The Tcpdump Group git mirrors - libpcap/blob - pcap-linktype.manmisc.in

   1 .\" Copyright (c) 1987, 1988, 1989, 1990, 1991, 1992, 1994, 1995, 1996, 1997
   2 .\"     The Regents of the University of California.  All rights reserved.
   3 .\" All rights reserved.
   4 .\"
   5 .\" Redistribution and use in source and binary forms, with or without
   6 .\" modification, are permitted provided that: (1) source code distributions
   7 .\" retain the above copyright notice and this paragraph in its entirety, (2)
   8 .\" distributions including binary code include the above copyright notice and
   9 .\" this paragraph in its entirety in the documentation or other materials
  10 .\" provided with the distribution, and (3) all advertising materials mentioning
  11 .\" features or use of this software display the following acknowledgement:
  12 .\" ``This product includes software developed by the University of California,
  13 .\" Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
  14 .\" the University nor the names of its contributors may be used to endorse
  15 .\" or promote products derived from this software without specific prior
  16 .\" written permission.
  17 .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
  18 .\" WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
  19 .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  20 .\"
  21 .TH PCAP-LINKTYPE @MAN_MISC_INFO@ "1 October 2024"
  22 .SH NAME
  23 pcap-linktype \- link-layer header types supported by libpcap
  24 .SH DESCRIPTION
  25 For a live capture or ``savefile'', libpcap supplies, as the return
  26 value of the
  27 .BR pcap_datalink (3PCAP)
  28 routine, a value that indicates the type of link-layer header at the
  29 beginning of the packets it provides.  This is not necessarily the type
  30 of link-layer header that the packets being captured have on the network
  31 from which they're being captured; for example, packets from an IEEE
  32 802.11 network might be provided by libpcap with Ethernet headers that
  33 the network adapter or the network adapter driver generates from the
  34 802.11 headers.  The names for those values begin with
  35 .BR DLT_ ,
  36 so they are sometimes called "DLT_ values".
  37 .PP
  38 The
  39 .BR pcap_datalink_val_to_name (3PCAP)
  40 and
  41 .BR pcap_datalink_name_to_val (3PCAP)
  42 routines can be used to translate between
  43 .B DLT_
  44 values and names.  Some capture devices support more than one link-layer
  45 header type.  The
  46 .BR pcap_list_datalinks (3PCAP)
  47 routine can be used to retrieve the supported link-layer header types of
  48 a capture device and the
  49 .BR pcap_set_datalink (3PCAP)
  50 routine can be used to change the link-layer header type of a capture
  51 device.
  52 .PP
  53 The values stored in the link-layer header type field in the savefile
  54 header are, in most but not all cases, the same as the values returned
  55 by
  56 .BR pcap_datalink ().
  57 The names for those values begin with
  58 .BR LINKTYPE_ .
  59 .PP
  60 The link-layer header types supported by libpcap are described at
  61 https://www.tcpdump.org/linktypes.html .
  62 .SH SEE ALSO
  63 .BR pcap (3PCAP)