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<html><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><!--Converted with jLaTeX2HTML 2002 (1.62) JA patch-1.4patched version by: Kenshi Muto, Debian Project.LaTeX2HTML 2002 (1.62),original version by: Nikos Drakos, CBLU, University of Leeds* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan* with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --><HTML><HEAD><TITLE>39.4.1.0.1 Configuration</TITLE><META NAME="description" CONTENT="39.4.1.0.1 Configuration"><META NAME="keywords" CONTENT="everything"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"><META NAME="Generator" CONTENT="jLaTeX2HTML v2002 JA patch-1.4"><META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css"><LINK REL="STYLESHEET" HREF="everything.css" tppabs="http://www.isi.edu/nsnam/ns/doc/everything.css"><LINK REL="previous" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html"><LINK REL="up" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html"><LINK REL="next" HREF="node548.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node548.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html9815" HREF="node548.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node548.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html9809" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html9805" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html9811" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html9813" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html9816" HREF="node548.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node548.html">39.4.2 IP Network Objects</A><B> Up:</B> <A NAME="tex2html9810" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html">39.4.1 Pcap/BPF Network Objects</A><B> Previous:</B> <A NAME="tex2html9806" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html">39.4.1 Pcap/BPF Network Objects</A>   <B> <A NAME="tex2html9812" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html9814" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H4><A NAME="SECTION09141010000000000000">39.4.1.0.1 Configuration</A></H4>Pcap network objects may be configured as either associated with alive network or with a trace file.If associated with a live network, the particular network interfaceto be used may be specified, as well as an optional promiscuous flag.As with all network objects, they may be opened for reading or writing.Here is an example:<PRE> set me [exec hostname] set pf1 [new Network/Pcap/Live] $pf1 set promisc_ true set intf [$pf1 open readonly] puts "pf1 configured on interface $intf" set filt "(ip src host foobar) and (not ether broadcast)" set nbytes [$pf1 filter $filt] puts "filter compiled to $nbytes bytes" puts "drops: [$pf1 pdrops], pkts: [$pf1 pkts]"</PRE>This example first determines the name of the local system whichwill be used in constructing a BPF/libpcap filter predicate.The <TT>new Network/Pcap/Live</TT> call creates an instance of thepcap network object for capturing live traffic.The <TT>promisc_</TT> flag tells the packet filter whether it shouldconfigure the undelying interface in promiscuous mode (if it is supported).The <TT>open</TT> call activates the packet filter, and may be specifiedas <TT>readonly</TT>, <TT>writeonly</TT>, or <TT>readwrite</TT>.It returns the name of the network interface the filter is associatedwith.The <TT>open</TT> call takes an optional extra parameter (not illustrated)indicating the name of the interface to use in cases where a particularinterface should be used on a multi-homed host.The <TT>filter</TT> method is used to create a BPF-compatible packetfilter program which is loaded into the underlying BPF machinery.The <TT>filter</TT> method returns the number of bytes used by thefilter predicate. The <TT>pdrops</TT> and <TT>pkts</TT> methods are available for statisticscollection.They report the number of packets dropped by the filter due to buffer exhaustion and thetotal number of packets that arrived at the filter, respectively(<EM>not</EM> the number of packets accepted by the filter).<P><HR><!--Navigation Panel--><A NAME="tex2html9815" HREF="node548.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node548.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html9809" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html9805" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html9811" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html9813" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html9816" HREF="node548.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node548.html">39.4.2 IP Network Objects</A><B> Up:</B> <A NAME="tex2html9810" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html">39.4.1 Pcap/BPF Network Objects</A><B> Previous:</B> <A NAME="tex2html9806" HREF="node546.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node546.html">39.4.1 Pcap/BPF Network Objects</A>   <B> <A NAME="tex2html9812" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html9814" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <!--End of Navigation Panel--><ADDRESS>2003-09-23</ADDRESS></BODY></HTML>⌨️ 快捷键说明
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