@(#) $Header: /tcpdump/master/libpcap/README,v 1.27.2.1 2003/11/15 23:29:19 guy Exp $ (LBL) LIBPCAP 0.8 Now maintained by "The Tcpdump Group" See www.tcpdump.org Please send inquiries/comments/reports to tcpdump-workers@tcpdump.org Anonymous CVS is available via: cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master login (password "anoncvs") cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master checkout libpcap Version 0.8 of LIBPCAP can be retrieved with the CVS tag "libpcap_0_8rel1": cvs -d :pserver:tcpdump@cvs.tcpdump.org:/tcpdump/master checkout -r libpcap_0_8rel1 libpcap Please send patches against the master copy to patches@tcpdump.org. formerly from Lawrence Berkeley National Laboratory Network Research Group ftp://ftp.ee.lbl.gov/libpcap.tar.Z (0.4) This directory contains source code for libpcap, a system-independent interface for user-level packet capture. libpcap provides a portable framework for low-level network monitoring. Applications include network statistics collection, security monitoring, network debugging, etc. Since almost every system vendor provides a different interface for packet capture, and since we've developed several tools that require this functionality, we've created this system-independent API to ease in porting and to alleviate the need for several system-dependent packet capture modules in each application. Note well: this interface is new and is likely to change. For some platforms there are README.{system} files that discuss issues with the OS's interface for packet capture on those platforms, such as how to enable support for that interface in the OS, if it's not built in by default. The libpcap interface supports a filtering mechanism based on the architecture in the BSD packet filter. BPF is described in the 1993 Winter Usenix paper ``The BSD Packet Filter: A New Architecture for User-level Packet Capture''. A compressed PostScript version can be found at ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z or http://www.tcpdump.org/papers/bpf-usenix93.ps.Z and a gzipped version can be found at http://www.tcpdump.org/papers/bpf-usenix93.ps.gz A PDF version can be found at http://www.tcpdump.org/papers/bpf-usenix93.pdf Although most packet capture interfaces support in-kernel filtering, libpcap utilizes in-kernel filtering only for the BPF interface. On systems that don't have BPF, all packets are read into user-space and the BPF filters are evaluated in the libpcap library, incurring added overhead (especially, for selective filters). Ideally, libpcap would translate BPF filters into a filter program that is compatible with the underlying kernel subsystem, but this is not yet implemented. BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, and OpenBSD. DEC OSF/1/Digital UNIX/Tru64 UNIX uses the packetfilter interface but has been extended to accept BPF filters (which libpcap utilizes). Also, you can add BPF filter support to Ultrix using the kernel source and/or object patches available in: ftp://gatekeeper.dec.com/pub/DEC/net/bpfext42.tar.Z. Linux, in the 2.2 kernel and later kernels, has a "Socket Filter" mechanism that accepts BPF filters; see the README.linux file for information on configuring that option. Problems, bugs, questions, desirable enhancements, etc. should be sent to the address "tcpdump-workers@tcpdump.org". Bugs, support requests, and feature requests may also be submitted on the SourceForge site for libpcap at http://sourceforge.net/projects/libpcap/ Source code contributions, etc. should be sent to the email address "patches@tcpdump.org", or submitted as patches on the SourceForge site for libpcap. Current versions can be found at www.tcpdump.org, or the SourceForge site for libpcap. - The TCPdump team