x25(7) - f38

1x25(7)                 Miscellaneous Information Manual                 x25(7)
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NAME

6       x25 - ITU-T X.25 / ISO-8208 protocol interface
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SYNOPSIS

9       #include <sys/socket.h>
10       #include <linux/x25.h>
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12       x25_socket = socket(AF_X25, SOCK_SEQPACKET, 0);
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DESCRIPTION

15       X25  sockets  provide  an  interface to the X.25 packet layer protocol.
16       This allows applications to communicate over a public X.25 data network
17       as  standardized by International Telecommunication Union's recommenda‐
18       tion X.25 (X.25 DTE-DCE mode).  X25 sockets can also be used for commu‐
19       nication  without  an  intermediate X.25 network (X.25 DTE-DTE mode) as
20       described in ISO-8208.
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22       Message boundaries are preserved — a read(2) from  a  socket  will  re‐
23       trieve the same chunk of data as output with the corresponding write(2)
24       to the peer socket.  When necessary, the kernel takes care of  segment‐
25       ing  and  reassembling long messages by means of the X.25 M-bit.  There
26       is no hard-coded upper limit for the message size.   However,  reassem‐
27       bling of a long message might fail if there is a temporary lack of sys‐
28       tem resources or when other constraints (such as socket memory or  buf‐
29       fer size limits) become effective.  If that occurs, the X.25 connection
30       will be reset.
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32   Socket addresses
33       The AF_X25 socket address family uses the struct sockaddr_x25 for  rep‐
34       resenting network addresses as defined in ITU-T recommendation X.121.
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36           struct sockaddr_x25 {
37               sa_family_t sx25_family;    /* must be AF_X25 */
38               x25_address sx25_addr;      /* X.121 Address */
39           };
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41       sx25_addr contains a char array x25_addr[] to be interpreted as a null-
42       terminated string.  sx25_addr.x25_addr[] consists  of  up  to  15  (not
43       counting  the terminating null byte) ASCII characters forming the X.121
44       address.  Only the decimal digit characters from '0'  to  '9'  are  al‐
45       lowed.
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47   Socket options
48       The following X.25-specific socket options can be set by using setsock‐
49       opt(2) and read with getsockopt(2)  with  the  level  argument  set  to
50       SOL_X25.
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52       X25_QBITINCL
53              Controls whether the X.25 Q-bit (Qualified Data Bit) is accessi‐
54              ble by the user.  It expects an integer argument.  If set  to  0
55              (default),  the  Q-bit is never set for outgoing packets and the
56              Q-bit of incoming packets is ignored.  If set  to  1,  an  addi‐
57              tional  first  byte  is  prepended  to each message read from or
58              written to the socket.  For data read from the socket, a 0 first
59              byte  indicates  that  the  Q-bits of the corresponding incoming
60              data packets were not set.  A first byte with value 1  indicates
61              that  the  Q-bit  of the corresponding incoming data packets was
62              set.  If the first byte of the data written to the socket is  1,
63              the  Q-bit  of  the  corresponding outgoing data packets will be
64              set.  If the first byte is 0, the Q-bit will not be set.
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VERSIONS

67       The AF_X25 protocol family is a new feature of Linux 2.2.
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BUGS

70       Plenty, as the X.25 PLP implementation is CONFIG_EXPERIMENTAL.
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72       This man page is incomplete.
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74       There is no dedicated application programmer's  header  file  yet;  you
75       need  to  include the kernel header file <linux/x25.h>.  CONFIG_EXPERI‐
76       MENTAL might also imply that future versions of the interface  are  not
77       binary compatible.
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79       X.25  N-Reset events are not propagated to the user process yet.  Thus,
80       if a reset occurred, data might be lost without notice.
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NAME

SYNOPSIS

DESCRIPTION

VERSIONS

BUGS

SEE ALSO