cf2ca148d9
Add missing sysctls to inet.4 and icmp.4, using references to ip.4 for variables and groups documented there. Add sysctl.8 to "see also" and intro to variable section. Rename "MIB Variables" section to "MIB (sysctl) Variables", as most people will associate with sysctl. Revise history: the ICMP implementation was in 4.2BSD. Reviewed by: manpages(pauamma) Differential Revision: https://reviews.freebsd.org/D36003
259 lines
8.7 KiB
Groff
259 lines
8.7 KiB
Groff
.\" Copyright (c) 1986, 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. 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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.\" @(#)icmp.4 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd August 1, 2022
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.Dt ICMP 4
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.Os
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.Sh NAME
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.Nm icmp
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.Nd Internet Control Message Protocol
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.In netinet/in.h
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.Ft int
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.Fn socket AF_INET SOCK_RAW proto
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.Sh DESCRIPTION
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.Tn ICMP
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is the error and control message protocol used
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by
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.Tn IP
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and the Internet protocol family.
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It may be accessed
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through a
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.Dq raw socket
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for network monitoring
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and diagnostic functions.
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The
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.Fa proto
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parameter to the socket call to create an
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.Tn ICMP
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socket
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is obtained from
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.Xr getprotobyname 3 .
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.Tn ICMP
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sockets are connectionless,
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and are normally used with the
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.Xr sendto 2
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and
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.Xr recvfrom 2
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calls, though the
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.Xr connect 2
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call may also be used to fix the destination for future
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packets (in which case the
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.Xr read 2
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or
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.Xr recv 2
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and
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.Xr write 2
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or
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.Xr send 2
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system calls may be used).
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.Pp
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Outgoing packets automatically have an
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.Tn IP
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header prepended to
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them (based on the destination address).
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Incoming packets are received with the
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.Tn IP
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header and options intact.
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.Ss Types
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ICMP messages are classified according to the type and code fields
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present in the ICMP header.
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The abbreviations for the types and codes may be used in rules in
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.Xr pf.conf 5 .
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The following types are defined:
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.Bl -column x xxxxxxxxxxxx -offset indent
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.It Sy Num Ta Sy Abbrev. Ta Sy Description
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.It 0 Ta echorep Ta "Echo reply"
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.It 3 Ta unreach Ta "Destination unreachable"
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.It 4 Ta squench Ta "Packet loss, slow down"
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.It 5 Ta redir Ta "Shorter route exists"
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.It 6 Ta althost Ta "Alternate host address"
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.It 8 Ta echoreq Ta "Echo request"
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.It 9 Ta routeradv Ta "Router advertisement"
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.It 10 Ta routersol Ta "Router solicitation"
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.It 11 Ta timex Ta "Time exceeded"
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.It 12 Ta paramprob Ta "Invalid IP header"
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.It 13 Ta timereq Ta "Timestamp request"
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.It 14 Ta timerep Ta "Timestamp reply"
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.It 15 Ta inforeq Ta "Information request"
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.It 16 Ta inforep Ta "Information reply"
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.It 17 Ta maskreq Ta "Address mask request"
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.It 18 Ta maskrep Ta "Address mask reply"
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.It 30 Ta trace Ta Traceroute
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.It 31 Ta dataconv Ta "Data conversion problem"
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.It 32 Ta mobredir Ta "Mobile host redirection"
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.It 33 Ta ipv6-where Ta "IPv6 where-are-you"
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.It 34 Ta ipv6-here Ta "IPv6 i-am-here"
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.It 35 Ta mobregreq Ta "Mobile registration request"
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.It 36 Ta mobregrep Ta "Mobile registration reply"
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.It 39 Ta skip Ta SKIP
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.It 40 Ta photuris Ta Photuris
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.El
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.Pp
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The following codes are defined:
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.Bl -column x xxxxxxxxxxxx xxxxxxxx -offset indent
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.It Sy Num Ta Sy Abbrev. Ta Sy Type Ta Sy Description
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.It 0 Ta net-unr Ta unreach Ta "Network unreachable"
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.It 1 Ta host-unr Ta unreach Ta "Host unreachable"
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.It 2 Ta proto-unr Ta unreach Ta "Protocol unreachable"
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.It 3 Ta port-unr Ta unreach Ta "Port unreachable"
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.It 4 Ta needfrag Ta unreach Ta "Fragmentation needed but DF bit set"
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.It 5 Ta srcfail Ta unreach Ta "Source routing failed"
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.It 6 Ta net-unk Ta unreach Ta "Network unknown"
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.It 7 Ta host-unk Ta unreach Ta "Host unknown"
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.It 8 Ta isolate Ta unreach Ta "Host isolated"
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.It 9 Ta net-prohib Ta unreach Ta "Network administratively prohibited"
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.It 10 Ta host-prohib Ta unreach Ta "Host administratively prohibited"
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.It 11 Ta net-tos Ta unreach Ta "Invalid TOS for network"
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.It 12 Ta host-tos Ta unreach Ta "Invalid TOS for host"
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.It 13 Ta filter-prohib Ta unreach Ta "Prohibited access"
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.It 14 Ta host-preced Ta unreach Ta "Precedence violation"
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.It 15 Ta cutoff-preced Ta unreach Ta "Precedence cutoff"
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.It 0 Ta redir-net Ta redir Ta "Shorter route for network"
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.It 1 Ta redir-host Ta redir Ta "Shorter route for host"
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.It 2 Ta redir-tos-net Ta redir Ta "Shorter route for TOS and network"
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.It 3 Ta redir-tos-host Ta redir Ta "Shorter route for TOS and host"
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.It 0 Ta normal-adv Ta routeradv Ta "Normal advertisement"
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.It 16 Ta common-adv Ta routeradv Ta "Selective advertisement"
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.It 0 Ta transit Ta timex Ta "Time exceeded in transit"
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.It 1 Ta reassemb Ta timex Ta "Time exceeded in reassembly"
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.It 0 Ta badhead Ta paramprob Ta "Invalid option pointer"
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.It 1 Ta optmiss Ta paramprob Ta "Missing option"
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.It 2 Ta badlen Ta paramprob Ta "Invalid length"
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.It 1 Ta unknown-ind Ta photuris Ta "Unknown security index"
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.It 2 Ta auth-fail Ta photuris Ta "Authentication failed"
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.It 3 Ta decrypt-fail Ta photuris Ta "Decryption failed"
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.El
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.Ss MIB (sysctl) Variables
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The
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.Tn ICMP
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protocol implements a number of variables in the
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.Va net.inet.icmp
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branch of the
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.Xr sysctl 3
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MIB, which can also be read or modified with
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.Xr sysctl 8 .
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.Bl -tag -width ".Va icmplim_output"
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.It Va bmcastecho
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.Pq Vt boolean
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Enable/disable ICMP replies received via broadcast or multicast.
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Defaults to false.
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.It Va drop_redirect
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.Pq Vt boolean
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Enable/disable dropping of ICMP Redirect packets.
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Defaults to false.
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.It Va icmplim
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.Pq Vt integer
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Bandwidth limit for ICMP replies in packets/second.
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If set to zero, no limiting will occur.
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Defaults to 200.
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.It Va icmplim_output
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.Pq Vt boolean
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Enable/disable logging of ICMP replies bandwidth limiting.
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Defaults to true.
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.It Va log_redirect
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.Pq Vt boolean
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Enable/disable logging of ICMP Redirect packets.
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Defaults to false.
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.It Va maskfake
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.Pq Vt "unsigned integer"
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When
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.Va maskrepl
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is set and this value is non-zero,
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it will be used instead of the real address mask when
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the system replies to an ICMP Address Mask Request packet.
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Defaults to 0.
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.It Va maskrepl
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.Pq Vt boolean
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Enable/disable replies to ICMP Address Mask Request packets.
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Defaults to false.
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.It Va quotelen
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.Pq Vt integer
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Number of bytes from original packet to quote in ICMP reply.
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This number is internally enforced to be at least 8 bytes (per RFC792)
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and at most the maximal space left in the ICMP reply mbuf.
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.It Va redirtimeout
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.Pq Vt integer
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Delay in seconds before expiring route created by ICMP redirect.
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.It Va reply_from_interface
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.Pq Vt boolean
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Use the IP address of the interface the packet came in through for
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responses to packets which are not directly addressed to us.
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If enabled, this rule is processed before all others.
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By default, continue with normal source selection.
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Enabling this option is particularly useful on routers because it
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makes external traceroutes show the actual path a packet has taken
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instead of the possibly different return path.
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.It Va reply_src
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.Pq Vt str
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An interface name used for the ICMP reply source in response to packets
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which are not directly addressed to us.
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By default continue with normal source selection.
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.It Va tstamprepl
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.Pq Vt boolean
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Enable/disable replies to ICMP Timestamp packets.
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Defaults to true.
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.El
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.Sh ERRORS
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A socket operation may fail with one of the following errors returned:
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.Bl -tag -width Er
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.It Bq Er EISCONN
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when trying to establish a connection on a socket which
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already has one, or when trying to send a datagram with the destination
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address specified and the socket is already connected;
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.It Bq Er ENOTCONN
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when trying to send a datagram, but
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no destination address is specified, and the socket has not been
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connected;
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.It Bq Er ENOBUFS
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when the system runs out of memory for
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an internal data structure;
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.It Bq Er EADDRNOTAVAIL
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when an attempt is made to create a
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socket with a network address for which no network interface
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exists.
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.El
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.Sh SEE ALSO
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.Xr recv 2 ,
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.Xr send 2 ,
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.Xr sysctl 3 ,
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.Xr inet 4 ,
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.Xr intro 4 ,
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.Xr ip 4 ,
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.Xr pf.conf 5 ,
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.Xr sysctl 8
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.Sh HISTORY
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The
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.Nm
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protocol implementation appeared in
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.Bx 4.2 .
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