107 lines
3.9 KiB
Plaintext
107 lines
3.9 KiB
Plaintext
LIBPCAP 1.x.y
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www.tcpdump.org
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Please send inquiries/comments/reports to:
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tcpdump-workers@lists.tcpdump.org
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Anonymous Git is available via:
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git clone git://bpf.tcpdump.org/libpcap
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Please submit patches by forking the branch on GitHub at
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http://github.com/the-tcpdump-group/libpcap/tree/master
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and issuing a pull request.
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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/old/libpcap-0.4a7.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
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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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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, OpenBSD, DragonFly
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BSD, and Mac OS X; an older, modified and undocumented version is
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standard in AIX. {DEC OSF/1, Digital UNIX, Tru64 UNIX} uses the
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packetfilter interface but has been extended to accept BPF filters
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(which libpcap utilizes). Also, you can add BPF filter support to
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Ultrix using the kernel source and/or object patches available in:
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http://www.tcpdump.org/other/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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Note to Linux distributions and *BSD systems that include libpcap:
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There's now a rule to make a shared library, which should work on Linux
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and *BSD, among other platforms.
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It sets the soname of the library to "libpcap.so.1"; this is what it
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should be, *NOT* libpcap.so.1.x or libpcap.so.1.x.y or something such as
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that.
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We've been maintaining binary compatibility between libpcap releases for
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quite a while; there's no reason to tie a binary linked with libpcap to
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a particular release of libpcap.
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Problems, bugs, questions, desirable enhancements, etc. should be sent
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to the address "tcpdump-workers@lists.tcpdump.org". Bugs, support
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requests, and feature requests may also be submitted on the GitHub issue
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tracker for libpcap at
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https://github.com/the-tcpdump-group/libpcap/issues
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Source code contributions, etc. should be sent to the email address
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above or submitted by forking the branch on GitHub at
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http://github.com/the-tcpdump-group/libpcap/tree/master
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and issuing a pull request.
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Current versions can be found at www.tcpdump.org.
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- The TCPdump team
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