528 lines
24 KiB
Groff
528 lines
24 KiB
Groff
.\"
|
|
.\" ipfw - a utility for manipulating the configuration of an IP firewall.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" @(#)ipfw.1
|
|
.\"
|
|
.TH ipfw 1 "October 27, 1994" "" "FreeBSD"
|
|
|
|
.SH NAME
|
|
ipfw - a utility for manipulating the configuration of an IP firewall.
|
|
.SH SYNOPSIS
|
|
.na
|
|
.B ipfw
|
|
.RB [options]
|
|
.SH DESCRIPTION
|
|
The
|
|
.B ipfw
|
|
command is used to configure an active IP firewall, setting masks on just
|
|
what sites are allowed to connect through it, which packets are rejected,
|
|
etc.
|
|
.SH OPTIONS
|
|
The command-line syntax of this command is rather involved, and rather than
|
|
spend a lot of time that I just don't have at the moment creating a
|
|
.B real
|
|
man page, with properly formatted sections and all, I'm just going to loosely
|
|
format the README I got. This really needs an nroff expert to go through
|
|
it with a chainsaw and do a
|
|
.N REAL
|
|
job of formatting it! This all looks rather horrible at present, and
|
|
I would actually almost recommend that you simply read the man page text
|
|
directly, rather than trying to format it. Sorry, but I do NOT speak
|
|
nroff, nor do I ever wish to learn how! :-) [-jkh].
|
|
.PP
|
|
For a sample kernel configuration file that will enable the right kernel
|
|
features necessary for firewalling, see
|
|
.I /sys/i386/conf/IPFIREWALL
|
|
.
|
|
.PP
|
|
.B WARNING!!! WARNING!!! WARNING!!! WARNING!!! WARNING!!! WARNING!!!
|
|
.PP
|
|
This utility can be used to put your machine into very dysfunctional state,
|
|
so if you want to test it then you should first make sure to read this man page
|
|
all the way through, and don't run it anywhere from the system console!
|
|
Using
|
|
.I ipfw
|
|
incorrectly is a really good way to kick yourself off your own machine
|
|
if you're logged in over a network! Also make sure to never set this
|
|
utility to be setuid root! It's a blatant security hole that way.
|
|
Instead, run it as root or from "/etc/rc.local" as part of the boot process.
|
|
It's also a good idea to use the checkb or checkf command options (see below)
|
|
to pass some test packets through the firewalls that you've defined before
|
|
going "live".
|
|
.PP
|
|
You may find it useful to create a file in which the first line is
|
|
.I firewall flush
|
|
to flush any existing firewalls before defining the explicit firewalls
|
|
that you wish to use. This will ensure that you're always working from a
|
|
known state.
|
|
.PP
|
|
The syntax for the
|
|
.BI ipfirewall
|
|
command option is rather complex and yet simple at the same time (if you know
|
|
what I mean). There are seven sub-commands, and probably the easiest way to
|
|
get into this is to give you a roughly BNF style grammar for the command
|
|
(curly brackets are used for precedence, alternatives are separated by |,
|
|
optional things are enclosed in square brackets, white space is required if
|
|
it appears below and must not appear if there isn't any between the tokens
|
|
below (i.e. no white space around periods, colons or slashes, whitespace
|
|
required between all other tokens)):
|
|
.PP
|
|
.nf
|
|
command ::= ipfirewall <list> | <flush> | <check> | <add> | <del>
|
|
<list> ::= list
|
|
<flush> ::= flush
|
|
<check> ::= { checkb[locking] | checkf[orwarding] } <chkparms>
|
|
<add> ::= { addb[locking] | addf[orwarding] } <add-del-parms>
|
|
<del> ::= { delb[locking] | delf[orwarding] } <add-del-parms>
|
|
<chkparms> ::= <protocol> from <ipaddr> <port> to <ipaddr> <port>
|
|
<protocol> ::= tcp | udp
|
|
<ipaddr> ::= <int>.<int>.<int>.<int> | <hostname>
|
|
<hostname> ::= a host name from /etc/hosts
|
|
<port> ::= <int> | <service>
|
|
<service> ::= a service from /etc/services
|
|
<int> ::= a non-negative integer
|
|
<add-del-parms> ::= { accept | deny } { <universal_firewall> | <protocol_firewall> }
|
|
<universal_firewall> ::= all from <masked_ipaddr> to <masked_ipaddr>
|
|
<masked_ipaddr> ::= { <ipaddr>/<bits> } | { <ipaddr>:<ipaddr> } | <ipaddr>
|
|
<bits> ::= integer in the range 0 to 32 inclusive
|
|
<protocol_firewall> ::= <protocol> from <end_firewall> to <end_firewall>
|
|
<end_firewall> ::= <masked_ipaddr> <port_list>
|
|
<port_list> ::= [ <port>:<port> ] <sub_port_list>
|
|
<sub_port_list> ::= <port> [ <sub_port_list> ]
|
|
.fi
|
|
.PP
|
|
Although I think that the above grammar is complete, it isn't exactly what
|
|
one would call easy to comprehend! Here's the basic idea along with what
|
|
each of the forms mean:
|
|
.PP
|
|
The
|
|
.I ipfirewall list
|
|
command prints a list of the firewalls on both the
|
|
forwarding and blocking chain in some more or less comprehensible format.
|
|
.PP
|
|
The
|
|
.I ipfirewall flush
|
|
command empties the two firewall chains.
|
|
.PP
|
|
The
|
|
.I ipfirewall addblocking
|
|
and
|
|
.I ipfirewall addforwarding
|
|
commands take a firewall description and add the firewall to the appropriate
|
|
firewall chain. Note that you'll probably need to add some descriptions more
|
|
then once, which will naturally take more then one entry in memory. It does
|
|
not lead to significant degradation of performance, so don't worry about it.
|
|
.PP
|
|
The
|
|
.I ipfirewall delblocking
|
|
and
|
|
.I ipfirewall delforwarding
|
|
commands take a firewall description and delete the firewall from the
|
|
appropriate firewall chain. The description must exactly match that given
|
|
to an earlier add command. One delete command removes ALL matching entries
|
|
from firewall chains.
|
|
.PP
|
|
There are two basic kinds of firewall descriptions. Universal firewall
|
|
descriptions match all IP packets between specified pairs of hosts.
|
|
Universal firewalls only check IP addresses (e.g. they match any combination
|
|
of protocol and port numbers). Protocol-specific firewalls match either
|
|
TCP/IP or UDP/IP packets between specified pairs of hosts. In addition
|
|
to host descriptions, protocol-specific firewalls optionally take a
|
|
description of which port numbers to match.
|
|
.PP
|
|
A host description consists of an IP address and a mask. The IP address
|
|
is specified as either a domain name or in the familiar
|
|
nn.nn.nn.nn format. The mask indicates how much of the IP address
|
|
should be looked at when vetting packets. There are two ways to
|
|
specify the mask. The first way is to suffix the IP address in the
|
|
firewall with a slash and an integer in the range 0 through 32 inclusive.
|
|
This integer is taken to be the number of high order bits of the IP
|
|
address which are to be checked (for example, 192.153.211.0/24 checks
|
|
the top 24 bits of the IP address, 192.153.211.17/32 checks all the
|
|
bits and 0.0.0.0/0 checks none of the bits (i.e. all IP addresses are
|
|
matched by this example)). The second way to specify a mask is to
|
|
suffix the IP address with a colon followed by another IP address.
|
|
This second address is the mask. Specifications equivalent to the
|
|
above three examples using this syntax would be
|
|
.PP
|
|
.nf
|
|
192.153.211.0:255.255.255.0
|
|
192.153.211.17:255.255.255.255
|
|
0.0.0.0:0.0.0.0
|
|
.fi
|
|
.PP
|
|
The first form is taken from the syntax accepted by a Telebit NetBlazer.
|
|
The second form is more along the lines of how a netmask is specified
|
|
in /etc/netmasks. Finally, if no mask is specified then a mask of all
|
|
1's is supplied (i.e. no mask is equivalent to /32 or :255.255.255.255).
|
|
.PP
|
|
The optional description of port numbers to mask can take three forms.
|
|
The simplest form is to omit the list in which case all port numbers
|
|
match. The next form is to specify a list of port numbers (either as
|
|
positive integers or service names from /etc/services). The final form
|
|
is actually a special case of the second form in which the first pair
|
|
of port numbers is separated by a colon instead of white space. This
|
|
pair specifies a range of port numbers (i.e. x:y specifies that all
|
|
ports between x and y inclusive should match). A port description
|
|
matches a particular port number if any of the following is true:
|
|
.nf
|
|
- the port description is null
|
|
|
|
- the first pair of port numbers is a range and the port number
|
|
is in the range (inclusive)
|
|
|
|
- the port number is equal to any of the port numbers in the list
|
|
.fi
|
|
.PP
|
|
There is a limit of a total of 10 port numbers in the source and
|
|
destination port lists. This limit is arbitrary and easy to increase.
|
|
It is determined by the value of the IP_FIREWALL_MAX_PORTS #define
|
|
variable in ip_firewall.h. Each increase of 1 for this value adds two
|
|
bytes to the size of each firewall. Since the size of a firewall is only
|
|
slightly over 30 bytes right now, this limit of 10 could probably
|
|
be increased by quite a bit before it became a concern. I've been
|
|
thinking of increasing it to 20 which would be longer than any
|
|
reasonable firewall would need and would only consume 20 more bytes
|
|
per firewall. The counter argument to any increase is that it is
|
|
always possible to construct an equivalent set of two or more firewalls
|
|
that behaves like a single firewall with a really long port list.
|
|
.PP
|
|
This probably all sounds hopelessly complicated. It is actually not
|
|
all that tricky (I'm just not very good at explaining it yet). A few
|
|
examples will probably help a lot now:
|
|
.PP
|
|
Block all IP packets originating from the host hackers-den:
|
|
.PP
|
|
.nf
|
|
ipfirewall addb deny all from hackers-den to 0.0.0.0/0
|
|
.fi
|
|
.PP
|
|
Block all telnet packets to our telnet server from anywhere:
|
|
.PP
|
|
.nf
|
|
ipfirewall addb deny tcp from 0.0.0.0/0 to mymachine/32 telnet
|
|
.fi
|
|
.PP
|
|
Don't forward telnet, rlogin and rsh packets onto our local
|
|
class C network:
|
|
.PP
|
|
.nf
|
|
ipfirewall addf deny tcp from 0.0.0.0/0 to ournetwork/24 telnet login shell
|
|
.fi
|
|
.PP
|
|
Don't let anyone on the local machine or any machine inside
|
|
our local network ftp access to games.com:
|
|
.PP
|
|
.nf
|
|
ipfirewall addb deny tcp from games.com ftp to 0.0.0.0/0
|
|
.fi
|
|
.PP
|
|
This last one might look a little strange. It doesn't prevent
|
|
anyone from sending packets to the games.com ftp server. What it
|
|
does do is block any packets that the games.com ftp server sends
|
|
back!
|
|
.PP
|
|
The
|
|
.I ipfirewall checkblocking
|
|
and
|
|
.I ipfirewall checkforwarding
|
|
commands take a description of an IP packet and check to see if the blocking
|
|
or forwarding chain of firewalls respectively accept or reject the packet.
|
|
It is used to make sure that the firewalls that you've defined work as
|
|
expected. The basic syntax is probably best understood by looking at
|
|
a couple of examples:
|
|
.PP
|
|
.nf
|
|
ipfirewall checkb from bsdi.com 3001 to mymachine telnet
|
|
.fi
|
|
.PP
|
|
checks to see if the blocking firewall will block a telnet packet from
|
|
a telnet session originating on bsdi.com to the host mymachine will be
|
|
blocked or not. Note that someone connecting to our telnet server
|
|
could be using practically any port number. To be really sure, the
|
|
firewall used to prevent access should be as simple as possible and/or
|
|
you should try a variety of port numbers in addition to the rather
|
|
arbitrarily chosen port of 3001.
|
|
.PP
|
|
One final note on the check* ,add* and del* command syntax. The noise word
|
|
"to" exists in the syntax so that I can detect the end of a list of
|
|
port numbers in the from description. Since I needed a noise word to
|
|
detect this case, I added the noise word "from" in front of the from
|
|
case for consistency.
|
|
.PP
|
|
Finally, have a look at the file
|
|
.I "/usr/share/misc/ipfw.samp.filters"
|
|
. It is the set of filters that I run at home [Danny].
|
|
.PP
|
|
Also check
|
|
.I "/usr/share/misc/ipfw.samp.scripts"
|
|
For examples of individual access restrictions.
|
|
We [NetVision] use those for our dial-in PPP/SLIP users to allow some of them
|
|
to access our internal networks, while disallowing others.
|
|
This way we open access for the user's IP when he enters the system and shut it
|
|
down when he leaves. All such changes may be applyed at any time,
|
|
and so entries added and deleted from firewall while the system is
|
|
is working have no other side effects [Ugen].
|
|
|
|
.SH "TECHNICAL DETAILS"
|
|
A bit of a description of how the firewalls are applied (i.e. what happens in
|
|
the kernel) may be instructive to the advanced firewall-builder:
|
|
.PP
|
|
When an IP packet is received, the ipintr() routine in ip_input.c is
|
|
called. This routine does a bit of basic error checking. If it
|
|
detects any errors in the packet it generally drops the packet on
|
|
the floor. The idea behind the ipfirewall facility is to treat packets
|
|
that we don't want to accept as bad packets (i.e. drop them on the
|
|
floor). The ipfirewall facility intercedes in the normal processing
|
|
at two points. Just after the basic sanity checks are done, we pass
|
|
any packets not targeted at the loopback network (127.0.0.0/8) to the
|
|
firewall checker along with the chain of blocking firewalls.If the firewall
|
|
checker tells us to block the packet then we branch to the "bad:" label
|
|
in ipintr() which is where all bad packets are dropped on the floor.
|
|
Otherwise, we allow normal processing of the packet to continue. The
|
|
exact point at which we intercede was chosen to be after the basic
|
|
sanity checking and before the option processing is done. We want to
|
|
be after the basic sanity checking so that we don't have to be able
|
|
to handle complete garbage. We want to be before the option processing
|
|
because option processing is done in separate rather complex routine.
|
|
Why bother doing this special processing if we might be dropping the
|
|
packet?
|
|
.PP
|
|
The second point at which we intercede is when a packet is about to be
|
|
forwarded to another host. All such packets are passed to the ip_forward
|
|
routine. The ipfirewall code is at the very top of this routine. If
|
|
the packet isn't targetted at the loopback interface (is it possible
|
|
that it could be when we reach this point? I doubt it but safety first)
|
|
then pass the packet to the firewall checker along with the forwarding
|
|
firewall chain. If the firewall checker indicates that the packet should
|
|
not be forwarded then we drop in (using code copied from a few lines
|
|
further into the routine which drops broadcast packets which are not
|
|
to be forwarded).
|
|
.PP
|
|
There are a couple of consequences of this approach:
|
|
.PP
|
|
1) Packets which are blocked are never forwarded (something to keep
|
|
in mind when designing firewalls).
|
|
.PP
|
|
2) Packets targeted at the loopback interface (127.0.0.0/8) are never
|
|
blocked. Blocking packets to the loopback interface seems pointless
|
|
and potentially quite confusing. It also makes a possibly common
|
|
case very cheap.
|
|
.PP
|
|
3) The sender of a packet which is blocked receives no indication that
|
|
the packet was dropped. The Telebit NetBlazer can be configured to
|
|
silently drop a blocked packet or to send back a "you can't get there
|
|
from here" packet to the sender. Implementing the later would have
|
|
been more work (possibly quite a bit more, I don't really know). Also,
|
|
I don't see any reason to give a potential hacker any more information
|
|
than necessary. Dropping the packet into the bit bucket seems like
|
|
the best way to keep a hacker guessing. [Danny]
|
|
.PP
|
|
(I am working on this feature, it would be made optional and
|
|
configurable by some ICMP_UNREACH_ON_DROP option, or such [Ugen]).
|
|
.PP
|
|
The firewall checker takes two parameters. The first parameter is a pointer
|
|
to the packet in question. The second parameter is a pointer to the
|
|
appropriate firewall chain. At the present time, the firewall checker passes
|
|
these parameters to a second routine which is the real firewall checker.
|
|
If the real checker says NO then an appropriate message is printed
|
|
onto the console. This is useful for debugging purposes. Whether or
|
|
not it remains in the long term depends on whether it is considered useful
|
|
for logging purposes (I'm a little reluctant to leave it in since it
|
|
provides a hacker with a way to commit a "denial of service" offense
|
|
against you by filling up your /var/log/messages file's file system
|
|
with error messages. There are ways of preventing this but ... [Danny]).
|
|
In default configuration now no information about dropped packets
|
|
printed.You may, however, define it as i do by adding
|
|
.I options IPFIREWALL_VERBOSE
|
|
to your kernel configuration file. Very useful thingy! [Ugen]
|
|
|
|
.PP
|
|
A return value of 0 from this routine (or the real firewall checker)
|
|
indicates that the packet is to be dropped. A value of 1 indicates
|
|
that the packet is to be accepted. In the early testing stages you
|
|
might want to make the top level firewall checker always return 1 even
|
|
if the real checker returns 0 just in case the real firewall checker
|
|
screws up (or your firewalls aren't as well designed as they should be).
|
|
In fact, this might be a useful optional feature (providing a way to
|
|
leave a door unlocked doesn't seem all that wise but it has to be
|
|
balanced against the inconvenience to legitimate users who might get
|
|
screwed up by poorly designed firewalls).
|
|
|
|
.PP
|
|
The real firewall returns 1 (accept the packet) if the chain is empty. If
|
|
efficiency is a concern (which it is in this code), this check should
|
|
be done in ip_input.c before calling the firewall checker.
|
|
|
|
.PP
|
|
Assuming that there is a firewall chain to scan through, the real firewall
|
|
checker picks up the src and dst IP addresses from the IP packet. It
|
|
then goes through the firewall chain looking for the first firewall that
|
|
matches the packet. Once a matching firewall has been found, a value of
|
|
1 is returned if the firewall is an accept firewall and a value of 0 is
|
|
returned otherwise.
|
|
.PP
|
|
The following processing is done for each firewall on the chain:
|
|
.PP
|
|
1) check the src and dst IP addresses. If they don't match then
|
|
there isn't any point in looking any further at this firewall.
|
|
This check is done by anding the packet's IP addresses the
|
|
with appropriate masks and comparing the results to the
|
|
appropriate addresses in the firewall. Note that the mask is
|
|
NOT applied to the address in the firewall. If it has any 1
|
|
bits that are 0 bits in the mask then the firewall will never
|
|
match (this will be checked in ipfirewall soon). If the addresses
|
|
match then we continue with the next step.
|
|
.PP
|
|
2) If the firewall is a universal firewall then we've got a match.
|
|
Return either 0 or 1 as appropriate. Otherwise, continue with
|
|
the next step.
|
|
.PP
|
|
3) Examine the IP protocol from the packet. If we havn't had to
|
|
look at it before then we get it and set a local variable to
|
|
IP_FIREWALL_TCP for TCP/IP packets, IP_FIREWALL_UDP for UDP/IP
|
|
packets, IP_FIREWALL_ICMP for ICMP packets, and IP_FIREWALL_UNIVERSAL
|
|
for all other packet types. Also, if the packet is a TCP/IP or
|
|
a UDP/IP packet, save the source and destination port numbers
|
|
at this point (taking advantage of the fact that the port numbers
|
|
are stored in the same place in either a TCP/IP or a UDP/IP
|
|
packet header). If the packet is neither a TCP/IP or a UDP/IP
|
|
packet then this firewall won't match it (on to the next firewall).
|
|
If this packet's protocol doesn't match this firewall's protocol
|
|
(which can't be universal or we wouldn't be here) then on to
|
|
the next firewall. Otherwise, continue with the next step.
|
|
.PP
|
|
4) We're checking either a TCP/IP or a UDP/IP packet. If the
|
|
firewall's source port list is empty or the packet's source
|
|
port matches something in the source port list AND if the firewall's
|
|
destination port list is empty or the packet's destination
|
|
port matches something in the destination port list then
|
|
we've got a match (return 0 or 1 as appropriate). Otherwise,
|
|
on to the next firewall.
|
|
.PP
|
|
As indicated above, if no packet on the chain matches the packet then
|
|
it is accepted if the first firewall was a deny firewall and it is rejected
|
|
if the first firewall was an accept packet. This is equivalent to the
|
|
default behaviour of a Telebit NetBlazer. They provide a way to override
|
|
this behaviour. I'm not convinced that it is necessary (I'm open to
|
|
suggestions).
|
|
.PP
|
|
That's about it for the firewall checker. The
|
|
.I ipfw
|
|
program communicates with the kernel part of the firewall facility by making
|
|
setsockopt calls on RAW IP sockets. Only root is allowed to open a RAW IP
|
|
socket. This ensures that only root uses
|
|
.I ipfw to manipulate the firewall facility.
|
|
Also, somewhere in the kernel source or on a man page, I read that the
|
|
RAW IP setsockopt calls are intended for manipulating the IP protocol layer
|
|
as opposed to manipulating any particular instance of a socket. This seems
|
|
like a reasonable description of what the firewall setsockopt command
|
|
codes do.
|
|
.PP
|
|
There are seven setsockopt command codes defined by the firewall facility
|
|
(in netinet/in.h). They are:
|
|
.PP
|
|
.nf
|
|
IP_FLUSH_FIREWALLS flush (i.e. free) both firewall chains.
|
|
|
|
IP_ADD_FORWARDING_FIREWALL add firewall pointed at by optval parm to
|
|
the end of the forwarding firewall chain.
|
|
|
|
IP_ADD_BLOCKING_FIREWALL add firewall pointed at by optval parm to
|
|
the end of the blocking firewall chain.
|
|
|
|
IP_DEL_FORWARDING_FIREWALL delete firewall pointed at by optval parm
|
|
from the forwarding firewall chain.
|
|
|
|
IP_DEL_BLOCKING_FIREWALL delete firewall pointed at by optval parm
|
|
from the blocking firewall chain.
|
|
|
|
IP_CHECK_FORWARDING_FIREWALL pass the IP packet do the firewall checker
|
|
along with the forwarding firewall chain.
|
|
Return 0 if packet was accepted, -1 (with
|
|
errno set to EACCES) if it wasn't.
|
|
|
|
IP_CHECK_BLOCKING_FIREWALL pass the IP packet do the firewall checker
|
|
along with the blocking firewall chain.
|
|
Return 0 if packet was accepted, -1 (with
|
|
errno set to EACCES) if it wasn't.
|
|
|
|
The IP_ADD_* and IP_DEL_* command codes do a fair bit of validity checking.
|
|
It is quite unlikely that a garbage firewall could get past them that
|
|
would cause major problems in the firewall checker. It IS possible for
|
|
a garbage packet to get past the checks which causes major grief because
|
|
it either blocks or accepts packets according to unusual rules (the rules
|
|
will conform to the ones described above but will probably come as quite
|
|
a surprise).
|
|
|
|
The IP_CHECK_* command codes expect the optval parameter to point
|
|
to a struct ip immediately followed by a header appropriate to the protocol
|
|
value described in the ip_p field of the ip header. The exact requirements
|
|
are as follows:
|
|
|
|
- The length of the optval parameter must be at least
|
|
|
|
sizeof(struct ip) + 2 * sizeof(u_short)
|
|
|
|
since this is the amount of memory that might be referenced by
|
|
the firewall checker.
|
|
|
|
- The ip_hl field of the ip structure must be equal to
|
|
|
|
sizeof(struct ip) / sizeof(int)
|
|
|
|
since this value indicates that the tcp/udp/??? header immediately
|
|
follows the ip header (appropriate for the purposes that this
|
|
interface is intended for).
|
|
|
|
Failure to follow these rules (for either the IP_ADD_*,IP_DEL_* or the
|
|
IP_CHECK_*_FIREWALL commands) will result in a return value of -1 with
|
|
errno set to EINVAL (for now, it will also result in an appropriate
|
|
message on the console).
|
|
|
|
To read current configuration of firewalls,the kvm_read() function used.
|
|
Symbols,which you have to find are :
|
|
struct ip_firewall * ip_firewall_blocking_chain ;
|
|
struct ip_firewall * ip_firewall_forwarding_chain ;
|
|
Both are pointers to the linked list of firewall entries.
|
|
Of course, you must at least be a member of group kmem to read kernel
|
|
symbols.
|
|
.fi
|
|
.PP
|
|
There are a couple of additional details that are worth reading about in
|
|
the ip_firewall.h file. Other than that, let the authors know how you do!
|
|
If you have any problems, you may call Danny Boulet at home (403 449-1835)
|
|
or send e-mail to <danny@BouletFermat.ab.ca>. If you call, please keep in
|
|
mind that Danny lives in the Canadian Mountain timezone (GMT-0600).
|
|
.PP
|
|
You may also reach some commercial users of this package (and also those
|
|
responsible for porting it to FreeBSD and adding several additional
|
|
commands), at 972-4-550-330, or via email at <ugen@NetVision.net.il>.
|
|
If you call, remember that Ugen lives in the Israel timezone, which is GMT+02.
|
|
|
|
.SH FILES
|
|
/usr/share/misc/ipfw.samp.filters
|
|
/usr/share/misc/ipfw.samp.scripts
|
|
.SH "BUGS"
|
|
You can very easily hose your machine utterly if you don't know what you're
|
|
doing. Dieses Befehl ist nur fuer Experten!
|
|
.SH "SEE ALSO"
|
|
.BR reboot (1) ,
|
|
.PP
|
|
.BR /sys/i386/conf/IPFIREWALL
|
|
.SH AUTHORS
|
|
Daniel Boulet <danny@BouletFermat.ab.ca>
|
|
.PP
|
|
Ugen J.S.Antsilevich <ugen@NetVision.net.il>
|
|
.PP
|
|
Jordan K. Hubbard <jkh@FreeBSD.org> [Crimes committed in this manpage]
|