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94 lines
3.9 KiB
94 lines
3.9 KiB
LIBPCAP 1.x.y
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=============
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[](https://travis-ci.org/the-tcpdump-group/libpcap)
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[](https://ci.appveyor.com/project/guyharris/libpcap)
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Now maintained by "The Tcpdump Group"
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https://www.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/old/libpcap-0.4a7.tar.Z
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To report a security issue please send an e-mail to security@tcpdump.org.
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To report bugs and other problems, contribute patches, request a
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feature, provide generic feedback etc please see the file
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[CONTRIBUTING.md](CONTRIBUTING.md) in the libpcap source tree root.
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The directory doc/ has README files about specific operating systems and
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options.
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Anonymous Git is available via:
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https://github.com/the-tcpdump-group/libpcap.git
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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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https://www.tcpdump.org/papers/bpf-usenix93.ps.Z
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and a gzipped version can be found at
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https://www.tcpdump.org/papers/bpf-usenix93.ps.gz
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A PDF version can be found at
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https://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 macOS; an older, modified and undocumented version is standard
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in AIX. {DEC OSF/1, Digital UNIX, Tru64 UNIX} uses the packetfilter
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interface but has been extended to accept BPF filters (which libpcap
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utilizes). Also, you can add BPF filter support to Ultrix using the
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kernel source and/or object patches available in:
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https://www.tcpdump.org/other/bpfext42.tar.Z
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Linux has a number of BPF based systems, and libpcap does not support
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any of the eBPF mechanisms as yet, although it supports many of the
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memory mapped receive mechanisms.
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See the [README.linux](doc/README.linux.md) file for more information.
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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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