The Tcpdump Group git mirrors - libpcap/blob - README

   1 To report a security issue please send an e-mail to security@tcpdump.org.
   2
   3 To report bugs and other problems, contribute patches, request a
   4 feature, provide generic feedback etc please see the file
   5 CONTRIBUTING in the libpcap source tree root.
   6
   7 LIBPCAP 1.x.y
   8 Now maintained by "The Tcpdump Group"
   9 www.tcpdump.org
  10
  11 Anonymous Git is available via:
  12         git clone git://bpf.tcpdump.org/libpcap
  13
  14 formerly from   Lawrence Berkeley National Laboratory
  15                 Network Research Group <libpcap@ee.lbl.gov>
  16                 ftp://ftp.ee.lbl.gov/old/libpcap-0.4a7.tar.Z
  17
  18 This directory contains source code for libpcap, a system-independent
  19 interface for user-level packet capture.  libpcap provides a portable
  20 framework for low-level network monitoring.  Applications include
  21 network statistics collection, security monitoring, network debugging,
  22 etc.  Since almost every system vendor provides a different interface
  23 for packet capture, and since we've developed several tools that
  24 require this functionality, we've created this system-independent API
  25 to ease in porting and to alleviate the need for several
  26 system-dependent packet capture modules in each application.
  27
  28 For some platforms there are README.{system} files that discuss issues
  29 with the OS's interface for packet capture on those platforms, such as
  30 how to enable support for that interface in the OS, if it's not built in
  31 by default.
  32
  33 The libpcap interface supports a filtering mechanism based on the
  34 architecture in the BSD packet filter.  BPF is described in the 1993
  35 Winter Usenix paper ``The BSD Packet Filter: A New Architecture for
  36 User-level Packet Capture''.  A compressed PostScript version can be
  37 found at
  38
  39         ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z
  40
  41 or
  42
  43         http://www.tcpdump.org/papers/bpf-usenix93.ps.Z
  44
  45 and a gzipped version can be found at
  46
  47         http://www.tcpdump.org/papers/bpf-usenix93.ps.gz
  48
  49 A PDF version can be found at
  50
  51         http://www.tcpdump.org/papers/bpf-usenix93.pdf
  52
  53 Although most packet capture interfaces support in-kernel filtering,
  54 libpcap utilizes in-kernel filtering only for the BPF interface.
  55 On systems that don't have BPF, all packets are read into user-space
  56 and the BPF filters are evaluated in the libpcap library, incurring
  57 added overhead (especially, for selective filters).  Ideally, libpcap
  58 would translate BPF filters into a filter program that is compatible
  59 with the underlying kernel subsystem, but this is not yet implemented.
  60
  61 BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, OpenBSD, DragonFly
  62 BSD, and Mac OS X; an older, modified and undocumented version is
  63 standard in AIX.  {DEC OSF/1, Digital UNIX, Tru64 UNIX} uses the
  64 packetfilter interface but has been extended to accept BPF filters
  65 (which libpcap utilizes).  Also, you can add BPF filter support to
  66 Ultrix using the kernel source and/or object patches available in:
  67
  68         http://www.tcpdump.org/other/bpfext42.tar.Z
  69
  70 Linux, in the 2.2 kernel and later kernels, has a "Socket Filter"
  71 mechanism that accepts BPF filters; see the README.linux file for
  72 information on configuring that option.
  73
  74 Note to Linux distributions and *BSD systems that include libpcap:
  75
  76 There's now a rule to make a shared library, which should work on Linux
  77 and *BSD, among other platforms.
  78
  79 It sets the soname of the library to "libpcap.so.1"; this is what it
  80 should be, *NOT* libpcap.so.1.x or libpcap.so.1.x.y or something such as
  81 that.
  82
  83 We've been maintaining binary compatibility between libpcap releases for
  84 quite a while; there's no reason to tie a binary linked with libpcap to
  85 a particular release of libpcap.
  86
  87 Current versions can be found at www.tcpdump.org.
  88
  89  - The TCPdump team