firewall logging on and off when at elevated securelevel(8). It would
be nice to be able to only lock these at securelevel >= 3, like rules
are, but there is no such functionality at present. I don't see reason
to be adding features to securelevel(8) with MAC being merged into 5.0.
PR: kern/39396
Reviewed by: luigi
MFC after: 1 week
Implement the M_SKIP_FIREWALL bit in m_flags to avoid loops
for firewall-generated packets (the constant has to go in sys/mbuf.h).
Better comments on keepalive generation, and enforce dyn_rst_lifetime
and dyn_fin_lifetime to be less than dyn_keepalive_period.
Enforce limits (up to 64k) on the number of dynamic buckets, and
retry allocation with smaller sizes.
Raise default number of dynamic rules to 4096.
Improved handling of set of rules -- now you can atomically
enable/disable multiple sets, move rules from one set to another,
and swap sets.
sbin/ipfw/ipfw2.c:
userland support for "noerror" pipe attribute.
userland support for sets of rules.
minor improvements on rule parsing and printing.
sbin/ipfw/ipfw.8:
more documentation on ipfw2 extensions, differences from ipfw1
(so we can use the same manpage for both), stateful rules,
and some additional examples.
Feedback and more examples needed here.
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).
Following Darren's suggestion, make Dijkstra happy and rewrite the
ipfw_chk() main loop removing a lot of goto's and using instead a
variable to store match status.
Add a lot of comments to explain what instructions are supposed to
do and how -- this should ease auditing of the code and make people
more confident with it.
In terms of code size: the entire file takes about 12700 bytes of text,
about 3K of which are for the main function, ipfw_chk(), and 2K (ouch!)
for ipfw_log().
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.
