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 respose 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 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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.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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