pcapy.xml

<?xml version='1.0'?>
<!DOCTYPE part PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
               "docbook/dtd/xml/4.1.2/docbookx.dtd" [
  <!ENTITY corest "CORE SECURITY TECHNOLOGIES">
]>
<part>
  <partinfo>
    <copyright>
      <year>2016-2018</year>
      <holder>&corest;</holder>
    </copyright>
    <corpauthor>&corest;</corpauthor>
    <keywordset>
      <keyword>pcap</keyword>
      <keyword>packet</keyword>
      <keyword>capture</keyword>
      <keyword>python</keyword>
    </keywordset>
    <revhistory>
      <revision>
        <revnumber>Revision: 16</revnumber>
        <date>Date: 2018-06-04</date>
        <authorinitials>Author: jkohen</authorinitials>
        <revremark>2018 updated</revremark>
      </revision>
    </revhistory>
  </partinfo>
  <title>Pcapy Reference</title>

  <reference>
    <title>Pcapy Module Reference</title>
    <refentry>
      <refnamediv>
        <refname>open_live</refname>
        <refpurpose>Obtain a packet capture descriptor to look at packets on the network</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              Reader <function>open_live</function>
            </funcdef>
            <paramdef>
              string <parameter>device</parameter>
            </paramdef>
            <paramdef>
              int <parameter>snaplen</parameter>
            </paramdef>
            <paramdef>
              int <parameter>promisc</parameter>
            </paramdef>
            <paramdef>
              int <parameter>to_ms</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>open_live</function> is used to obtain a packet
          capture descriptor to look at packets on the network.
          <parameter>device</parameter> is a string that specifies the
          network device to open; on Linux systems with 2.2 or later
          kernels, a device argument of <literal>any</literal> or
          <constant>NULL</constant> can be used to capture packets
          from all interfaces. <parameter>snaplen</parameter>
          specifies the maximum number of bytes to capture.
          <parameter>promisc</parameter> specifies if the interface is
          to be put into promiscuous mode. (Note that even if this
          parameter is false, the interface could well be in
          promiscuous mode for some other reason.) For now, this
          doesn't work on the <literal>any</literal> device; if an
          argument of <literal>any</literal> or
          <constant>NULL</constant> is supplied, the
          <parameter>promisc</parameter> flag is ignored.
          <parameter>to_ms</parameter> specifies the read timeout in
          milliseconds. The read timeout is used to arrange that the
          read not necessarily return immediately when a packet is
          seen, but that it wait for some amount of time to allow more
          packets to arrive and to read multiple packets from the OS
          kernel in one operation. Not all platforms support a read
          timeout; on platforms that don't, the read timeout is
          ignored.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>open_offline</refname>
        <refpurpose>
          Obtain a packet capture descriptor to look at packets on a <glossterm>savefile</glossterm>
        </refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              Reader <function>open_offline</function>
            </funcdef>
            <paramdef>
              string <parameter>filename</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>open_offline</function> is called to open a
          <glossterm>savefile</glossterm> for reading. <parameter>filename</parameter>
          specifies the name of the file to open. The file has the
          same format as those used by
          <citerefentry>
            <refentrytitle>tcpdump</refentrytitle>
            <manvolnum>8</manvolnum>
          </citerefentry> and
          <citerefentry>
            <refentrytitle>tcpslice</refentrytitle>
            <manvolnum>8</manvolnum>
          </citerefentry>. The name
          <filename>-</filename> is a synonym for
          <filename class="devicefile">stdin</filename>.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>lookupdev</refname>
        <refpurpose>
          Return a network device suitable for use with
          <function>open_live</function>
        </refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              string <function>lookupdev</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>lookupdev</function> returns the name of a network
          device suitable for use with <function>open_live</function>.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>findalldevs</refname>
        <refpurpose>Obtain the list of available network devices</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              string[] <function>findalldevs</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>findalldevs</function> constructs a list of
          network devices that can be opened with
          <function>open_live</function>. (Note that there may be
          network devices that cannot be opened with
          <function>open_live</function>, because, for example, that
          process might not have sufficient privileges to open them
          for capturing; if so, those devices will not appear on the
          list.)
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>compile</refname>
        <refpurpose>Compile a BPF filter</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              Bpf <function>compile</function>
            </funcdef>
            <paramdef>
              int <parameter>linktype</parameter>
            </paramdef>
            <paramdef>
              int <parameter>snaplen</parameter>
            </paramdef>
            <paramdef>
              string <parameter>filter</parameter>
            </paramdef>
            <paramdef>
              int <parameter>optimize</parameter>
            </paramdef>
            <paramdef>
              int32 <parameter>netmask</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>compile</function> is used to compile the
          <parameter>filter</parameter> into a filter program.
          <function>snaplen</function> specifies the maximum number of
          bytes to capture. <parameter>optimize</parameter> controls
          whether optimization on the resulting code is performed.
          <parameter>netmask</parameter> specifies the netmask of the
          local network.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>create</refname>
        <refpurpose>Creates a non-activated packet capture handle to look at packets on the network</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              Reader  <function>create</function>
            </funcdef>
            <paramdef>
              string <parameter>device</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>create</function> is used to create a 
          packet capture handle to look at packets on the network.
          The returned handle must be activated with
          <function>activate()</function> before packets can be captured
          with it; options for the capture, such as promiscuous mode,
          can be set on the handle before activating it.
        </para>
      </refsect1>
    </refentry>
  </reference>

  <reference>
    <title>Reader Object Reference</title>
    <refentry>
      <refnamediv>
        <refname>dispatch</refname>
        <refname>loop</refname>
        <refpurpose>Collect and process packets</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>dispatch</function>
            </funcdef>
            <paramdef>
              int <parameter>maxcant</parameter>
            </paramdef>
            <paramdef>
              void <parameter>(* callback)</parameter>
              <funcparams>Pkthdr, string</funcparams>
            </paramdef>
          </funcprototype>

          <funcprototype>
            <funcdef>
              int <function>loop</function>
            </funcdef>
            <paramdef>
              int <parameter>maxcant</parameter>
            </paramdef>
            <paramdef>
              void <parameter>(* callback)</parameter>
              <funcparams>Pkthdr, string</funcparams>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>dispatch</function> is used to collect and process
          packets. <parameter>maxcant</parameter> specifies the
          maximum number of packets to process before returning. This
          is not a minimum number; when reading a live capture, only
          one bufferful of packets is read at a time, so fewer than
          <parameter>maxcant</parameter> packets may be processed. A
          <parameter>cnt</parameter> of <literal>-1</literal>
          processes all the packets received in one buffer when
          reading a live capture, or all the packets in the file when
          reading a <glossterm>savefile</glossterm>. <parameter>callback</parameter>
          specifies a routine to be called with two arguments: a
          <classname>Pkthdr</classname> instance describing the data
          passed and the data itself.
        </para>
        <para>
          The number of packets read is returned.
          <returnvalue>0</returnvalue> is returned if no packets were
          read from a live capture (if, for example, they were
          discarded because they didn't pass the packet filter, or if,
          on platforms that support a read timeout that starts before
          any packets arrive, the timeout expires before any  packets
          arrive, or if the file descriptor for the capture device is
          in non-blocking mode and no packets were available to be
          read) or if no more packets are available in a <glossterm>savefile</glossterm>.
        </para>
        <note>
          <para>
            When reading a live capture, <function>dispatch</function>
            will not necessarily return when the read times out; on
            some platforms, the read timeout isn't supported, and, on
            other platforms, the timer doesn't start until at least
            one packet arrives. This means that the read timeout
            should <emphasis>not</emphasis> be used in, for example,
            an interactive application, to allow the packet capture
            loop to poll for user input periodically, as there's no
            guarantee that <function>dispatch</function> will return
            after the timeout expires.
          </para>
        </note>
        <para>
          <function>loop</function> is similar to
          <function>dispatch</function> except it keeps reading
          packets until <parameter>maxcant</parameter> packets are
          processed or an error occurs. It does
          <emphasis>not</emphasis> return when live read timeouts
          occur. Rather, specifying a non-zero read timeout to
          <function>open_live</function> and then calling
          <function>dispatch</function> allows the reception and
          processing of any packets that arrive when the timeout
          occurs. A negative <parameter>maxcant</parameter> causes
          <function>loop</function> to loop forever (or at least until
          an error occurs). <returnvalue>0</returnvalue> is returned
          if <parameter>maxcant</parameter> is exhausted.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>next</refname>
        <refpurpose>Collect the next packet</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              (Pkthdr, string) <function>next</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>next</function> reads the next packet (by calling
          <function>dispatch</function> with a
          <parameter>maxcant</parameter> of <constant>1</constant>)
          and returns a tuple (header, data) where
          <parameter>header</parameter> is a
          <classname>Pkthdr</classname> instance describing the data
          passed and <parameter>data</parameter> is the data itself.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>stats</refname>
        <refpurpose>get capture statistics</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              (int32, int32, int32) <function>stats</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>stats</function> returns statistics on the current
          capture as a tuple (recv, drop, ifdrop)
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>setfilter</refname>
        <refpurpose>Specify a filter</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              <function>setfilter</function>
            </funcdef>
            <paramdef>
              string <parameter>filter</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>setfilter</function> is used to specify a filter
          for this object.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>getfd</refname>
        <refpurpose>get a file descriptor on which a select() can be
        done for a live capture</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>getfd</function>
            </funcdef>
            <paramdef>
              string <parameter>filter</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>getfd</function> returns, on UNIX, a file descriptor
          number for a file descriptor on which one can do a select(),
          poll(), epoll_wait(), kevent(), or other such call to wait
          for it to be possible to read packets without blocking, if
          such a descriptor exists, or -1, if no such descriptor exists.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>set_snaplen</refname>
        <refpurpose>Set the snapshot length for a not-yet-activated
        capture handle</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>set_snaplen</function>
            </funcdef>
            <paramdef>
              int <parameter>snaplen</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>set_snaplen</function> sets the snapshot length
          to be used on a capture handle when the handle is activated
          to snaplen.
          <function>set_snaplen</function> returns 0 on success
          or PCAP_ERROR_ACTIVATED if called on a capture handle that
          has been activated.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>set_promisc</refname>
        <refpurpose>Set promiscuous mode for a not-yet-activated
        capture handle</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>set_promisc</function>
            </funcdef>
            <paramdef>
              int <parameter>promisc</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>set_promisc</function> sets whether promiscuous mode
          should be set on a capture handle when the handle is activated.
          If promisc is non-zero, promiscuous mode will be set, otherwise
          it will not be set.
          <function>set_promisc</function> returns 0 on success
          or PCAP_ERROR_ACTIVATED if called on a capture handle that
          has been activated.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>set_timeout</refname>
        <refpurpose>Set the read timeout for a not-yet-activated
        capture handle</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>set_timeout</function>
            </funcdef>
            <paramdef>
              int <parameter>timeout</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>set_timeout</function> sets the read timeout
          that will be used on a capture handle when the handle
          is activated to to_ms, which is in units of milliseconds.
          <function>set_timeout</function> returns 0 on success
          or PCAP_ERROR_ACTIVATED if called on a capture handle that
          has been activated.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>set_buffer_size</refname>
        <refpurpose>Set the buffer size for a not-yet-activated capture handle
        capture handle</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>set_buffer_size</function>
            </funcdef>
            <paramdef>
              int <parameter>buffer_size</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>set_buffer_size</function> sets the buffer size
          that will be used on a capture handle when the handle is
          activated to buffer_size, which is in units of bytes.
          <function>set_buffer_size</function> returns 0 on success
          or PCAP_ERROR_ACTIVATED if called on a capture handle that
          has been activated.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>activate</refname>
        <refpurpose>Activate a capture handle</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>activate</function>
            </funcdef>
            <void />
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>activate</function> is used to activate a
          packet capture handle to look at packets on the network,
          with the options that were set on the handle being in effect.
          <function>activate</function> returns 0 on success without
          warnings, a non-zero positive value on success with warnings,
          and a negative value on error. A non-zero return value indicates
          what warning or error condition occurred.
          has been activated.
          See https://www.tcpdump.org/manpages/pcap_activate.3pcap.html for
          all possible return values.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>getnet</refname>
        <refname>getmask</refname>
        <refpurpose>Get the associated network number and mask</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int32 <function>getnet</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>

        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int32 <function>getmask</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>getnet</function> and <function>getmask</function>
          are used to determine the network number and mask associated
          with the network device attached to this
          <classname>Reader</classname>.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>datalink</refname>
        <refpurpose>Obtain the link layer type</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>datalink</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>datalink</function> returns the link layer type; link layer types it can return include:
          <variablelist>
            <varlistentry>
              <term>
                <constant>DLT_NULL</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>BSD</acronym> loopback encapsulation; the
                  link layer header is a 4-byte field, in host
                  byte order, containing a <constant>PF_</constant>
                  value from <filename
         class="headerfile">socket.h</filename> for the
                  network-layer protocol of the packet.
                </simpara>
                <note>
                  <simpara>
                    <quote>host byte order</quote> is the byte order
                    of the machine on which the packets are captured,
                    and the <constant>PF_</constant> values are for
                    the <acronym>OS</acronym> of the machine on which
                    the packets are captured; if a live capture is
                    being done, <quote>host byte order</quote> is the
                    byte order of the machine capturing the packets,
                    and the <constant>PF_</constant> values are those
                    of the <acronym>OS</acronym> of the machine
                    capturing the packets, but if a <glossterm>savefile</glossterm> is being
                    read, the byte order and <constant>PF_</constant>
                    values are <emphasis>not</emphasis> necessarily
                    those of the machine reading the capture file.
                  </simpara>
                </note>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_EN10MB</constant>
              </term>
              <listitem>
                <simpara>Ethernet (10Mb, 100Mb, 1000Mb, and up)</simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_IEEE802</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>IEEE</acronym> 802.5 Token Ring
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_ARCNET</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>ARCNET</acronym>
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_SLIP</constant>
              </term>
              <listitem>
                <para>
                  <acronym>SLIP</acronym>; the link layer header contains, in order:
                  <itemizedlist>
                    <listitem>
                      <simpara>
                        a 1-byte flag, which is
                        <literal>0</literal> for packets received by
                        the machine and <literal>1</literal> for
                        packets sent by the machine.
                      </simpara>
                    </listitem>

                    <listitem>
                      <para>
                        a 1-byte field, the upper 4 bits of which indicate the type of packet, as per <acronym>RFC</acronym> 1144:

                        <itemizedlist>
                          <listitem>
                            <simpara>
                              <literal>0x40</literal>; an unmodified
                              <acronym>IP</acronym> datagram
                              (<constant>TYPE_IP</constant>)
                            </simpara>
                          </listitem>

                          <listitem>
                            <simpara>
                              <literal>0x70</literal>; an
                              uncompressed-<acronym>TCP/IP</acronym>
                              datagram
                              (<constant>UNCOMPRESSED_TCP</constant>),
                              with that byte being the first byte of
                              the raw <acronym>IP</acronym> header on
                              the wire, containing the connection
                              number in the protocol field
                            </simpara>
                          </listitem>

                          <listitem>
                            <simpara>
                              <literal>0x80</literal>; a
                              compressed-<acronym>TCP/IP</acronym>
                              datagram
                              (<constant>COMPRESSED_TCP</constant>),
                              with that byte being the first byte of
                              the compressed <acronym>TCP/IP</acronym>
                              datagram header
                            </simpara>
                          </listitem>
                        </itemizedlist>
                      </para>
                    </listitem>

                    <listitem>
                      <simpara>
                        for <constant>UNCOMPRESSED_TCP</constant>, the
                        rest of the modified <acronym>IP</acronym>
                        header, and for
                        <constant>COMPRESSED_TCP</constant>, the
                        compressed <acronym>TCP/IP</acronym> datagram
                        header
                      </simpara>
                    </listitem>

                  </itemizedlist>
                  for a total of 16 bytes; the uncompressed <acronym>IP</acronym> datagram follows the header.
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_PPP</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>PPP</acronym>; if the first 2 bytes are
                  <literal>0xff</literal> and <literal>0x03</literal>,
                  it's <acronym>PPP</acronym> in
                  <acronym>HDLC</acronym>-like framing, with the
                  <acronym>PPP</acronym> header following those two
                  bytes, otherwise it's <acronym>PPP</acronym> without
                  framing, and the packet begins with the
                  <acronym>PPP</acronym> header.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_FDDI</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>FDDI</acronym>
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_ATM_RFC1483</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>RFC</acronym> 1483
                  <acronym>LLC/SNAP</acronym>-encapsulated
                  <acronym>ATM</acronym>; the packet begins with an
                  <acronym>IEEE</acronym> 802.2 <acronym>LLC</acronym>
                  header.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_RAW</constant>
              </term>
              <listitem>
                <simpara>
                  Raw <acronym>IP</acronym>; the packet begins with an
                  <acronym>IP</acronym> header.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_PPP_SERIAL</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>PPP</acronym> in
                  <acronym>HDLC</acronym>-like framing, as per
                  <acronym>RFC</acronym> 1662, or Cisco
                  <acronym>PPP</acronym> with <acronym>HDLC</acronym>
                  framing, as per section 4.3.1 of
                  <acronym>RFC</acronym> 1547; the first byte will be
                  <literal>0xFF</literal> for <acronym>PPP</acronym>
                  in <acronym>HDLC</acronym>-like framing, and
                  will be <literal>0x0F</literal> or
                  <literal>0x8F</literal> for Cisco
                  <acronym>PPP</acronym> with <acronym>HDLC</acronym>
                  framing.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_PPP_ETHER</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>PPPoE</acronym>; the packet begins with a
                  <acronym>PPPoE</acronym> header, as per
                  <acronym>RFC</acronym> 2516.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_C_HDLC</constant>
              </term>
              <listitem>
                <simpara>
                  Cisco <acronym>PPP</acronym> with
                  <acronym>HDLC</acronym> framing, as per section
                   4.3.1 of <acronym>RFC</acronym> 1547.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_IEEE802_11</constant>
              </term>
              <listitem>
                <simpara>
                  <acronym>IEEE</acronym> 802.11 wireless
                  <acronym>LAN</acronym>.
                </simpara>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_LOOP</constant>
              </term>
              <listitem>
                <simpara>
                  OpenBSD loopback encapsulation; the link layer
                  header is a 4-byte field, in network byte
                  order, containing a <constant>PF_</constant> value
                  from OpenBSD's <filename
     class="headerfile">socket.h</filename> for the
                  network-layer protocol of the packet.
                </simpara>
                <note>
                  <simpara>
                    Note that, if a <glossterm>savefile</glossterm> is being read, those
                    <constant>PF_</constant> values are
                    <emphasis>not</emphasis> necessarily those of the
                    machine reading the capture file.
                  </simpara>
                </note>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_LINUX_SLL</constant>
              </term>
              <listitem>
                <para>
                  Linux cooked capture encapsulation; the link layer
                  header contains, in order:

                  <itemizedlist>
                    <listitem>
                      <para>
                        a 2-byte "packet  type",  in  network
                        byte order, which is one of:

                        <itemizedlist>
                          <listitem>
                            <simpara>
                              <literal>0</literal>; packet was sent to
                              us by somebody else.
                            </simpara>
                          </listitem>

                          <listitem>
                            <simpara>
                              <literal>1</literal>; packet was
                              broadcast by somebody else.
                            </simpara>
                          </listitem>

                          <listitem>
                            <simpara>
                              <literal>2</literal>; packet was
                              multicast, but not broadcast, by
                              somebody else.
                            </simpara>
                          </listitem>

                          <listitem>
                            <simpara>
                              <literal>3</literal>; packet was sent by
                              somebody else to somebody else.
                            </simpara>
                          </listitem>

                          <listitem>
                            <simpara>
                              <literal>4</literal>; packet was sent by
                              us.
                            </simpara>
                          </listitem>
                        </itemizedlist>
                      </para>
                    </listitem>

                    <listitem>
                      <simpara>
                        a 2-byte field, in network byte order,
                        containing a Linux
                        <constant>ARPHRD_</constant> value for the
                        link layer device type.
                      </simpara>
                    </listitem>

                    <listitem>
                      <simpara>
                        a 2-byte field, in network byte order,
                        containing the length of the link layer
                        address of the sender of the packet (which
                        could be 0).
                      </simpara>
                    </listitem>

                    <listitem>
                      <simpara>
                        an 8-byte field containing that number
                        of bytes of the link layer header (if there
                        are more than 8 bytes, only the first 8 are
                        present).
                      </simpara>
                    </listitem>

                    <listitem>
                      <simpara>
                        a 2-byte field containing an Ethernet
                        protocol type, in network byte order, or
                        containing <literal>1</literal> for Novell
                        802.3 frames without an 802.2
                        <acronym>LLC</acronym> header or
                        <literal>4</literal> for frames beginning with
                        an 802.2 <acronym>LLC</acronym> header.
                      </simpara>
                    </listitem>
                  </itemizedlist>
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <constant>DLT_LTALK</constant>
              </term>
              <listitem>
                <simpara>
                  Apple LocalTalk; the packet begins with an AppleTalk
                  <acronym>LLAP</acronym> header.
                </simpara>
              </listitem>
            </varlistentry>
          </variablelist>
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>getnonblock / setnonblock</refname>
        <refpurpose>
          Manipulate the
          <firstterm>non-blocking</firstterm> flag
        </refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>getnonblock</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>

        <funcsynopsis>
          <funcprototype>
            <funcdef>
              <function>setnonblock</function>
            </funcdef>
            <paramdef>
              int <parameter>state</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>getnonblock</function> returns the current
          non-blocking state of the capture descriptor; it
          always returns <returnvalue>0</returnvalue> on <glossterm>savefile</glossterm>s.
        </para>
      </refsect1>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>setnonblock</function> puts a capture descriptor,
          opened with <function>open_live</function>, into
          non-blocking mode, or takes it out of
          non-blocking mode, depending on whether the
          <parameter>state</parameter> argument is non-zero or
          zero. It has no effect on <glossterm>savefile</glossterm>s. In non-blocking
          mode, an attempt to read from the capture descriptor with
          <function>dispatch</function> will, if no packets are
          currently available to be read, return
          <returnvalue>0</returnvalue> immediately rather than
          blocking waiting for packets to arrive.
          <function>loop</function> and <function>next</function> will
          not work in non-blocking mode.
        </para>
      </refsect1>
    </refentry>

    <refentry>
      <refnamediv>
        <refname>dump_open</refname>
        <refpurpose>Create a Dumper object</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              Dumper <function>dump_open</function>
            </funcdef>
            <paramdef>
              string <parameter>filename</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>dump_open</function> is called to open a <glossterm>savefile</glossterm>
          for writing and associate it to a newly created
          <classname>Dumper</classname> instance. The name
          <filename>-</filename> is a synonym for <filename
	    class="devicefile">stdout</filename>.
          <parameter>filename</parameter> specifies the name of the
          file to open.
        </para>
      </refsect1>
    </refentry>

    <refentry>
        <refnamediv>
            <refname>close</refname>
            <refpurpose>
                Close a Reader
            </refpurpose>
        </refnamediv>
        <refsynopsisdiv>
            <funcsynopsis>
              <funcprototype>
                <funcdef>
                  Reader <function>close</function>
                </funcdef>
                <void/>
              </funcprototype>
            </funcsynopsis>
        </refsynopsisdiv>
        <refsect1>
            <title>DESCRIPTION</title>
            <para>
              <function>close</function> closes a <classname>Reader</classname> using pcap_close.
            </para>
        </refsect1>
    </refentry>

  </reference>

  <reference>
    <title>Dumper Object Reference</title>
    <refentry>
      <refnamediv>
        <refname>dump</refname>
        <refpurpose>
          Dump a packet to a <glossterm>savefile</glossterm>
        </refpurpose>
      </refnamediv>
      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              <function>dump</function>
            </funcdef>
            <paramdef>
              Pkthdr <parameter>header</parameter>
            </paramdef>
            <paramdef>
              string <parameter>data</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>dump</function> outputs a packet to the <glossterm>savefile</glossterm>
          opened with <function>dump_open</function> from type
          <classname>Reader</classname>.
        </para>
      </refsect1>
    </refentry>
    <refentry>
        <refnamediv>
            <refname>close</refname>
            <refpurpose>
                Close a Dumper
            </refpurpose>
        </refnamediv>
        <refsynopsisdiv>
            <funcsynopsis>
              <funcprototype>
                <funcdef>
                  Dumper <function>close</function>
                </funcdef>
                <void/>
              </funcprototype>
            </funcsynopsis>
        </refsynopsisdiv>
        <refsect1>
            <title>DESCRIPTION</title>
            <para>
              <function>close</function> closes a <classname>Dumper</classname>.
            </para>
        </refsect1>
    </refentry>
  </reference>

  <reference>
    <title>Pkthdr Object Reference</title>
    <refentry>
      <refnamediv>
        <refname>getts</refname>
        <refname>getcaplen</refname>
        <refname>getlen</refname>
        <refpurpose>Obtain packet header information</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              (long, long) <function>getts</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>

        <funcsynopsis>
          <funcprototype>
            <funcdef>
              long <function>getcaplen</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>

        <funcsynopsis>
          <funcprototype>
            <funcdef>
              long <function>getlen</function>
            </funcdef>
            <void/>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>getts</function>, <function>getcaplen</function>
          and <function>getlen</function> return the timestamp,
          capture length and total length fields of the packet header,
          respectively.
        </para>
        <para>
          Timestamp is a tuple with two elements: the number of
          seconds since the Epoch, and the amount of microseconds past
          the current second. The capture length is the number of
          bytes of the packet that are available from the capture.
          Finally, total length gives the length of the packet, in
          bytes (which might be more than the number of bytes
          available from the capture, if the length of the packet is
          larger than the maximum number of bytes to capture).
        </para>
      </refsect1>
    </refentry>
  </reference>

  <reference>
    <title>Bpf Object Reference</title>
    <refentry>
      <refnamediv>
        <refname>filter</refname>
        <refpurpose>Test a packet against a compiled filter</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>
              int <function>filter</function>
            </funcdef>
            <paramdef>
              string <parameter>packet</parameter>
            </paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsect1>
        <title>DESCRIPTION</title>
        <para>
          <function>filter</function> tests a packet against a
          compiled filter as returned by
          <classname>pcapy</classname>'s <function>compile</function>.
          If the packet is allowed to pass through
          <returnvalue>-1</returnvalue> is returned, otherwise
          <function>filter</function> returns
          <returnvalue>0</returnvalue>.
        </para>
      </refsect1>
    </refentry>
  </reference>

  <bibliography>
    <title>Bibliography</title>
    <bibliodiv>
      <title>Sources</title>
      <biblioentry>
        <bibliomisc>
          Portions of this work based on
          <citerefentry>
            <refentrytitle>pcap</refentrytitle>
            <manvolnum>3</manvolnum>
          </citerefentry> by the Lawrence
          Berkeley National Laboratory, University of California,
          Berkeley, CA.
        </bibliomisc>
      </biblioentry>
    </bibliodiv>
  </bibliography>
</part>