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