95 lines
3.7 KiB
Plaintext
95 lines
3.7 KiB
Plaintext
@(#) $Header: /tcpdump/master/libpcap/README,v 1.30 2004/10/12 02:02:28 guy Exp $ (LBL)
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LIBPCAP 0.9
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Now maintained by "The Tcpdump Group"
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See www.tcpdump.org
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Please send inquiries/comments/reports to tcpdump-workers@tcpdump.org
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Anonymous CVS is available via:
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cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master login
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(password "anoncvs")
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cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master checkout libpcap
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Version 0.9 of LIBPCAP can be retrieved with the CVS tag "libpcap_0_9rel1":
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cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master checkout -r libpcap_0_9rel1 libpcap
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Please send patches against the master copy to patches@tcpdump.org.
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formerly from Lawrence Berkeley National Laboratory
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Network Research Group <libpcap@ee.lbl.gov>
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ftp://ftp.ee.lbl.gov/libpcap.tar.Z (0.4)
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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
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require this functionality, we've created this system-independent API
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to ease in porting and to alleviate the need for several
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system-dependent packet capture modules in each application.
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Note well: this interface is new and is likely to change.
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For some platforms there are README.{system} files that discuss issues
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with the OS's interface for packet capture on those platforms, such as
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how to enable support for that interface in the OS, if it's not built in
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by default.
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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 1993
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Winter Usenix paper ``The BSD Packet Filter: A New Architecture for
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User-level Packet Capture''. A compressed PostScript version can be
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found at
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ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z
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or
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http://www.tcpdump.org/papers/bpf-usenix93.ps.Z
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and a gzipped version can be found at
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http://www.tcpdump.org/papers/bpf-usenix93.ps.gz
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A PDF version can be found at
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http://www.tcpdump.org/papers/bpf-usenix93.pdf
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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). Ideally, libpcap
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would translate BPF filters into a filter program that is compatible
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with the underlying kernel subsystem, but this is not yet implemented.
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BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, and OpenBSD. DEC
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OSF/1/Digital UNIX/Tru64 UNIX uses the packetfilter interface but has
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been extended to accept BPF filters (which libpcap utilizes). Also, you
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can add BPF filter support to Ultrix using the kernel source and/or
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object patches available in:
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ftp://gatekeeper.dec.com/pub/DEC/net/bpfext42.tar.Z.
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Linux, in the 2.2 kernel and later kernels, has a "Socket Filter"
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mechanism that accepts BPF filters; see the README.linux file for
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information on configuring that option.
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Problems, bugs, questions, desirable enhancements, etc. should be sent
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to the address "tcpdump-workers@tcpdump.org". Bugs, support requests,
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and feature requests may also be submitted on the SourceForge site for
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libpcap at
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http://sourceforge.net/projects/libpcap/
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Source code contributions, etc. should be sent to the email address
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"patches@tcpdump.org", or submitted as patches on the SourceForge site
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for libpcap.
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Current versions can be found at www.tcpdump.org, or the SourceForge
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site for libpcap.
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- The TCPdump team
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