.\" $OpenBSD: spp.4,v 1.8 2003/06/02 23:30:12 millert Exp $ .\" $NetBSD: spp.4,v 1.3 1994/11/30 16:22:33 jtc Exp $ .\" .\" Copyright (c) 1985, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)spp.4 8.2 (Berkeley) 4/19/94 .\" .Dd April 19, 1994 .Dt SPP 4 .Os .Sh NAME .Nm spp .Nd Xerox Sequenced Packet Protocol .Sh SYNOPSIS .Fd #include .Fd #include .Fd #include .Ft int .Fn socket AF_NS SOCK_STREAM 0 .Ft int .Fn socket AF_NS SOCK_SEQPACKET 0 .Sh DESCRIPTION The .Tn SPP protocol provides a reliable, flow-controlled, two-way transmission of data. It is a byte-stream protocol used to support the .Dv SOCK_STREAM abstraction. .Tn SPP uses the standard .Tn NS Ns (tm) address formats. .Pp Sockets utilizing the .Tn SPP protocol are either .Dq active or .Dq passive . Active sockets initiate connections to passive sockets. By default .Tn SPP sockets are created active; to create a passive socket the .Xr listen 2 system call must be used after binding the socket with the .Xr bind 2 system call. Only passive sockets may use the .Xr accept 2 call to accept incoming connections. Only active sockets may use the .Xr connect 2 call to initiate connections. .Pp Passive sockets may .Dq underspecify their location to match incoming connection requests from multiple networks. This technique, termed .Dq wildcard addressing , allows a single server to provide service to clients on multiple networks. To create a socket which listens on all networks, the .Tn NS address of all zeroes must be bound. The .Tn SPP port may still be specified at this time; if the port is not specified the system will assign one. Once a connection has been established the socket's address is fixed by the peer entity's location. The address assigned to the socket is the address associated with the network interface through which packets are being transmitted and received. Normally this address corresponds to the peer entity's network. .Pp If the .Dv SOCK_SEQPACKET socket type is specified, each packet received has the actual 12 byte sequenced packet header left for the user to inspect: .Bd -literal -offset indent struct sphdr { u_char sp_cc; /* connection control */ #define SP_EM 0x10 /* end of message */ u_char sp_dt; /* datastream type */ u_short sp_sid; u_short sp_did; u_short sp_seq; u_short sp_ack; u_short sp_alo; }; .Ed .Pp This facilitates the implementation of higher level Xerox protocols which make use of the data stream type field and the end of message bit. Conversely, the user is required to supply a 12 byte header, the only part of which inspected is the data stream type and end of message fields. .Pp For either socket type, packets received with the Attention bit sent are interpreted as out of band data. Data sent with .Dq send(..., ..., ..., Dv MSG_OOB ) cause the attention bit to be set. .Sh DIAGNOSTICS A socket operation may fail with one of the following errors returned: .Bl -tag -width [EADDRNOTAVAIL] .It Bq Er EISCONN when trying to establish a connection on a socket which already has one; .It Bq Er ENOBUFS when the system runs out of memory for an internal data structure; .It Bq Er ETIMEDOUT when a connection was dropped due to excessive retransmissions; .It Bq Er ECONNRESET when the remote peer forces the connection to be closed; .It Bq Er ECONNREFUSED when the remote peer actively refuses connection establishment (usually because no process is listening to the port); .It Bq Er EADDRINUSE when an attempt is made to create a socket with a port which has already been allocated; .It Bq Er EADDRNOTAVAIL when an attempt is made to create a socket with a network address for which no network interface exists. .El .Sh SOCKET OPTIONS .Bl -tag -width SO_DEFAULT_HEADERS .It Dv SO_DEFAULT_HEADERS when set, this determines the data stream type and whether the end of message bit is to be set on every ensuing packet. .It Dv SO_MTU This specifies the maximum amount of user data in a single packet. The default is 576 bytes - sizeof(struct spidp). This quantity affects windowing \- increasing it without increasing the amount of buffering in the socket will lower the number of unread packets accepted. Anything larger than the default will not be forwarded by a bona fide .Tn XEROX product internetwork router. The data argument for the setsockopt call must be an unsigned short. .El .Sh SEE ALSO .Xr netintro 4 , .Xr ns 4 .Sh HISTORY The .Nm protocol appeared in .Bx 4.3 . .Sh BUGS There should be some way to reflect record boundaries in a stream. For stream mode, there should be an option to get the data stream type of the record the user process is about to receive.