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98 lines
2.0 KiB
Groff
98 lines
2.0 KiB
Groff
.\"
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.\" $FreeBSD$
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.\"
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.Dd September 1, 2006
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.Dt IPFW 4
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.Os
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.Sh NAME
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.Nm ipfw
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.Nd IP packet filter and traffic accounting
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.Sh SYNOPSIS
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To compile
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.Ns Nm
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into the kernel, place the following option in the kernel configuration
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file:
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.Bd -ragged -offset indent
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.Cd "options IPFIREWALL"
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.Ed
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.Pp
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Other kernel options related to
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.Ns Nm
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which may also be useful are:
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.Bd -ragged -offset indent
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.Cd "options IPFIREWALL_DEFAULT_TO_ACCEPT"
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.Cd "options IPFIREWALL_FORWARD"
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.Cd "options IPFIREWALL_VERBOSE"
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.Cd "options IPFIREWALL_VERBOSE_LIMIT=100"
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.Ed
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.Pp
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To load
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.Ns Nm
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as a module at boot time, add the following line into the
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.Xr loader.conf 5
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file:
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.Bd -literal -offset indent
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ipfw_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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system facility allows filtering,
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redirecting, and other operations on
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.Tn IP
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packets travelling through
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network interfaces.
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.Pp
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The default behavior of
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.Nm
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is to block all incoming and outgoing traffic.
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This behavior can be modified, to allow all traffic through the
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.Nm
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firewall by default, by enabling the
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.Dv IPFIREWALL_DEFAULT_TO_ACCEPT
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kernel option.
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This option may be useful when configuring
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.Nm
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for the first time.
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If the default
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.Nm
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behavior is to allow everything, it is easier to cope with
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firewall-tuning mistakes which may accidentally block all traffic.
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.Pp
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To enable logging of packets passing through
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.Nm ,
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enable the
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.Dv IPFIREWALL_VERBOSE
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kernel option.
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The
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.Dv IPFIREWALL_VERBOSE_LIMIT
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option will prevent
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.Xr syslogd 8
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from flooding system logs or causing local Denial of Service.
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This option may be set to the number of packets which will be logged on
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a per-entry basis before the entry is rate-limited.
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.Pp
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Policy routing and transparent forwarding features of
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.Nm
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can be enabled by
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.Dv IPFIREWALL_FORWARD
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kernel option.
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.Pp
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The user interface for
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.Nm
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is implemented by the
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.Xr ipfw 8
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utility, so please refer to the
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.Xr ipfw 8
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manpage for a complete description of the
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.Nm
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capabilities and how to use it.
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.Sh SEE ALSO
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.Xr setsockopt 2 ,
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.Xr divert 4 ,
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.Xr ip 4 ,
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.Xr ipfw 8 ,
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.Xr sysctl 8 ,
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.Xr syslogd 8 ,
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.Xr pfil 9
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