492 lines
11 KiB
Groff
492 lines
11 KiB
Groff
.\"
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.\" $FreeBSD$
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.\"
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.Dd March 13, 2000
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.Dt IP6FW 8
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.Os FreeBSD
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.Sh NAME
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.Nm ip6fw
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.Nd controlling utility for IPv6 firewall
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.Sh SYNOPSIS
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.Nm
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.Ar file
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.Nm ip6fw
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.Op Fl f | Fl q
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flush
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.Nm ip6fw
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.Op Fl q
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zero
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.Op Ar number ...
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.Nm ip6fw
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delete
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.Ar number ...
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.Nm ip6fw
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.Op Fl aftN
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list
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.Op Ar number ...
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.Nm ip6fw
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.Op Fl ftN
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show
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.Op Ar number ...
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.Nm ip6fw
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.Op Fl q
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add
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.Op Ar number
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.Ar action
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.Op log
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.Ar proto
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from
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.Ar src
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to
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.Ar dst
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.Op via Ar name | ipv6no
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.Op Ar options
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.Sh DESCRIPTION
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If used as shown in the first synopsis line, the
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.Ar file
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will be read line by line and applied as arguments to the
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.Nm
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command.
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.Pp
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The
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.Nm
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code works by going through the rule-list for each packet,
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until a match is found.
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All rules have two associated counters, a packet count and
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a byte count.
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These counters are updated when a packet matches the rule.
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.Pp
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The rules are ordered by a
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.Dq line-number
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from 1 to 65534 that is used
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to order and delete rules.
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Rules are tried in increasing order, and the
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first rule that matches a packet applies.
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Multiple rules may share the same number and apply in
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the order in which they were added.
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.Pp
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If a rule is added without a number, it is numbered 100 higher
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than the previous rule.
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If the highest defined rule number is
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greater than 65434, new rules are appended to the last rule.
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.Pp
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The delete operation deletes the first rule with number
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.Ar number ,
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if any.
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.Pp
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The list command prints out the current rule set.
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.Pp
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The show command is equivalent to `ip6fw -a list'.
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.Pp
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The zero operation zeroes the counters associated with rule number
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.Ar number .
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.Pp
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The flush operation removes all rules.
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.Pp
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Any command beginning with a
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.Sq # ,
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or being all blank, is ignored.
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.Pp
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One rule is always present:
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.Bd -literal -offset center
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65535 deny all from any to any
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.Ed
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.Pp
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This rule is the default policy, i.e., don't allow anything at all.
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Your job in setting up rules is to modify this policy to match your
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needs.
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.Pp
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The following options are available:
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.Bl -tag -width flag
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.It Fl a
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While listing, show counter values. See also
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.Dq show
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command.
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.It Fl f
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Don't ask for confirmation for commands that can cause problems if misused
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(ie; flush).
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.Ar Note ,
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if there is no tty associated with the process, this is implied.
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.It Fl q
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While adding, zeroing or flushing, be quiet about actions (implies '-f').
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This is useful for adjusting rules by executing multiple ip6fw commands in a
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script (e.g. sh /etc/rc.firewall), or by processing a file of many ip6fw rules,
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across a remote login session. If a flush is performed in normal
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(verbose) mode, it prints a message. Because all rules are flushed, the
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message cannot be delivered to the login session, the login session is
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closed and the remainder of the ruleset is not processed. Access to the
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console is required to recover.
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.It Fl t
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While listing, show last match timestamp.
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.It Fl N
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Try to resolve addresses and service names in output.
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.El
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.Pp
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.Ar action :
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.Bl -hang -offset flag -width 1234567890123456
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.It Ar allow
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Allow packets that match rule.
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The search terminates.
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Aliases are
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.Ar pass ,
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.Ar permit ,
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and
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.Ar accept .
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.It Ar deny
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Discard packets that match this rule.
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The search terminates.
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.Ar Drop
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is an alias for
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.Ar deny .
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.It Ar reject
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(Deprecated.) Discard packets that match this rule, and try to send an ICMPv6
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host unreachable notice.
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The search terminates.
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.It Ar unreach code
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Discard packets that match this rule, and try to send an ICMPv6
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unreachable notice with code
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.Ar code ,
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where
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.Ar code
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is a number from zero to 255, or one of these aliases:
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.Ar noroute ,
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.Ar admin ,
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.Ar notneighbor ,
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.Ar addr ,
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or
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.Ar noport ,
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The search terminates.
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.It Ar reset
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TCP packets only.
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Discard packets that match this rule,
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and try to send a TCP reset (RST) notice.
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The search terminates
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.Em (not working yet) .
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.It Ar count
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Update counters for all packets that match rule.
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The search continues with the next rule.
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.It Ar skipto number
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Skip all subsequent rules numbered less than
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.Ar number .
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The search continues with the first rule numbered
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.Ar number
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or higher.
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.El
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.Pp
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If the kernel was compiled with
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.Dv IP6FIREWALL_VERBOSE ,
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then when a packet matches a rule with the
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.Dq log
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keyword a message will be printed on the console.
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If the kernel was compiled with the
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.Dv IP6FIREWALL_VERBOSE_LIMIT
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option, then logging will cease after the number of packets
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specified by the option are received for that particular
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chain entry. Logging may then be re-enabled by clearing
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the packet counter for that entry.
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.Pp
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Console logging and the log limit are adjustable dynamically
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through the
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.Xr sysctl 8
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interface.
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.Pp
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.Ar proto :
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.Bl -hang -offset flag -width 1234567890123456
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.It Ar ipv6
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All packets match.
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The alias
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.Ar all
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has the same effect.
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.It Ar tcp
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Only TCP packets match.
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.It Ar udp
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Only UDP packets match.
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.It Ar ipv6-icmp
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Only ICMPv6 packets match.
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.It Ar <number|name>
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Only packets for the specified protocol matches (see
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.Pa /etc/protocols
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for a complete list).
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.El
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.Pp
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.Ar src
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and
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.Ar dst :
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.Bl -hang -offset flag
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.It Ar <address/prefixlen>
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.Op Ar ports
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.El
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.Pp
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The
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.Em <address/prefixlen>
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may be specified as:
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.Bl -hang -offset flag -width 1234567890123456
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.It Ar ipv6no
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An ipv6number of the form
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.Li fec0::1:2:3:4.
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.It Ar ipv6no/prefixlen
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An ipv6number with a prefix length of the form
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.Li fec0::1:2:3:4/112.
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.El
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.Pp
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The sense of the match can be inverted by preceding an address with the
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.Dq not
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modifier, causing all other addresses to be matched instead.
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This
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does not affect the selection of port numbers.
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.Pp
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With the TCP and UDP protocols, optional
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.Em ports
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may be specified as:
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.Pp
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.Bl -hang -offset flag
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.It Ns {port|port-port} Ns Op ,port Ns Op ,...
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.El
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.Pp
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Service names (from
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.Pa /etc/services )
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may be used instead of numeric port values.
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A range may only be specified as the first value,
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and the length of the port list is limited to
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.Dv IP6_FW_MAX_PORTS
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(as defined in
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.Pa /usr/src/sys/netinet/ip6_fw.h )
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ports.
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.Pp
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Fragmented packets which have a non-zero offset (i.e. not the first
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fragment) will never match a rule which has one or more port
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specifications. See the
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.Ar frag
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option for details on matching fragmented packets.
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.Pp
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Rules can apply to packets when they are incoming, or outgoing, or both.
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The
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.Ar in
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keyword indicates the rule should only match incoming packets.
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The
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.Ar out
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keyword indicates the rule should only match outgoing packets.
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.Pp
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To match packets going through a certain interface, specify
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the interface using
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.Ar via :
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.Bl -hang -offset flag -width 1234567890123456
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.It Ar via ifX
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Packet must be going through interface
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.Ar ifX.
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.It Ar via if*
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Packet must be going through interface
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.Ar ifX ,
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where X is any unit number.
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.It Ar via any
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Packet must be going through
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.Em some
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interface.
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.It Ar via ipv6no
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Packet must be going through the interface having IPv6 address
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.Ar ipv6no .
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.El
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.Pp
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The
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.Ar via
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keyword causes the interface to always be checked.
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If
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.Ar recv
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or
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.Ar xmit
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is used instead of
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.Ar via ,
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then the only receive or transmit interface (respectively) is checked.
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By specifying both, it is possible to match packets based on both receive
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and transmit interface, e.g.:
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.Pp
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.Dl "ip6fw add 100 deny ip from any to any out recv ed0 xmit ed1"
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.Pp
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The
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.Ar recv
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interface can be tested on either incoming or outgoing packets, while the
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.Ar xmit
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interface can only be tested on outgoing packets.
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So
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.Ar out
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is required (and
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.Ar in
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invalid) whenver
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.Ar xmit
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is used.
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Specifying
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.Ar via
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together with
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.Ar xmit
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or
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.Ar recv
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is invalid.
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.Pp
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A packet may not have a receive or transmit interface: packets originating
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from the local host have no receive interface. while packets destined for
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the local host have no transmit interface.
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.Pp
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Additional
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.Ar options :
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.Bl -hang -offset flag -width 1234567890123456
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.It frag
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Matches if the packet is a fragment and this is not the first fragment
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of the datagram.
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.Ar frag
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may not be used in conjunction with either
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.Ar tcpflags
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or TCP/UDP port specifications.
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.It in
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Matches if this packet was on the way in.
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.It out
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Matches if this packet was on the way out.
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.It ipv6options Ar spec
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Matches if the IPv6 header contains the comma separated list of
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options specified in
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.Ar spec .
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The supported IPv6 options are:
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.Ar hopopt
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(hop-by-hop options header),
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.Ar route
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(routing header),
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.Ar frag
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(fragment header),
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.Ar esp
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(encapsulating security payload),
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.Ar ah
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(authentication header),
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.Ar nonxt
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(no next header), and
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.Ar opts
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(destination options header).
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The absence of a particular option may be denoted
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with a
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.Dq !
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.Em (not working yet).
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.It established
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Matches packets that have the RST or ACK bits set.
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TCP packets only.
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.It setup
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Matches packets that have the SYN bit set but no ACK bit.
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TCP packets only.
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.It tcpflags Ar spec
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Matches if the TCP header contains the comma separated list of
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flags specified in
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.Ar spec .
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The supported TCP flags are:
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.Ar fin ,
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.Ar syn ,
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.Ar rst ,
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.Ar psh ,
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.Ar ack ,
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and
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.Ar urg .
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The absence of a particular flag may be denoted
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with a
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.Dq ! .
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A rule which contains a
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.Ar tcpflags
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specification can never match a fragmented packet which has
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a non-zero offset. See the
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.Ar frag
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option for details on matching fragmented packets.
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.It icmptypes Ar types
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Matches if the ICMPv6 type is in the list
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.Ar types .
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The list may be specified as any combination of ranges
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or individual types separated by commas.
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.El
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.Sh CHECKLIST
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Here are some important points to consider when designing your
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rules:
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.Bl -bullet -hang -offset flag
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.It
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Remember that you filter both packets going in and out.
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Most connections need packets going in both directions.
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.It
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Remember to test very carefully.
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It is a good idea to be near the console when doing this.
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.It
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Don't forget the loopback interface.
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.El
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.Sh FINE POINTS
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There is one kind of packet that the firewall will always discard,
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that is an IPv6 fragment with a fragment offset of one.
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This is a valid packet, but it only has one use, to try to circumvent
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firewalls.
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.Pp
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If you are logged in over a network, loading the KLD version of
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.Nm
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is probably not as straightforward as you would think
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.Em (not supported).
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I recommend this command line:
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.Bd -literal -offset center
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kldload /modules/ip6fw_mod.o && \e
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ip6fw add 32000 allow all from any to any
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.Ed
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.Pp
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Along the same lines, doing an
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.Bd -literal -offset center
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ip6fw flush
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.Ed
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.Pp
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in similar surroundings is also a bad idea.
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.Sh PACKET DIVERSION
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not supported.
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.Sh EXAMPLES
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This command adds an entry which denies all tcp packets from
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.Em hacker.evil.org
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to the telnet port of
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.Em wolf.tambov.su
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from being forwarded by the host:
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.Pp
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.Dl ip6fw add deny tcp from hacker.evil.org to wolf.tambov.su 23
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.Pp
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This one disallows any connection from the entire hackers network to
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my host:
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.Pp
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.Dl ip6fw addf deny all from fec0::123:45:67:0/112 to my.host.org
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.Pp
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Here is a good usage of the list command to see accounting records
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and timestamp information:
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.Pp
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.Dl ip6fw -at l
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.Pp
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or in short form without timestamps:
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.Pp
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.Dl ip6fw -a l
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.Pp
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.Sh SEE ALSO
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.Xr ip 4 ,
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.Xr ipfirewall 4 ,
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.Xr protocols 5 ,
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.Xr services 5 ,
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.Xr reboot 8 ,
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.Xr sysctl 8 ,
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.Xr syslogd 8
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.Sh BUGS
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.Pp
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.Em WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!
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.Pp
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This program can put your computer in rather unusable state.
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When
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using it for the first time, work on the console of the computer, and
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do
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.Em NOT
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do anything you don't understand.
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.Pp
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When manipulating/adding chain entries, service and protocol names are
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not accepted.
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.Sh AUTHORS
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.An Ugen J. S. Antsilevich ,
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.An Poul-Henning Kamp ,
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.An Alex Nash ,
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.An Archie Cobbs .
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API based upon code written by
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.An Daniel Boulet
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for BSDI.
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.Sh HISTORY
|
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.Nm
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|
first appeared in
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.Fx 4.0 .
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