capture_pcapfile.c

/*
    This file is part of Kismet

    Kismet is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    Kismet is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Kismet; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* capture_pcapfile
 *
 * Basic capture binary, written in pure C, which interfaces via the Kismet
 * simple capture protocol and feeds packets from a pcap file.
 *
 * This could have been implemented in C++ but serves as an example of a simple,
 * very low resource capture method.
 *
 * This uses some of the pure-C code included in Kismet - pure-c implementations
 * of the datasource protocol, a basic ringbuffer implementation, and the msgpuck
 * library which is a pure-c simple msgpack library.
 *
 * This uses basic threading to show how to do an asynchronous read from a source;
 * while a pcapfile will never stall, other sources could.  
 *
 * The select() loop for IO with the IPC channel is performed in the primary
 * thread, and an IO thread is spawned to process data from the pcap file.  This
 * allows us to expand to interesting options, like realtime pcap replay which
 * delays the IO as if they were real packets.
 *
 * The DLT is automatically propagated from the pcap file, or can be overridden
 * with a source command.
 *
 * The communications channel is a file descriptor pair, passed via command
 * line arguments, --in-fd= and --out-fd=
 *
 * We parse additional options from the source definition itself, such as a DLT
 * override, once we open the protocol
 *
 */

#include <pcap.h>
#include <getopt.h>
#include <pthread.h>
#include <fcntl.h>

/* According to POSIX.1-2001, POSIX.1-2008 */
#include <sys/select.h>

/* According to earlier standards */
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>

#include <unistd.h>
#include <errno.h>

#include <arpa/inet.h>

#include "config.h"
#include "capture_framework.h"

typedef struct {
    pcap_t *pd;
    char *pcapfname;
    int datalink_type;
    int override_dlt;
    int realtime;
    struct timeval last_ts;
} local_pcap_t;

int probe_callback(kis_capture_handler_t *caph, uint32_t seqno, char *definition,
        char *msg, char **uuid, KismetExternal__Command *frame,
        cf_params_interface_t **ret_interface, 
        cf_params_spectrum_t **ret_spectrum) {
    char *placeholder = NULL;
    int placeholder_len;

    *uuid = NULL;

    char *pcapfname = NULL;

    struct stat sbuf;

    char errstr[PCAP_ERRBUF_SIZE] = "";

    pcap_t *pd;

    *ret_spectrum = NULL;

    *ret_interface = cf_params_interface_new();
    *ret_spectrum = NULL;

    /* pcapfile does not support channel ops */
    (*ret_interface)->chanset = NULL;
    (*ret_interface)->channels = NULL;
    (*ret_interface)->channels_len = 0;

    if ((placeholder_len = cf_parse_interface(&placeholder, definition)) <= 0) {
        snprintf(msg, STATUS_MAX, "Unable to find PCAP file name in definition"); 
        return 0;
    }

    pcapfname = strndup(placeholder, placeholder_len);

    if (stat(pcapfname, &sbuf) < 0) {
        return 0;
    }

    if (!S_ISREG(sbuf.st_mode)) {
        snprintf(msg, STATUS_MAX, "File '%s' is not a regular file", pcapfname);
        return 0;
    }

    pd = pcap_open_offline(pcapfname, errstr);
    if (strlen(errstr) > 0) {
        snprintf(msg, STATUS_MAX, "%s", errstr);
        return -1;
    }

    pcap_close(pd);

    /* Kluge a UUID out of the name */
    snprintf(errstr, PCAP_ERRBUF_SIZE, "%08X-0000-0000-0000-0000%08X",
            adler32_csum((unsigned char *) "kismet_cap_pcapfile", 
                strlen("kismet_cap_pcapfile")) & 0xFFFFFFFF,
            adler32_csum((unsigned char *) pcapfname, 
                strlen(pcapfname)) & 0xFFFFFFFF);
    *uuid = strdup(errstr);


    return 1;
}

int open_callback(kis_capture_handler_t *caph, uint32_t seqno, char *definition,
        char *msg, uint32_t *dlt, char **uuid, KismetExternal__Command *frame,
        cf_params_interface_t **ret_interface, 
        cf_params_spectrum_t **ret_spectrum) {
    char *placeholder = NULL;
    int placeholder_len;

    char *pcapfname = NULL;

    struct stat sbuf;

    local_pcap_t *local_pcap = (local_pcap_t *) caph->userdata;

    char errstr[PCAP_ERRBUF_SIZE] = "";

    /* pcapfile does not support channel ops */
    *ret_interface = cf_params_interface_new();
    *ret_spectrum = NULL;

    *uuid = NULL;
    *dlt = 0;

    /* Clean up any old state */
    if (local_pcap->pcapfname != NULL) {
        free(local_pcap->pcapfname);
        local_pcap->pcapfname = NULL;
    }

    if (local_pcap->pd != NULL) {
        pcap_close(local_pcap->pd);
        local_pcap->pd = NULL;
    }

    if ((placeholder_len = cf_parse_interface(&placeholder, definition)) <= 0) {
        /* What was not an error during probe definitely is an error during open */
        snprintf(msg, STATUS_MAX, "Unable to find PCAP file name in definition");
        return -1;
    }

    pcapfname = strndup(placeholder, placeholder_len);

    local_pcap->pcapfname = pcapfname;

    if (stat(pcapfname, &sbuf) < 0) {
        snprintf(msg, STATUS_MAX, "Unable to find pcapfile '%s'", pcapfname);
        return -1;
    }

    /* We don't check for regular file during open, only probe; we don't want to 
     * open a fifo during probe and then cause a glitch, but we could open it during
     * normal operation */

    local_pcap->pd = pcap_open_offline(pcapfname, errstr);
    if (strlen(errstr) > 0) {
        snprintf(msg, STATUS_MAX, "%s", errstr);
        return -1;
    }

    local_pcap->datalink_type = pcap_datalink(local_pcap->pd);
    *dlt = local_pcap->datalink_type;

    /* Kluge a UUID out of the name */
    snprintf(errstr, PCAP_ERRBUF_SIZE, "%08X-0000-0000-0000-0000%08X",
            adler32_csum((unsigned char *) "kismet_cap_pcapfile", 
                strlen("kismet_cap_pcapfile")) & 0xFFFFFFFF,
            adler32_csum((unsigned char *) pcapfname, 
                strlen(pcapfname)) & 0xFFFFFFFF);
    *uuid = strdup(errstr);

    /* Succesful open with no channel, hop, or chanset data */
    snprintf(msg, STATUS_MAX, "Opened pcapfile '%s' for playback", pcapfname);

    if ((placeholder_len = cf_find_flag(&placeholder, "realtime", definition)) > 0) {
        if (strncasecmp(placeholder, "true", placeholder_len) == 0) {
            snprintf(errstr, PCAP_ERRBUF_SIZE, 
                    "Pcapfile '%s' will replay in realtime", pcapfname);
            cf_send_message(caph, errstr, MSGFLAG_INFO);
            local_pcap->realtime = 1;
        }
    }

    return 1;
}

void pcap_dispatch_cb(u_char *user, const struct pcap_pkthdr *header,
        const u_char *data)  {
    kis_capture_handler_t *caph = (kis_capture_handler_t *) user;
    local_pcap_t *local_pcap = (local_pcap_t *) caph->userdata;
    int ret;
    unsigned long delay_usec = 0;

    /* If we're doing 'realtime' playback, delay accordingly based on the
     * previous packet. 
     *
     * Because we're in our own thread, we can block as long as we want - this
     * simulates blocking IO for capturing from hardware, too.
     */
    if (local_pcap->realtime) {
        if (local_pcap->last_ts.tv_sec == 0 && local_pcap->last_ts.tv_usec == 0) {
            delay_usec = 0;
        } else {
            /* Catch corrupt pcaps w/ inconsistent times */
            if (header->ts.tv_sec < local_pcap->last_ts.tv_sec) {
                delay_usec = 0;
            } else {
                delay_usec = (header->ts.tv_sec - local_pcap->last_ts.tv_sec) * 1000000L;
            }

            if (header->ts.tv_usec < local_pcap->last_ts.tv_usec) {
                delay_usec += (1000000L - local_pcap->last_ts.tv_usec) + 
                    header->ts.tv_usec;
            } else {
                delay_usec += header->ts.tv_usec - local_pcap->last_ts.tv_usec;
            }

        }

        local_pcap->last_ts.tv_sec = header->ts.tv_sec;
        local_pcap->last_ts.tv_usec = header->ts.tv_usec;

        if (delay_usec != 0) {
            usleep(delay_usec);
        }
    }

    /* Try repeatedly to send the packet; go into a thread wait state if
     * the write buffer is full & we'll be woken up as soon as it flushes
     * data out in the main select() loop */
    while (1) {
        if ((ret = cf_send_data(caph, 
                        NULL, NULL, NULL,
                        header->ts, 
                        local_pcap->datalink_type,
                        header->caplen, (uint8_t *) data)) < 0) {
            pcap_breakloop(local_pcap->pd);
            cf_send_error(caph, 0, "unable to send DATA frame");
            cf_handler_spindown(caph);
        } else if (ret == 0) {
            /* Go into a wait for the write buffer to get flushed */
            // fprintf(stderr, "debug - pcapfile - dispatch_cb - no room in write buffer - waiting for it to have more space\n");
            cf_handler_wait_ringbuffer(caph);
            continue;
        } else {
            break;
        }
    }
}

void capture_thread(kis_capture_handler_t *caph) {
    local_pcap_t *local_pcap = (local_pcap_t *) caph->userdata;
    char errstr[PCAP_ERRBUF_SIZE];
    char *pcap_errstr;

    pcap_loop(local_pcap->pd, -1, pcap_dispatch_cb, (u_char *) caph);

    pcap_errstr = pcap_geterr(local_pcap->pd);

    snprintf(errstr, PCAP_ERRBUF_SIZE, "Pcapfile '%s' closed: %s", 
            local_pcap->pcapfname, 
            strlen(pcap_errstr) == 0 ? "end of pcapfile reached" : pcap_errstr );

    cf_send_message(caph, errstr, MSGFLAG_INFO);

    /* Instead of dying, spin forever in a sleep loop */
    while (1) {
        sleep(1);
    }

    /* cf_handler_spindown(caph); */
}

int main(int argc, char *argv[]) {
    local_pcap_t local_pcap = {
        .pd = NULL,
        .pcapfname = NULL,
        .datalink_type = -1,
        .override_dlt = -1,
        .realtime = 0,
        .last_ts.tv_sec = 0,
        .last_ts.tv_usec = 0
    };

#if 0
    /* Remap stderr so we can log debugging to a file */
    FILE *sterr;
    sterr = fopen("/tmp/capture_pcapfile.stderr", "a");
    dup2(fileno(sterr), STDERR_FILENO);
#endif

    /* fprintf(stderr, "CAPTURE_PCAPFILE launched on pid %d\n", getpid()); */

    kis_capture_handler_t *caph = cf_handler_init("pcapfile");

    if (caph == NULL) {
        fprintf(stderr, "FATAL: Could not allocate basic handler data, your system "
                "is very low on RAM or something is wrong.\n");
        return -1;
    }

    /* Set the local data ptr */
    cf_handler_set_userdata(caph, &local_pcap);

    /* Set the callback for opening a pcapfile */
    cf_handler_set_open_cb(caph, open_callback);

    /* Set the callback for probing an interface */
    cf_handler_set_probe_cb(caph, probe_callback);

    /* Set the capture thread */
    cf_handler_set_capture_cb(caph, capture_thread);

    if (cf_handler_parse_opts(caph, argc, argv) < 1) {
        cf_print_help(caph, argv[0]);
        return -1;
    }

    cf_handler_loop(caph);

    cf_handler_free(caph);

    return 1;
}