Provided by: libpcap0.8-dev_1.1.1-10_i386 bug

NAME

       pcap-savefile - libpcap savefile format

DESCRIPTION

       NOTE:  applications  and  libraries should, if possible, use libpcap to
       read savefiles, rather than having their own code  to  read  savefiles.
       If,  in  the  future,  a  new  file  format  is  supported  by libpcap,
       applications and libraries using libpcap to read savefiles will be able
       to  read  the  new  format of savefiles, but applications and libraries
       using their own code to read savefiles  will  have  to  be  changed  to
       support the new file format.

       ``Savefiles''  read  and  written  by  libpcap  and  applications using
       libpcap start with a per-file  header.   The  format  of  the  per-file
       header is:

              +------------------------------+
              |        Magic number          |
              +--------------+---------------+
              |Major version | Minor version |
              +--------------+---------------+
              |      Time zone offset        |
              +------------------------------+
              |     Time stamp accuracy      |
              +------------------------------+
              |       Snapshot length        |
              +------------------------------+
              |   Link-layer header type     |
              +------------------------------+
       All  fields  in  the  per-file header are in the byte order of the host
       writing the file.  The first field in the per-file header is  a  4-byte
       magic  number,  with the value 0xa1b2c3d4.  The magic number, when read
       by a host with the same byte order as the host  that  wrote  the  file,
       will  have  the  value  0xa1b2c3d4,  and,  when read by a host with the
       opposite byte order as the host that wrote  the  file,  will  have  the
       value  0xd4c3b2a1.   That allows software reading the file to determine
       whether the byte order of the host that wrote the file is the  same  as
       the  byte  order  of the host on which the file is being read, and thus
       whether the values in the per-file and per-packet headers  need  to  be
       byte-swapped.

       Following this are:

              A  2-byte  file format major version number; the current version
              number is 2.

              A 2-byte file format minor version number; the  current  version
              number is 4.

              A 4-byte time zone offset; this is always 0.

              A  4-byte number giving the accuracy of time stamps in the file;
              this is always 0.

              A 4-byte number giving the "snapshot  length"  of  the  capture;
              packets  longer  than  the  snapshot length are truncated to the
              snapshot length, so that, if the snapshot length is N, only  the
              first  N  bytes of a packet longer than N bytes will be saved in
              the capture.

              a 4-byte number giving the link-layer header type for packets in
              the  capture; see pcap-linktype(7) for the LINKTYPE_ values that
              can appear in this field.

       Following the per-file header are zero or  more  packets;  each  packet
       begins  with  a per-packet header, which is immediately followed by the
       raw packet data.  The format of the per-packet header is:

              +---------------------------------------+
              |      Time stamp, seconds value        |
              +---------------------------------------+
              |    Time stamp, microseconds value     |
              +---------------------------------------+
              |    Length of captured packet data     |
              +---------------------------------------+
              |Un-truncated length of the packet data |
              +---------------------------------------+
       All fields in the per-packet header are in the byte order of  the  host
       writing  the  file.   The  per-packet  header  begins with a time stamp
       giving the approximate time the packet was  captured;  the  time  stamp
       consists of a 4-byte value, giving the time in seconds since January 1,
       1970, 00:00:00 UTC, followed by a 4-byte  value,  giving  the  time  in
       microseconds  since  that  second.   Following  that are a 4-byte value
       giving the number of bytes of captured data that follow the  per-packet
       header  and  a  4-byte value giving the number of bytes that would have
       been present had the packet not been truncated by the snapshot  length.
       The two lengths will be equal if the number of bytes of packet data are
       less than or equal to the snapshot length.

SEE ALSO

       pcap(3PCAP), pcap-linktype(7)

                                21 October 2008               PCAP-SAVEFILE(5)