1 @(#) $Header: /tcpdump/master/libpcap/README,v 1.34 2008-12-14 19:44:14 guy Exp $ (LBL) 2 3 LIBPCAP 1.x.y 4 5 www.tcpdump.org 6 7 Please send inquiries/comments/reports to: 8 tcpdump-workers (a] lists.tcpdump.org 9 10 Anonymous Git is available via: 11 git clone git://bpf.tcpdump.org/libpcap 12 13 Please submit patches by forking the branch on GitHub at 14 15 http://github.com/the-tcpdump-group/libpcap/tree/master 16 17 and issuing a pull request. 18 19 formerly from Lawrence Berkeley National Laboratory 20 Network Research Group <libpcap (a] ee.lbl.gov> 21 ftp://ftp.ee.lbl.gov/old/libpcap-0.4a7.tar.Z 22 23 This directory contains source code for libpcap, a system-independent 24 interface for user-level packet capture. libpcap provides a portable 25 framework for low-level network monitoring. Applications include 26 network statistics collection, security monitoring, network debugging, 27 etc. Since almost every system vendor provides a different interface 28 for packet capture, and since we've developed several tools that 29 require this functionality, we've created this system-independent API 30 to ease in porting and to alleviate the need for several 31 system-dependent packet capture modules in each application. 32 33 For some platforms there are README.{system} files that discuss issues 34 with the OS's interface for packet capture on those platforms, such as 35 how to enable support for that interface in the OS, if it's not built in 36 by default. 37 38 The libpcap interface supports a filtering mechanism based on the 39 architecture in the BSD packet filter. BPF is described in the 1993 40 Winter Usenix paper ``The BSD Packet Filter: A New Architecture for 41 User-level Packet Capture''. A compressed PostScript version can be 42 found at 43 44 ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z 45 46 or 47 48 http://www.tcpdump.org/papers/bpf-usenix93.ps.Z 49 50 and a gzipped version can be found at 51 52 http://www.tcpdump.org/papers/bpf-usenix93.ps.gz 53 54 A PDF version can be found at 55 56 http://www.tcpdump.org/papers/bpf-usenix93.pdf 57 58 Although most packet capture interfaces support in-kernel filtering, 59 libpcap utilizes in-kernel filtering only for the BPF interface. 60 On systems that don't have BPF, all packets are read into user-space 61 and the BPF filters are evaluated in the libpcap library, incurring 62 added overhead (especially, for selective filters). Ideally, libpcap 63 would translate BPF filters into a filter program that is compatible 64 with the underlying kernel subsystem, but this is not yet implemented. 65 66 BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, OpenBSD, DragonFly 67 BSD, and Mac OS X; an older, modified and undocumented version is 68 standard in AIX. {DEC OSF/1, Digital UNIX, Tru64 UNIX} uses the 69 packetfilter interface but has been extended to accept BPF filters 70 (which libpcap utilizes). Also, you can add BPF filter support to 71 Ultrix using the kernel source and/or object patches available in: 72 73 http://www.tcpdump.org/other/bpfext42.tar.Z 74 75 Linux, in the 2.2 kernel and later kernels, has a "Socket Filter" 76 mechanism that accepts BPF filters; see the README.linux file for 77 information on configuring that option. 78 79 Note to Linux distributions and *BSD systems that include libpcap: 80 81 There's now a rule to make a shared library, which should work on Linux 82 and *BSD, among other platforms. 83 84 It sets the soname of the library to "libpcap.so.1"; this is what it 85 should be, *NOT* libpcap.so.1.x or libpcap.so.1.x.y or something such as 86 that. 87 88 We've been maintaining binary compatibility between libpcap releases for 89 quite a while; there's no reason to tie a binary linked with libpcap to 90 a particular release of libpcap. 91 92 Problems, bugs, questions, desirable enhancements, etc. should be sent 93 to the address "tcpdump-workers (a] lists.tcpdump.org". Bugs, support 94 requests, and feature requests may also be submitted on the GitHub issue 95 tracker for libpcap at 96 97 https://github.com/the-tcpdump-group/libpcap/issues 98 99 Source code contributions, etc. should be sent to the email address 100 above or submitted by forking the branch on GitHub at 101 102 http://github.com/the-tcpdump-group/libpcap/tree/master 103 104 and issuing a pull request. 105 106 Current versions can be found at www.tcpdump.org. 107 108 - The TCPdump team 109
