By avalon on Jan 17, 2007
So i've been implementing some new features in ipfilter, whether or not they make it a 5.0, I'm not sure...maybe a few people can let me know what they think about that..
So what are these new features?
There are 3 new commands for ipnat.conf:
- rewrite - change both source and address fields for incoming or outgoing packets
- encap - encapsulated the packet in a new IP header (this will be compatible, I hope, with IPENCAP tunnels elsewhere0
- divert - encapsulate the packet into an IP+UDP packet
To help people use these, I've rewritten the ipnat.conf man page.
A divert rule looks like this:
divert in on le0 proto udp from any to any port = 53 -> src 127.0.0.1,54 dst 127.0.0.1,5300;
note the ";" on the end of the line. To the left of the "->" is the original packet to be matched, on the right, the IP/UDP header to create and put in front of the packet. Reply packets from that socket will have the IP+UDP headers removed when they get back to IPFilter. I'm hoping this will provide cross-platform "divert" functionality but it needs more widespread testing than what I've been able to achieve.
encap is pretty much the same as divert, minus the port numbers to the right of "->".
Rewrites have a subset of the combined functionality of rdr/map rules. As an example of how the man page has been rewritten, I've included the contents of it for this new command below.
You can now use ipmon.conf to as the place to specify how log records are sent to syslog (facility & priority) rather than needing to do it in filter rules.
As part of the "keep state" options, you can now specify a rule group to which ICMP replies can be filtered by - "... keep state(icmp-head icmprules)"
It is also now possible to position stateful filtering checks, inbound and outbound nat lookups. If this is done, the traditional checks are no longer performed. This is done as follows:
call now fr_checkstate in on le0 from any to any call now fr_ipfnatin in on ppp0 all call now fr_ipfnatout out on bge0 from bge0/32 to any
Oh, being 5.0.0, it is a development version, there's nothing release quality about it (well, you might argue that for others too .. >:->), this is just to get some feedback from people on features and enable some people to try/test a few things out beyond my limited scope. Perhaps most importantly, most of my work to date has been limited to using NetBSD.
It can be downloaded from ip_fil5.0.0.tar.gz. MD5 (/home/darrenr/ip_fil5.0.0.tar.gz) = 7798797c1929cb55c182d3088f40b0b5
REWRITING SOURCE AND DESTINATION Whilst the above two commands provide a lot of flexibility in changing addressing fields in packets, often it can be of benefit to translate both source and destination at the same time or to change the source address on input or the destination address on output. Doing all of these things can be accomplished using rewrite NAT rules. A rewrite rule requires the same level of packet matching as before, protocol and source/destination information but in addition allows either in or out to be specified like this: rewrite in on ppp0 proto tcp from any to any port = 80 -> src 0/0 dst 127.0.0.1,3128; rewrite out on ppp0 from any to any -> src 0/32 dst 10.1.1.0/24; On the RHS we can specify both new source and destination information to place into the packet being sent out. As with other rules used in ipnat.conf, there are shortcuts syntaxes available to use the original address information (0/0) and the address associated with the network interface (0/32.) For TCP and UDP, both address and port information can be changed. At present it is only possible to specify either a range of port numbers to be used (X-Y) or a single port number (=X) as follows: rewrite in on le0 proto tcp from any to any port = 80 -> src 0/0,2000-20000 dst 127.0.0.1,port = 3128; There are four fields that are stepped through in enumerating the num- ber space available for creating a new destination: source address source port destination address destination port If one of these happens to be a static then it will be skipped and the next one incremented. As an example: rewrite out on le0 proto tcp from any to any port = 80 -> src 188.8.131.52/8,5000-5999 dst 184.108.40.206/24,6000-6999; The translated packets would be: 1st src=220.127.116.11,5000 dst=18.104.22.168,6000 2nd src=22.214.171.124,5000 dst=126.96.36.199,6000 3rd src=188.8.131.52,5001 dst=184.108.40.206,6000 4th src=220.127.116.11,5001 dst=18.104.22.168,6000 5th src=22.214.171.124,5001 dst=126.96.36.199,6001 6th src=188.8.131.52,5001 dst=184.108.40.206,6001 and so on. As with map rules, it is possible to specify a range of addresses by including the word range before the addresses: rewrite from any to any port = 80 -> src 220.127.116.11 - 18.104.22.168 dst 22.214.171.124 - 126.96.36.199;