1@(#) $Header: /tcpdump/master/libpcap/README,v 1.30 2004/10/12 02:02:28 guy Exp $ (LBL) 2 3LIBPCAP 0.9 4Now maintained by "The Tcpdump Group" 5See www.tcpdump.org 6 7Please send inquiries/comments/reports to tcpdump-workers@tcpdump.org 8 9Anonymous CVS is available via: 10 cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master login 11 (password "anoncvs") 12 cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master checkout libpcap 13 14Version 0.9 of LIBPCAP can be retrieved with the CVS tag "libpcap_0_9rel1": 15 cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master checkout -r libpcap_0_9rel1 libpcap 16 17Please send patches against the master copy to patches@tcpdump.org. 18 19formerly from Lawrence Berkeley National Laboratory 20 Network Research Group <libpcap@ee.lbl.gov> 21 ftp://ftp.ee.lbl.gov/libpcap.tar.Z (0.4) 22 23This directory contains source code for libpcap, a system-independent 24interface for user-level packet capture. libpcap provides a portable 25framework for low-level network monitoring. Applications include 26network statistics collection, security monitoring, network debugging, 27etc. Since almost every system vendor provides a different interface 28for packet capture, and since we've developed several tools that 29require this functionality, we've created this system-independent API 30to ease in porting and to alleviate the need for several 31system-dependent packet capture modules in each application. 32 33Note well: this interface is new and is likely to change. 34 35For some platforms there are README.{system} files that discuss issues 36with the OS's interface for packet capture on those platforms, such as 37how to enable support for that interface in the OS, if it's not built in 38by default. 39 40The libpcap interface supports a filtering mechanism based on the 41architecture in the BSD packet filter. BPF is described in the 1993 42Winter Usenix paper ``The BSD Packet Filter: A New Architecture for 43User-level Packet Capture''. A compressed PostScript version can be 44found at 45 46 ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z 47 48or 49 50 http://www.tcpdump.org/papers/bpf-usenix93.ps.Z 51 52and a gzipped version can be found at 53 54 http://www.tcpdump.org/papers/bpf-usenix93.ps.gz 55 56A PDF version can be found at 57 58 http://www.tcpdump.org/papers/bpf-usenix93.pdf 59 60Although most packet capture interfaces support in-kernel filtering, 61libpcap utilizes in-kernel filtering only for the BPF interface. 62On systems that don't have BPF, all packets are read into user-space 63and the BPF filters are evaluated in the libpcap library, incurring 64added overhead (especially, for selective filters). Ideally, libpcap 65would translate BPF filters into a filter program that is compatible 66with the underlying kernel subsystem, but this is not yet implemented. 67 68BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, and OpenBSD. DEC 69OSF/1/Digital UNIX/Tru64 UNIX uses the packetfilter interface but has 70been extended to accept BPF filters (which libpcap utilizes). Also, you 71can add BPF filter support to Ultrix using the kernel source and/or 72object patches available in: 73 74 ftp://gatekeeper.dec.com/pub/DEC/net/bpfext42.tar.Z. 75 76Linux, in the 2.2 kernel and later kernels, has a "Socket Filter" 77mechanism that accepts BPF filters; see the README.linux file for 78information on configuring that option. 79 80Problems, bugs, questions, desirable enhancements, etc. should be sent 81to the address "tcpdump-workers@tcpdump.org". Bugs, support requests, 82and feature requests may also be submitted on the SourceForge site for 83libpcap at 84 85 http://sourceforge.net/projects/libpcap/ 86 87Source code contributions, etc. should be sent to the email address 88"patches@tcpdump.org", or submitted as patches on the SourceForge site 89for libpcap. 90 91Current versions can be found at www.tcpdump.org, or the SourceForge 92site for libpcap. 93 94 - The TCPdump team 95