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