1 [[!meta title="IPFW2 Documentation"]]
2 [[!meta robots="index, follow"]]
15 IPFW is a controlling utility for ipfw/ipacct facilities for FreeBSD 2.0 which released in November, 1994. After 20 years of evolution. it becomes a stateful firewall which supports Layer2 to Layer4. It is comprised of several components: the kernel firewall filter rule processor and its integrated packet accounting facility, the logging facility, NAT, the dummynet(4) traffic shaper, a forward facility, a bridge facility, and an ipstealth facility. It is one of the most advanced opensource firewall.
17 I am rewriting IPFW2 from scratch for DragonflyBSD, and IPFW2 will be in modular design. all the functionality are originally from loadable modules and should be not that difficult for normal users/developer to create a module in order to their own requirement.
18 ## Brief notes on design
19 Before user start to use the ipfw utility to add rules, the ipfw kernel should be enable/loaded into the kernel. by running below command
23 the basic ipfw module will be loaded into kernel, also the basic functionalities. in order to user more function which is implemented in other modules, users can run below command
27 so the 'layer2' module will be loaded, for example in this scenario, user can start to fire below command
29 ipfw add allow all from any to any layer2
31 it means user want to add add rule which allow all the layer2 traffic. when user fire the command in the console, actually in the back-end, it will do below things.
33 1. ipfw retrieve the module name list from the kernel
34 2. ipfw load the module accordingly
35 3. ipfw start to parse the parameters
36 4. inject into the kernel
38 In the kernel space, when the traffic comes, it will filter again the rule, in each ipfw_insn has unique module + opcode. it will automatically link to the filter function which will be registered during the module was loaded.
40 ## Compare with FreeBSD's ipfw
41 Comparing to the IPFW from FreeBSD,this IPFW for DragonflyBSD is:
43 **Much more extensible**
45 Every feature/function needs to be identified by an ID, but there are only 8bits space to store the ID, so theoretically it can support 256 features/functions in maximum.
47 In this IPFW for DragonflyBSD, the space for ID are the same, so also 8bits, but one space for each module and it has 8bits for module ID, so so theoretically it can have 256 modules and 256 features/functions in each module, so 256*256 feature/functions in maximum.
51 In this IPFW for DragonflyBSD, the rules are much more concise. for example, the simple rule command like "ipfw add allow ip from any to any". the "from any to any" actually is just try to make the rule more readable. but actually "ipfw add allow ip" is much more concise. and another example "ipfw add allow ip from 1.1.1.1 to any" cannot be better than "ipfw add allow from 1.1.1.1". because "from any " and "to any" are actually useless.
53 **Much more flexible**
55 It supports concise mode and full mode which is same as IPFW in FreeBSD in user angle of view.
60 Modules are loadable,and every module comes with a kernel part and userspace part. the kernel part need to be loaded manually, and the userpsace part can be loaded automatically when user fires the ipfw command.
62 When the ipfw module was loaded, it comes with 2 opcodes in order to support the default behavior of the ipfw. so below 2 opcodes are embeded in the ipfw.ko
65 by fire command `kldload ipfw', the default module is loaded. and all other modules are relying on this module.
67 Basic Module contains all the basic features. it has multiple opcodes list below.
95 ## How to create a module