1 # LIBPCAP 1.x.y by [The Tcpdump Group](https://www.tcpdump.org) 2 3 **To report a security issue please send an e-mail to security (a] tcpdump.org.** 4 5 To report bugs and other problems, contribute patches, request a 6 feature, provide generic feedback etc please see the 7 [guidelines for contributing](CONTRIBUTING.md). 8 9 The [documentation directory](doc/) has README files about specific 10 operating systems and options. 11 12 Anonymous Git is available via: 13 14 https://github.com/the-tcpdump-group/libpcap.git 15 16 This directory contains source code for libpcap, a system-independent 17 interface for user-level packet capture. libpcap provides a portable 18 framework for low-level network monitoring. Applications include 19 network statistics collection, security monitoring, network debugging, 20 etc. Since almost every system vendor provides a different interface 21 for packet capture, and since we've developed several tools that 22 require this functionality, we've created this system-independent API 23 to ease in porting and to alleviate the need for several 24 system-dependent packet capture modules in each application. 25 26 ```text 27 formerly from Lawrence Berkeley National Laboratory 28 Network Research Group <libpcap (a] ee.lbl.gov> 29 ftp://ftp.ee.lbl.gov/old/libpcap-0.4a7.tar.Z 30 ``` 31 32 ### Support for particular platforms and BPF 33 For some platforms there are `README.{system}` files that discuss issues 34 with the OS's interface for packet capture on those platforms, such as 35 how to enable support for that interface in the OS, if it's not built in 36 by default. 37 38 The libpcap interface supports a filtering mechanism based on the 39 architecture in the BSD packet filter. BPF is described in the 1993 40 Winter Usenix paper ``The BSD Packet Filter: A New Architecture for 41 User-level Packet Capture'' 42 ([compressed PostScript](https://www.tcpdump.org/papers/bpf-usenix93.ps.Z), 43 [gzipped PostScript](https://www.tcpdump.org/papers/bpf-usenix93.ps.gz), 44 [PDF](https://www.tcpdump.org/papers/bpf-usenix93.pdf)). 45 46 Although most packet capture interfaces support in-kernel filtering, 47 libpcap utilizes in-kernel filtering only for the BPF interface. 48 On systems that don't have BPF, all packets are read into user-space 49 and the BPF filters are evaluated in the libpcap library, incurring 50 added overhead (especially, for selective filters). Ideally, libpcap 51 would translate BPF filters into a filter program that is compatible 52 with the underlying kernel subsystem, but this is not yet implemented. 53 54 BPF is standard in 4.4BSD, BSD/OS, NetBSD, FreeBSD, OpenBSD, DragonFly 55 BSD, macOS, and Solaris 11; an older, modified and undocumented version 56 is standard in AIX. {DEC OSF/1, Digital UNIX, Tru64 UNIX} uses the 57 packetfilter interface but has been extended to accept BPF filters 58 (which libpcap utilizes). 59 60 Linux has a number of BPF based systems, and libpcap does not support 61 any of the eBPF mechanisms as yet, although it supports many of the 62 memory mapped receive mechanisms. 63 See the [Linux-specific README](doc/README.linux) for more information. 64 65 ### Note to Linux distributions and *BSD systems that include libpcap: 66 67 There's now a rule to make a shared library, which should work on Linux 68 and *BSD, among other platforms. 69 70 It sets the soname of the library to `libpcap.so.1`; this is what it 71 should be, **NOT** `libpcap.so.1.x` or `libpcap.so.1.x.y` or something such as 72 that. 73 74 We've been maintaining binary compatibility between libpcap releases for 75 quite a while; there's no reason to tie a binary linked with libpcap to 76 a particular release of libpcap. 77
Indexes created Wed Apr 15 00:22:22 UTC 2026