IDP(4)                    OpenBSD Programmer's Manual                   IDP(4)

NAME
     idp - Xerox Internet Datagram Protocol

SYNOPSIS
     #include <sys/socket.h>
     #include <netns/ns.h>
     #include <netns/idp.h>

     int
     socket(AF_NS, SOCK_DGRAM, 0);

DESCRIPTION
     IDP is a simple, unreliable datagram protocol which is used to support
     the SOCK_DGRAM abstraction for the Internet protocol family.  IDP sockets
     are connectionless, and are normally used with the sendto and recvfrom
     calls, though the connect(2) call may also be used to fix the destination
     for future packets (in which case the recv(2) or read(2) and send(2) or
     write(2) system calls may be used).

     Xerox protocols are built vertically on top of IDP. Thus, IDP address
     formats are identical to those used by SPP. Note that the IDP port space
     is the same as the SPP port space (i.e. a IDP port may be ``connected''
     to a SPP port, with certain options enabled below).  In addition broad-
     cast packets may be sent (assuming the underlying network supports this)
     by using a reserved ``broadcast address''; this address is network inter-
     face dependent.

DIAGNOSTICS
     A socket operation may fail with one of the following errors returned:

     [EISCONN]        when trying to establish a connection on a socket which
                      already has one, or when trying to send a datagram with
                      the destination address specified and the socket is al-
                      ready connected;

     [ENOTCONN]       when trying to send a datagram, but no destination ad-
                      dress is specified, and the socket hasn't been connect-
                      ed;

     [ENOBUFS]        when the system runs out of memory for an internal data
                      structure;

     [EADDRINUSE]     when an attempt is made to create a socket with a port
                      which has already been allocated;

     [EADDRNOTAVAIL]  when an attempt is made to create a socket with a net-
                      work address for which no network interface exists.

SOCKET OPTIONS
     [SO_ALL_PACKETS]        When set, this option defeats automatic process-
                             ing of Error packets, and Sequence Protocol pack-
                             ets.

     [SO_DEFAULT_HEADERS]    The user provides the kernel an IDP header, from
                             which it gleans the Packet Type.  When requested,
                             the kernel will provide an IDP header, showing
                             the default packet type, and local and foreign
                             addresses, if connected.

     [SO_HEADERS_ON_INPUT]   When set, the first 30 bytes of any data returned
                             from a read or recv from will be the initial 30
                             bytes of the IDP packet, as described by

                                   struct idp {
                                           u_short         idp_sum;
                                           u_short         idp_len;
                                           u_char          idp_tc;
                                           u_char          idp_pt;
                                           struct ns_addr  idp_dna;
                                           struct ns_addr  idp_sna;
                                   };

                             This allows the user to determine the packet
                             type, and whether the packet was a multi-cast
                             packet or directed specifically at the local
                             host.  When requested, gives the current state of
                             the option, (NSP_RAWIN or 0).

     [SO_HEADERS_ON_OUTPUT]  When set, the first 30 bytes of any data sent
                             will be the initial 30 bytes of the IDP packet.
                             This allows the user to determine the packet
                             type, and whether the packet should be multi-cast
                             packet or directed specifically at the local
                             host.  You can also misrepresent the sender of
                             the packet.  When requested, gives the current
                             state of the option.  (NSP_RAWOUT or 0).

     [SO_SEQNO]              When requested, this returns a sequence number
                             which is not likely to be repeated until the ma-
                             chine crashes or a very long time has passed.  It
                             is useful in constructing Packet Exchange Proto-
                             col packets.

SEE ALSO
     recv(2), send(2), netintro(4), ns(4)

HISTORY
     The idp protocol appeared in 4.3BSD.

OpenBSD 2.9                      June 5, 1993                                2
