268 lines
7.8 KiB
Groff
268 lines
7.8 KiB
Groff
.\" Copyright (c) 1983, 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. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. 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.
|
|
.\"
|
|
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
|
|
.\" $Id: tcp.4,v 1.8 1997/02/22 13:24:45 peter Exp $
|
|
.\"
|
|
.Dd February 14, 1995
|
|
.Dt TCP 4
|
|
.Os BSD 4.2
|
|
.Sh NAME
|
|
.Nm tcp
|
|
.Nd Internet Transmission Control Protocol
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/types.h>
|
|
.Fd #include <sys/socket.h>
|
|
.Fd #include <netinet/in.h>
|
|
.Ft int
|
|
.Fn socket AF_INET SOCK_STREAM 0
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Tn TCP
|
|
protocol provides reliable, flow-controlled, two-way
|
|
transmission of data. It is a byte-stream protocol used to
|
|
support the
|
|
.Dv SOCK_STREAM
|
|
abstraction. TCP uses the standard
|
|
Internet address format and, in addition, provides a per-host
|
|
collection of
|
|
.Dq port addresses .
|
|
Thus, each address is composed
|
|
of an Internet address specifying the host and network, with
|
|
a specific
|
|
.Tn TCP
|
|
port on the host identifying the peer entity.
|
|
.Pp
|
|
Sockets utilizing the tcp protocol are either
|
|
.Dq active
|
|
or
|
|
.Dq passive .
|
|
Active sockets initiate connections to passive
|
|
sockets. By default
|
|
.Tn TCP
|
|
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.
|
|
.Tn TCP
|
|
also supports a more datagram-like mode, called Transaction
|
|
.Tn TCP ,
|
|
which is described in
|
|
.Xr ttcp 4 .
|
|
.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 Internet
|
|
address
|
|
.Dv INADDR_ANY
|
|
must be bound. The
|
|
.Tn TCP
|
|
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.
|
|
.Pp
|
|
.Tn TCP
|
|
supports a number of socket options which can be set with
|
|
.Xr setsockopt 2
|
|
and tested with
|
|
.Xr getsockopt 2 :
|
|
.Bl -tag -width TCP_NODELAYx
|
|
.It Dv TCP_NODELAY
|
|
Under most circumstances,
|
|
.Tn TCP
|
|
sends data when it is presented;
|
|
when outstanding data has not yet been acknowledged, it gathers
|
|
small amounts of output to be sent in a single packet once
|
|
an acknowledgement is received.
|
|
For a small number of clients, such as window systems
|
|
that send a stream of mouse events which receive no replies,
|
|
this packetization may cause significant delays.
|
|
The boolean option
|
|
.Dv TCP_NODELAY
|
|
defeats this algorithm.
|
|
.It Dv TCP_MAXSEG
|
|
By default, a sender\- and receiver-TCP
|
|
will negotiate among themselves to determine the maximum segment size
|
|
to be used for each connection. The
|
|
.Dv TCP_MAXSEG
|
|
option allows the user to determine the result of this negotiation,
|
|
and to reduce it if desired.
|
|
.It Dv TCP_NOOPT
|
|
.Tn TCP
|
|
usually sends a number of options in each packet, corresponding to
|
|
various
|
|
.Tn TCP
|
|
extensions which are provided in this implementation. The boolean
|
|
option
|
|
.Dv TCP_NOOPT
|
|
is provided to disable
|
|
.Tn TCP
|
|
option use on a per-connection basis.
|
|
.It Dv TCP_NOPUSH
|
|
By convention, the sender-TCP
|
|
will set the
|
|
.Dq push
|
|
bit and begin transmission immediately (if permitted) at the end of
|
|
every user call to
|
|
.Xr write 2
|
|
or
|
|
.Xr writev 2 .
|
|
The
|
|
.Dv TCP_NOPUSH
|
|
option is provided to allow servers to easily make use of Transaction
|
|
TCP (see
|
|
.Xr ttcp 4 ).
|
|
When the option is set to a non-zero value,
|
|
.Tn TCP
|
|
will delay sending any data at all until either the socket is closed,
|
|
or the internal send buffer is filled.
|
|
.El
|
|
.Pp
|
|
The option level for the
|
|
.Xr setsockopt 2
|
|
call is the protocol number for
|
|
.Tn TCP ,
|
|
available from
|
|
.Xr getprotobyname 3 ,
|
|
or
|
|
.Dv IPPROTO_TCP .
|
|
All options are declared in
|
|
.Aq Pa netinet/tcp.h .
|
|
.Pp
|
|
Options at the
|
|
.Tn IP
|
|
transport level may be used with
|
|
.Tn TCP ;
|
|
see
|
|
.Xr ip 4 .
|
|
Incoming connection requests that are source-routed are noted,
|
|
and the reverse source route is used in responding.
|
|
.Sh MIB VARIABLES
|
|
The
|
|
.Nm
|
|
protocol implements three variables in the
|
|
.Li net.inet
|
|
branch of the
|
|
.Xr sysctl 3
|
|
MIB.
|
|
.Bl -tag -width TCPCTL_DO_RFC1644
|
|
.It Dv TCPCTL_DO_RFC1323
|
|
.Pq tcp.rfc1323
|
|
Implement the window scaling and timestamp options of RFC 1323
|
|
(default true).
|
|
.It Dv TCPCTL_DO_RFC1644
|
|
.Pq tcp.rfc1644
|
|
Implement Transaction
|
|
.Tn TCP ,
|
|
as described in RFC 1644.
|
|
.It Dv TCPCTL_MSSDFLT
|
|
.Pq tcp.mssdflt
|
|
The default value used for the maximum segment size
|
|
.Pq Dq MSS
|
|
when no advice to the contrary is received from MSS negotiation.
|
|
.El
|
|
.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.
|
|
.It Bq Er EAFNOSUPPORT
|
|
when an attempt is made to bind or connect a socket to a multicast
|
|
address.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr getsockopt 2 ,
|
|
.Xr socket 2 ,
|
|
.Xr sysctl 3 ,
|
|
.Xr inet 4 ,
|
|
.Xr intro 4 ,
|
|
.Xr ip 4 ,
|
|
.Xr ttcp 4
|
|
.Rs
|
|
.%A V. Jacobson, R. Braden, and D. Borman
|
|
.%T "TCP Extensions for High Performance"
|
|
.%O RFC 1323
|
|
.Re
|
|
.Rs
|
|
.%A R. Braden
|
|
.%T "T/TCP \- TCP Extensions for Transactions"
|
|
.%O RFC 1644
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
protocol appeared in
|
|
.Bx 4.2 .
|
|
The RFC 1323 extensions for window scaling and timestamps were added
|
|
in
|
|
.Bx 4.4 .
|