pcap-dag.c

用来监视网络通信数据的源代码和应用程序,方便网络程序底层开发.

  
	return processed;
}

/*
 *  Get a handle for a live capture from the given DAG device.  Passing a NULL
 *  device will result in a failure.  The promisc flag is ignored because DAG
 *  cards are always promiscuous.  The to_ms parameter is also ignored as it is
 *  not supported in hardware.
 *  
 *  See also pcap(3).
 */
pcap_t *dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebuf) {
  char conf[30]; /* dag configure string */
  pcap_t *handle;
  char *s;
  int n;
  
  if (device == NULL) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE, "device is NULL: %s", pcap_strerror(errno));
    return NULL;
  }
  /* Allocate a handle for this session. */

  handle = malloc(sizeof(*handle));
  if (handle == NULL) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc %s: %s", device, pcap_strerror(errno));
    return NULL;
  }
  
  /* Initialize some components of the pcap structure. */
  
  memset(handle, 0, sizeof(*handle));

  if (strstr(device, "/dev") == NULL) {
    char * newDev = (char *)malloc(strlen(device) + 6);
    newDev[0] = '\0';
    strcat(newDev, "/dev/");
    strcat(newDev,device);
    device = newDev;
  } else {
	device = strdup(device);
  }

  if (device == NULL) {
	snprintf(ebuf, PCAP_ERRBUF_SIZE, "str_dup: %s\n", pcap_strerror(errno));
	goto fail;
  }

  /* setup device parameters */
  if((handle->fd = dag_open((char *)device)) < 0) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_open %s: %s", device, pcap_strerror(errno));
    goto fail;
  }

  /* set the card snap length to the specified snaplen parameter */
  if (snaplen == 0 || snaplen > MAX_DAG_SNAPLEN) {
    snaplen = MAX_DAG_SNAPLEN;
  } else if (snaplen < MIN_DAG_SNAPLEN) {
    snaplen = MIN_DAG_SNAPLEN;
  }
  /* snap len has to be a multiple of 4 */
  snprintf(conf, 30, "varlen slen=%d", (snaplen + 3) & ~3); 

  fprintf(stderr, "Configuring DAG with '%s'.\n", conf);
  if(dag_configure(handle->fd, conf) < 0) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE,"dag_configure %s: %s\n", device, pcap_strerror(errno));
    goto fail;
  }
  
  if((handle->md.dag_mem_base = dag_mmap(handle->fd)) == MAP_FAILED) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE,"dag_mmap %s: %s\n", device, pcap_strerror(errno));
    goto fail;
  }
  
  if(dag_start(handle->fd) < 0) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_start %s: %s\n", device, pcap_strerror(errno));
    goto fail;
  }

  /*
   * Important! You have to ensure bottom is properly
   * initialized to zero on startup, it won't give you
   * a compiler warning if you make this mistake!
   */
  handle->md.dag_mem_bottom = 0;
  handle->md.dag_mem_top = 0;

  /* TODO: query the card */
  handle->md.dag_fcs_bits = 32;
  if ((s = getenv("ERF_FCS_BITS")) != NULL) {
    if ((n = atoi(s)) == 0 || n == 16|| n == 32) {
      handle->md.dag_fcs_bits = n;
    } else {
      snprintf(ebuf, PCAP_ERRBUF_SIZE,
        "pcap_open_live %s: bad ERF_FCS_BITS value (%d) in environment\n", device, n);
      goto fail;
    }
  }

  handle->snapshot	= snaplen;
  /*handle->md.timeout	= to_ms; */

  if ((handle->linktype = dag_get_datalink(handle)) < 0) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE, "dag_get_linktype %s: unknown linktype\n", device);
	goto fail;
  }
  
  handle->bufsize = 0;

  if (new_pcap_dag(handle) < 0) {
    snprintf(ebuf, PCAP_ERRBUF_SIZE, "new_pcap_dag %s: %s\n", device, pcap_strerror(errno));
	goto fail;
  }

  /*
   * "select()" and "poll()" don't (yet) work on DAG device descriptors.
   */
  handle->selectable_fd = -1;

#ifdef linux
  handle->md.device = (char *)device;
#else
  free((char *)device);
  device = NULL;
#endif

  handle->read_op = dag_read;
  handle->setfilter_op = dag_setfilter;
  handle->set_datalink_op = dag_set_datalink;
  handle->getnonblock_op = pcap_getnonblock_fd;
  handle->setnonblock_op = dag_setnonblock;
  handle->stats_op = dag_stats;
  handle->close_op = dag_platform_close;

  return handle;

fail:
  if (device != NULL) {
	free((char *)device);
  }
  if (handle != NULL) {
	free(handle);
  }

  return NULL;
}

static int dag_stats(pcap_t *p, struct pcap_stat *ps) {
  /* This needs to be filled out correctly.  Hopefully a dagapi call will
     provide all necessary information.
  */
  /*p->md.stat.ps_recv = 0;*/
  /*p->md.stat.ps_drop = 0;*/
  
  *ps = p->md.stat;
 
  return 0;
}

/*
 * Get from "/proc/dag" all interfaces listed there; if they're
 * already in the list of interfaces we have, that won't add another
 * instance, but if they're not, that'll add them.
 *
 * We don't bother getting any addresses for them.
 *
 * We also don't fail if we couldn't open "/proc/dag"; we just leave
 * the list of interfaces as is.
 */
int
dag_platform_finddevs(pcap_if_t **devlistp, char *errbuf)
{
  FILE *proc_dag_f;
  char linebuf[512];
  int linenum;
  unsigned char *p;
  char name[512];	/* XXX - pick a size */
  char *q;
  int ret = 0;

  /* Quick exit if /proc/dag not readable */
  proc_dag_f = fopen("/proc/dag", "r");
  if (proc_dag_f == NULL)
  {
    int i;
    char dev[16] = "dagx";

    for (i = '0'; ret == 0 && i <= '9'; i++) {
      dev[3] = i;
      if (pcap_add_if(devlistp, dev, 0, NULL, errbuf) == -1) {
        /*
         * Failure.
         */
        ret = -1;
      }
    }
          
    return (ret);
  }

  for (linenum = 1;
        fgets(linebuf, sizeof linebuf, proc_dag_f) != NULL; linenum++) {
    
    /*
     * Skip the first two lines - they're headers.
     */
    if (linenum <= 2)
      continue;

    p = &linebuf[0];

    if (*p == '\0' || *p == '\n' || *p != 'D')
      continue;  /* not a Dag line */

    /*
     * Get the interface name.
     */
    q = &name[0];
    while (*p != '\0' && *p != ':') {
      if (*p != ' ')
        *q++ = tolower(*p++);
      else
        p++;
    }
    *q = '\0';

    /*
     * Add an entry for this interface, with no addresses.
     */
    p[strlen(p) - 1] = '\0'; /* get rid of \n */
    if (pcap_add_if(devlistp, name, 0, strdup(p + 2), errbuf) == -1) {
      /*
       * Failure.
       */
      ret = -1;
      break;
    }
  }
  if (ret != -1) {
    /*
     * Well, we didn't fail for any other reason; did we
     * fail due to an error reading the file?
     */
    if (ferror(proc_dag_f)) {
      (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
          "Error reading /proc/dag: %s",
          pcap_strerror(errno));
      ret = -1;
    }
  }

  (void)fclose(proc_dag_f);
  return (ret);
}

/*
 * Installs the given bpf filter program in the given pcap structure.  There is
 * no attempt to store the filter in kernel memory as that is not supported
 * with DAG cards.
 */
static int dag_setfilter(pcap_t *p, struct bpf_program *fp) {
  if (!p)
    return -1;
  if (!fp) {
    strncpy(p->errbuf, "setfilter: No filter specified",
	    sizeof(p->errbuf));
    return -1;
  }

  /* Make our private copy of the filter */

  if (install_bpf_program(p, fp) < 0) {
    snprintf(p->errbuf, sizeof(p->errbuf),
	     "malloc: %s", pcap_strerror(errno));
    return -1;
  }

  p->md.use_bpf = 0;

  return (0);
}

static int
dag_set_datalink(pcap_t *p, int dlt)
{
	return (0);
}

static int
dag_setnonblock(pcap_t *p, int nonblock, char *errbuf)
{
	/*
	 * Set non-blocking mode on the FD.
	 * XXX - is that necessary?  If not, don't bother calling it,
	 * and have a "dag_getnonblock()" function that looks at
	 * "p->md.dag_offset_flags".
	 */
	if (pcap_setnonblock_fd(p, nonblock, errbuf) < 0)
		return (-1);

	if (nonblock) {
		p->md.dag_offset_flags |= DAGF_NONBLOCK;
	} else {
		p->md.dag_offset_flags &= ~DAGF_NONBLOCK;
	}
	return (0);
}
		
static int
dag_get_datalink(pcap_t *p)
{
  int linktype = -1;

  /* Check the type through a dagapi call.
  */
  switch(dag_linktype(p->fd)) {
  case TYPE_HDLC_POS: {
      dag_record_t *record;

      /* peek at the first available record to see if it is PPP */
      while ((p->md.dag_mem_top - p->md.dag_mem_bottom) < (dag_record_size + 4)) {
        p->md.dag_mem_top = dag_offset(p->fd, &(p->md.dag_mem_bottom), 0);
      }
      record = (dag_record_t *)(p->md.dag_mem_base + p->md.dag_mem_bottom);

      if ((ntohl(record->rec.pos.hdlc) & 0xffff0000) == 0xff030000) {
        linktype = DLT_PPP_SERIAL;
        fprintf(stderr, "Set DAG linktype to %d (DLT_PPP_SERIAL)\n", linktype);
      } else {
        linktype = DLT_CHDLC;
        fprintf(stderr, "Set DAG linktype to %d (DLT_CHDLC)\n", linktype);
      }
      break;
    }
  case TYPE_ETH:
    linktype = DLT_EN10MB;
    fprintf(stderr, "Set DAG linktype to %d (DLT_EN10MB)\n", linktype);
    break;
  case TYPE_ATM: 
    linktype = DLT_ATM_RFC1483;
    fprintf(stderr, "Set DAG linktype to %d (DLT_ATM_RFC1483)\n", linktype);
    break;
  case TYPE_LEGACY:
    linktype = DLT_NULL;
    fprintf(stderr, "Set DAG linktype to %d (DLT_NULL)\n", linktype);
    break;
  default:
    fprintf(stderr, "Unknown DAG linktype %d\n", dag_linktype(p->fd));
    break;
  }

  return linktype;
}