hln;

    memcpy(p, dst_addr, 4);
    p += 4;

    now = MONOTONIC_US();
    err = sendto(sock, buf, p - buf, 0, (struct sockaddr *) HE, sizeof(*HE));
    if (err == p - buf) {
        last = now;
        sent++;
        if (!(option_mask32 & UNICASTING))
            brd_sent++;
    }
    return err;
}

static void finish(void) ATTRIBUTE_NORETURN;
static void finish(void)
{
    if (!(option_mask32 & QUIET)) {
        printf("Sent %u probe(s) (%u broadcast(s))\n"
            "Received %u repl%s"
            " (%u request(s), %u broadcast(s))\n",
            sent, brd_sent,
            received, (received == 1) ? "ies" : "y",
            req_recv, brd_recv);
    }
    if (option_mask32 & DAD)
        exit(!!received);
    if (option_mask32 & UNSOLICITED)
        exit(0);
    exit(!received);
}

static void catcher(void)
{
    static unsigned start;

    unsigned now;

    now = MONOTONIC_US();
    if (start == 0)
        start = now;

    if (count == 0 || (timeout_us && (now - start) > (timeout_us + 500000)))
        finish();

    count--;

    if (last == 0 || (now - last) > 500000) {
        send_pack(&src, &dst, &me, &he);
        if (count == 0 && (option_mask32 & UNSOLICITED))
            finish();
    }
    alarm(1);
}

static int recv_pack(unsigned char *buf, int len, struct sockaddr_ll *FROM)
{
    struct arphdr *ah = (struct arphdr *) buf;
    unsigned char *p = (unsigned char *) (ah + 1);
    struct in_addr src_ip, dst_ip;

    /* Filter out wild packets */
    if (FROM->sll_pkttype != PACKET_HOST
     && FROM->sll_pkttype != PACKET_BROADCAST
     && FROM->sll_pkttype != PACKET_MULTICAST)
        return 0;

    /* Only these types are recognised */
    if (ah->ar_op != htons(ARPOP_REQUEST) && ah->ar_op != htons(ARPOP_REPLY))
        return 0;

    /* ARPHRD check and this darned FDDI hack here :-( */
    if (ah->ar_hrd != htons(FROM->sll_hatype)
     && (FROM->sll_hatype != ARPHRD_FDDI || ah->ar_hrd != htons(ARPHRD_ETHER)))
        return 0;

    /* Protocol must be IP. */
    if (ah->ar_pro != htons(ETH_P_IP))
        return 0;
    if (ah->ar_pln != 4)
        return 0;
    if (ah->ar_hln != me.sll_halen)
        return 0;
    if (len < sizeof(*ah) + 2 * (4 + ah->ar_hln))
        return 0;
    memcpy(&src_ip, p + ah->ar_hln, 4);
    memcpy(&dst_ip, p + ah->ar_hln + 4 + ah->ar_hln, 4);
    if (!(option_mask32 & DAD)) {
        if (src_ip.s_addr != dst.s_addr)
            return 0;
        if (src.s_addr != dst_ip.s_addr)
            return 0;
        if (memcmp(p + ah->ar_hln + 4, &me.sll_addr, ah->ar_hln))
            return 0;
    } else {
        /* DAD packet was:
           src_ip = 0 (or some src)
           src_hw = ME
           dst_ip = tested address
           dst_hw = <unspec>

           We fail, if receive request/reply with:
           src_ip = tested_address
           src_hw != ME
           if src_ip in request was not zero, check
           also that it matches to dst_ip, otherwise
           dst_ip/dst_hw do not matter.
         */
        if (src_ip.s_addr != dst.s_addr)
            return 0;
        if (memcmp(p, &me.sll_addr, me.sll_halen) == 0)
            return 0;
        if (src.s_addr && src.s_addr != dst_ip.s_addr)
            return 0;
    }
    if (!(option_mask32 & QUIET)) {
        int s_printed = 0;

        printf("%scast re%s from %s [%s]",
            FROM->sll_pkttype == PACKET_HOST ? "Uni" : "Broad",
            ah->ar_op == htons(ARPOP_REPLY) ? "ply" : "quest",
            inet_ntoa(src_ip),
            ether_ntoa((struct ether_addr *) p));
        if (dst_ip.s_addr != src.s_addr) {
            printf("for %s ", inet_ntoa(dst_ip));
            s_printed = 1;
        }
        if (memcmp(p + ah->ar_hln + 4, me.sll_addr, ah->ar_hln)) {
            if (!s_printed)
                printf("for ");
            printf("[%s]",
                ether_ntoa((struct ether_addr *) p + ah->ar_hln + 4));
        }

        if (last) {
            printf(" %u.%03ums\n", last / 1000, last % 1000);
        } else {
            printf(" UNSOLICITED?\n");
        }
        fflush(stdout);
    }
    received++;
    if (FROM->sll_pkttype != PACKET_HOST)
        brd_recv++;
    if (ah->ar_op == htons(ARPOP_REQUEST))
        req_recv++;
    if (option_mask32 & QUIT_ON_REPLY)
        finish();
    if (!(option_mask32 & BCAST_ONLY)) {
        memcpy(he.sll_addr, p, me.sll_halen);
        option_mask32 |= UNICASTING;
    }
    return 1;
}

int arping_main(int argc, char **argv);
int arping_main(int argc, char **argv)
{
    const char *device = "eth0";
    int ifindex;
    char *source = NULL;
    char *target;
    unsigned char *packet;

    sock = xsocket(PF_PACKET, SOCK_DGRAM, 0);

    // Drop suid root privileges
    xsetuid(getuid());

    {
        unsigned opt;
        char *str_count, *str_timeout;

        /* Dad also sets quit_on_reply.
         * Advert also sets unsolicited.
         */
        opt_complementary = "=1:Df:AU";
        opt = getopt32(argv, "DUAqfbc:w:I:s:",
                &str_count, &str_timeout, &device, &source);
        if (opt & 0x40) /* -c: count */
            count = xatou(str_count);
        if (opt & 0x80) /* -w: timeout */
            timeout_us = xatou_range(str_timeout, 0, INT_MAX/2000000) * 1000000;
        //if (opt & 0x100) /* -I: interface */
        if (strlen(device) >= IF_NAMESIZE) {
            bb_error_msg_and_die("interface name '%s' is too long",
                            device);
        }
        //if (opt & 0x200) /* -s: source */
        option_mask32 &= 0x3f; /* set respective flags */
    }

    target = argv[optind];

    xfunc_error_retval = 2;

    {
        struct ifreq ifr;

        memset(&ifr, 0, sizeof(ifr));
        strncpy(ifr.ifr_name, device, IFNAMSIZ - 1);
        ioctl_or_perror_and_die(sock, SIOCGIFINDEX, &ifr, "interface %s not found", device);
        ifindex = ifr.ifr_ifindex;

        xioctl(sock, SIOCGIFFLAGS, (char *) &ifr);

        if (!(ifr.ifr_flags & IFF_UP)) {
            bb_error_msg_and_die("interface %s is down", device);
        }
        if (ifr.ifr_flags & (IFF_NOARP | IFF_LOOPBACK)) {
            bb_error_msg("interface %s is not ARPable", device);
            return (option_mask32 & DAD ? 0 : 2);
        }
    }

    if (!inet_aton(target, &dst)) {
        len_and_sockaddr *lsa;
        lsa = xhost_and_af2sockaddr(target, 0, AF_INET);
        memcpy(&dst, &lsa->sin.sin_addr.s_addr, 4);
        if (ENABLE_FEATURE_CLEAN_UP)
            free(lsa);
    }

    if (source && !inet_aton(source, &src)) {
        bb_error_msg_and_die("invalid source address %s", source);
    }

    if (!(option_mask32 & DAD) && (option_mask32 & UNSOLICITED) && src.s_addr == 0)
        src = dst;

    if (!(option_mask32 & DAD) || src.s_addr) {
        struct sockaddr_in saddr;
        int probe_fd = xsocket(AF_INET, SOCK_DGRAM, 0);

        if (device) {
            if (setsockopt(probe_fd, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device) + 1) == -1)
                bb_error_msg("warning: interface %s is ignored", device);
        }
        memset(&saddr, 0, sizeof(saddr));
        saddr.sin_family = AF_INET;
        if (src.s_addr) {
            saddr.sin_addr = src;
            xbind(probe_fd, (struct sockaddr *) &saddr, sizeof(saddr));
        } else if (!(option_mask32 & DAD)) {
            socklen_t alen = sizeof(saddr);

            saddr.sin_port = htons(1025);
            saddr.sin_addr = dst;

            if (setsockopt(probe_fd, SOL_SOCKET, SO_DONTROUTE, &const_int_1, sizeof(const_int_1)) == -1)
                bb_perror_msg("warning: setsockopt(SO_DONTROUTE)");
            xconnect(probe_fd, (struct sockaddr *) &saddr, sizeof(saddr));
            if (getsockname(probe_fd, (struct sockaddr *) &saddr, &alen) == -1) {
                bb_error_msg_and_die("getsockname");
            }
            src = saddr.sin_addr;
        }
        close(probe_fd);
    }

    me.sll_family = AF_PACKET;
    me.sll_ifindex = ifindex;
    me.sll_protocol = htons(ETH_P_ARP);
    xbind(sock, (struct sockaddr *) &me, sizeof(me));

    {
        socklen_t alen = sizeof(me);

        if (getsockname(sock, (struct sockaddr *) &me, &alen) == -1) {
            bb_error_msg_and_die("getsockname");
        }
    }
    if (me.sll_halen == 0) {
        bb_error_msg("interface \"%s\" is not ARPable (no ll address)", device);
        return (option_mask32 & DAD ? 0 : 2);
    }
    he = me;
    memset(he.sll_addr, -1, he.sll_halen);

    if (!(option_mask32 & QUIET)) {
        printf("ARPING to %s from %s via %s\n",
            inet_ntoa(dst), inet_ntoa(src),
            device ? device : "unknown");
    }

    if (!src.s_addr && !(option_mask32 & DAD)) {
        bb_error_msg_and_die("no src address in the non-DAD mode");
    }

    {
        struct sigaction sa;

        memset(&sa, 0, sizeof(sa));
        sa.sa_flags = SA_RESTART;

        sa.sa_handler = (void (*)(int)) finish;
        sigaction(SIGINT, &sa, NULL);

        sa.sa_handler = (void (*)(int)) catcher;
        sigaction(SIGALRM, &sa, NULL);
    }

    catcher();

    packet = xmalloc(4096);
    while (1) {
        sigset_t sset, osset;
        struct sockaddr_ll from;
        socklen_t alen = sizeof(from);
        int cc;

        cc = recvfrom(sock, packet, 4096, 0, (struct sockaddr *) &from, &alen);
        if (cc < 0) {
            bb_perror_msg("recvfrom");
            continue;
        }
        sigemptyset(&sset);
        sigaddset(&sset, SIGALRM);
        sigaddset(&sset, SIGINT);
        sigprocmask(SIG_BLOCK, &sset, &osset);
        recv_pack(packet, cc, &from);
        sigprocmask(SIG_SETMASK, &osset, NULL);
    }
}