IDP(4) MachTen 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
send(2), recv(2), intro(4), ns(4)

HISTORY
The idp protocol appeared in 4.3BSD.

4.3 Berkeley Distribution June 5, 1993 2