Provided by: libpcap0.8-dev_1.0.0-1_i386 bug

NAME

       pcap-linktype - link-layer header types supported by libpcap

DESCRIPTION

       For  a  live  capture  or ‘‘savefile’’, libpcap supplies, as the return
       value of the pcap_datalink(3PCAP) routine, a value that  indicates  the
       type  of link-layer header at the beginning of the packets it provides.
       This is not necessarily the type of link-layer header that the  packets
       being  captured  have on the network from which they’re being captured;
       for example, packets from an IEEE 802.11 network might be  provided  by
       libpcap  with  Ethernet headers that the network adapter or the network
       adapter driver generates from the 802.11 headers.  The names for  those
       values begin with DLT_, so they are sometimes called "DLT_ values".

       The  values  stored in the link-layer header type field in the savefile
       header are, in most but not all cases, the same as the values  returned
       by pcap_datalink().  The names for those values begin with LINKTYPE_.

       The  link-layer header types supported by libpcap are listed here.  The
       value  corresponding  to  LINKTYPE_  names   are   given;   the   value
       corresponding  to  DLT_  values are, in some cases, platform dependent,
       and are not given; applications should check for particular DLT_ values
       by name.

            DLT_NULL; LINKTYPE_NULL=0
                 BSD loopback encapsulation; the link layer header is a 4-byte
                 field, in host  byte  order,  containing  a  PF_  value  from
                 socket.h for the network-layer protocol of the packet.

                 Note  that  ‘‘host  byte  order’’  is  the  byte order of the
                 machine on which the packets are captured, and the PF_ values
                 are  for  the  OS  of  the  machine  on which the packets are
                 captured; if a  live  capture  is  being  done,  ‘‘host  byte
                 order’’  is  the  byte  order  of  the  machine capturing the
                 packets, and the PF_ values  are  those  of  the  OS  of  the
                 machine capturing the packets, but if a ‘‘savefile’’ is being
                 read, the byte order and PF_ values are not necessarily those
                 of the machine reading the capture file.

            DLT_EN10MB; LINKTYPE_ETHERNET=1
                 Ethernet  (10Mb, 100Mb, 1000Mb, and up); the 10MB in the DLT_
                 name is historical.

            DLT_IEEE802; LINKTYPE_TOKEN_RING=6
                 IEEE 802.5 Token Ring;  the  IEEE802  in  the  DLT_  name  is
                 historical.

            DLT_ARCNET; LINKTYPE_ARCNET=7
                 ARCNET

            DLT_SLIP; LINKTYPE_SLIP=8
                 SLIP; the link layer header contains, in order:

                      a  1-byte  flag,  which is 0 for packets received by the
                      machine and 1 for packets sent by the machine;

                      a 1-byte field, the upper 4 bits of which  indicate  the
                      type of packet, as per RFC 1144:

                           0x40 an unmodified IP datagram (TYPE_IP);

                           0x70 an      uncompressed-TCP      IP      datagram
                                (UNCOMPRESSED_TCP), with that byte  being  the
                                first  byte  of the raw IP header on the wire,
                                containing  the  connection  number   in   the
                                protocol field;

                           0x80 a compressed-TCP IP datagram (COMPRESSED_TCP),
                                with that byte being the  first  byte  of  the
                                compressed TCP/IP datagram header;

                      for  UNCOMPRESSED_TCP,  the  rest  of  the  modified  IP
                      header, and for COMPRESSED_TCP,  the  compressed  TCP/IP
                      datagram header;

                 for a total of 16 bytes; the uncompressed IP datagram follows
                 the header.

            DLT_PPP; LINKTYPE_PPP=9
                 PPP; if the first 2 bytes are 0xff  and  0x03,  it’s  PPP  in
                 HDLC-like  framing,  with  the PPP header following those two
                 bytes, otherwise it’s PPP without  framing,  and  the  packet
                 begins with the PPP header.

            DLT_FDDI; LINKTYPE_FDDI=10
                 FDDI

            DLT_ATM_RFC1483; LINKTYPE_ATM_RFC1483=100
                 RFC 1483 LLC/SNAP-encapsulated ATM; the packet begins with an
                 IEEE 802.2 LLC header.

            DLT_RAW; LINKTYPE_RAW=101
                 raw IP; the packet begins with an IP header.

            DLT_PPP_SERIAL; LINKTYPE_PPP_HDLC=50
                 PPP in HDLC-like framing, as per RFC 1662, or Cisco PPP  with
                 HDLC  framing,  as  per  section 4.3.1 of RFC 1547; the first
                 byte will be 0xFF for PPP in HDLC-like framing, and  will  be
                 0x0F or 0x8F for Cisco PPP with HDLC framing.

            DLT_PPP_ETHER; LINKTYPE_PPP_ETHER=51
                 PPPoE;  the  packet  begins  with  a PPPoE header, as per RFC
                 2516.

            DLT_C_HDLC; LINKTYPE_C_HDLC=104
                 Cisco PPP with HDLC framing, as  per  section  4.3.1  of  RFC
                 1547.

            DLT_IEEE802_11; LINKTYPE_IEEE802_11=105
                 IEEE 802.11 wireless LAN

            DLT_FRELAY; LINKTYPE_FRELAY=107
                 Frame Relay

            DLT_LOOP; LINKTYPE_LOOP=108
                 OpenBSD  loopback  encapsulation;  the link layer header is a
                 4-byte field, in network byte order, containing a  PF_  value
                 from OpenBSD’s socket.h for the network-layer protocol of the
                 packet.

                 Note that, if a ‘‘savefile’’ is being read, those PF_  values
                 are  not necessarily those of the machine reading the capture
                 file.

            DLT_LINUX_SLL; LINKTYPE_LINUX_SLL=113
                 Linux "cooked" capture encapsulation; the link  layer  header
                 contains, in order:

                      a  2-byte "packet type", in network byte order, which is
                      one of:

                           0    packet was sent to us by somebody else

                           1    packet was broadcast by somebody else

                           2    packet was multicast, but  not  broadcast,  by
                                somebody else

                           3    packet  was  sent by somebody else to somebody
                                else

                           4    packet was sent by us

                      a 2-byte field, in  network  byte  order,  containing  a
                      Linux ARPHRD_ value for the link layer device type;

                      a  2-byte  field,  in network byte order, containing the
                      length of the link layer address of the  sender  of  the
                      packet (which could be 0);

                      an  8-byte  field containing that number of bytes of the
                      link layer header (if there are more than 8 bytes,  only
                      the first 8 are present);

                      a  2-byte field containing an Ethernet protocol type, in
                      network byte order, or containing  1  for  Novell  802.3
                      frames  without  an  802.2  LLC  header  or 4 for frames
                      beginning with an 802.2 LLC header.

            DLT_LTALK; LINKTYPE_LTALK=104
                 Apple LocalTalk; the packet begins  with  an  AppleTalk  LLAP
                 header.

            DLT_PFLOG; LINKTYPE_PFLOG=117
                 OpenBSD  pflog;  the  link  layer  header  contains  a struct
                 pfloghdr structure, as defined by the host on which the  file
                 was  saved.  (This differs from operating system to operating
                 system and release to release; there is nothing in  the  file
                 to indicate what the layout of that structure is.)

            DLT_PRISM_HEADER; LINKTYPE_PRISM_HEADER=119
                 Prism  monitor mode information followed by an 802.11 header.

            DLT_IP_OVER_FC; LINKTYPE_IP_OVER_FC=122
                 RFC 2625 IP-over-Fibre Channel, with  the  link-layer  header
                 being the Network_Header as described in that RFC.

            DLT_SUNATM; LINKTYPE_SUNATM=123
                 SunATM devices; the link layer header contains, in order:

                      a  1-byte flag field, containing a direction flag in the
                      uppermost bit, which is set for packets  transmitted  by
                      the  machine  and  clear  for  packets  received  by the
                      machine, and a 4-byte traffic type in  the  low-order  4
                      bits, which is one of:

                           0    raw traffic

                           1    LANE traffic

                           2    LLC-encapsulated traffic

                           3    MARS traffic

                           4    IFMP traffic

                           5    ILMI traffic

                           6    Q.2931 traffic

                      a 1-byte VPI value;

                      a 2-byte VCI field, in network byte order.

            DLT_IEEE802_11_RADIO; LINKTYPE_IEEE802_11_RADIO=127
                 link-layer  information  followed  by  an 802.11 header - see
                 http://www.shaftnet.org/~pizza/software/capturefrm.txt for  a
                 description of the link-layer information.

            DLT_ARCNET_LINUX; LINKTYPE_ARCNET_LINUX=129
                 ARCNET,  with no exception frames, reassembled packets rather
                 than raw frames, and an extra 16-bit offset field between the
                 destination host and type bytes.

            DLT_LINUX_IRDA; LINKTYPE_LINUX_IRDA=144
                 Linux-IrDA  packets,  with a DLT_LINUX_SLL header followed by
                 the IrLAP header.

            DLT_LINUX_LAPD; LINKTYPE_LINUX_LAPD=177
                 LAPD (Q.921) frames, with a DLT_LINUX_SLL header captured via
                 vISDN.

SEE ALSO

       pcap_datalink(3PCAP)

                                23 October 2008               PCAP-LINKTYPE(7)