pcap-dbus.c

Go to the documentation of this file.

/*
 * Copyright (c) 2012 Jakub Zawadzki
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 * products derived from this software without specific prior written
 * permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
 
#include <string.h>
 
#include <time.h>
#include <sys/time.h>
 
#include <dbus/dbus.h>
 
#include "pcap-int.h"
#include "pcap-dbus.h"
 
/*
 * Private data for capturing on D-Bus.
 */
struct pcap_dbus {
    DBusConnection *conn;
    u_int   packets_read;   /* count of packets read */
};
 
static int
dbus_read(pcap_t *handle, int max_packets _U_, pcap_handler callback, u_char *user)
{
    struct pcap_dbus *handlep = handle->priv;
 
    struct pcap_pkthdr pkth;
    DBusMessage *message;
 
    char *raw_msg;
    int raw_msg_len;
 
    int count = 0;
 
    message = dbus_connection_pop_message(handlep->conn);
 
    while (!message) {
        /* XXX handle->opt.timeout = timeout_ms; */
        if (!dbus_connection_read_write(handlep->conn, 100)) {
            snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Connection closed");
            return -1;
        }
 
        if (handle->break_loop) {
            handle->break_loop = 0;
            return -2;
        }
 
        message = dbus_connection_pop_message(handlep->conn);
    }
 
    if (dbus_message_is_signal(message, DBUS_INTERFACE_LOCAL, "Disconnected")) {
        snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Disconnected");
        return -1;
    }
 
    if (dbus_message_marshal(message, &raw_msg, &raw_msg_len)) {
        pkth.caplen = pkth.len = raw_msg_len;
        /* pkth.caplen = min (payload_len, handle->snapshot); */
 
        gettimeofday(&pkth.ts, NULL);
        if (handle->fcode.bf_insns == NULL ||
            pcap_filter(handle->fcode.bf_insns, (u_char *)raw_msg, pkth.len, pkth.caplen)) {
            handlep->packets_read++;
            callback(user, &pkth, (u_char *)raw_msg);
            count++;
        }
 
        dbus_free(raw_msg);
    }
    return count;
}
 
static int
dbus_write(pcap_t *handle, const void *buf, int size)
{
    /* XXX, not tested */
    struct pcap_dbus *handlep = handle->priv;
 
    DBusError error = DBUS_ERROR_INIT;
    DBusMessage *msg;
 
    if (!(msg = dbus_message_demarshal(buf, size, &error))) {
        snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "dbus_message_demarshal() failed: %s", error.message);
        dbus_error_free(&error);
        return -1;
    }
 
    dbus_connection_send(handlep->conn, msg, NULL);
    dbus_connection_flush(handlep->conn);
 
    dbus_message_unref(msg);
    return 0;
}
 
static int
dbus_stats(pcap_t *handle, struct pcap_stat *stats)
{
    struct pcap_dbus *handlep = handle->priv;
 
    stats->ps_recv = handlep->packets_read;
    stats->ps_drop = 0;
    stats->ps_ifdrop = 0;
    return 0;
}
 
static void
dbus_cleanup(pcap_t *handle)
{
    struct pcap_dbus *handlep = handle->priv;
 
    dbus_connection_unref(handlep->conn);
 
    pcap_cleanup_live_common(handle);
}
 
/*
 * We don't support non-blocking mode.  I'm not sure what we'd
 * do to support it and, given that we don't support select()/
 * poll()/epoll_wait()/kevent() etc., it probably doesn't
 * matter.
 */
static int
dbus_getnonblock(pcap_t *p)
{
    snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
        "Non-blocking mode isn't supported for capturing on D-Bus");
    return (-1);
}
 
static int
dbus_setnonblock(pcap_t *p, int nonblock _U_)
{
    snprintf(p->errbuf, PCAP_ERRBUF_SIZE,
        "Non-blocking mode isn't supported for capturing on D-Bus");
    return (-1);
}
 
static int
dbus_activate(pcap_t *handle)
{
#define EAVESDROPPING_RULE "eavesdrop=true,"
 
    static const char *rules[] = {
        EAVESDROPPING_RULE "type='signal'",
        EAVESDROPPING_RULE "type='method_call'",
        EAVESDROPPING_RULE "type='method_return'",
        EAVESDROPPING_RULE "type='error'",
    };
 
    #define N_RULES sizeof(rules)/sizeof(rules[0])
 
    struct pcap_dbus *handlep = handle->priv;
    const char *dev = handle->opt.device;
 
    DBusError error = DBUS_ERROR_INIT;
    u_int i;
 
    if (strcmp(dev, "dbus-system") == 0) {
        if (!(handlep->conn = dbus_bus_get(DBUS_BUS_SYSTEM, &error))) {
            snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Failed to get system bus: %s", error.message);
            dbus_error_free(&error);
            return PCAP_ERROR;
        }
 
    } else if (strcmp(dev, "dbus-session") == 0) {
        if (!(handlep->conn = dbus_bus_get(DBUS_BUS_SESSION, &error))) {
            snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Failed to get session bus: %s", error.message);
            dbus_error_free(&error);
            return PCAP_ERROR;
        }
 
    } else if (strncmp(dev, "dbus://", 7) == 0) {
        const char *addr = dev + 7;
 
        if (!(handlep->conn = dbus_connection_open(addr, &error))) {
            snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Failed to open connection to: %s: %s", addr, error.message);
            dbus_error_free(&error);
            return PCAP_ERROR;
        }
 
        if (!dbus_bus_register(handlep->conn, &error)) {
            snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Failed to register bus %s: %s\n", addr, error.message);
            dbus_error_free(&error);
            return PCAP_ERROR;
        }
 
    } else {
        snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't get bus address from %s", handle->opt.device);
        return PCAP_ERROR;
    }
 
    /* Initialize some components of the pcap structure. */
    handle->bufsize = 0;
    handle->offset = 0;
    handle->linktype = DLT_DBUS;
    handle->read_op = dbus_read;
    handle->inject_op = dbus_write;
    handle->setfilter_op = install_bpf_program; /* XXX, later add support for dbus_bus_add_match() */
    handle->setdirection_op = NULL;
    handle->set_datalink_op = NULL;      /* can't change data link type */
    handle->getnonblock_op = dbus_getnonblock;
    handle->setnonblock_op = dbus_setnonblock;
    handle->stats_op = dbus_stats;
    handle->cleanup_op = dbus_cleanup;
 
#ifndef _WIN32
    /*
     * Unfortunately, trying to do a select()/poll()/epoll_wait()/
     * kevent()/etc. on a D-Bus connection isn't a simple
     * case of "give me an FD on which to wait".
     *
     * Apparently, you have to register "add watch", "remove watch",
     * and "toggle watch" functions with
     * dbus_connection_set_watch_functions(),
     * keep a *set* of FDs, add to that set in the "add watch"
     * function, subtract from it in the "remove watch" function,
     * and either add to or subtract from that set in the "toggle
     * watch" function, and do the wait on *all* of the FDs in the
     * set.  (Yes, you need the "toggle watch" function, so that
     * the main loop doesn't itself need to check for whether
     * a given watch is enabled or disabled - most libpcap programs
     * know nothing about D-Bus and shouldn't *have* to know anything
     * about D-Bus other than how to decode D-Bus messages.)
     *
     * Implementing that would require considerable changes in
     * the way libpcap exports "selectable FDs" to its client.
     * Until that's done, we just say "you can't do that".
     */
    handle->selectable_fd = handle->fd = -1;
#endif
 
    if (handle->opt.rfmon) {
        /*
         * Monitor mode doesn't apply to dbus connections.
         */
        dbus_cleanup(handle);
        return PCAP_ERROR_RFMON_NOTSUP;
    }
 
    /*
     * Turn a negative snapshot value (invalid), a snapshot value of
     * 0 (unspecified), or a value bigger than the normal maximum
     * value, into the maximum message length for D-Bus (128MB).
     */
    if (handle->snapshot <= 0 || handle->snapshot > 134217728)
        handle->snapshot = 134217728;
 
    /* dbus_connection_set_max_message_size(handlep->conn, handle->snapshot); */
    if (handle->opt.buffer_size != 0)
        dbus_connection_set_max_received_size(handlep->conn, handle->opt.buffer_size);
 
    for (i = 0; i < N_RULES; i++) {
        dbus_bus_add_match(handlep->conn, rules[i], &error);
        if (dbus_error_is_set(&error)) {
            dbus_error_free(&error);
 
            /* try without eavesdrop */
            dbus_bus_add_match(handlep->conn, rules[i] + strlen(EAVESDROPPING_RULE), &error);
            if (dbus_error_is_set(&error)) {
                snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Failed to add bus match: %s\n", error.message);
                dbus_error_free(&error);
                dbus_cleanup(handle);
                return PCAP_ERROR;
            }
        }
    }
 
    return 0;
}
 
pcap_t *
dbus_create(const char *device, char *ebuf, int *is_ours)
{
    pcap_t *p;
 
    if (strcmp(device, "dbus-system") &&
        strcmp(device, "dbus-session") &&
        strncmp(device, "dbus://", 7))
    {
        *is_ours = 0;
        return NULL;
    }
 
    *is_ours = 1;
    p = PCAP_CREATE_COMMON(ebuf, struct pcap_dbus);
    if (p == NULL)
        return (NULL);
 
    p->activate_op = dbus_activate;
    /*
     * Set these up front, so that, even if our client tries
     * to set non-blocking mode before we're activated, or
     * query the state of non-blocking mode, they get an error,
     * rather than having the non-blocking mode option set
     * for use later.
     */
    p->getnonblock_op = dbus_getnonblock;
    p->setnonblock_op = dbus_setnonblock;
    return (p);
}
 
int
dbus_findalldevs(pcap_if_list_t *devlistp, char *err_str)
{
    /*
     * The notion of "connected" vs. "disconnected" doesn't apply.
     * XXX - what about the notions of "up" and "running"?
     */
    if (add_dev(devlistp, "dbus-system",
        PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE, "D-Bus system bus",
        err_str) == NULL)
        return -1;
    if (add_dev(devlistp, "dbus-session",
        PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE, "D-Bus session bus",
        err_str) == NULL)
        return -1;
    return 0;
}