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Bring the man page more into line with reality.

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This commit is contained in:
Alexander Langer 1996-06-15 01:38:51 +00:00
parent 77ae30e9cc
commit 3f21e4122d
1 changed files with 94 additions and 259 deletions
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353
sbin/ipfw/ipfw.8
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@ -11,12 +11,15 @@
flush
.Nm ipfw
zero
.Oo
.Ar number
.Oc
.Nm ipfw
delete
.Ar number
.Nm ipfw
.Oo
.Fl aN
.Fl atN
.Oc
list
.Nm ipfw
@ -64,7 +67,7 @@ One rule is always present:
65535 deny all from any to any
.Ed
this is rule is the default policy, ie. don't allow anything at all.
this rule is the default policy, ie. don't allow anything at all.
Your job in setting up rules is to modify this policy to match your
needs.
.Pp
@ -73,19 +76,23 @@ The following options are available:
.It Fl a
While listing, show counter values. This option is the only way to see
accounting records.
.It Fl t
While listing, show last match timestamp.
.It Fl N
Try to resolve addresses.
Try to resolve addresses and service names.
.El
.Pp
.Ar action :
.Bl -hang -offset flag -width 1234567890123456
.It Nm accept
Accept packets that match rule.
.It Nm allow
Allow packets that match rule.
The search terminates.
.It Nm pass
same as accept.
Same as allow.
.It Nm accept
Same as allow.
.It Nm count
update counters for all packets that match rule.
Update counters for all packets that match rule.
The search continues with next rule.
.It Nm deny
Discard packets that match this rule.
@ -98,6 +105,12 @@ The search terminates.
When a packet matches a rule with the
.Nm log
keyword, a message will be printed on the console.
If the kernel was compiled with the
.Nm IP_FIREWALL_VERBOSE_LIMIT
option, then logging will cease after the number of packets
specified by the option are recieved for that particular
chain entry. Logging may then be re-enabled by clearing
the packet counter for that entry.
.Pp
.Ar proto :
.Bl -hang -offset flag -width 1234567890123456
@ -116,6 +129,14 @@ Only ICMP packets match.
.Ar src
and
.Ar dst :
.Pp
.Bl -hang -offset flag
.It <address/mask> [ports]
.El
.Pp
The
.Em <address/mask>
may be specified as:
.Bl -hang -offset flag -width 1234567890123456
.It Ar ipno
An ipnumber of the form 1.2.3.4.
@ -128,6 +149,25 @@ An ipnumber with a mask width of the form 1.2.3.4:255.255.240.0
In this case all ip numbers from 1.2.0.0 to 1.2.15.255 will match.
.El
.Pp
With the TCP and UDP
.Em protocols ,
an optional
.Em port
may be specified as:
.Pp
.Bl -hang -offset flag
.It Ns {port|port:port} Ns Op ,port Ns Op ,...
.El
.Pp
Service names (from
.Pa /etc/services )
may not be used instead of a numeric port value.
Also, note that a range may only be specified as the first value,
and the port list is limited to
.Nm IP_FW_MAX_PORTS
(as defined in /usr/src/sys/netinet/ip_fw.h)
ports.
.Pp
If ``via''
.Ar name
is specified, only packets received via or on their way out of an interface
@ -145,14 +185,27 @@ will match this rule.
.Ar options :
.Bl -hang -offset flag -width 1234567890123456
.It frag
Matches is the packet is a fragment and this is not the first fragment
Matches if the packet is a fragment and this is not the first fragment
of the datagram.
.It in
Matches if this packet was on the way in.
.It out
Matches if this packet was on the way out.
.It ipoptions Ar spec
Not yet documented. Look in the source: src/sys/netnet/ipfw.c.
Matches if the IP header contains the comma separated list of
options specified in
.Ar spec .
The supported IP options are:
.Nm ssrr
(strict source route),
.Nm lsrr
(loose source route),
.Nm rr
(record packet route), and
.Nm ts
(timestamp).
The absence of a particular option may be denoted
with a ``!''.
.It established
Matches packets that do not have the SYN bit set.
TCP packets only.
@ -160,8 +213,24 @@ TCP packets only.
Matches packets that have the SYN bit set but no ACK bit.
TCP packets only.
.It tcpflags Ar spec
Not yet documented. Look in the source: src/sys/netnet/ipfw.c.
TCP packets only.
Matches if the TCP header contains the comma separated list of
flags specified in
.Ar spec .
The supported TCP flags are:
.Nm fin ,
.Nm syn ,
.Nm rst ,
.Nm psh ,
.Nm ack ,
and
.Nm urg .
The absence of a particular flag may be denoted
with a ``!''.
.It icmptypes Ar types
Matches if the ICMP type is in the list
.Ar types .
The list may be specified as any combination of ranges
or individual types separated by commas.
.El
.Sh CHECKLIST
Here are some important points to consider when designing your
@ -169,12 +238,16 @@ rules:
.Bl -bullet -hang -offset flag -width 1234567890123456
.It
Remember that you filter both packets going in and out.
Most connections needs packets going in both directions.
Most connections need packets going in both directions.
.It
Remember to test very carefully.
It is a good idea to be near the console when doint this.
It is a good idea to be near the console when doing this.
.It
Don't forget the loopback interface.
.It
Don't filter
.Nm all
if you are also specifying a port.
.El
.Sh FINE POINTS
There is one kind of packet that the firewall will always discard,
@ -191,226 +264,12 @@ modload /lkm/ipfw_mod.o && \e
ipfw add 32000 allow all from any to any
.Ed
Along the same lines, doing a
Along the same lines, doing an
.Bd -literal -offset center
ipfw flush
.Ed
in similar surroundings is also a bad idea.
.Sh WARNING
This manual page is out of date beyond this point!
It is left here until some new text can be written.
.Sh OLD
In the first synopsis form,
.Nm
controls the firewall and accounting chains. In the second
synopsis form,
.Nm
sets the global firewall / accounting properties and
show the chain list's contents.
.Pp
.Pp
These are the valid
.Ar entry_actions :
.Bl -hang -offset flag -width 1234567890123456
.It Nm addf[irewall]
add entry to firewall chain.
.It Nm delf[irewall]
remove entry from firewall chain.
.It Nm adda[ccounting]
add entry to accounting chain.
.It Nm dela[ccounting]
remove entry from accounting chain.
.It Nm clr[accounting]
clear counters for accounting chain entry.
.El
.Pp
If no
.Ar entry_action
is specified, it will default to
.Nm addf[irewall]
or
.Nm adda[ccounting] ,
depending on the
.Ar chain_entry_pattern
specified.
.Pp
The valid
.Ar chain_actions
are:
.Bl -hang -offset flag -width 123456789
.It Nm f[lush]
remove all entries in firewall / accounting chains.
.It Nm l[ist]
display all entries in firewall / accounting chains.
.It Nm z[ero]
clear chain counters (accounting only).
.It Nm p[olicy]
set default policy properties.
.El
.Pp
The
.Ar chain_entry_pattern
structure is:
.Pp
.Dl [keyword] [protocol] [address pattern]
.Pp
For the firewall chain, valid
.Em keywords
are:
.Bl -hang -offset flag -width 12345678
.It Nm reject
Reject the packet, and send an
.Tn ICMP HOST_UNREACHABLE
packet to the source.
.It Nm lreject
The same as
.Nm reject ,
but also log the packets details.
.It Nm deny
Reject the packet.
.It Nm ldeny
The same as
.Nm deny ,
but also log the packets details.
.It Nm log
Accept the packet, and log it.
.It Nm accept
Accept the packet (obviously).
.It Nm pass
A synonym for accept.
.El
.Pp
For the accounting chain, valid
.Em keywords
are:
.Bl -tag -width flag
.It Nm single
Log packets matching entry.
.It Nm bidirectional
Log packets matching entry and also those going in the
opposite direction (from
.Dq dst
to
.Dq src ) .
.El
.Pp
Each keyword will be recognized by the shortest unambiguous prefix.
.Pp
Recognized
.Em protocols
are:
.Bl -hang -offset flag -width 123456
.It Nm all
Matches any IP packet.
.It Nm icmp
Matches ICMP packets.
.It Nm tcp
Matches TCP packets.
.It Nm udp
Matches UDP packets.
.It Nm syn
Matches the TCP SYN packet used in initiating a TCP connection. It
does not match the packet returned from a destination machine which
has the SYN and ACK bits set.
.El
.Pp
The
.Em address pattern
is:
.Pp
.Dl from <address/mask>[ports] to <address/mask][ports] [via <interface>]
.Pp
You can only specify
.Em ports
with
.Em protocols
which actually have ports (TCP, UDP and SYN).
.Pp
The order of
.Sq from/to/via
keywords is unimportant. You can skip any of them, which will be
then substituted by default entry matching any
.Sq from/to/via
packet kind.
.Pp
The
.Em <address/mask>
is defined as:
.Pp
.Dl <address|name>[/mask_bits|:mask_pattern]
.Pp
.Em mask bits
is the decimal number of bits set in the address mask.
.Em mask pattern
has the form of an IP address to be AND'ed logically with the address
given. The keyword
.Em any
can be used to specify
.Dq any IP .
The IP address or name given is
.Em NOT
checked, and the wrong value
causes the entry to not match anything.
.Pp
The
.Em ports
to be blocked are specified as:
.Dl Ns port Ns Op ,port Ns Op ,...
or:
.Dl port:port
.Pp
to specify a range of ports. The name of a service (from
.Pa /etc/services )
can be used instead of
a numeric port value.
.Pp
The
.Em via <interface>
entry is optional and may specify IP address/domain name of local IP
interface, or interface name (e.g.
.Em ed0 )
to match only packets coming
through this interface. The keyword
.Em via
can be substituted by
.Em on ,
for readability reasons.
.Pp
The
.Em l[ist]
command may be passed:
.Pp
.Dl f[irewall] | a[ccounting]
.Pp
to list specific chain or none to list all of chains. The long output
format (default) is compatible with the syntax used by the
.Nm
utility.
.Pp
The
.Em f[lush]
command may be passed:
.Pp
.Dl f[irewall] | a[ccounting]
.Pp
to remove all entries from firewall or from accounting chain. Without
an argument it will remove all entries from both chains.
.Pp
The
.Em z[ero]
command needs no arguments. This command clears all counters for the
entire accounting chain.
.Pp
The
.Em p[olicy]
command can be given
.Pp
.Dl a[ccept] | d[eny]
.Pp
to set default policy as denial/acceptance. Without an argument, the
current policy status is displayed.
.Sh EXAMPLES
This command adds an entry which denies all tcp packets from
.Em hacker.evil.org
@ -418,7 +277,7 @@ to the telnet port of
.Em wolf.tambov.su
from being forwarded by the host:
.Pp
.Dl ipfw addf deny tcp from hacker.evil.org to wolf.tambov.su telnet
.Dl ipfw add deny tcp from hacker.evil.org to wolf.tambov.su 23
.Pp
This one disallows any connection from the entire hackers network to
my host:
@ -427,15 +286,12 @@ my host:
.Pp
Here is good usage of list command to see accounting records:
.Pp
.Dl ipfw -sa list accounting
.Dl ipfw -aT l
.Pp
or in short form
.Pp
.Dl ipfw -sa l a
.Dl ipfw -a l
.Pp
Many more examples can be found in the file:
.Dl Pa /usr/share/FAQ/ipfw.FAQ
(missing for the moment)
.Sh SEE ALSO
.Xr gethostbyname 3 ,
.Xr getservbyport 3 ,
@ -445,20 +301,6 @@ Many more examples can be found in the file:
.Xr reboot 8 ,
.Xr syslogd 8
.Sh BUGS
Currently there is no method for filtering out specific types of ICMP
packets. Either you don't filter ICMP at all, or all ICMP packets are
filtered.
.Pp
The system has an optional rule weighting system for the firewall chain.
This means that rules are not used in the order that they are specified.
To enable this feature, you need to recompile your kernel, see the
.I LINT
configuration for details.
In general you do not want that.
.Pp
To see what rule ordering is used, use the
.Em list
command.
.Pp
.Em WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!
.Pp
@ -468,14 +310,8 @@ do
.Em NOT
do anything you don't understand.
.Pp
Remember that
.Dq ipfw flush
can solve all the problems. Bear in mind that
.Dq ipfw policy deny
combined with some wrong chain entry (possible the only entry, which
is designed to deny some external packets), can close your computer
from the outer world for good (or at least until you can get to the
console).
When manipulating/adding chain entries, service names are
not accepted.
.Sh HISTORY
Initially this utility was written for BSDI by:
.Pp
@ -485,6 +321,5 @@ The FreeBSD version is written completely by:
.Pp
.Dl Ugen J.S.Antsilevich <ugen@FreeBSD.ORG>
.Pp
while the synopsis is partially compatible with the old one.
.Pp
This has all been extensively rearranged by Poul-Henning Kamp.
This has all been extensively rearranged by Poul-Henning Kamp and
Alex Nash.