X25(4)              Linux Programmer's Manual              X25(4)

NAME
       x25, PF_X25 - ITU-T X.25 / ISO-8208 protocol interface.

SYNOPSIS
       #include <sys/socket.h>
       #include <linux/x25.h>

       x25_socket = socket(PF_X25, SOCK_SEQPACKET, 0);

DESCRIPTION
       X25  sockets provide an interface to the X.25 packet layer
       protocol.  This allows applications to communicate over  a
       public  X.25 data network as standardised by International
       Telecommunication Union's recommendation X.25  (X.25  DTE-
       DCE  mode). X25 sockets can also be used for communication
       without an intermediate X.25 network (X.25  DTE-DTE  mode)
       as described in ISO-8208.

       Message boundaries are preserved - a read(2) from a socket
       will retrieve the same chunk of data as  output  with  the
       corresponding write(2) to the peer socket. When necessary,
       the kernel takes care of segmenting and re-assembling long
       messages  by  means  of  the X.25 M-bit. There is no hard-
       coded upper limit for the message size. However, re-assem-
       bling of a long message might fail if there is a temporary
       lack of system resources or when other  constraints  (such
       as  socket memory or buffer size limits) become effective.
       If that occurs, the X.25 connection will be reset.

SOCKET ADDRESSES
       The AF_X25 socket address family  uses  the  struct  sock-
       addr_x25  for representing network addresses as defined in
       ITU-T recommendation X.121.

              struct sockaddr_x25 {
                      sa_family_t sx25_family;/* must be AF_X25 */
                      x25_address sx25_addr;  /* X.121 Address */
              };

       sx25_addr contains a char array x25_addr[] to be interpre-
       tated  as  a null-terminated string.  sx25_addr.x25_addr[]
       consists of up to 15  (not  counting  the  terminating  0)
       ASCII characters forming the X.121 address.  Only the dec-
       imal digit characters from `0' to `9' are allowed.

SOCKET OPTIONS
       The following X.25 specific socket options can be  set  by
       using  setsockopt(2)  and read with getsockopt(2) with the
       level parameter set to SOL_X25.

       X25_QBITINCL
              Controls whether the  X.25  Q-bit  (Qualified  Data
              Bit) is accessible by the user. It expects an inte-
              ger argument. If set to 0 (default), the  Q-bit  is
              never  set  for  outgoing  packets and the Q-bit of
              incoming packets is ignored. If set to 1, an  addi-
              tional first byte is prepended to each message read
              from or written to the socket. For data  read  from
              the  socket,  a  0 first byte indicates that the Q-
              bits of the  corresponding  incoming  data  packets
              were  not  set. A first byte with value 1 indicates
              that the Q-bit of the corresponding  incoming  data
              packets  was  set.   If  the first byte of the data
              written to the socket is 1 the Q-bit of the  corre-
              sponding  outgoing data packets will be set. If the
              first bit is 0 the Q-bit will not be set.

BUGS
       Plenty, as the X.25 PLP implementation  is  CONFIG_EXPERI-
       MENTAL.

       This man page is incomplete.

       There is no dedicated application programmer's header file
       yet;  you  need  to  include  the   kernel   header   file
       <linux/x25.h>.   CONFIG_EXPERIMENTAL might also imply that
       future versions of the interface are not  binary  compati-
       ble.

       X.25 N-Reset events are not propagated to the user process
       yet. Thus, if a reset occurred, data might be lost without
       notice.

SEE ALSO
       socket(4), socket(2)

       Jonathan Simon Naylor: "The Re-Analysis and Re-Implementa-
       tion       of       X.25."        The        URL        is
       ftp://ftp.pspt.fi/pub/ham/linux/ax25/x25doc.tgz

VERSIONS
       The  PF_X25 protocol family is a new feature of Linux 2.2.

Linux Man Page              1 Dez 1998                          1