1To report a security issue please send an e-mail to security@tcpdump.org. 2 3To report bugs and other problems, contribute patches, request a 4feature, provide generic feedback etc please see the file 5[CONTRIBUTING](CONTRIBUTING.md) in the libpcap source tree root. 6 7The directory doc/ has README files about specific operating systems and 8options. 9 10LIBPCAP 1.x.y 11Now maintained by "The Tcpdump Group" 12https://www.tcpdump.org 13 14Anonymous Git is available via: 15 https://github.com/the-tcpdump-group/libpcap.git 16 17formerly from Lawrence Berkeley National Laboratory 18 Network Research Group <libpcap@ee.lbl.gov> 19 ftp://ftp.ee.lbl.gov/old/libpcap-0.4a7.tar.Z 20 21This directory contains source code for libpcap, a system-independent 22interface for user-level packet capture. libpcap provides a portable 23framework for low-level network monitoring. Applications include 24network statistics collection, security monitoring, network debugging, 25etc. Since almost every system vendor provides a different interface 26for packet capture, and since we've developed several tools that 27require this functionality, we've created this system-independent API 28to ease in porting and to alleviate the need for several 29system-dependent packet capture modules in each application. 30 31For some platforms there are README.{system} files that discuss issues 32with the OS's interface for packet capture on those platforms, such as 33how to enable support for that interface in the OS, if it's not built in 34by default. 35 36The libpcap interface supports a filtering mechanism based on the 37architecture in the BSD packet filter. BPF is described in the 1993 38Winter Usenix paper ``The BSD Packet Filter: A New Architecture for 39User-level Packet Capture''. A compressed PostScript version can be 40found at 41 42 ftp://ftp.ee.lbl.gov/papers/bpf-usenix93.ps.Z 43 44or 45 46 https://www.tcpdump.org/papers/bpf-usenix93.ps.Z 47 48and a gzipped version can be found at 49 50 https://www.tcpdump.org/papers/bpf-usenix93.ps.gz 51 52A PDF version can be found at 53 54 https://www.tcpdump.org/papers/bpf-usenix93.pdf 55 56Although most packet capture interfaces support in-kernel filtering, 57libpcap utilizes in-kernel filtering only for the BPF interface. 58On systems that don't have BPF, all packets are read into user-space 59and the BPF filters are evaluated in the libpcap library, incurring 60added overhead (especially, for selective filters). Ideally, libpcap 61would translate BPF filters into a filter program that is compatible 62with the underlying kernel subsystem, but this is not yet implemented. 63 64BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, OpenBSD, DragonFly 65BSD, and macOS; an older, modified and undocumented version is standard 66in AIX. {DEC OSF/1, Digital UNIX, Tru64 UNIX} uses the packetfilter 67interface but has been extended to accept BPF filters (which libpcap 68utilizes). Also, you can add BPF filter support to Ultrix using the 69kernel source and/or object patches available in: 70 71 https://www.tcpdump.org/other/bpfext42.tar.Z 72 73Linux has a number of BPF based systems, and libpcap does not support 74any of the eBPF mechanisms as yet, although it supports many of the 75memory mapped receive mechanisms. 76See the [README.linux](doc/README.linux.md) file for more information. 77 78Note to Linux distributions and *BSD systems that include libpcap: 79 80There's now a rule to make a shared library, which should work on Linux 81and *BSD, among other platforms. 82 83It sets the soname of the library to "libpcap.so.1"; this is what it 84should be, *NOT* libpcap.so.1.x or libpcap.so.1.x.y or something such as 85that. 86 87We've been maintaining binary compatibility between libpcap releases for 88quite a while; there's no reason to tie a binary linked with libpcap to 89a particular release of libpcap. 90 91Current versions can be found at https://www.tcpdump.org. 92 93 - The TCPdump group 94