source: MondoRescue/branches/2.2.5/mindi-busybox/networking/pscan.c

/*
 * Pscan is a mini port scanner implementation for busybox
 *
 * Copyright 2007 Tito Ragusa <farmatito@tiscali.it>
 *
 * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
 */

#include "libbb.h"

/* debugging */
#ifdef DEBUG_PSCAN
#define DMSG(...) bb_error_msg(__VA_ARGS__)
#define DERR(...) bb_perror_msg(__VA_ARGS__)
#else
#define DMSG(...) ((void)0)
#define DERR(...) ((void)0)
#endif

static const char *port_name(unsigned port)
{
    struct servent *server;

    server = getservbyport(htons(port), NULL);
    if (server)
        return server->s_name;
    return "unknown";
}

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

int pscan_main(int argc, char **argv);
int pscan_main(int argc, char **argv)
{
    const char *opt_max_port = "1024";      /* -P: default max port */
    const char *opt_min_port = "1";         /* -p: default min port */
    const char *opt_timeout = "5000";       /* -t: default timeout in msec */
    /* We estimate rtt and wait rtt*4 before concluding that port is
     * totally blocked. min rtt of 5 ms may be too low if you are
     * scanning an Internet host behind saturated/traffic shaped link.
     * Rule of thumb: with min_rtt of N msec, scanning 1000 ports
     * will take N seconds at absolute minimum */
    const char *opt_min_rtt = "5";          /* -T: default min rtt in msec */
    len_and_sockaddr *lsap;
    int s;
    unsigned port, max_port, nports;
    unsigned closed_ports = 0;
    unsigned open_ports = 0;
    /* all in usec */
    unsigned timeout;
    unsigned min_rtt;
    unsigned rtt_4;
    unsigned start;

    opt_complementary = "=1"; /* exactly one non-option */
    getopt32(argv, "p:P:t:T:", &opt_min_port, &opt_max_port, &opt_timeout, &opt_min_rtt);
    argv += optind;
    max_port = xatou_range(opt_max_port, 1, 65535);
    port = xatou_range(opt_min_port, 1, max_port);
    nports = max_port - port + 1;
    rtt_4 = timeout = xatou_range(opt_timeout, 1, INT_MAX/1000 / 4) * 1000;
    min_rtt = xatou_range(opt_min_rtt, 1, INT_MAX/1000 / 4) * 1000;

    DMSG("min_rtt %u timeout %u", min_rtt, timeout);

    lsap = xhost2sockaddr(*argv, port);
    printf("Scanning %s ports %u to %u\n Port\tProto\tState\tService\n",
            *argv, port, max_port);

    for (; port <= max_port; port++) {
        DMSG("rtt %u", rtt_4);

        /* The SOCK_STREAM socket type is implemented on the TCP/IP protocol. */
        set_nport(lsap, htons(port));
        s = xsocket(lsap->sa.sa_family, SOCK_STREAM, 0);

        /* We need unblocking socket so we don't need to wait for ETIMEOUT. */
        /* Nonblocking connect typically "fails" with errno == EINPROGRESS */
        ndelay_on(s);
        DMSG("connect to port %u", port);
        start = MONOTONIC_US();
        if (connect(s, &lsap->sa, lsap->len) == 0) {
            /* Unlikely, for me even localhost fails :) */
            DMSG("connect succeeded");
            goto open;
        }
        /* Check for untypical errors... */
        if (errno != EAGAIN && errno != EINPROGRESS
         && errno != ECONNREFUSED
        ) {
            bb_perror_nomsg_and_die();
        }

        while (1) {
            if (errno == ECONNREFUSED) {
                DMSG("port %u: ECONNREFUSED", port);
                closed_ports++;
                break;
            }
            DERR("port %u errno %d @%u", port, errno, MONOTONIC_US() - start);
            if ((MONOTONIC_US() - start) > rtt_4)
                break;
            /* Can sleep (much) longer than specified delay.
             * We check rtt BEFORE we usleep, otherwise
             * on localhost we'll do zero writes done (!)
             * before we exceed (rather small) rtt */
            usleep(rtt_4/8);
            DMSG("write to port %u @%u", port, MONOTONIC_US() - start);
            if (write(s, " ", 1) >= 0) { /* We were able to write to the socket */
 open:
                open_ports++;
                printf("%5u\ttcp\topen\t%s\n", port, port_name(port));
                break;
            }
        }
        DMSG("out of loop @%u", MONOTONIC_US() - start);

        /* Estimate new rtt - we don't want to wait entire timeout
         * for each port. *4 allows for rise in net delay.
         * We increase rtt quickly (*4), decrease slowly (4/8 == 1/2)
         * because we don't want to accidentally miss ports. */
        rtt_4 = (MONOTONIC_US() - start) * 4;
        if (rtt_4 < min_rtt)
            rtt_4 = min_rtt;
        if (rtt_4 > timeout)
            rtt_4 = timeout;
        /* Clean up */
        close(s);
    }
    if (ENABLE_FEATURE_CLEAN_UP) free(lsap);

    printf("%d closed, %d open, %d timed out ports\n",
                    closed_ports,
                    open_ports,
                    nports - (closed_ports + open_ports));
    return EXIT_SUCCESS;
}