1995-03-06 14:37:58 +03:00
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$NetBSD: README,v 1.2 1995/03/06 11:38:07 mycroft Exp $
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1995-03-06 14:32:59 +03:00
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@(#) Header: README,v 1.7 94/06/20 18:56:55 leres Exp (LBL)
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LIBPCAP 0.0
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Lawrence Berkeley Laboratory
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Network Research Group
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libpcap@ee.lbl.gov
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ftp://ftp.ee.lbl.gov/libpcap-*.tar.Z
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This directory contains source code for libpcap, a system-independent
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interface for user-level packet capture. libpcap provides a portable
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framework for low-level network monitoring. Applications include
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network statistics collection, security monitoring, network debugging,
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etc. Since almost every system vendor provides a different interface
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for packet capture, and since we've developed several tools that require
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these interfaces, we've created this system-independent API to ease in
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porting and to alleviate the need for several system-dependent packet
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capture modules in each application.
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THIS IS AN ALPHA-QUALITY RELEASE. The interface is brand new and is
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likely to change. If you code to this interface, and want to track
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future versions, be prepared to update your code. We admit that this
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release is premature, but we're releasing it anyway because the tcpdump-3.0
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distribution requires it.
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libpcap has been built and tested under SGI Irix 4.x & 5.2, SunOS 4.x,
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Solaris 2.3, BSD/386 v1.1, DEC/OSF v1.3 v2.0, and Ultrix 4.x. SunOS 3.5
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4.3BSD Reno/Tahoe and 4.4BSD are supported as well, but we currently
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do not have the resources to carry out testing in these environments
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(we suspect you'll run into problems under these systems -- please
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send us the patches if you fix any porting problems).
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The libpcap interface supports a filtering mechanism based on the
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architecture in the BSD packet filter. BPF is described in the
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1993 Winter Usenix paper ``The BSD Packet Filter: A New Architecture
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for User-level Packet Capture''. A compressed postscript version is in
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ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z.
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Although most packet capture interfaces support in-kernel filtering,
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libpcap utilizes in-kernel filtering only for the BPF interface.
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On systems that don't have BPF, all packets are read into user-space
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and the BPF filters are evaluated in the libpcap library, incurring
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added overhead (especially, for selective filters). We haven't tried
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taking advantage of other packet filter models first because they
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aren't general enough (i.e., only simple filters can be evaluated),
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and second because we don't have the time to modify the code generator
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(or write a filter translator) and BPF is more efficient anyway.
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BPF is standard in 4.4BSD, BSD/386, NetBSD, and FreeBSD. DEC OSF/1
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uses the packetfilter interface but has been extended to accept
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BPF filters (which libpcap utilizes). Also, you can add BPF filter
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support to Ultrix using the kernel source and/or object patches
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available in
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ftp://gatekeeper.dec.com/pub/DEC/net/bpfext42.tar.Z.
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Please send bugs and comments to libpcap@ee.lbl.gov.
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- Steve McCanne (mccanne@ee.lbl.gov)
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Craig Leres (leres@ee.lbl.gov)
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Van Jacobson (van@ee.lbl.gov)
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