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<html><head><meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"><title>Part I. Pcapy Reference</title><meta name="generator" content="DocBook XSL Stylesheets V1.40"><meta name="keywords" content="pcap, packet, capture, python"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="part" id="id2720626"><div class="titlepage"><div><h1 class="title"><a name="id2720626"></a>Pcapy Reference</h1></div><div><h3 class="corpauthor">CORE SECURITY TECHNOLOGIES</h3></div><div><p class="copyright">Copyright © 2003 CORE SECURITY TECHNOLOGIES</p></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="3"><b>Revision History</b></th></tr><tr><td align="left">Revision $Revision: 1.2 $</td><td align="left">$Date: 2003/10/23 17:24:27 $</td><td align="left">$Author: jkohen $</td></tr><tr><td align="left" colspan="3">Initial revision</td></tr></table></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt>I <a href="#id2720790">Pcapy Module Reference</a></dt><dd><dl><dt><a href="#id2720796">open_live</a></dt><dt><a href="#id2720974">open_offline</a></dt><dt><a href="#id2721096">lookupdev</a></dt><dt><a href="#id2716618">findalldevs</a></dt><dt><a href="#id2766688">compile</a></dt></dl></dd><dt>II <a href="#id2720711">Reader Object Reference</a></dt><dd><dl><dt><a href="#id2720717">dispatch</a></dt><dt><a href="#id2723103">next</a></dt><dt><a href="#id2723279">setfilter</a></dt><dt><a href="#id2723348">getnet</a></dt><dt><a href="#id2723448">datalink</a></dt><dt><a href="#id2718490">getnonblock</a></dt><dt><a href="#id2718128">dump_open</a></dt></dl></dd><dt>III <a href="#id2718727">Dumper Object Reference</a></dt><dd><dl><dt><a href="#id2718732">dump</a></dt></dl></dd><dt>IV <a href="#id2718829">Pkthdr Object Reference</a></dt><dd><dl><dt><a href="#id2718835">getts</a></dt></dl></dd><dt>V <a href="#id2781073">Bpf Object Reference</a></dt><dd><dl><dt><a href="#id2781080">filter</a></dt></dl></dd><dt><a href="#id2781178">Bibliography</a></dt></dl></div><div class="reference"><div class="titlepage"><div><h1 class="title"><a name="id2720790"></a>Pcapy Module Reference</h1></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="#id2720796">open_live</a></dt><dt><a href="#id2720974">open_offline</a></dt><dt><a href="#id2721096">lookupdev</a></dt><dt><a href="#id2716618">findalldevs</a></dt><dt><a href="#id2766688">compile</a></dt></dl></div><div class="refentry"><h1 class="title"><a name="id2720796"></a>open_live</h1><div class="refnamediv"><a name="id2720799"></a><h2>Name</h2>open_live — Obtain a packet capture descriptor to look at packets on the network</div><div class="refsynopsisdiv"><a name="id2720813"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2720817"><a name="id2720817"></a><p><code><code class="funcdef">Reader <b class="fsfunc">open_live</b></code>(<var class="pdparam">device</var>, <var class="pdparam">snaplen</var>, <var class="pdparam">promisc</var>, <var class="pdparam">to_ms</var>);<br>string <var class="pdparam">device</var>;<br>int <var class="pdparam">snaplen</var>;<br>int <var class="pdparam">promisc</var>;<br>int <var class="pdparam">to_ms</var>;</code></p></div></div><div class="refsect1"><a name="id2720875"></a><h2><a name="id2720875"></a>DESCRIPTION</h2><p>
<tt>open_live</tt> is used to obtain a packet
capture descriptor to look at packets on the network.
<i><tt>device</tt></i> is a string that specifies the
network device to open; on Linux systems with 2.2 or later
kernels, a device argument of <tt>any</tt> or
<tt>NULL</tt> can be used to capture packets
from all interfaces. <i><tt>snaplen</tt></i>
specifies the maximum number of bytes to capture.
<i><tt>promisc</tt></i> 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 <tt>any</tt> device; if an
argument of <tt>any</tt> or
<tt>NULL</tt> is supplied, the
<i><tt>promisc</tt></i> flag is ignored.
<i><tt>to_ms</tt></i> 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.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2720974"></a>open_offline</h1><div class="refnamediv"><a name="id2720977"></a><h2>Name</h2>open_offline — Obtain a packet capture descriptor to look at packets on a <i>savefile</i></div><div class="refsynopsisdiv"><a name="id2720994"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2720997"><a name="id2720997"></a><p><code><code class="funcdef">Reader <b class="fsfunc">open_offline</b></code>(<var class="pdparam">filename</var>);<br>string <var class="pdparam">filename</var>;</code></p></div></div><div class="refsect1"><a name="id2721028"></a><h2><a name="id2721028"></a>DESCRIPTION</h2><p>
<tt>open_offline</tt> is called to open a
<i>savefile</i> for reading. <i><tt>filename</tt></i>
specifies the name of the file to open. The file has the
same format as those used by
tcpdump(8) and
tcpslice(8). The name
<tt>-</tt> is a synonym for
<tt>stdin</tt>.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2721096"></a>lookupdev</h1><div class="refnamediv"><a name="id2721099"></a><h2>Name</h2>lookupdev — Return a network device suitable for use with
<tt>open_live</tt></div><div class="refsynopsisdiv"><a name="id2721118"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2721121"><a name="id2721121"></a><p><code><code class="funcdef">string <b class="fsfunc">lookupdev</b></code>();</code></p></div></div><div class="refsect1"><a name="id2721144"></a><h2><a name="id2721144"></a>DESCRIPTION</h2><p>
<tt>lookupdev</tt> returns the name of a network
device suitable for use with <tt>open_live</tt>.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2716618"></a>findalldevs</h1><div class="refnamediv"><a name="id2766659"></a><h2>Name</h2>findalldevs — Obtain the list of available network devices</div><div class="refsynopsisdiv"><a name="id2780797"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2780800"><a name="id2780800"></a><p><code><code class="funcdef">string[] <b class="fsfunc">findalldevs</b></code>();</code></p></div></div><div class="refsect1"><a name="id2766782"></a><h2><a name="id2766782"></a>DESCRIPTION</h2><p>
<tt>findalldevs</tt> constructs a list of
network devices that can be opened with
<tt>open_live</tt>. (Note that there may be
network devices that cannot be opened with
<tt>open_live</tt>, 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.)
</p></div></div><div class="refentry"><h1 class="title"><a name="id2766688"></a>compile</h1><div class="refnamediv"><a name="id2766691"></a><h2>Name</h2>compile — Compile a BPF filter</div><div class="refsynopsisdiv"><a name="id2766704"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2766707"><a name="id2766707"></a><p><code><code class="funcdef">Bpf <b class="fsfunc">compile</b></code>(<var class="pdparam">linktype</var>, <var class="pdparam">snaplen</var>, <var class="pdparam">filter</var>, <var class="pdparam">optimize</var>, <var class="pdparam">netmask</var>);<br>int <var class="pdparam">linktype</var>;<br>int <var class="pdparam">snaplen</var>;<br>string <var class="pdparam">filter</var>;<br>int <var class="pdparam">optimize</var>;<br>int32 <var class="pdparam">netmask</var>;</code></p></div></div><div class="refsect1"><a name="id2720660"></a><h2><a name="id2720660"></a>DESCRIPTION</h2><p>
<tt>compile</tt> is used to compile the
<i><tt>filter</tt></i> into a filter program.
<tt>snaplen</tt> specifies the maximum number of
bytes to capture. <i><tt>optimize</tt></i> controls
whether optimization on the resulting code is performed.
<i><tt>netmask</tt></i> specifies the netmask of the
local network.
</p></div></div></div><div class="reference"><div class="titlepage"><div><h1 class="title"><a name="id2720711"></a>Reader Object Reference</h1></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="#id2720717">dispatch</a></dt><dt><a href="#id2723103">next</a></dt><dt><a href="#id2723279">setfilter</a></dt><dt><a href="#id2723348">getnet</a></dt><dt><a href="#id2723448">datalink</a></dt><dt><a href="#id2718490">getnonblock</a></dt><dt><a href="#id2718128">dump_open</a></dt></dl></div><div class="refentry"><h1 class="title"><a name="id2720717"></a>dispatch</h1><div class="refnamediv"><a name="id2720720"></a><h2>Name</h2>dispatch, loop — Collect and process packets</div><div class="refsynopsisdiv"><a name="id2718931"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2718935"><a name="id2718935"></a><p><code><code class="funcdef">int <b class="fsfunc">dispatch</b></code>(<var class="pdparam">maxcant</var>, <var class="pdparam">(* callback)</var>);<br>int <var class="pdparam">maxcant</var>;<br>void <var class="pdparam">(* callback)</var>
(Pkthdr, string);</code></p><p><code><code class="funcdef">int <b class="fsfunc">loop</b></code>(<var class="pdparam">maxcant</var>, <var class="pdparam">(* callback)</var>);<br>int <var class="pdparam">maxcant</var>;<br>void <var class="pdparam">(* callback)</var>
(Pkthdr, string);</code></p></div></div><div class="refsect1"><a name="id2719017"></a><h2><a name="id2719017"></a>DESCRIPTION</h2><p>
<tt>dispatch</tt> is used to collect and process
packets. <i><tt>maxcant</tt></i> 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
<i><tt>maxcant</tt></i> packets may be processed. A
<i><tt>cnt</tt></i> of <tt>-1</tt>
processes all the packets received in one buffer when
reading a live capture, or all the packets in the file when
reading a <i>savefile</i>. <i><tt>callback</tt></i>
specifies a routine to be called with two arguments: a
<tt>Pkthdr</tt> instance describing the data
passed and the data itself.
</p><p>
The number of packets read is returned.
0 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 <i>savefile</i>.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title"><a name="id2723188"></a>Note</h3><p>
When reading a live capture, <tt>dispatch</tt>
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 <i>not</i> 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 <tt>dispatch</tt> will return
after the timeout expires.
</p></div><p>
<tt>loop</tt> is similar to
<tt>dispatch</tt> except it keeps reading
packets until <i><tt>maxcant</tt></i> packets are
processed or an error occurs. It does
<i>not</i> return when live read timeouts
occur. Rather, specifying a non–zero read timeout to
<tt>open_live</tt> and then calling
<tt>dispatch</tt> allows the reception and
processing of any packets that arrive when the timeout
occurs. A negative <i><tt>maxcant</tt></i> causes
<tt>loop</tt> to loop forever (or at least until
an error occurs). 0 is returned
if <i><tt>maxcant</tt></i> is exhausted.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2723103"></a>next</h1><div class="refnamediv"><a name="id2723106"></a><h2>Name</h2>next — Collect the next packet</div><div class="refsynopsisdiv"><a name="id2723120"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2723123"><a name="id2723123"></a><p><code><code class="funcdef">(Pkthdr, string) <b class="fsfunc">next</b></code>();</code></p></div></div><div class="refsect1"><a name="id2723147"></a><h2><a name="id2723147"></a>DESCRIPTION</h2><p>
<tt>next</tt> reads the next packet (by calling
<tt>dispatch</tt> with a
<i><tt>maxcant</tt></i> of <tt>1</tt>)
and returns a tuple (header, data) where
<i><tt>header</tt></i> is a
<tt>Pkthdr</tt> instance describing the data
passed and <i><tt>data</tt></i> is the data itself.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2723279"></a>setfilter</h1><div class="refnamediv"><a name="id2723282"></a><h2>Name</h2>setfilter — Specify a filter</div><div class="refsynopsisdiv"><a name="id2723294"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2723298"><a name="id2723298"></a><p><code><code class="funcdef"><b class="fsfunc">setfilter</b></code>(<var class="pdparam">filter</var>);<br>string <var class="pdparam">filter</var>;</code></p></div></div><div class="refsect1"><a name="id2723327"></a><h2><a name="id2723327"></a>DESCRIPTION</h2><p>
<tt>setfilter</tt> is used to specify a filter
for this object.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2723348"></a>getnet</h1><div class="refnamediv"><a name="id2723351"></a><h2>Name</h2>getnet, getmask — Get the associated network number and mask</div><div class="refsynopsisdiv"><a name="id2723367"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2723370"><a name="id2723370"></a><p><code><code class="funcdef">int32 <b class="fsfunc">getnet</b></code>();</code></p></div><div class="funcsynopsis" id="id2723392"><a name="id2723392"></a><p><code><code class="funcdef">int32 <b class="fsfunc">getmask</b></code>();</code></p></div></div><div class="refsect1"><a name="id2723415"></a><h2><a name="id2723415"></a>DESCRIPTION</h2><p>
<tt>getnet</tt> and <tt>getmask</tt>
are used to determine the network number and mask associated
with the network device attached to this
<tt>Reader</tt>.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2723448"></a>datalink</h1><div class="refnamediv"><a name="id2723451"></a><h2>Name</h2>datalink — Obtain the link layer type</div><div class="refsynopsisdiv"><a name="id2723463"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2723466"><a name="id2723466"></a><p><code><code class="funcdef">int <b class="fsfunc">datalink</b></code>();</code></p></div></div><div class="refsect1"><a name="id2723489"></a><h2><a name="id2723489"></a>DESCRIPTION</h2><p>
<tt>datalink</tt> returns the link layer type; link layer types it can return include:
<div class="variablelist"><dl><dt><a name="id2723510"></a><span class="term"><tt>DLT_NULL</tt></span></dt><dd><p>
BSD loopback encapsulation; the
link layer header is a 4–byte field, in host
byte order, containing a <tt>PF_</tt>
value from <tt>socket.h</tt> for the
network–layer protocol of the packet.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title"><a name="id2723550"></a>Note</h3><p>
“host byte order” is the byte order
of the machine on which the packets are captured,
and the <tt>PF_</tt> values are for
the OS of the machine on which
the packets are captured; if a live capture is
being done, “host byte order” is the
byte order of the machine capturing the packets,
and the <tt>PF_</tt> values are those
of the OS of the machine
capturing the packets, but if a <i>savefile</i> is being
read, the byte order and <tt>PF_</tt>
values are <i>not</i> necessarily
those of the machine reading the capture file.
</p></div></dd><dt><a name="id2723606"></a><span class="term"><tt>DLT_EN10MB</tt></span></dt><dd><p>Ethernet (10Mb, 100Mb, 1000Mb, and up)</p></dd><dt><a name="id2723624"></a><span class="term"><tt>DLT_IEEE802</tt></span></dt><dd><p>IEEE 802.5 Token Ring</p></dd><dt><a name="id2723645"></a><span class="term"><tt>DLT_ARCNET</tt></span></dt><dd><p>ARCNET</p></dd><dt><a name="id2723536"></a><span class="term"><tt>DLT_SLIP</tt></span></dt><dd><p><a name="id2717681"></a>
SLIP; the link layer header contains, in order:
<div class="itemizedlist"><ul><li><a name="id2717695"></a><p>
a 1–byte flag, which is
<tt>0</tt> for packets received by
the machine and <tt>1</tt> for
packets sent by the machine.
</p></li><li><p><a name="id2717721"></a>
a 1–byte field, the upper 4 bits of which indicate the type of packet, as per RFC 1144:
<div class="itemizedlist"><ul><li><a name="id2717736"></a><p>
<tt>0x40</tt>; an unmodified
IP datagram
(<tt>TYPE_IP</tt>)
</p></li><li><a name="id2717760"></a><p>
<tt>0x70</tt>; an
uncompressed–TCP/IP
datagram
(<tt>UNCOMPRESSED_TCP</tt>),
with that byte being the first byte of
the raw IP header on
the wire, containing the connection
number in the protocol field
</p></li><li><a name="id2717791"></a><p>
<tt>0x80</tt>; a
compressed–TCP/IP
datagram
(<tt>COMPRESSED_TCP</tt>),
with that byte being the first byte of
the compressed TCP/IP
datagram header
</p></li></ul></div>
</p></li><li><a name="id2717824"></a><p>
for <tt>UNCOMPRESSED_TCP</tt>, the
rest of the modified IP
header, and for
<tt>COMPRESSED_TCP</tt>, the
compressed TCP/IP datagram
header
</p></li></ul></div>
for a total of 16 bytes; the uncompressed IP datagram follows the header.
</p></dd><dt><a name="id2717860"></a><span class="term"><tt>DLT_PPP</tt></span></dt><dd><p>
PPP; if the first 2 bytes are
<tt>0xff</tt> and <tt>0x03</tt>,
it's PPP in
HDLC–like framing, with the
PPP header following those two
bytes, otherwise it's PPP without
framing, and the packet begins with the
PPP header.
</p></dd><dt><a name="id2717919"></a><span class="term"><tt>DLT_FDDI</tt></span></dt><dd><p>FDDI</p></dd><dt><a name="id2717938"></a><span class="term"><tt>DLT_ATM_RFC1483</tt></span></dt><dd><p>
RFC 1483
LLC/SNAP–encapsulated
ATM; the packet begins with an
IEEE 802.2 LLC
header.
</p></dd><dt><a name="id2717976"></a><span class="term"><tt>DLT_RAW</tt></span></dt><dd><p>
Raw IP; the packet begins with an
IP header.
</p></dd><dt><a name="id2718002"></a><span class="term"><tt>DLT_PPP_SERIAL</tt></span></dt><dd><p>
PPP in
HDLC–like framing, as per
RFC 1662, or Cisco
PPP with HDLC
framing, as per section §4.3.1 of
RFC 1547; the first byte will be
<tt>0xFF</tt> for PPP
in HDLC–like framing, and
will be <tt>0x0F</tt> or
<tt>0x8F</tt> for Cisco
PPP with HDLC
framing.
</p></dd><dt><a name="id2718179"></a><span class="term"><tt>DLT_PPP_ETHER</tt></span></dt><dd><p>
PPPoE; the packet begins with a
PPPoE header, as per
RFC 2516.
</p></dd><dt><a name="id2718208"></a><span class="term"><tt>DLT_C_HDLC</tt></span></dt><dd><p>
Cisco PPP with
HDLC framing, as per section
§ 4.3.1 of RFC 1547.
</p></dd><dt><a name="id2718045"></a><span class="term"><tt>DLT_IEEE802_11</tt></span></dt><dd><p>
IEEE 802.11 wireless
LAN.
</p></dd><dt><a name="id2718071"></a><span class="term"><tt>DLT_LOOP</tt></span></dt><dd><p>
OpenBSD loopback encapsulation; the link layer
header is a 4–byte field, in network byte
order, containing a <tt>PF_</tt> value
from OpenBSD's <tt>socket.h</tt> for the
network–layer protocol of the packet.
</p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title"><a name="id2718249"></a>Note</h3><p>
Note that, if a <i>savefile</i> is being read, those
<tt>PF_</tt> values are
<i>not</i> necessarily those of the
machine reading the capture file.
</p></div></dd><dt><a name="id2718273"></a><span class="term"><tt>DLT_LINUX_SLL</tt></span></dt><dd><p><a name="id2718281"></a>
Linux cooked capture encapsulation; the link layer
header contains, in order:
<div class="itemizedlist"><ul><li><p><a name="id2718292"></a>
a 2–byte "packet type", in network
byte order, which is one of:
<div class="itemizedlist"><ul><li><a name="id2718303"></a><p>
<tt>0</tt>; packet was sent to
us by somebody else.
</p></li><li><a name="id2718320"></a><p>
<tt>1</tt>; packet was
broadcast by somebody else.
</p></li><li><a name="id2718336"></a><p>
<tt>2</tt>; packet was
multicast, but not broadcast, by
somebody else.
</p></li><li><a name="id2718353"></a><p>
<tt>3</tt>; packet was sent by
somebody else to somebody else.
</p></li><li><a name="id2718369"></a><p>
<tt>4</tt>; packet was sent by
us.
</p></li></ul></div>
</p></li><li><a name="id2718388"></a><p>
a 2–byte field, in network byte order,
containing a Linux
<tt>ARPHRD_</tt> value for the
link layer device type.
</p></li><li><a name="id2718403"></a><p>
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).
</p></li><li><a name="id2718414"></a><p>
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).
</p></li><li><a name="id2718426"></a><p>
a 2–byte field containing an Ethernet
protocol type, in network byte order, or
containing <tt>1</tt> for Novell
802.3 frames without an 802.2
LLC header or
<tt>4</tt> for frames beginning with
an 802.2 LLC header.
</p></li></ul></div>
</p></dd><dt><a name="id2718463"></a><span class="term"><tt>DLT_LTALK</tt></span></dt><dd><p>
Apple LocalTalk; the packet begins with an AppleTalk
LLAP header.
</p></dd></dl></div>
</p></div></div><div class="refentry"><h1 class="title"><a name="id2718490"></a>getnonblock</h1><div class="refnamediv"><a name="id2718494"></a><h2>Name</h2>getnonblock, setnonblock — Manipulate the
<i>non–blocking</i> flag</div><div class="refsynopsisdiv"><a name="id2718514"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2718516"><a name="id2718516"></a><p><code><code class="funcdef">int <b class="fsfunc">getnonblock</b></code>();</code></p></div><div class="funcsynopsis" id="id2718538"><a name="id2718538"></a><p><code><code class="funcdef"><b class="fsfunc">setnonblock</b></code>(<var class="pdparam">state</var>);<br>int <var class="pdparam">state</var>;</code></p></div></div><div class="refsect1"><a name="id2718567"></a><h2><a name="id2718567"></a>DESCRIPTION</h2><p>
<tt>getnonblock</tt> returns the current
non–blocking state of the capture descriptor; it
always returns 0 on <i>savefile</i>s.
</p></div><div class="refsect1"><a name="id2718596"></a><h2><a name="id2718596"></a>DESCRIPTION</h2><p>
<tt>setnonblock</tt> puts a capture descriptor,
opened with <tt>open_live</tt>, into
non–blocking mode, or takes it out of
non–blocking mode, depending on whether the
<i><tt>state</tt></i> argument is non–zero or
zero. It has no effect on <i>savefile</i>s. In non–blocking
mode, an attempt to read from the capture descriptor with
<tt>dispatch</tt> will, if no packets are
currently available to be read, return
0 immediately rather than
blocking waiting for packets to arrive.
<tt>loop</tt> and <tt>next</tt> will
not work in non–blocking mode.
</p></div></div><div class="refentry"><h1 class="title"><a name="id2718128"></a>dump_open</h1><div class="refnamediv"><a name="id2718622"></a><h2>Name</h2>dump_open — Create a Dumper object</div><div class="refsynopsisdiv"><a name="id2718635"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2718639"><a name="id2718639"></a><p><code><code class="funcdef">Dumper <b class="fsfunc">dump_open</b></code>(<var class="pdparam">filename</var>);<br>string <var class="pdparam">filename</var>;</code></p></div></div><div class="refsect1"><a name="id2718669"></a><h2><a name="id2718669"></a>DESCRIPTION</h2><p>
<tt>dump_open</tt> is called to open a <i>savefile</i>
for writing and associate it to a newly created
<tt>Dumper</tt> instance. The name
<tt>-</tt> is a synonym for <tt>stdout</tt>.
<i><tt>filename</tt></i> specifies the name of the
file to open.
</p></div></div></div><div class="reference"><div class="titlepage"><div><h1 class="title"><a name="id2718727"></a>Dumper Object Reference</h1></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="#id2718732">dump</a></dt></dl></div><div class="refentry"><h1 class="title"><a name="id2718732"></a>dump</h1><div class="refnamediv"><a name="id2718735"></a><h2>Name</h2>dump — Dump a packet to a <i>savefile</i></div><div class="refsynopsisdiv"><a name="id2718751"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2718755"><a name="id2718755"></a><p><code><code class="funcdef"><b class="fsfunc">dump</b></code>(<var class="pdparam">header</var>, <var class="pdparam">data</var>);<br>Pkthdr <var class="pdparam">header</var>;<br>string <var class="pdparam">data</var>;</code></p></div></div><div class="refsect1"><a name="id2718793"></a><h2><a name="id2718793"></a>DESCRIPTION</h2><p>
<tt>dump</tt> outputs a packet to the <i>savefile</i>
opened with <tt>dump_open</tt> from type
<tt>Reader</tt>.
</p></div></div></div><div class="reference"><div class="titlepage"><div><h1 class="title"><a name="id2718829"></a>Pkthdr Object Reference</h1></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="#id2718835">getts</a></dt></dl></div><div class="refentry"><h1 class="title"><a name="id2718835"></a>getts</h1><div class="refnamediv"><a name="id2718838"></a><h2>Name</h2>getts, getcaplen, getlen — Obtain packet header information</div><div class="refsynopsisdiv"><a name="id2780956"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2780959"><a name="id2780959"></a><p><code><code class="funcdef">(long, long) <b class="fsfunc">getts</b></code>();</code></p></div><div class="funcsynopsis" id="id2780980"><a name="id2780980"></a><p><code><code class="funcdef">long <b class="fsfunc">getcaplen</b></code>();</code></p></div><div class="funcsynopsis" id="id2781001"><a name="id2781001"></a><p><code><code class="funcdef">long <b class="fsfunc">getlen</b></code>();</code></p></div></div><div class="refsect1"><a name="id2781024"></a><h2><a name="id2781024"></a>DESCRIPTION</h2><p>
<tt>getts</tt>, <tt>getcaplen</tt>
and <tt>getlen</tt> return the timestamp,
capture length and total length fields of the packet header,
respectively.
</p><p>
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).
</p></div></div></div><div class="reference"><div class="titlepage"><div><h1 class="title"><a name="id2781073"></a>Bpf Object Reference</h1></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><a href="#id2781080">filter</a></dt></dl></div><div class="refentry"><h1 class="title"><a name="id2781080"></a>filter</h1><div class="refnamediv"><a name="id2781083"></a><h2>Name</h2>filter — Test a packet against a compiled filter</div><div class="refsynopsisdiv"><a name="id2781096"></a><h2>Synopsis</h2><div class="funcsynopsis" id="id2781099"><a name="id2781099"></a><p><code><code class="funcdef">int <b class="fsfunc">filter</b></code>(<var class="pdparam">packet</var>);<br>string <var class="pdparam">packet</var>;</code></p></div></div><div class="refsect1"><a name="id2781129"></a><h2><a name="id2781129"></a>DESCRIPTION</h2><p>
<tt>filter</tt> tests a packet against a
compiled filter as returned by
<tt>pcapy</tt>'s <tt>compile</tt>.
If the packet is allowed to pass through
-1 is returned, otherwise
<tt>filter</tt> returns
0.
</p></div></div></div><div id="id2781178" class="bibliography"><div class="titlepage"><div><h2 class="title"><a name="id2781178"></a>Bibliography</h2></div></div><div class="bibliodiv"><h3 class="title"><a name="id2781186">Sources</a></h3><div id="id2781192" class="biblioentry"><a name="id2781192"></a><p><span class="bibliomisc">
Portions of this work based on
pcap(3) by the Lawrence
Berkeley National Laboratory, University of California,
Berkeley, CA.
. </span></p></div></div></div></div></body></html>