spp man page on 4.4BSD

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SPP(4)			 BSD Kernel Interfaces Manual			SPP(4)

     spp — Xerox Sequenced Packet Protocol

     #include <sys/socket.h>
     #include <netns/ns.h>
     #include <netns/sp.h>

     socket(AF_NS, SOCK_STREAM, 0);

     socket(AF_NS, SOCK_SEQPACKET, 0);

     The SPP protocol provides reliable, flow-controlled, two-way transmission
     of data.  It is a byte-stream protocol used to support the SOCK_STREAM
     abstraction.  SPP uses the standard NS(tm) address formats.

     Sockets utilizing the SPP protocol are either “active” or “passive”.
     Active sockets initiate connections to passive sockets.  By default SPP
     sockets are created active; to create a passive socket the listen(2) sys‐
     tem call must be used after binding the socket with the bind(2) system
     call.  Only passive sockets may use the accept(2) call to accept incoming
     connections.  Only active sockets may use the connect(2) call to initiate

     Passive sockets may “underspecify” their location to match incoming con‐
     nection requests from multiple networks.  This technique, termed
     “wildcard addressing”, allows a single server to provide service to
     clients on multiple networks.  To create a socket which listens on all
     networks, the NS address of all zeroes must be bound.  The 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
     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.

     If the SOCK_SEQPACKET socket type is specified, each packet received has
     the actual 12 byte sequenced packet header left for the user to inspect:

	   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;

     This facilitates the implementation of higher level Xerox protocols which
     make use of the data stream type field and the end of message bit.	 Con‐
     versely, 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.

     For either socket type, packets received with the Attention bit sent are
     interpreted as out of band data.  Data sent with “send(..., ..., ...,
     MSG_OOB”) cause the attention bit to be set.

     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;

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

     [ETIMEDOUT]      when a connection was dropped due to excessive retrans‐

     [ECONNRESET]     when the remote peer forces the connection to be closed;

     [ECONNREFUSED]   when the remote peer actively refuses connection estab‐
		      lishment (usually because no process is listening to the

     [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.

     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.

     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 window‐
			 ing - 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 XEROX
			 product internetwork router.  The data argument for
			 the setsockopt call must be an unsigned short.

     intro(4), ns(4)

     The spp protocol appeared in 4.3BSD.

     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.

4.3 Berkeley Distribution	April 19, 1994	     4.3 Berkeley Distribution

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