For incoming packets, the packet's source address is checked if it
belongs to a directly connected network. If the network is directly
connected, then the interface the packet came on in is compared to
the interface the network is connected to. When incoming interface
and directly connected interface are not the same, the packet does
not match.
Usage example:
ipfw add deny ip from any to any not antispoof in
Manpage education by: ru
source address of a packet exists in the routing table. The
default route is ignored because it would match everything and
render the check pointless.
This option is very useful for routers with a complete view of
the Internet (BGP) in the routing table to reject packets with
spoofed or unrouteable source addresses.
Example:
ipfw add 1000 deny ip from any to any not versrcreach
also known in Cisco-speak as:
ip verify unicast source reachable-via any
Reviewed by: luigi
them mostly with packet tags (one case is handled by using an mbuf flag
since the linkage between "caller" and "callee" is direct and there's no
need to incur the overhead of a packet tag).
This is (mostly) work from: sam
Silence from: -arch
Approved by: bms(mentor), sam, rwatson
if_xname, if_dname, and if_dunit. if_xname is the name of the interface
and if_dname/unit are the driver name and instance.
This change paves the way for interface renaming and enhanced pseudo
device creation and configuration symantics.
Approved By: re (in principle)
Reviewed By: njl, imp
Tested On: i386, amd64, sparc64
Obtained From: NetBSD (if_xname)
Set 31 is still special because rules belonging to it are not deleted
by the "ipfw flush" command, but must be deleted explicitly with
"ipfw delete set 31" or by individual rule numbers.
This implement a flexible form of "persistent rules" which you might
want to have available even after an "ipfw flush".
Note that this change does not violate POLA, because you could not
use set 31 in a ruleset before this change.
sbin/ipfw changes to allow manipulation of set 31 will follow shortly.
Suggested by: Paul Richards
comes in on is the same interface that we would route out of to get to
the packet's source address. Essentially automates an anti-spoofing
check using the information in the routing table.
Experimental. The usage and rule format for the feature may still be
subject to change.
The bugfix (ipfw2.c) makes the handling of port numbers with
a dash in the name, e.g. ftp-data, consistent with old ipfw:
use \\ before the - to consider it as part of the name and not
a range separator.
The new feature (all this description will go in the manpage):
each rule now belongs to one of 32 different sets, which can
be optionally specified in the following form:
ipfw add 100 set 23 allow ip from any to any
If "set N" is not specified, the rule belongs to set 0.
Individual sets can be disabled, enabled, and deleted with the commands:
ipfw disable set N
ipfw enable set N
ipfw delete set N
Enabling/disabling of a set is atomic. Rules belonging to a disabled
set are skipped during packet matching, and they are not listed
unless you use the '-S' flag in the show/list commands.
Note that dynamic rules, once created, are always active until
they expire or their parent rule is deleted.
Set 31 is reserved for the default rule and cannot be disabled.
All sets are enabled by default. The enable/disable status of the sets
can be shown with the command
ipfw show sets
Hopefully, this feature will make life easier to those who want to
have atomic ruleset addition/deletion/tests. Examples:
To add a set of rules atomically:
ipfw disable set 18
ipfw add ... set 18 ... # repeat as needed
ipfw enable set 18
To delete a set of rules atomically
ipfw disable set 18
ipfw delete set 18
ipfw enable set 18
To test a ruleset and disable it and regain control if something
goes wrong:
ipfw disable set 18
ipfw add ... set 18 ... # repeat as needed
ipfw enable set 18 ; echo "done "; sleep 30 && ipfw disable set 18
here if everything goes well, you press control-C before
the "sleep" terminates, and your ruleset will be left
active. Otherwise, e.g. if you cannot access your box,
the ruleset will be disabled after the sleep terminates.
I think there is only one more thing that one might want, namely
a command to assign all rules in set X to set Y, so one can
test a ruleset using the above mechanisms, and once it is
considered acceptable, make it part of an existing ruleset.
just because you leave your session idle.
Also, put in a fix for 64-bit architectures (to be revised).
In detail:
ip_fw.h
* Reorder fields in struct ip_fw to avoid alignment problems on
64-bit machines. This only masks the problem, I am still not
sure whether I am doing something wrong in the code or there
is a problem elsewhere (e.g. different aligmnent of structures
between userland and kernel because of pragmas etc.)
* added fields in dyn_rule to store ack numbers, so we can
generate keepalives when the dynamic rule is about to expire
ip_fw2.c
* use a local function, send_pkt(), to generate TCP RST for Reset rules;
* save about 250 bytes by cleaning up the various snprintf()
in ipfw_log() ...
* ... and use twice as many bytes to implement keepalives
(this seems to be working, but i have not tested it extensively).
Keepalives are generated once every 5 seconds for the last 20 seconds
of the lifetime of a dynamic rule for an established TCP flow. The
packets are sent to both sides, so if at least one of the endpoints
is responding, the timeout is refreshed and the rule will not expire.
You can disable this feature with
sysctl net.inet.ip.fw.dyn_keepalive=0
(the default is 1, to have them enabled).
MFC after: 1 day
(just kidding... I will supply an updated version of ipfw2 for
RELENG_4 tomorrow).
now it should support all the instructions of the old ipfw.
Fix some bugs in the user interface, /sbin/ipfw.
Please check this code against your rulesets, so i can fix the
remaining bugs (if any, i think they will be mostly in /sbin/ipfw).
Once we have done a bit of testing, this code is ready to be MFC'ed,
together with a bunch of other changes (glue to ipfw, and also the
removal of some global variables) which have been in -current for
a couple of weeks now.
MFC after: 7 days
This code makes use of variable-size kernel representation of rules
(exactly the same concept of BPF instructions, as used in the BSDI's
firewall), which makes firewall operation a lot faster, and the
code more readable and easier to extend and debug.
The interface with the rest of the system is unchanged, as witnessed
by this commit. The only extra kernel files that I am touching
are if_fw.h and ip_dummynet.c, which is quite tied to ipfw. In
userland I only had to touch those programs which manipulate the
internal representation of firewall rules).
The code is almost entirely new (and I believe I have written the
vast majority of those sections which were taken from the former
ip_fw.c), so rather than modifying the old ip_fw.c I decided to
create a new file, sys/netinet/ip_fw2.c . Same for the user
interface, which is in sbin/ipfw/ipfw2.c (it still compiles to
/sbin/ipfw). The old files are still there, and will be removed
in due time.
I have not renamed the header file because it would have required
touching a one-line change to a number of kernel files.
In terms of user interface, the new "ipfw" is supposed to accepts
the old syntax for ipfw rules (and produce the same output with
"ipfw show". Only a couple of the old options (out of some 30 of
them) has not been implemented, but they will be soon.
On the other hand, the new code has some very powerful extensions.
First, you can put "or" connectives between match fields (and soon
also between options), and write things like
ipfw add allow ip from { 1.2.3.4/27 or 5.6.7.8/30 } 10-23,25,1024-3000 to any
This should make rulesets slightly more compact (and lines longer!),
by condensing 2 or more of the old rules into single ones.
Also, as an example of how easy the rules can be extended, I have
implemented an 'address set' match pattern, where you can specify
an IP address in a format like this:
10.20.30.0/26{18,44,33,22,9}
which will match the set of hosts listed in braces belonging to the
subnet 10.20.30.0/26 . The match is done using a bitmap, so it is
essentially a constant time operation requiring a handful of CPU
instructions (and a very small amount of memmory -- for a full /24
subnet, the instruction only consumes 40 bytes).
Again, in this commit I have focused on functionality and tried
to minimize changes to the other parts of the system. Some performance
improvement can be achieved with minor changes to the interface of
ip_fw_chk_t. This will be done later when this code is settled.
The code is meant to compile unmodified on RELENG_4 (once the
PACKET_TAG_* changes have been merged), for this reason
you will see #ifdef __FreeBSD_version in a couple of places.
This should minimize errors when (hopefully soon) it will be time
to do the MFC.
packet forwarding state ("annotations") during ip processing.
The code is considerably cleaner now.
The variables removed by this change are:
ip_divert_cookie used by divert sockets
ip_fw_fwd_addr used for transparent ip redirection
last_pkt used by dynamic pipes in dummynet
Removal of the first two has been done by carrying the annotations
into volatile structs prepended to the mbuf chains, and adding
appropriate code to add/remove annotations in the routines which
make use of them, i.e. ip_input(), ip_output(), tcp_input(),
bdg_forward(), ether_demux(), ether_output_frame(), div_output().
On passing, remove a bug in divert handling of fragmented packet.
Now it is the fragment at offset 0 which sets the divert status of
the whole packet, whereas formerly it was the last incoming fragment
to decide.
Removal of last_pkt required a change in the interface of ip_fw_chk()
and dummynet_io(). On passing, use the same mechanism for dummynet
annotations and for divert/forward annotations.
option IPFIREWALL_FORWARD is effectively useless, the code to
implement it is very small and is now in by default to avoid the
obfuscation of conditionally compiled code.
NOTES:
* there is at least one global variable left, sro_fwd, in ip_output().
I am not sure if/how this can be removed.
* I have deliberately avoided gratuitous style changes in this commit
to avoid cluttering the diffs. Minor stule cleanup will likely be
necessary
* this commit only focused on the IP layer. I am sure there is a
number of global variables used in the TCP and maybe UDP stack.
* despite the number of files touched, there are absolutely no API's
or data structures changed by this commit (except the interfaces of
ip_fw_chk() and dummynet_io(), which are internal anyways), so
an MFC is quite safe and unintrusive (and desirable, given the
improved readability of the code).
MFC after: 10 days
were totally useless and have been removed.
ip_input.c, ip_output.c:
Properly initialize the "ip" pointer in case the firewall does an
m_pullup() on the packet.
Remove some debugging code forgotten long ago.
ip_fw.[ch], bridge.c:
Prepare the grounds for matching MAC header fields in bridged packets,
so we can have 'etherfw' functionality without a lot of kernel and
userland bloat.
+ implement "limit" rules, which permit to limit the number of sessions
between certain host pairs (according to masks). These are a special
type of stateful rules, which might be of interest in some cases.
See the ipfw manpage for details.
+ merge the list pointers and ipfw rule descriptors in the kernel, so
the code is smaller, faster and more readable. This patch basically
consists in replacing "foo->rule->bar" with "rule->bar" all over
the place.
I have been willing to do this for ages!
MFC after: 1 week
and speed. No new functionality added (yet) apart from a bugfix.
MFC will occur in due time and probably in stages.
BUGFIX: fix a problem in old code which prevented reallocation of
the hash table for dynamic rules (there is a PR on this).
OTHER CHANGES: minor changes to the internal struct for static and dynamic rules.
Requires rebuild of ipfw binary.
Add comments to show how data structures are linked together.
(It probably makes no sense to keep the chain pointers separate
from actual rule descriptors. They will be hopefully merged soon.
keep a (sysctl-readable) counter for the number of static rules,
to speed up IP_FW_GET operations
initial support for a "grace time" for expired connections, so we
can set timeouts for closing connections to much shorter times.
merge zero_entry() and resetlog_entry(), they use basically the
same code.
clean up and reduce replication of code for removing rules,
both for readability and code size.
introduce a separate lifetime for dynamic UDP rules.
fix a problem in old code which prevented reallocation of
the hash table for dynamic rules (PR ...)
restructure dynamic rule descriptors
introduce some local variables to avoid multiple dereferencing of
pointer chains (reduces code size and hopefully increases speed).
address is configured on a interface. This is useful for routers with
dynamic interfaces. It is now possible to say:
0100 allow tcp from any to any established
0200 skipto 1000 tcp from any to any
0300 allow ip from any to any
1000 allow tcp from 1.2.3.4 to me 22
1010 deny tcp from any to me 22
1020 allow tcp from any to any
and not have to worry about the behaviour if dynamic interfaces configure
new IP numbers later on.
The check is semi expensive (traverses the interface address list)
so it should be protected as in the above example if high performance
is a requirement.
reserved and now allocated TCP flags in incoming packets. This patch
stops overloading those bits in the IP firewall rules, and moves
colliding flags to a seperate field, ipflg. The IPFW userland
management tool, ipfw(8), is updated to reflect this change. New TCP
flags related to ECN are now included in tcp.h for reference, although
we don't currently implement TCP+ECN.
o To use this fix without completely rebuilding, it is sufficient to copy
ip_fw.h and tcp.h into your appropriate include directory, then rebuild
the ipfw kernel module, and ipfw tool, and install both. Note that a
mismatch between module and userland tool will result in incorrect
installation of firewall rules that may have unexpected effects. This
is an MFC candidate, following shakedown. This bug does not appear
to affect ipfilter.
Reviewed by: security-officer, billf
Reported by: Aragon Gouveia <aragon@phat.za.net>
It also squashes 99% of packet kiddie synflood orgies. For example, to
rate syn packets without MSS,
ipfw pipe 10 config 56Kbit/s queue 10Packets
ipfw add pipe 10 tcp from any to any in setup tcpoptions !mss
Submitted by: Richard A. Steenbergen <ras@e-gerbil.net>
is an application space macro and the applications are supposed to be free
to use it as they please (but cannot). This is consistant with the other
BSD's who made this change quite some time ago. More commits to come.
- Implement 'ipfw tee' (finally)
- Divert packets by calling new function divert_packet() directly instead
of going through protosw[].
- Replace kludgey global variable 'ip_divert_port' with a function parameter
to divert_packet()
- Replace kludgey global variable 'frag_divert_port' with a function parameter
to ip_reass()
- style(9) fixes
Reviewed by: julian, green
with a match probability to achieve non-deterministic behaviour of
the firewall. This can be extremely useful for testing purposes
such as simulating random packet drop without having to use dummynet
(which already does the same thing), and simulating multipath effects
and the associated out-of-order delivery (this time in conjunction
with dummynet).
The overhead on normal rules is just one comparison with 0.
Since it would have been trivial to implement this by just adding
a field to the ip_fw structure, I decided to do it in a
backward-compatible way (i.e. struct ip_fw is unchanged, and as a
consequence you don't need to recompile ipfw if you don't want to
use this feature), since this was also useful for -STABLE.
When, at some point, someone decides to change struct ip_fw, please
add a length field and a version number at the beginning, so userland
apps can keep working even if they are out of sync with the kernel.
_or_ you may specify "log logamount number" to set logging specifically
the rule.
In addition, "ipfw resetlog" has been added, which will reset the
logging counters on any/all rule(s). ipfw resetlog does not affect
the packet/byte counters (as ipfw reset does), and is the only "set"
command that can be run at securelevel >= 3.
This should address complaints about not being able to set logging
amounts, not being able to restart logging at a high securelevel,
and not being able to just reset logging without resetting all of the
counters in a rule.
- unifdef -DCOMPAT_IPFW (this was on by default already)
- remove traces of in-kernel ip_nat package, it was never committed.
- Make IPFW and DUMMYNET initialize themselves rather than depend on
compiled-in hooks in ip_init(). This means they initialize the same
way both in-kernel and as kld modules. (IPFW initializes now :-)
another specialized mbuf type in the process. Also clean up some
of the cruft surrounding IPFW, multicast routing, RSVP, and other
ill-explored corners.
Any packet that can be matched by a ipfw rule can be redirected
transparently to another port or machine. Redirection to another port
mostly makes sense with tcp, where a session can be set up
between a proxy and an unsuspecting client. Redirection to another machine
requires that the other machine also be expecting to receive the forwarded
packets, as their headers will not have been modified.
/sbin/ipfw must be recompiled!!!
Reviewed by: Peter Wemm <peter@freebsd.org>
Submitted by: Chrisy Luke <chrisy@flix.net>
consequence, ipfw's list command now adjusts its output at runtime
based on the largest packet/byte counter values.
NOTE:
o The ipfw struct has changed requiring a recompile of both kernel
and userland ipfw utility.
o This probably should not be brought into 2.2.
PR: 3738
accommodate the expanded name, the ICMP types bitmap has been
reduced from 256 bits to 32.
A recompile of kernel and user level ipfw is required.
To be merged into 2.2 after a brief period in -current.
PR: bin/4209
Reviewed by: Archie Cobbs <archie@whistle.com>
these are quite extensive additions to the ipfw code.
they include a change to the API because the old method was
broken, but the user view is kept the same.
The new code allows a particular match to skip forward to a particular
line number, so that blocks of rules can be
used without checking all the intervening rules.
There are also many more ways of rejecting
connections especially TCP related, and
many many more ...
see the man page for a complete description.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
This stuff should not be too destructive if the IPDIVERT is not compiled in..
be aware that this changes the size of the ip_fw struct
so ipfw needs to be recompiled to use it.. more changes coming to clean this up.
- Log ICMP type during verbose output.
- Added IPFIREWALL_VERBOSE_LIMIT option to prevent denial of service
attacks via syslog flooding.
- Filter based on ICMP type.
- Timestamp chain entries when they are matched.
- Interfaces can now be matched with a wildcard specification (i.e.
will match any interface unit for a given name).
- Prevent the firewall chain from being manipulated when securelevel
is greater than 2.
- Fixed bug that allowed the default policy to be deleted.
- Ability to zero individual accounting entries.
- Remove definitions of old_chk_ptr and old_ctl_ptr when compiling
ipfw as a lkm.
- Remove some redundant code shared between ip_fw_init and ipfw_load.
Closes PRs: 1192, 1219, and 1267.
Close the ip-fragment hole.
Waste less memory.
Rewrite to contemporary more readable style.
Kill separate IPACCT facility, use "accept" rules in IPFIREWALL.
Filter incoming >and< outgoing packets.
Replace "policy" by sticky "deny all" rule.
Rules have numbers used for ordering and deletion.
Remove "rerorder" code entirely.
Count packet & bytecount matches for rules.
Code in -current & -stable is now the same.
matching IP options..Check and test this - i made only a couple
of rough tests and this could be buggy.. Ipaccounting can't use
IP Options (and i don't see any need to cound packets with specific
options either..)
More to come...
1) Firewall is not subdivided on forwarding / blocking chains
anymore.Actually only one chain left-it was the blocking one.
2) LKM support.ip_fwdef.c is function pointers definition and
goes into kernel along with all INET stuff.
