0afc94c17a
bottom of the manpages and order them consistently. GNU groff doesn't care about the ordering, and doesn't even mention CAVEATS and SECURITY CONSIDERATIONS as common sections and where to put them. Found by: mdocml lint run Reviewed by: ru
298 lines
8.9 KiB
Groff
298 lines
8.9 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" From: @(#)inet.4 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd April 9, 2005
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.Dt INET 4
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.Os
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.Sh NAME
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.Nm inet
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.Nd Internet protocol family
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.Sh SYNOPSIS
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.In sys/types.h
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.In netinet/in.h
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.Sh DESCRIPTION
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The Internet protocol family is a collection of protocols
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layered atop the
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.Em Internet Protocol
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.Pq Tn IP
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transport layer, and utilizing the Internet address format.
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The Internet family provides protocol support for the
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.Dv SOCK_STREAM , SOCK_DGRAM ,
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and
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.Dv SOCK_RAW
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socket types; the
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.Dv SOCK_RAW
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interface provides access to the
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.Tn IP
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protocol.
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.Sh ADDRESSING
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Internet addresses are four byte quantities, stored in
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network standard format (on little endian machines, such as the
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.Tn alpha ,
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.Tn amd64 ,
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.Tn i386
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and
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.Tn ia64
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these are word and byte reversed).
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The include file
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.In netinet/in.h
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defines this address
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as a discriminated union.
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.Pp
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Sockets bound to the Internet protocol family utilize
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the following addressing structure,
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.Bd -literal -offset indent
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struct sockaddr_in {
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uint8_t sin_len;
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sa_family_t sin_family;
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in_port_t sin_port;
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struct in_addr sin_addr;
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char sin_zero[8];
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};
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.Ed
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.Pp
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Sockets may be created with the local address
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.Dv INADDR_ANY
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to affect
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.Dq wildcard
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matching on incoming messages.
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The address in a
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.Xr connect 2
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or
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.Xr sendto 2
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call may be given as
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.Dv INADDR_ANY
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to mean
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.Dq this host .
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The distinguished address
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.Dv INADDR_BROADCAST
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is allowed as a shorthand for the broadcast address on the primary
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network if the first network configured supports broadcast.
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.Sh PROTOCOLS
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The Internet protocol family is comprised of
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the
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.Tn IP
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network protocol, Internet Control
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Message Protocol
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.Pq Tn ICMP ,
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Internet Group Management Protocol
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.Pq Tn IGMP ,
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Transmission Control
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Protocol
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.Pq Tn TCP ,
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and User Datagram Protocol
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.Pq Tn UDP .
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.Tn TCP
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is used to support the
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.Dv SOCK_STREAM
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abstraction while
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.Tn UDP
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is used to support the
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.Dv SOCK_DGRAM
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abstraction.
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A raw interface to
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.Tn IP
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is available
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by creating an Internet socket of type
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.Dv SOCK_RAW .
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The
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.Tn ICMP
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message protocol is accessible from a raw socket.
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.Pp
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The 32-bit Internet address contains both network and host parts.
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However, direct examination of addresses is discouraged.
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For those
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programs which absolutely need to break addresses into their component
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parts, the following
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.Xr ioctl 2
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commands are provided for a datagram socket in the Internet domain;
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they have the same form as the
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.Dv SIOCIFADDR
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command (see
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.Xr intro 4 ) .
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.Pp
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.Bl -tag -width SIOCSIFNETMASK
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.It Dv SIOCSIFNETMASK
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Set interface network mask.
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The network mask defines the network part of the address;
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if it contains more of the address than the address type would indicate,
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then subnets are in use.
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.It Dv SIOCGIFNETMASK
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Get interface network mask.
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.El
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.Ss MIB Variables
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A number of variables are implemented in the net.inet branch of the
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.Xr sysctl 3
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MIB.
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In addition to the variables supported by the transport protocols
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(for which the respective manual pages may be consulted),
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the following general variables are defined:
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.Bl -tag -width IPCTL_FASTFORWARDING
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.It Dv IPCTL_FORWARDING
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.Pq ip.forwarding
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Boolean: enable/disable forwarding of IP packets.
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Defaults to off.
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.It Dv IPCTL_FASTFORWARDING
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.Pq ip.fastforwarding
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Boolean: enable/disable the use of
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.Tn fast IP forwarding
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code.
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Defaults to off.
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When
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.Tn fast IP forwarding
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is enabled, IP packets are forwarded directly to the appropriate network
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interface with direct processing to completion, which greatly improves
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the throughput.
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All packets for local IP addresses, non-unicast, or with IP options are
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handled by the normal IP input processing path.
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All features of the normal (slow) IP forwarding path are supported
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including firewall (through
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.Xr pfil 9
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hooks) checking, except
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.Xr ipsec 4
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tunnel brokering.
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The
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.Tn IP fastforwarding
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path does not generate ICMP redirect or source quench messages.
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.It Dv IPCTL_SENDREDIRECTS
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.Pq ip.redirect
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Boolean: enable/disable sending of ICMP redirects in response to
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.Tn IP
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packets for which a better, and for the sender directly reachable, route
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and next hop is known.
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Defaults to on.
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.It Dv IPCTL_DEFTTL
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.Pq ip.ttl
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Integer: default time-to-live
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.Pq Dq TTL
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to use for outgoing
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.Tn IP
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packets.
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.It Dv IPCTL_ACCEPTSOURCEROUTE
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.Pq ip.accept_sourceroute
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Boolean: enable/disable accepting of source-routed IP packets (default false).
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.It Dv IPCTL_SOURCEROUTE
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.Pq ip.sourceroute
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Boolean: enable/disable forwarding of source-routed IP packets (default false).
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.It Dv IPCTL_RTEXPIRE
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.Pq ip.rtexpire
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Integer: lifetime in seconds of protocol-cloned
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.Tn IP
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routes after the last reference drops (default one hour).
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This value varies dynamically as described above.
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.It Dv IPCTL_RTMINEXPIRE
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.Pq ip.rtminexpire
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Integer: minimum value of ip.rtexpire (default ten seconds).
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This value has no effect on user modifications, but restricts the dynamic
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adaptation described above.
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.It Dv IPCTL_RTMAXCACHE
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.Pq ip.rtmaxcache
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Integer: trigger level of cached, unreferenced, protocol-cloned routes
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which initiates dynamic adaptation (default 128).
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.It Va ip.process_options
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Integer: control IP options processing.
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By setting this variable to 0, all IP options in the incoming packets
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will be ignored, and the packets will be passed unmodified.
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By setting to 1, IP options in the incoming packets will be processed
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accordingly.
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By setting to 2, an
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.Tn ICMP
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.Dq "prohibited by filter"
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message will be sent back in response to incoming packets with IP options.
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Default is 1.
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This
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.Xr sysctl 8
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variable affects packets destined for a local host as well as packets
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forwarded to some other host.
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.It Va ip.random_id
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Boolean: control IP IDs generation behaviour.
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Setting this
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.Xr sysctl 8
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to non-zero causes the ID field in IP packets to be randomized instead of
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incremented by 1 with each packet generated.
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This closes a minor information leak which allows remote observers to
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determine the rate of packet generation on the machine by watching the
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counter.
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In the same time, on high-speed links, it can decrease the ID reuse
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cycle greatly.
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Default is 0 (sequential IP IDs).
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IPv6 flow IDs and fragment IDs are always random.
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.It Va ip.maxfragpackets
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Integer: maximum number of fragmented packets the host will accept and hold
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in the reassembling queue simultaneously.
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0 means that the host will not accept any fragmented packets.
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\-1 means that the host will accept as many fragmented packets as it receives.
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.It Va ip.maxfragsperpacket
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Integer: maximum number of fragments the host will accept and hold
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in the reassembling queue for a packet.
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0 means that the host will not accept any fragmented packets.
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.El
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.Sh SEE ALSO
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.Xr ioctl 2 ,
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.Xr socket 2 ,
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.Xr sysctl 3 ,
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.Xr icmp 4 ,
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.Xr intro 4 ,
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.Xr ip 4 ,
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.Xr ipfirewall 4 ,
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.Xr route 4 ,
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.Xr tcp 4 ,
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.Xr udp 4 ,
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.Xr pfil 9
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.Rs
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.%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
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.%B PS1
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.%N 7
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.Re
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.Rs
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.%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"
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.%B PS1
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.%N 8
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.Re
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.Sh HISTORY
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The
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.Nm
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protocol interface appeared in
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.Bx 4.2 .
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The
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.Dq protocol cloning
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code appeared in
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.Fx 2.1 .
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.Sh CAVEATS
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The Internet protocol support is subject to change as
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the Internet protocols develop.
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Users should not depend
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on details of the current implementation, but rather
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the services exported.
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