1.\" 2.\" $FreeBSD$ 3.\" 4.Dd July 27, 2010 5.Dt IPFW 8 6.Os 7.Sh NAME 8.Nm ipfw 9.Nd User interface for firewall, traffic shaper, packet scheduler, 10in-kernel NAT. 11.Sh SYNOPSIS 12.Ss FIREWALL CONFIGURATION 13.Nm 14.Op Fl cq 15.Cm add 16.Ar rule 17.Nm 18.Op Fl acdefnNStT 19.Op Cm set Ar N 20.Brq Cm list | show 21.Op Ar rule | first-last ... 22.Nm 23.Op Fl f | q 24.Op Cm set Ar N 25.Cm flush 26.Nm 27.Op Fl q 28.Op Cm set Ar N 29.Brq Cm delete | zero | resetlog 30.Op Ar number ... 31.Pp 32.Nm 33.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 34.Nm 35.Cm set move 36.Op Cm rule 37.Ar number Cm to Ar number 38.Nm 39.Cm set swap Ar number number 40.Nm 41.Cm set show 42.Ss SYSCTL SHORTCUTS 43.Pp 44.Nm 45.Cm enable 46.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 47.Nm 48.Cm disable 49.Brq Cm firewall | altq | one_pass | debug | verbose | dyn_keepalive 50.Pp 51.Ss LOOKUP TABLES 52.Nm 53.Cm table Ar number Cm add Ar addr Ns Oo / Ns Ar masklen Oc Op Ar value 54.Nm 55.Cm table Ar number Cm delete Ar addr Ns Op / Ns Ar masklen 56.Nm 57.Cm table 58.Brq Ar number | all 59.Cm flush 60.Nm 61.Cm table 62.Brq Ar number | all 63.Cm list 64.Pp 65.Ss DUMMYNET CONFIGURATION (TRAFFIC SHAPER AND PACKET SCHEDULER) 66.Nm 67.Brq Cm pipe | queue | sched 68.Ar number 69.Cm config 70.Ar config-options 71.Nm 72.Op Fl s Op Ar field 73.Brq Cm pipe | queue | sched 74.Brq Cm delete | list | show 75.Op Ar number ... 76.Pp 77.Ss IN-KERNEL NAT 78.Nm 79.Op Fl q 80.Cm nat 81.Ar number 82.Cm config 83.Ar config-options 84.Pp 85.Nm 86.Op Fl cfnNqS 87.Oo 88.Fl p Ar preproc 89.Oo 90.Ar preproc-flags 91.Oc 92.Oc 93.Ar pathname 94.Sh DESCRIPTION 95The 96.Nm 97utility is the user interface for controlling the 98.Xr ipfw 4 99firewall, the 100.Xr dummynet 4 101traffic shaper/packet scheduler, and the 102in-kernel NAT services. 103.Pp 104A firewall configuration, or 105.Em ruleset , 106is made of a list of 107.Em rules 108numbered from 1 to 65535. 109Packets are passed to the firewall 110from a number of different places in the protocol stack 111(depending on the source and destination of the packet, 112it is possible for the firewall to be 113invoked multiple times on the same packet). 114The packet passed to the firewall is compared 115against each of the rules in the 116.Em ruleset , 117in rule-number order 118(multiple rules with the same number are permitted, in which case 119they are processed in order of insertion). 120When a match is found, the action corresponding to the 121matching rule is performed. 122.Pp 123Depending on the action and certain system settings, packets 124can be reinjected into the firewall at some rule after the 125matching one for further processing. 126.Pp 127A ruleset always includes a 128.Em default 129rule (numbered 65535) which cannot be modified or deleted, 130and matches all packets. 131The action associated with the 132.Em default 133rule can be either 134.Cm deny 135or 136.Cm allow 137depending on how the kernel is configured. 138.Pp 139If the ruleset includes one or more rules with the 140.Cm keep-state 141or 142.Cm limit 143option, 144the firewall will have a 145.Em stateful 146behaviour, i.e., upon a match it will create 147.Em dynamic rules , 148i.e. rules that match packets with the same 5-tuple 149(protocol, source and destination addresses and ports) 150as the packet which caused their creation. 151Dynamic rules, which have a limited lifetime, are checked 152at the first occurrence of a 153.Cm check-state , 154.Cm keep-state 155or 156.Cm limit 157rule, and are typically used to open the firewall on-demand to 158legitimate traffic only. 159See the 160.Sx STATEFUL FIREWALL 161and 162.Sx EXAMPLES 163Sections below for more information on the stateful behaviour of 164.Nm . 165.Pp 166All rules (including dynamic ones) have a few associated counters: 167a packet count, a byte count, a log count and a timestamp 168indicating the time of the last match. 169Counters can be displayed or reset with 170.Nm 171commands. 172.Pp 173Each rule belongs to one of 32 different 174.Em sets 175, and there are 176.Nm 177commands to atomically manipulate sets, such as enable, 178disable, swap sets, move all rules in a set to another 179one, delete all rules in a set. 180These can be useful to 181install temporary configurations, or to test them. 182See Section 183.Sx SETS OF RULES 184for more information on 185.Em sets . 186.Pp 187Rules can be added with the 188.Cm add 189command; deleted individually or in groups with the 190.Cm delete 191command, and globally (except those in set 31) with the 192.Cm flush 193command; displayed, optionally with the content of the 194counters, using the 195.Cm show 196and 197.Cm list 198commands. 199Finally, counters can be reset with the 200.Cm zero 201and 202.Cm resetlog 203commands. 204.Pp 205.Ss COMMAND OPTIONS 206The following general options are available when invoking 207.Nm : 208.Bl -tag -width indent 209.It Fl a 210Show counter values when listing rules. 211The 212.Cm show 213command implies this option. 214.It Fl b 215Only show the action and the comment, not the body of a rule. 216Implies 217.Fl c . 218.It Fl c 219When entering or showing rules, print them in compact form, 220i.e., omitting the "ip from any to any" string 221when this does not carry any additional information. 222.It Fl d 223When listing, show dynamic rules in addition to static ones. 224.It Fl e 225When listing and 226.Fl d 227is specified, also show expired dynamic rules. 228.It Fl f 229Do not ask for confirmation for commands that can cause problems 230if misused, 231.No i.e. Cm flush . 232If there is no tty associated with the process, this is implied. 233.It Fl i 234When listing a table (see the 235.Sx LOOKUP TABLES 236section below for more information on lookup tables), format values 237as IP addresses. By default, values are shown as integers. 238.It Fl n 239Only check syntax of the command strings, without actually passing 240them to the kernel. 241.It Fl N 242Try to resolve addresses and service names in output. 243.It Fl q 244Be quiet when executing the 245.Cm add , 246.Cm nat , 247.Cm zero , 248.Cm resetlog 249or 250.Cm flush 251commands; 252(implies 253.Fl f ) . 254This is useful when updating rulesets by executing multiple 255.Nm 256commands in a script 257(e.g., 258.Ql sh\ /etc/rc.firewall ) , 259or by processing a file with many 260.Nm 261rules across a remote login session. 262It also stops a table add or delete 263from failing if the entry already exists or is not present. 264.Pp 265The reason why this option may be important is that 266for some of these actions, 267.Nm 268may print a message; if the action results in blocking the 269traffic to the remote client, 270the remote login session will be closed 271and the rest of the ruleset will not be processed. 272Access to the console would then be required to recover. 273.It Fl S 274When listing rules, show the 275.Em set 276each rule belongs to. 277If this flag is not specified, disabled rules will not be 278listed. 279.It Fl s Op Ar field 280When listing pipes, sort according to one of the four 281counters (total or current packets or bytes). 282.It Fl t 283When listing, show last match timestamp converted with ctime(). 284.It Fl T 285When listing, show last match timestamp as seconds from the epoch. 286This form can be more convenient for postprocessing by scripts. 287.El 288.Pp 289.Ss LIST OF RULES AND PREPROCESSING 290To ease configuration, rules can be put into a file which is 291processed using 292.Nm 293as shown in the last synopsis line. 294An absolute 295.Ar pathname 296must be used. 297The file will be read line by line and applied as arguments to the 298.Nm 299utility. 300.Pp 301Optionally, a preprocessor can be specified using 302.Fl p Ar preproc 303where 304.Ar pathname 305is to be piped through. 306Useful preprocessors include 307.Xr cpp 1 308and 309.Xr m4 1 . 310If 311.Ar preproc 312does not start with a slash 313.Pq Ql / 314as its first character, the usual 315.Ev PATH 316name search is performed. 317Care should be taken with this in environments where not all 318file systems are mounted (yet) by the time 319.Nm 320is being run (e.g.\& when they are mounted over NFS). 321Once 322.Fl p 323has been specified, any additional arguments are passed on to the preprocessor 324for interpretation. 325This allows for flexible configuration files (like conditionalizing 326them on the local hostname) and the use of macros to centralize 327frequently required arguments like IP addresses. 328.Pp 329.Ss TRAFFIC SHAPER CONFIGURATION 330The 331.Nm 332.Cm pipe , queue 333and 334.Cm sched 335commands are used to configure the traffic shaper and packet scheduler. 336See the 337.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 338Section below for details. 339.Pp 340If the world and the kernel get out of sync the 341.Nm 342ABI may break, preventing you from being able to add any rules. 343This can 344adversely effect the booting process. 345You can use 346.Nm 347.Cm disable 348.Cm firewall 349to temporarily disable the firewall to regain access to the network, 350allowing you to fix the problem. 351.Sh PACKET FLOW 352A packet is checked against the active ruleset in multiple places 353in the protocol stack, under control of several sysctl variables. 354These places and variables are shown below, and it is important to 355have this picture in mind in order to design a correct ruleset. 356.Bd -literal -offset indent 357 ^ to upper layers V 358 | | 359 +----------->-----------+ 360 ^ V 361 [ip(6)_input] [ip(6)_output] net.inet(6).ip(6).fw.enable=1 362 | | 363 ^ V 364 [ether_demux] [ether_output_frame] net.link.ether.ipfw=1 365 | | 366 +-->--[bdg_forward]-->--+ net.link.bridge.ipfw=1 367 ^ V 368 | to devices | 369.Ed 370.Pp 371The number of 372times the same packet goes through the firewall can 373vary between 0 and 4 depending on packet source and 374destination, and system configuration. 375.Pp 376Note that as packets flow through the stack, headers can be 377stripped or added to it, and so they may or may not be available 378for inspection. 379E.g., incoming packets will include the MAC header when 380.Nm 381is invoked from 382.Cm ether_demux() , 383but the same packets will have the MAC header stripped off when 384.Nm 385is invoked from 386.Cm ip_input() 387or 388.Cm ip6_input() . 389.Pp 390Also note that each packet is always checked against the complete ruleset, 391irrespective of the place where the check occurs, or the source of the packet. 392If a rule contains some match patterns or actions which are not valid 393for the place of invocation (e.g.\& trying to match a MAC header within 394.Cm ip_input 395or 396.Cm ip6_input ), 397the match pattern will not match, but a 398.Cm not 399operator in front of such patterns 400.Em will 401cause the pattern to 402.Em always 403match on those packets. 404It is thus the responsibility of 405the programmer, if necessary, to write a suitable ruleset to 406differentiate among the possible places. 407.Cm skipto 408rules can be useful here, as an example: 409.Bd -literal -offset indent 410# packets from ether_demux or bdg_forward 411ipfw add 10 skipto 1000 all from any to any layer2 in 412# packets from ip_input 413ipfw add 10 skipto 2000 all from any to any not layer2 in 414# packets from ip_output 415ipfw add 10 skipto 3000 all from any to any not layer2 out 416# packets from ether_output_frame 417ipfw add 10 skipto 4000 all from any to any layer2 out 418.Ed 419.Pp 420(yes, at the moment there is no way to differentiate between 421ether_demux and bdg_forward). 422.Sh SYNTAX 423In general, each keyword or argument must be provided as 424a separate command line argument, with no leading or trailing 425spaces. 426Keywords are case-sensitive, whereas arguments may 427or may not be case-sensitive depending on their nature 428(e.g.\& uid's are, hostnames are not). 429.Pp 430Some arguments (e.g. port or address lists) are comma-separated 431lists of values. 432In this case, spaces after commas ',' are allowed to make 433the line more readable. 434You can also put the entire 435command (including flags) into a single argument. 436E.g., the following forms are equivalent: 437.Bd -literal -offset indent 438ipfw -q add deny src-ip 10.0.0.0/24,127.0.0.1/8 439ipfw -q add deny src-ip 10.0.0.0/24, 127.0.0.1/8 440ipfw "-q add deny src-ip 10.0.0.0/24, 127.0.0.1/8" 441.Ed 442.Sh RULE FORMAT 443The format of firewall rules is the following: 444.Bd -ragged -offset indent 445.Bk -words 446.Op Ar rule_number 447.Op Cm set Ar set_number 448.Op Cm prob Ar match_probability 449.Ar action 450.Op Cm log Op Cm logamount Ar number 451.Op Cm altq Ar queue 452.Oo 453.Bro Cm tag | untag 454.Brc Ar number 455.Oc 456.Ar body 457.Ek 458.Ed 459.Pp 460where the body of the rule specifies which information is used 461for filtering packets, among the following: 462.Pp 463.Bl -tag -width "Source and dest. addresses and ports" -offset XXX -compact 464.It Layer-2 header fields 465When available 466.It IPv4 and IPv6 Protocol 467TCP, UDP, ICMP, etc. 468.It Source and dest. addresses and ports 469.It Direction 470See Section 471.Sx PACKET FLOW 472.It Transmit and receive interface 473By name or address 474.It Misc. IP header fields 475Version, type of service, datagram length, identification, 476fragment flag (non-zero IP offset), 477Time To Live 478.It IP options 479.It IPv6 Extension headers 480Fragmentation, Hop-by-Hop options, 481Routing Headers, Source routing rthdr0, Mobile IPv6 rthdr2, IPSec options. 482.It IPv6 Flow-ID 483.It Misc. TCP header fields 484TCP flags (SYN, FIN, ACK, RST, etc.), 485sequence number, acknowledgment number, 486window 487.It TCP options 488.It ICMP types 489for ICMP packets 490.It ICMP6 types 491for ICMP6 packets 492.It User/group ID 493When the packet can be associated with a local socket. 494.It Divert status 495Whether a packet came from a divert socket (e.g., 496.Xr natd 8 ) . 497.It Fib annotation state 498Whether a packet has been tagged for using a specific FIB (routing table) 499in future forwarding decisions. 500.El 501.Pp 502Note that some of the above information, e.g.\& source MAC or IP addresses and 503TCP/UDP ports, can be easily spoofed, so filtering on those fields 504alone might not guarantee the desired results. 505.Bl -tag -width indent 506.It Ar rule_number 507Each rule is associated with a 508.Ar rule_number 509in the range 1..65535, with the latter reserved for the 510.Em default 511rule. 512Rules are checked sequentially by rule number. 513Multiple rules can have the same number, in which case they are 514checked (and listed) according to the order in which they have 515been added. 516If a rule is entered without specifying a number, the kernel will 517assign one in such a way that the rule becomes the last one 518before the 519.Em default 520rule. 521Automatic rule numbers are assigned by incrementing the last 522non-default rule number by the value of the sysctl variable 523.Ar net.inet.ip.fw.autoinc_step 524which defaults to 100. 525If this is not possible (e.g.\& because we would go beyond the 526maximum allowed rule number), the number of the last 527non-default value is used instead. 528.It Cm set Ar set_number 529Each rule is associated with a 530.Ar set_number 531in the range 0..31. 532Sets can be individually disabled and enabled, so this parameter 533is of fundamental importance for atomic ruleset manipulation. 534It can be also used to simplify deletion of groups of rules. 535If a rule is entered without specifying a set number, 536set 0 will be used. 537.br 538Set 31 is special in that it cannot be disabled, 539and rules in set 31 are not deleted by the 540.Nm ipfw flush 541command (but you can delete them with the 542.Nm ipfw delete set 31 543command). 544Set 31 is also used for the 545.Em default 546rule. 547.It Cm prob Ar match_probability 548A match is only declared with the specified probability 549(floating point number between 0 and 1). 550This can be useful for a number of applications such as 551random packet drop or 552(in conjunction with 553.Nm dummynet ) 554to simulate the effect of multiple paths leading to out-of-order 555packet delivery. 556.Pp 557Note: this condition is checked before any other condition, including 558ones such as keep-state or check-state which might have side effects. 559.It Cm log Op Cm logamount Ar number 560Packets matching a rule with the 561.Cm log 562keyword will be made available for logging in two ways: 563if the sysctl variable 564.Va net.inet.ip.fw.verbose 565is set to 0 (default), one can use 566.Xr bpf 4 567attached to the 568.Xr ipfw0 569pseudo interface. There is no overhead if no 570.Xr bpf 571is attached to the pseudo interface. 572.Pp 573If 574.Va net.inet.ip.fw.verbose 575is set to 1, packets will be logged to 576.Xr syslogd 8 577with a 578.Dv LOG_SECURITY 579facility up to a maximum of 580.Cm logamount 581packets. 582If no 583.Cm logamount 584is specified, the limit is taken from the sysctl variable 585.Va net.inet.ip.fw.verbose_limit . 586In both cases, a value of 0 means unlimited logging. 587.Pp 588Once the limit is reached, logging can be re-enabled by 589clearing the logging counter or the packet counter for that entry, see the 590.Cm resetlog 591command. 592.Pp 593Note: logging is done after all other packet matching conditions 594have been successfully verified, and before performing the final 595action (accept, deny, etc.) on the packet. 596.It Cm tag Ar number 597When a packet matches a rule with the 598.Cm tag 599keyword, the numeric tag for the given 600.Ar number 601in the range 1..65534 will be attached to the packet. 602The tag acts as an internal marker (it is not sent out over 603the wire) that can be used to identify these packets later on. 604This can be used, for example, to provide trust between interfaces 605and to start doing policy-based filtering. 606A packet can have multiple tags at the same time. 607Tags are "sticky", meaning once a tag is applied to a packet by a 608matching rule it exists until explicit removal. 609Tags are kept with the packet everywhere within the kernel, but are 610lost when packet leaves the kernel, for example, on transmitting 611packet out to the network or sending packet to a 612.Xr divert 4 613socket. 614.Pp 615To check for previously applied tags, use the 616.Cm tagged 617rule option. 618To delete previously applied tag, use the 619.Cm untag 620keyword. 621.Pp 622Note: since tags are kept with the packet everywhere in kernelspace, 623they can be set and unset anywhere in the kernel network subsystem 624(using the 625.Xr mbuf_tags 9 626facility), not only by means of the 627.Xr ipfw 4 628.Cm tag 629and 630.Cm untag 631keywords. 632For example, there can be a specialized 633.Xr netgraph 4 634node doing traffic analyzing and tagging for later inspecting 635in firewall. 636.It Cm untag Ar number 637When a packet matches a rule with the 638.Cm untag 639keyword, the tag with the number 640.Ar number 641is searched among the tags attached to this packet and, 642if found, removed from it. 643Other tags bound to packet, if present, are left untouched. 644.It Cm altq Ar queue 645When a packet matches a rule with the 646.Cm altq 647keyword, the ALTQ identifier for the given 648.Ar queue 649(see 650.Xr altq 4 ) 651will be attached. 652Note that this ALTQ tag is only meaningful for packets going "out" of IPFW, 653and not being rejected or going to divert sockets. 654Note that if there is insufficient memory at the time the packet is 655processed, it will not be tagged, so it is wise to make your ALTQ 656"default" queue policy account for this. 657If multiple 658.Cm altq 659rules match a single packet, only the first one adds the ALTQ classification 660tag. 661In doing so, traffic may be shaped by using 662.Cm count Cm altq Ar queue 663rules for classification early in the ruleset, then later applying 664the filtering decision. 665For example, 666.Cm check-state 667and 668.Cm keep-state 669rules may come later and provide the actual filtering decisions in 670addition to the fallback ALTQ tag. 671.Pp 672You must run 673.Xr pfctl 8 674to set up the queues before IPFW will be able to look them up by name, 675and if the ALTQ disciplines are rearranged, the rules in containing the 676queue identifiers in the kernel will likely have gone stale and need 677to be reloaded. 678Stale queue identifiers will probably result in misclassification. 679.Pp 680All system ALTQ processing can be turned on or off via 681.Nm 682.Cm enable Ar altq 683and 684.Nm 685.Cm disable Ar altq . 686The usage of 687.Va net.inet.ip.fw.one_pass 688is irrelevant to ALTQ traffic shaping, as the actual rule action is followed 689always after adding an ALTQ tag. 690.El 691.Ss RULE ACTIONS 692A rule can be associated with one of the following actions, which 693will be executed when the packet matches the body of the rule. 694.Bl -tag -width indent 695.It Cm allow | accept | pass | permit 696Allow packets that match rule. 697The search terminates. 698.It Cm check-state 699Checks the packet against the dynamic ruleset. 700If a match is found, execute the action associated with 701the rule which generated this dynamic rule, otherwise 702move to the next rule. 703.br 704.Cm Check-state 705rules do not have a body. 706If no 707.Cm check-state 708rule is found, the dynamic ruleset is checked at the first 709.Cm keep-state 710or 711.Cm limit 712rule. 713.It Cm count 714Update counters for all packets that match rule. 715The search continues with the next rule. 716.It Cm deny | drop 717Discard packets that match this rule. 718The search terminates. 719.It Cm divert Ar port 720Divert packets that match this rule to the 721.Xr divert 4 722socket bound to port 723.Ar port . 724The search terminates. 725.It Cm fwd | forward Ar ipaddr | tablearg Ns Op , Ns Ar port 726Change the next-hop on matching packets to 727.Ar ipaddr , 728which can be an IP address or a host name. 729The next hop can also be supplied by the last table 730looked up for the packet by using the 731.Cm tablearg 732keyword instead of an explicit address. 733The search terminates if this rule matches. 734.Pp 735If 736.Ar ipaddr 737is a local address, then matching packets will be forwarded to 738.Ar port 739(or the port number in the packet if one is not specified in the rule) 740on the local machine. 741.br 742If 743.Ar ipaddr 744is not a local address, then the port number 745(if specified) is ignored, and the packet will be 746forwarded to the remote address, using the route as found in 747the local routing table for that IP. 748.br 749A 750.Ar fwd 751rule will not match layer-2 packets (those received 752on ether_input, ether_output, or bridged). 753.br 754The 755.Cm fwd 756action does not change the contents of the packet at all. 757In particular, the destination address remains unmodified, so 758packets forwarded to another system will usually be rejected by that system 759unless there is a matching rule on that system to capture them. 760For packets forwarded locally, 761the local address of the socket will be 762set to the original destination address of the packet. 763This makes the 764.Xr netstat 1 765entry look rather weird but is intended for 766use with transparent proxy servers. 767.Pp 768To enable 769.Cm fwd 770a custom kernel needs to be compiled with the option 771.Cd "options IPFIREWALL_FORWARD" . 772.It Cm nat Ar nat_nr 773Pass packet to a 774nat instance 775(for network address translation, address redirect, etc.): 776see the 777.Sx NETWORK ADDRESS TRANSLATION (NAT) 778Section for further information. 779.It Cm pipe Ar pipe_nr 780Pass packet to a 781.Nm dummynet 782.Dq pipe 783(for bandwidth limitation, delay, etc.). 784See the 785.Sx TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 786Section for further information. 787The search terminates; however, on exit from the pipe and if 788the 789.Xr sysctl 8 790variable 791.Va net.inet.ip.fw.one_pass 792is not set, the packet is passed again to the firewall code 793starting from the next rule. 794.It Cm queue Ar queue_nr 795Pass packet to a 796.Nm dummynet 797.Dq queue 798(for bandwidth limitation using WF2Q+). 799.It Cm reject 800(Deprecated). 801Synonym for 802.Cm unreach host . 803.It Cm reset 804Discard packets that match this rule, and if the 805packet is a TCP packet, try to send a TCP reset (RST) notice. 806The search terminates. 807.It Cm reset6 808Discard packets that match this rule, and if the 809packet is a TCP packet, try to send a TCP reset (RST) notice. 810The search terminates. 811.It Cm skipto Ar number | tablearg 812Skip all subsequent rules numbered less than 813.Ar number . 814The search continues with the first rule numbered 815.Ar number 816or higher. 817It is possible to use the 818.Cm tablearg 819keyword with a skipto for a 820.Em computed 821skipto, but care should be used, as no destination caching 822is possible in this case so the rules are always walked to find it, 823starting from the 824.Cm skipto . 825.It Cm tee Ar port 826Send a copy of packets matching this rule to the 827.Xr divert 4 828socket bound to port 829.Ar port . 830The search continues with the next rule. 831.It Cm unreach Ar code 832Discard packets that match this rule, and try to send an ICMP 833unreachable notice with code 834.Ar code , 835where 836.Ar code 837is a number from 0 to 255, or one of these aliases: 838.Cm net , host , protocol , port , 839.Cm needfrag , srcfail , net-unknown , host-unknown , 840.Cm isolated , net-prohib , host-prohib , tosnet , 841.Cm toshost , filter-prohib , host-precedence 842or 843.Cm precedence-cutoff . 844The search terminates. 845.It Cm unreach6 Ar code 846Discard packets that match this rule, and try to send an ICMPv6 847unreachable notice with code 848.Ar code , 849where 850.Ar code 851is a number from 0, 1, 3 or 4, or one of these aliases: 852.Cm no-route, admin-prohib, address 853or 854.Cm port . 855The search terminates. 856.It Cm netgraph Ar cookie 857Divert packet into netgraph with given 858.Ar cookie . 859The search terminates. 860If packet is later returned from netgraph it is either 861accepted or continues with the next rule, depending on 862.Va net.inet.ip.fw.one_pass 863sysctl variable. 864.It Cm ngtee Ar cookie 865A copy of packet is diverted into netgraph, original 866packet continues with the next rule. 867See 868.Xr ng_ipfw 4 869for more information on 870.Cm netgraph 871and 872.Cm ngtee 873actions. 874.It Cm setfib Ar fibnum 875The packet is tagged so as to use the FIB (routing table) 876.Ar fibnum 877in any subsequent forwarding decisions. 878Initially this is limited to the values 0 through 15, see 879.Xr setfib 1 . 880Processing continues at the next rule. 881.It Cm reass 882Queue and reassemble ip fragments. 883If the packet is not fragmented, counters are updated and processing continues with the next rule. 884If the packet is the last logical fragment, the packet is reassembled and, if 885.Va net.inet.ip.fw.one_pass 886is set to 0, processing continues with the next rule, else packet is allowed to pass and search terminates. 887If the packet is a fragment in the middle, it is consumed and processing stops immediately. 888.Pp 889Fragments handling can be tuned via 890.Va net.inet.ip.maxfragpackets 891and 892.Va net.inet.ip.maxfragsperpacket 893which limit, respectively, the maximum number of processable fragments (default: 800) and 894the maximum number of fragments per packet (default: 16). 895.Pp 896NOTA BENE: since fragments do not contain port numbers, they should be avoided with the 897.Nm reass 898rule. 899Alternatively, direction-based (like 900.Nm in 901/ 902.Nm out 903) and source-based (like 904.Nm via 905) match patterns can be used to select fragments. 906.Pp 907Usually a simple rule like: 908.Bd -literal -offset indent 909# reassemble incoming fragments 910ipfw add reass all from any to any in 911.Ed 912.Pp 913is all you need at the beginning of your ruleset. 914.El 915.Ss RULE BODY 916The body of a rule contains zero or more patterns (such as 917specific source and destination addresses or ports, 918protocol options, incoming or outgoing interfaces, etc.) 919that the packet must match in order to be recognised. 920In general, the patterns are connected by (implicit) 921.Cm and 922operators -- i.e., all must match in order for the 923rule to match. 924Individual patterns can be prefixed by the 925.Cm not 926operator to reverse the result of the match, as in 927.Pp 928.Dl "ipfw add 100 allow ip from not 1.2.3.4 to any" 929.Pp 930Additionally, sets of alternative match patterns 931.Pq Em or-blocks 932can be constructed by putting the patterns in 933lists enclosed between parentheses ( ) or braces { }, and 934using the 935.Cm or 936operator as follows: 937.Pp 938.Dl "ipfw add 100 allow ip from { x or not y or z } to any" 939.Pp 940Only one level of parentheses is allowed. 941Beware that most shells have special meanings for parentheses 942or braces, so it is advisable to put a backslash \\ in front of them 943to prevent such interpretations. 944.Pp 945The body of a rule must in general include a source and destination 946address specifier. 947The keyword 948.Ar any 949can be used in various places to specify that the content of 950a required field is irrelevant. 951.Pp 952The rule body has the following format: 953.Bd -ragged -offset indent 954.Op Ar proto Cm from Ar src Cm to Ar dst 955.Op Ar options 956.Ed 957.Pp 958The first part (proto from src to dst) is for backward 959compatibility with earlier versions of 960.Fx . 961In modern 962.Fx 963any match pattern (including MAC headers, IP protocols, 964addresses and ports) can be specified in the 965.Ar options 966section. 967.Pp 968Rule fields have the following meaning: 969.Bl -tag -width indent 970.It Ar proto : protocol | Cm { Ar protocol Cm or ... } 971.It Ar protocol : Oo Cm not Oc Ar protocol-name | protocol-number 972An IP protocol specified by number or name 973(for a complete list see 974.Pa /etc/protocols ) , 975or one of the following keywords: 976.Bl -tag -width indent 977.It Cm ip4 | ipv4 978Matches IPv4 packets. 979.It Cm ip6 | ipv6 980Matches IPv6 packets. 981.It Cm ip | all 982Matches any packet. 983.El 984.Pp 985The 986.Cm ipv6 987in 988.Cm proto 989option will be treated as inner protocol. 990And, the 991.Cm ipv4 992is not available in 993.Cm proto 994option. 995.Pp 996The 997.Cm { Ar protocol Cm or ... } 998format (an 999.Em or-block ) 1000is provided for convenience only but its use is deprecated. 1001.It Ar src No and Ar dst : Bro Cm addr | Cm { Ar addr Cm or ... } Brc Op Oo Cm not Oc Ar ports 1002An address (or a list, see below) 1003optionally followed by 1004.Ar ports 1005specifiers. 1006.Pp 1007The second format 1008.Em ( or-block 1009with multiple addresses) is provided for convenience only and 1010its use is discouraged. 1011.It Ar addr : Oo Cm not Oc Bro 1012.Cm any | me | me6 | 1013.Cm table Ns Pq Ar number Ns Op , Ns Ar value 1014.Ar | addr-list | addr-set 1015.Brc 1016.Bl -tag -width indent 1017.It Cm any 1018matches any IP address. 1019.It Cm me 1020matches any IP address configured on an interface in the system. 1021.It Cm me6 1022matches any IPv6 address configured on an interface in the system. 1023The address list is evaluated at the time the packet is 1024analysed. 1025.It Cm table Ns Pq Ar number Ns Op , Ns Ar value 1026Matches any IPv4 address for which an entry exists in the lookup table 1027.Ar number . 1028If an optional 32-bit unsigned 1029.Ar value 1030is also specified, an entry will match only if it has this value. 1031See the 1032.Sx LOOKUP TABLES 1033section below for more information on lookup tables. 1034.El 1035.It Ar addr-list : ip-addr Ns Op Ns , Ns Ar addr-list 1036.It Ar ip-addr : 1037A host or subnet address specified in one of the following ways: 1038.Bl -tag -width indent 1039.It Ar numeric-ip | hostname 1040Matches a single IPv4 address, specified as dotted-quad or a hostname. 1041Hostnames are resolved at the time the rule is added to the firewall list. 1042.It Ar addr Ns / Ns Ar masklen 1043Matches all addresses with base 1044.Ar addr 1045(specified as an IP address, a network number, or a hostname) 1046and mask width of 1047.Cm masklen 1048bits. 1049As an example, 1.2.3.4/25 or 1.2.3.0/25 will match 1050all IP numbers from 1.2.3.0 to 1.2.3.127 . 1051.It Ar addr Ns : Ns Ar mask 1052Matches all addresses with base 1053.Ar addr 1054(specified as an IP address, a network number, or a hostname) 1055and the mask of 1056.Ar mask , 1057specified as a dotted quad. 1058As an example, 1.2.3.4:255.0.255.0 or 1.0.3.0:255.0.255.0 will match 10591.*.3.*. 1060This form is advised only for non-contiguous 1061masks. 1062It is better to resort to the 1063.Ar addr Ns / Ns Ar masklen 1064format for contiguous masks, which is more compact and less 1065error-prone. 1066.El 1067.It Ar addr-set : addr Ns Oo Ns / Ns Ar masklen Oc Ns Cm { Ns Ar list Ns Cm } 1068.It Ar list : Bro Ar num | num-num Brc Ns Op Ns , Ns Ar list 1069Matches all addresses with base address 1070.Ar addr 1071(specified as an IP address, a network number, or a hostname) 1072and whose last byte is in the list between braces { } . 1073Note that there must be no spaces between braces and 1074numbers (spaces after commas are allowed). 1075Elements of the list can be specified as single entries 1076or ranges. 1077The 1078.Ar masklen 1079field is used to limit the size of the set of addresses, 1080and can have any value between 24 and 32. 1081If not specified, 1082it will be assumed as 24. 1083.br 1084This format is particularly useful to handle sparse address sets 1085within a single rule. 1086Because the matching occurs using a 1087bitmask, it takes constant time and dramatically reduces 1088the complexity of rulesets. 1089.br 1090As an example, an address specified as 1.2.3.4/24{128,35-55,89} 1091or 1.2.3.0/24{128,35-55,89} 1092will match the following IP addresses: 1093.br 10941.2.3.128, 1.2.3.35 to 1.2.3.55, 1.2.3.89 . 1095.It Ar addr6-list : ip6-addr Ns Op Ns , Ns Ar addr6-list 1096.It Ar ip6-addr : 1097A host or subnet specified one of the following ways: 1098.Bl -tag -width indent 1099.It Ar numeric-ip | hostname 1100Matches a single IPv6 address as allowed by 1101.Xr inet_pton 3 1102or a hostname. 1103Hostnames are resolved at the time the rule is added to the firewall 1104list. 1105.It Ar addr Ns / Ns Ar masklen 1106Matches all IPv6 addresses with base 1107.Ar addr 1108(specified as allowed by 1109.Xr inet_pton 1110or a hostname) 1111and mask width of 1112.Cm masklen 1113bits. 1114.El 1115.Pp 1116No support for sets of IPv6 addresses is provided because IPv6 addresses 1117are typically random past the initial prefix. 1118.It Ar ports : Bro Ar port | port Ns \&- Ns Ar port Ns Brc Ns Op , Ns Ar ports 1119For protocols which support port numbers (such as TCP and UDP), optional 1120.Cm ports 1121may be specified as one or more ports or port ranges, separated 1122by commas but no spaces, and an optional 1123.Cm not 1124operator. 1125The 1126.Ql \&- 1127notation specifies a range of ports (including boundaries). 1128.Pp 1129Service names (from 1130.Pa /etc/services ) 1131may be used instead of numeric port values. 1132The length of the port list is limited to 30 ports or ranges, 1133though one can specify larger ranges by using an 1134.Em or-block 1135in the 1136.Cm options 1137section of the rule. 1138.Pp 1139A backslash 1140.Pq Ql \e 1141can be used to escape the dash 1142.Pq Ql - 1143character in a service name (from a shell, the backslash must be 1144typed twice to avoid the shell itself interpreting it as an escape 1145character). 1146.Pp 1147.Dl "ipfw add count tcp from any ftp\e\e-data-ftp to any" 1148.Pp 1149Fragmented packets which have a non-zero offset (i.e., not the first 1150fragment) will never match a rule which has one or more port 1151specifications. 1152See the 1153.Cm frag 1154option for details on matching fragmented packets. 1155.El 1156.Ss RULE OPTIONS (MATCH PATTERNS) 1157Additional match patterns can be used within 1158rules. 1159Zero or more of these so-called 1160.Em options 1161can be present in a rule, optionally prefixed by the 1162.Cm not 1163operand, and possibly grouped into 1164.Em or-blocks . 1165.Pp 1166The following match patterns can be used (listed in alphabetical order): 1167.Bl -tag -width indent 1168.It Cm // this is a comment. 1169Inserts the specified text as a comment in the rule. 1170Everything following // is considered as a comment and stored in the rule. 1171You can have comment-only rules, which are listed as having a 1172.Cm count 1173action followed by the comment. 1174.It Cm bridged 1175Alias for 1176.Cm layer2 . 1177.It Cm diverted 1178Matches only packets generated by a divert socket. 1179.It Cm diverted-loopback 1180Matches only packets coming from a divert socket back into the IP stack 1181input for delivery. 1182.It Cm diverted-output 1183Matches only packets going from a divert socket back outward to the IP 1184stack output for delivery. 1185.It Cm dst-ip Ar ip-address 1186Matches IPv4 packets whose destination IP is one of the address(es) 1187specified as argument. 1188.It Bro Cm dst-ip6 | dst-ipv6 Brc Ar ip6-address 1189Matches IPv6 packets whose destination IP is one of the address(es) 1190specified as argument. 1191.It Cm dst-port Ar ports 1192Matches IP packets whose destination port is one of the port(s) 1193specified as argument. 1194.It Cm established 1195Matches TCP packets that have the RST or ACK bits set. 1196.It Cm ext6hdr Ar header 1197Matches IPv6 packets containing the extended header given by 1198.Ar header . 1199Supported headers are: 1200.Pp 1201Fragment, 1202.Pq Cm frag , 1203Hop-to-hop options 1204.Pq Cm hopopt , 1205any type of Routing Header 1206.Pq Cm route , 1207Source routing Routing Header Type 0 1208.Pq Cm rthdr0 , 1209Mobile IPv6 Routing Header Type 2 1210.Pq Cm rthdr2 , 1211Destination options 1212.Pq Cm dstopt , 1213IPSec authentication headers 1214.Pq Cm ah , 1215and IPsec encapsulated security payload headers 1216.Pq Cm esp . 1217.It Cm fib Ar fibnum 1218Matches a packet that has been tagged to use 1219the given FIB (routing table) number. 1220.It Cm flow-id Ar labels 1221Matches IPv6 packets containing any of the flow labels given in 1222.Ar labels . 1223.Ar labels 1224is a comma separated list of numeric flow labels. 1225.It Cm frag 1226Matches packets that are fragments and not the first 1227fragment of an IP datagram. 1228Note that these packets will not have 1229the next protocol header (e.g.\& TCP, UDP) so options that look into 1230these headers cannot match. 1231.It Cm gid Ar group 1232Matches all TCP or UDP packets sent by or received for a 1233.Ar group . 1234A 1235.Ar group 1236may be specified by name or number. 1237.It Cm jail Ar prisonID 1238Matches all TCP or UDP packets sent by or received for the 1239jail whos prison ID is 1240.Ar prisonID . 1241.It Cm icmptypes Ar types 1242Matches ICMP packets whose ICMP type is in the list 1243.Ar types . 1244The list may be specified as any combination of 1245individual types (numeric) separated by commas. 1246.Em Ranges are not allowed . 1247The supported ICMP types are: 1248.Pp 1249echo reply 1250.Pq Cm 0 , 1251destination unreachable 1252.Pq Cm 3 , 1253source quench 1254.Pq Cm 4 , 1255redirect 1256.Pq Cm 5 , 1257echo request 1258.Pq Cm 8 , 1259router advertisement 1260.Pq Cm 9 , 1261router solicitation 1262.Pq Cm 10 , 1263time-to-live exceeded 1264.Pq Cm 11 , 1265IP header bad 1266.Pq Cm 12 , 1267timestamp request 1268.Pq Cm 13 , 1269timestamp reply 1270.Pq Cm 14 , 1271information request 1272.Pq Cm 15 , 1273information reply 1274.Pq Cm 16 , 1275address mask request 1276.Pq Cm 17 1277and address mask reply 1278.Pq Cm 18 . 1279.It Cm icmp6types Ar types 1280Matches ICMP6 packets whose ICMP6 type is in the list of 1281.Ar types . 1282The list may be specified as any combination of 1283individual types (numeric) separated by commas. 1284.Em Ranges are not allowed . 1285.It Cm in | out 1286Matches incoming or outgoing packets, respectively. 1287.Cm in 1288and 1289.Cm out 1290are mutually exclusive (in fact, 1291.Cm out 1292is implemented as 1293.Cm not in Ns No ). 1294.It Cm ipid Ar id-list 1295Matches IPv4 packets whose 1296.Cm ip_id 1297field has value included in 1298.Ar id-list , 1299which is either a single value or a list of values or ranges 1300specified in the same way as 1301.Ar ports . 1302.It Cm iplen Ar len-list 1303Matches IP packets whose total length, including header and data, is 1304in the set 1305.Ar len-list , 1306which is either a single value or a list of values or ranges 1307specified in the same way as 1308.Ar ports . 1309.It Cm ipoptions Ar spec 1310Matches packets whose IPv4 header contains the comma separated list of 1311options specified in 1312.Ar spec . 1313The supported IP options are: 1314.Pp 1315.Cm ssrr 1316(strict source route), 1317.Cm lsrr 1318(loose source route), 1319.Cm rr 1320(record packet route) and 1321.Cm ts 1322(timestamp). 1323The absence of a particular option may be denoted 1324with a 1325.Ql \&! . 1326.It Cm ipprecedence Ar precedence 1327Matches IPv4 packets whose precedence field is equal to 1328.Ar precedence . 1329.It Cm ipsec 1330Matches packets that have IPSEC history associated with them 1331(i.e., the packet comes encapsulated in IPSEC, the kernel 1332has IPSEC support and IPSEC_FILTERTUNNEL option, and can correctly 1333decapsulate it). 1334.Pp 1335Note that specifying 1336.Cm ipsec 1337is different from specifying 1338.Cm proto Ar ipsec 1339as the latter will only look at the specific IP protocol field, 1340irrespective of IPSEC kernel support and the validity of the IPSEC data. 1341.Pp 1342Further note that this flag is silently ignored in kernels without 1343IPSEC support. 1344It does not affect rule processing when given and the 1345rules are handled as if with no 1346.Cm ipsec 1347flag. 1348.It Cm iptos Ar spec 1349Matches IPv4 packets whose 1350.Cm tos 1351field contains the comma separated list of 1352service types specified in 1353.Ar spec . 1354The supported IP types of service are: 1355.Pp 1356.Cm lowdelay 1357.Pq Dv IPTOS_LOWDELAY , 1358.Cm throughput 1359.Pq Dv IPTOS_THROUGHPUT , 1360.Cm reliability 1361.Pq Dv IPTOS_RELIABILITY , 1362.Cm mincost 1363.Pq Dv IPTOS_MINCOST , 1364.Cm congestion 1365.Pq Dv IPTOS_ECN_CE . 1366The absence of a particular type may be denoted 1367with a 1368.Ql \&! . 1369.It Cm ipttl Ar ttl-list 1370Matches IPv4 packets whose time to live is included in 1371.Ar ttl-list , 1372which is either a single value or a list of values or ranges 1373specified in the same way as 1374.Ar ports . 1375.It Cm ipversion Ar ver 1376Matches IP packets whose IP version field is 1377.Ar ver . 1378.It Cm keep-state 1379Upon a match, the firewall will create a dynamic rule, whose 1380default behaviour is to match bidirectional traffic between 1381source and destination IP/port using the same protocol. 1382The rule has a limited lifetime (controlled by a set of 1383.Xr sysctl 8 1384variables), and the lifetime is refreshed every time a matching 1385packet is found. 1386.It Cm layer2 1387Matches only layer2 packets, i.e., those passed to 1388.Nm 1389from ether_demux() and ether_output_frame(). 1390.It Cm limit Bro Cm src-addr | src-port | dst-addr | dst-port Brc Ar N 1391The firewall will only allow 1392.Ar N 1393connections with the same 1394set of parameters as specified in the rule. 1395One or more 1396of source and destination addresses and ports can be 1397specified. 1398Currently, 1399only IPv4 flows are supported. 1400.It Cm lookup Bro Cm dst-ip | dst-port | src-ip | src-port | uid | jail Brc Ar N 1401Search an entry in lookup table 1402.Ar N 1403that matches the field specified as argument. 1404If not found, the match fails. 1405Otherwise, the match succeeds and 1406.Cm tablearg 1407is set to the value extracted from the table. 1408.Pp 1409This option can be useful to quickly dispatch traffic based on 1410certain packet fields. 1411See the 1412.Sx LOOKUP TABLES 1413section below for more information on lookup tables. 1414.It Cm { MAC | mac } Ar dst-mac src-mac 1415Match packets with a given 1416.Ar dst-mac 1417and 1418.Ar src-mac 1419addresses, specified as the 1420.Cm any 1421keyword (matching any MAC address), or six groups of hex digits 1422separated by colons, 1423and optionally followed by a mask indicating the significant bits. 1424The mask may be specified using either of the following methods: 1425.Bl -enum -width indent 1426.It 1427A slash 1428.Pq / 1429followed by the number of significant bits. 1430For example, an address with 33 significant bits could be specified as: 1431.Pp 1432.Dl "MAC 10:20:30:40:50:60/33 any" 1433.Pp 1434.It 1435An ampersand 1436.Pq & 1437followed by a bitmask specified as six groups of hex digits separated 1438by colons. 1439For example, an address in which the last 16 bits are significant could 1440be specified as: 1441.Pp 1442.Dl "MAC 10:20:30:40:50:60&00:00:00:00:ff:ff any" 1443.Pp 1444Note that the ampersand character has a special meaning in many shells 1445and should generally be escaped. 1446.Pp 1447.El 1448Note that the order of MAC addresses (destination first, 1449source second) is 1450the same as on the wire, but the opposite of the one used for 1451IP addresses. 1452.It Cm mac-type Ar mac-type 1453Matches packets whose Ethernet Type field 1454corresponds to one of those specified as argument. 1455.Ar mac-type 1456is specified in the same way as 1457.Cm port numbers 1458(i.e., one or more comma-separated single values or ranges). 1459You can use symbolic names for known values such as 1460.Em vlan , ipv4, ipv6 . 1461Values can be entered as decimal or hexadecimal (if prefixed by 0x), 1462and they are always printed as hexadecimal (unless the 1463.Cm -N 1464option is used, in which case symbolic resolution will be attempted). 1465.It Cm proto Ar protocol 1466Matches packets with the corresponding IP protocol. 1467.It Cm recv | xmit | via Brq Ar ifX | Ar if Ns Cm * | Ar ipno | Ar any 1468Matches packets received, transmitted or going through, 1469respectively, the interface specified by exact name 1470.Ns No ( Ar ifX Ns No ), 1471by device name 1472.Ns No ( Ar if Ns Ar * Ns No ), 1473by IP address, or through some interface. 1474.Pp 1475The 1476.Cm via 1477keyword causes the interface to always be checked. 1478If 1479.Cm recv 1480or 1481.Cm xmit 1482is used instead of 1483.Cm via , 1484then only the receive or transmit interface (respectively) 1485is checked. 1486By specifying both, it is possible to match packets based on 1487both receive and transmit interface, e.g.: 1488.Pp 1489.Dl "ipfw add deny ip from any to any out recv ed0 xmit ed1" 1490.Pp 1491The 1492.Cm recv 1493interface can be tested on either incoming or outgoing packets, 1494while the 1495.Cm xmit 1496interface can only be tested on outgoing packets. 1497So 1498.Cm out 1499is required (and 1500.Cm in 1501is invalid) whenever 1502.Cm xmit 1503is used. 1504.Pp 1505A packet might not have a receive or transmit interface: packets 1506originating from the local host have no receive interface, 1507while packets destined for the local host have no transmit 1508interface. 1509.It Cm setup 1510Matches TCP packets that have the SYN bit set but no ACK bit. 1511This is the short form of 1512.Dq Li tcpflags\ syn,!ack . 1513.It Cm sockarg 1514Matches packets that are associated to a local socket and 1515for which the SO_USER_COOKIE socket option has been set 1516to a non-zero value. As a side effect, the value of the 1517option is made available as 1518.Cm tablearg 1519value, which in turn can be used as 1520.Cm skipto 1521or 1522.Cm pipe 1523number. 1524.It Cm src-ip Ar ip-address 1525Matches IPv4 packets whose source IP is one of the address(es) 1526specified as an argument. 1527.It Cm src-ip6 Ar ip6-address 1528Matches IPv6 packets whose source IP is one of the address(es) 1529specified as an argument. 1530.It Cm src-port Ar ports 1531Matches IP packets whose source port is one of the port(s) 1532specified as argument. 1533.It Cm tagged Ar tag-list 1534Matches packets whose tags are included in 1535.Ar tag-list , 1536which is either a single value or a list of values or ranges 1537specified in the same way as 1538.Ar ports . 1539Tags can be applied to the packet using 1540.Cm tag 1541rule action parameter (see it's description for details on tags). 1542.It Cm tcpack Ar ack 1543TCP packets only. 1544Match if the TCP header acknowledgment number field is set to 1545.Ar ack . 1546.It Cm tcpdatalen Ar tcpdatalen-list 1547Matches TCP packets whose length of TCP data is 1548.Ar tcpdatalen-list , 1549which is either a single value or a list of values or ranges 1550specified in the same way as 1551.Ar ports . 1552.It Cm tcpflags Ar spec 1553TCP packets only. 1554Match if the TCP header contains the comma separated list of 1555flags specified in 1556.Ar spec . 1557The supported TCP flags are: 1558.Pp 1559.Cm fin , 1560.Cm syn , 1561.Cm rst , 1562.Cm psh , 1563.Cm ack 1564and 1565.Cm urg . 1566The absence of a particular flag may be denoted 1567with a 1568.Ql \&! . 1569A rule which contains a 1570.Cm tcpflags 1571specification can never match a fragmented packet which has 1572a non-zero offset. 1573See the 1574.Cm frag 1575option for details on matching fragmented packets. 1576.It Cm tcpseq Ar seq 1577TCP packets only. 1578Match if the TCP header sequence number field is set to 1579.Ar seq . 1580.It Cm tcpwin Ar win 1581TCP packets only. 1582Match if the TCP header window field is set to 1583.Ar win . 1584.It Cm tcpoptions Ar spec 1585TCP packets only. 1586Match if the TCP header contains the comma separated list of 1587options specified in 1588.Ar spec . 1589The supported TCP options are: 1590.Pp 1591.Cm mss 1592(maximum segment size), 1593.Cm window 1594(tcp window advertisement), 1595.Cm sack 1596(selective ack), 1597.Cm ts 1598(rfc1323 timestamp) and 1599.Cm cc 1600(rfc1644 t/tcp connection count). 1601The absence of a particular option may be denoted 1602with a 1603.Ql \&! . 1604.It Cm uid Ar user 1605Match all TCP or UDP packets sent by or received for a 1606.Ar user . 1607A 1608.Ar user 1609may be matched by name or identification number. 1610.It Cm verrevpath 1611For incoming packets, 1612a routing table lookup is done on the packet's source address. 1613If the interface on which the packet entered the system matches the 1614outgoing interface for the route, 1615the packet matches. 1616If the interfaces do not match up, 1617the packet does not match. 1618All outgoing packets or packets with no incoming interface match. 1619.Pp 1620The name and functionality of the option is intentionally similar to 1621the Cisco IOS command: 1622.Pp 1623.Dl ip verify unicast reverse-path 1624.Pp 1625This option can be used to make anti-spoofing rules to reject all 1626packets with source addresses not from this interface. 1627See also the option 1628.Cm antispoof . 1629.It Cm versrcreach 1630For incoming packets, 1631a routing table lookup is done on the packet's source address. 1632If a route to the source address exists, but not the default route 1633or a blackhole/reject route, the packet matches. 1634Otherwise, the packet does not match. 1635All outgoing packets match. 1636.Pp 1637The name and functionality of the option is intentionally similar to 1638the Cisco IOS command: 1639.Pp 1640.Dl ip verify unicast source reachable-via any 1641.Pp 1642This option can be used to make anti-spoofing rules to reject all 1643packets whose source address is unreachable. 1644.It Cm antispoof 1645For incoming packets, the packet's source address is checked if it 1646belongs to a directly connected network. 1647If the network is directly connected, then the interface the packet 1648came on in is compared to the interface the network is connected to. 1649When incoming interface and directly connected interface are not the 1650same, the packet does not match. 1651Otherwise, the packet does match. 1652All outgoing packets match. 1653.Pp 1654This option can be used to make anti-spoofing rules to reject all 1655packets that pretend to be from a directly connected network but do 1656not come in through that interface. 1657This option is similar to but more restricted than 1658.Cm verrevpath 1659because it engages only on packets with source addresses of directly 1660connected networks instead of all source addresses. 1661.El 1662.Sh LOOKUP TABLES 1663Lookup tables are useful to handle large sparse sets of 1664addresses or other search keys (e.g. ports, jail IDs). 1665In the rest of this section we will use the term ``address'' 1666to mean any unsigned value of up to 32-bit. 1667There may be up to 128 different lookup tables, numbered 0 to 127. 1668.Pp 1669Each entry is represented by an 1670.Ar addr Ns Op / Ns Ar masklen 1671and will match all addresses with base 1672.Ar addr 1673(specified as an IP address, a hostname or an unsigned integer) 1674and mask width of 1675.Ar masklen 1676bits. 1677If 1678.Ar masklen 1679is not specified, it defaults to 32. 1680When looking up an IP address in a table, the most specific 1681entry will match. 1682Associated with each entry is a 32-bit unsigned 1683.Ar value , 1684which can optionally be checked by a rule matching code. 1685When adding an entry, if 1686.Ar value 1687is not specified, it defaults to 0. 1688.Pp 1689An entry can be added to a table 1690.Pq Cm add , 1691or removed from a table 1692.Pq Cm delete . 1693A table can be examined 1694.Pq Cm list 1695or flushed 1696.Pq Cm flush . 1697.Pp 1698Internally, each table is stored in a Radix tree, the same way as 1699the routing table (see 1700.Xr route 4 ) . 1701.Pp 1702Lookup tables currently support only ports, jail IDs and IPv4 addresses. 1703.Pp 1704The 1705.Cm tablearg 1706feature provides the ability to use a value, looked up in the table, as 1707the argument for a rule action, action parameter or rule option. 1708This can significantly reduce number of rules in some configurations. 1709If two tables are used in a rule, the result of the second (destination) 1710is used. 1711The 1712.Cm tablearg 1713argument can be used with the following actions: 1714.Cm nat, pipe , queue, divert, tee, netgraph, ngtee, fwd, skipto 1715action parameters: 1716.Cm tag, untag, 1717rule options: 1718.Cm limit, tagged. 1719.Pp 1720When used with 1721.Cm fwd 1722it is possible to supply table entries with values 1723that are in the form of IP addresses or hostnames. 1724See the 1725.Sx EXAMPLES 1726Section for example usage of tables and the tablearg keyword. 1727.Pp 1728When used with the 1729.Cm skipto 1730action, the user should be aware that the code will walk the ruleset 1731up to a rule equal to, or past, the given number, and should therefore try keep the 1732ruleset compact between the skipto and the target rules. 1733.Sh SETS OF RULES 1734Each rule belongs to one of 32 different 1735.Em sets 1736, numbered 0 to 31. 1737Set 31 is reserved for the default rule. 1738.Pp 1739By default, rules are put in set 0, unless you use the 1740.Cm set N 1741attribute when entering a new rule. 1742Sets can be individually and atomically enabled or disabled, 1743so this mechanism permits an easy way to store multiple configurations 1744of the firewall and quickly (and atomically) switch between them. 1745The command to enable/disable sets is 1746.Bd -ragged -offset indent 1747.Nm 1748.Cm set Oo Cm disable Ar number ... Oc Op Cm enable Ar number ... 1749.Ed 1750.Pp 1751where multiple 1752.Cm enable 1753or 1754.Cm disable 1755sections can be specified. 1756Command execution is atomic on all the sets specified in the command. 1757By default, all sets are enabled. 1758.Pp 1759When you disable a set, its rules behave as if they do not exist 1760in the firewall configuration, with only one exception: 1761.Bd -ragged -offset indent 1762dynamic rules created from a rule before it had been disabled 1763will still be active until they expire. 1764In order to delete 1765dynamic rules you have to explicitly delete the parent rule 1766which generated them. 1767.Ed 1768.Pp 1769The set number of rules can be changed with the command 1770.Bd -ragged -offset indent 1771.Nm 1772.Cm set move 1773.Brq Cm rule Ar rule-number | old-set 1774.Cm to Ar new-set 1775.Ed 1776.Pp 1777Also, you can atomically swap two rulesets with the command 1778.Bd -ragged -offset indent 1779.Nm 1780.Cm set swap Ar first-set second-set 1781.Ed 1782.Pp 1783See the 1784.Sx EXAMPLES 1785Section on some possible uses of sets of rules. 1786.Sh STATEFUL FIREWALL 1787Stateful operation is a way for the firewall to dynamically 1788create rules for specific flows when packets that 1789match a given pattern are detected. 1790Support for stateful 1791operation comes through the 1792.Cm check-state , keep-state 1793and 1794.Cm limit 1795options of 1796.Nm rules . 1797.Pp 1798Dynamic rules are created when a packet matches a 1799.Cm keep-state 1800or 1801.Cm limit 1802rule, causing the creation of a 1803.Em dynamic 1804rule which will match all and only packets with 1805a given 1806.Em protocol 1807between a 1808.Em src-ip/src-port dst-ip/dst-port 1809pair of addresses 1810.Em ( src 1811and 1812.Em dst 1813are used here only to denote the initial match addresses, but they 1814are completely equivalent afterwards). 1815Dynamic rules will be checked at the first 1816.Cm check-state, keep-state 1817or 1818.Cm limit 1819occurrence, and the action performed upon a match will be the same 1820as in the parent rule. 1821.Pp 1822Note that no additional attributes other than protocol and IP addresses 1823and ports are checked on dynamic rules. 1824.Pp 1825The typical use of dynamic rules is to keep a closed firewall configuration, 1826but let the first TCP SYN packet from the inside network install a 1827dynamic rule for the flow so that packets belonging to that session 1828will be allowed through the firewall: 1829.Pp 1830.Dl "ipfw add check-state" 1831.Dl "ipfw add allow tcp from my-subnet to any setup keep-state" 1832.Dl "ipfw add deny tcp from any to any" 1833.Pp 1834A similar approach can be used for UDP, where an UDP packet coming 1835from the inside will install a dynamic rule to let the response through 1836the firewall: 1837.Pp 1838.Dl "ipfw add check-state" 1839.Dl "ipfw add allow udp from my-subnet to any keep-state" 1840.Dl "ipfw add deny udp from any to any" 1841.Pp 1842Dynamic rules expire after some time, which depends on the status 1843of the flow and the setting of some 1844.Cm sysctl 1845variables. 1846See Section 1847.Sx SYSCTL VARIABLES 1848for more details. 1849For TCP sessions, dynamic rules can be instructed to periodically 1850send keepalive packets to refresh the state of the rule when it is 1851about to expire. 1852.Pp 1853See Section 1854.Sx EXAMPLES 1855for more examples on how to use dynamic rules. 1856.Sh TRAFFIC SHAPER (DUMMYNET) CONFIGURATION 1857.Nm 1858is also the user interface for the 1859.Nm dummynet 1860traffic shaper, packet scheduler and network emulator, a subsystem that 1861can artificially queue, delay or drop packets 1862emulating the behaviour of certain network links 1863or queueing systems. 1864.Pp 1865.Nm dummynet 1866operates by first using the firewall to select packets 1867using any match pattern that can be used in 1868.Nm 1869rules. 1870Matching packets are then passed to either of two 1871different objects, which implement the traffic regulation: 1872.Bl -hang -offset XXXX 1873.It Em pipe 1874A 1875.Em pipe 1876emulates a 1877.Em link 1878with given bandwidth and propagation delay, 1879driven by a FIFO scheduler and a single queue with programmable 1880queue size and packet loss rate. 1881Packets are appended to the queue as they come out from 1882.Nm ipfw , 1883and then transferred in FIFO order to the link at the desired rate. 1884.It Em queue 1885A 1886.Em queue 1887is an abstraction used to implement packet scheduling 1888using one of several packet scheduling algorithms. 1889Packets sent to a 1890.Em queue 1891are first grouped into flows according to a mask on the 5-tuple. 1892Flows are then passed to the scheduler associated to the 1893.Em queue , 1894and each flow uses scheduling parameters (weight and others) 1895as configured in the 1896.Em queue 1897itself. 1898A scheduler in turn is connected to an emulated link, 1899and arbitrates the link's bandwidth among backlogged flows according to 1900weights and to the features of the scheduling algorithm in use. 1901.El 1902.Pp 1903In practice, 1904.Em pipes 1905can be used to set hard limits to the bandwidth that a flow can use, whereas 1906.Em queues 1907can be used to determine how different flows share the available bandwidth. 1908.Pp 1909A graphical representation of the binding of queues, 1910flows, schedulers and links is below. 1911.Bd -literal -offset indent 1912 (flow_mask|sched_mask) sched_mask 1913 +---------+ weight Wx +-------------+ 1914 | |->-[flow]-->--| |-+ 1915 -->--| QUEUE x | ... | | | 1916 | |->-[flow]-->--| SCHEDuler N | | 1917 +---------+ | | | 1918 ... | +--[LINK N]-->-- 1919 +---------+ weight Wy | | +--[LINK N]-->-- 1920 | |->-[flow]-->--| | | 1921 -->--| QUEUE y | ... | | | 1922 | |->-[flow]-->--| | | 1923 +---------+ +-------------+ | 1924 +-------------+ 1925.Ed 1926It is important to understand the role of the SCHED_MASK 1927and FLOW_MASK, which are configured through the commands 1928.Dl "ipfw sched N config mask SCHED_MASK ..." 1929and 1930.Dl "ipfw queue X config mask FLOW_MASK ..." . 1931.Pp 1932The SCHED_MASK is used to assign flows to one or more 1933scheduler instances, one for each 1934value of the packet's 5-tuple after applying SCHED_MASK. 1935As an example, using ``src-ip 0xffffff00'' creates one instance 1936for each /24 destination subnet. 1937.Pp 1938The FLOW_MASK, together with the SCHED_MASK, is used to split 1939packets into flows. As an example, using 1940``src-ip 0x000000ff'' 1941together with the previous SCHED_MASK makes a flow for 1942each individual source address. In turn, flows for each /24 1943subnet will be sent to the same scheduler instance. 1944.Pp 1945The above diagram holds even for the 1946.Em pipe 1947case, with the only restriction that a 1948.Em pipe 1949only supports a SCHED_MASK, and forces the use of a FIFO 1950scheduler (these are for backward compatibility reasons; 1951in fact, internally, a 1952.Nm dummynet's 1953pipe is implemented exactly as above). 1954.Pp 1955There are two modes of 1956.Nm dummynet 1957operation: 1958.Dq normal 1959and 1960.Dq fast . 1961The 1962.Dq normal 1963mode tries to emulate a real link: the 1964.Nm dummynet 1965scheduler ensures that the packet will not leave the pipe faster than it 1966would on the real link with a given bandwidth. 1967The 1968.Dq fast 1969mode allows certain packets to bypass the 1970.Nm dummynet 1971scheduler (if packet flow does not exceed pipe's bandwidth). 1972This is the reason why the 1973.Dq fast 1974mode requires less CPU cycles per packet (on average) and packet latency 1975can be significantly lower in comparison to a real link with the same 1976bandwidth. 1977The default mode is 1978.Dq normal . 1979The 1980.Dq fast 1981mode can be enabled by setting the 1982.Va net.inet.ip.dummynet.io_fast 1983.Xr sysctl 8 1984variable to a non-zero value. 1985.Pp 1986.Ss PIPE, QUEUE AND SCHEDULER CONFIGURATION 1987The 1988.Em pipe , 1989.Em queue 1990and 1991.Em scheduler 1992configuration commands are the following: 1993.Bd -ragged -offset indent 1994.Cm pipe Ar number Cm config Ar pipe-configuration 1995.Pp 1996.Cm queue Ar number Cm config Ar queue-configuration 1997.Pp 1998.Cm sched Ar number Cm config Ar sched-configuration 1999.Ed 2000.Pp 2001The following parameters can be configured for a pipe: 2002.Pp 2003.Bl -tag -width indent -compact 2004.It Cm bw Ar bandwidth | device 2005Bandwidth, measured in 2006.Sm off 2007.Op Cm K | M 2008.Brq Cm bit/s | Byte/s . 2009.Sm on 2010.Pp 2011A value of 0 (default) means unlimited bandwidth. 2012The unit must immediately follow the number, as in 2013.Pp 2014.Dl "ipfw pipe 1 config bw 300Kbit/s" 2015.Pp 2016If a device name is specified instead of a numeric value, as in 2017.Pp 2018.Dl "ipfw pipe 1 config bw tun0" 2019.Pp 2020then the transmit clock is supplied by the specified device. 2021At the moment only the 2022.Xr tun 4 2023device supports this 2024functionality, for use in conjunction with 2025.Xr ppp 8 . 2026.Pp 2027.It Cm delay Ar ms-delay 2028Propagation delay, measured in milliseconds. 2029The value is rounded to the next multiple of the clock tick 2030(typically 10ms, but it is a good practice to run kernels 2031with 2032.Dq "options HZ=1000" 2033to reduce 2034the granularity to 1ms or less). 2035The default value is 0, meaning no delay. 2036.Pp 2037.It Cm burst Ar size 2038If the data to be sent exceeds the pipe's bandwidth limit 2039(and the pipe was previously idle), up to 2040.Ar size 2041bytes of data are allowed to bypass the 2042.Nm dummynet 2043scheduler, and will be sent as fast as the physical link allows. 2044Any additional data will be transmitted at the rate specified 2045by the 2046.Nm pipe 2047bandwidth. 2048The burst size depends on how long the pipe has been idle; 2049the effective burst size is calculated as follows: 2050MAX( 2051.Ar size 2052, 2053.Nm bw 2054* pipe_idle_time). 2055.Pp 2056.It Cm profile Ar filename 2057A file specifying the additional overhead incurred in the transmission 2058of a packet on the link. 2059.Pp 2060Some link types introduce extra delays in the transmission 2061of a packet, e.g. because of MAC level framing, contention on 2062the use of the channel, MAC level retransmissions and so on. 2063From our point of view, the channel is effectively unavailable 2064for this extra time, which is constant or variable depending 2065on the link type. Additionally, packets may be dropped after this 2066time (e.g. on a wireless link after too many retransmissions). 2067We can model the additional delay with an empirical curve 2068that represents its distribution. 2069.Bd -literal -offset indent 2070 cumulative probability 2071 1.0 ^ 2072 | 2073 L +-- loss-level x 2074 | ****** 2075 | * 2076 | ***** 2077 | * 2078 | ** 2079 | * 2080 +-------*-------------------> 2081 delay 2082.Ed 2083The empirical curve may have both vertical and horizontal lines. 2084Vertical lines represent constant delay for a range of 2085probabilities. 2086Horizontal lines correspond to a discontinuity in the delay 2087distribution: the pipe will use the largest delay for a 2088given probability. 2089.Pp 2090The file format is the following, with whitespace acting as 2091a separator and '#' indicating the beginning a comment: 2092.Bl -tag -width indent 2093.It Cm name Ar identifier 2094optional name (listed by "ipfw pipe show") 2095to identify the delay distribution; 2096.It Cm bw Ar value 2097the bandwidth used for the pipe. 2098If not specified here, it must be present 2099explicitly as a configuration parameter for the pipe; 2100.It Cm loss-level Ar L 2101the probability above which packets are lost. 2102(0.0 <= L <= 1.0, default 1.0 i.e. no loss); 2103.It Cm samples Ar N 2104the number of samples used in the internal 2105representation of the curve (2..1024; default 100); 2106.It Cm "delay prob" | "prob delay" 2107One of these two lines is mandatory and defines 2108the format of the following lines with data points. 2109.It Ar XXX Ar YYY 21102 or more lines representing points in the curve, 2111with either delay or probability first, according 2112to the chosen format. 2113The unit for delay is milliseconds. 2114Data points do not need to be sorted. 2115Also, the number of actual lines can be different 2116from the value of the "samples" parameter: 2117.Nm 2118utility will sort and interpolate 2119the curve as needed. 2120.El 2121.Pp 2122Example of a profile file: 2123.Bd -literal -offset indent 2124name bla_bla_bla 2125samples 100 2126loss-level 0.86 2127prob delay 21280 200 # minimum overhead is 200ms 21290.5 200 21300.5 300 21310.8 1000 21320.9 1300 21331 1300 2134#configuration file end 2135.Ed 2136.El 2137.Pp 2138The following parameters can be configured for a queue: 2139.Pp 2140.Bl -tag -width indent -compact 2141.It Cm pipe Ar pipe_nr 2142Connects a queue to the specified pipe. 2143Multiple queues (with the same or different weights) can be connected to 2144the same pipe, which specifies the aggregate rate for the set of queues. 2145.Pp 2146.It Cm weight Ar weight 2147Specifies the weight to be used for flows matching this queue. 2148The weight must be in the range 1..100, and defaults to 1. 2149.El 2150.Pp 2151The following parameters can be configured for a scheduler: 2152.Pp 2153.Bl -tag -width indent -compact 2154.It Cm type Ar {fifo | wf2qp | rr | qfq} 2155specifies the scheduling algorithm to use. 2156.Bl -tag -width indent -compact 2157.It cm fifo 2158is just a FIFO scheduler (which means that all packets 2159are stored in the same queue as they arrive to the scheduler). 2160FIFO has O(1) per-packet time complexity, with very low 2161constants (estimate 60-80ns on a 2Ghz desktop machine) 2162but gives no service guarantees. 2163.It Cm wf2qp 2164implements the WF2Q+ algorithm, which is a Weighted Fair Queueing 2165algorithm which permits flows to share bandwidth according to 2166their weights. Note that weights are not priorities; even a flow 2167with a minuscule weight will never starve. 2168WF2Q+ has O(log N) per-packet processing cost, where N is the number 2169of flows, and is the default algorithm used by previous versions 2170dummynet's queues. 2171.It Cm rr 2172implements the Deficit Round Robin algorithm, which has O(1) processing 2173costs (roughly, 100-150ns per packet) 2174and permits bandwidth allocation according to weights, but 2175with poor service guarantees. 2176.It Cm qfq 2177implements the QFQ algorithm, which is a very fast variant of 2178WF2Q+, with similar service guarantees and O(1) processing 2179costs (roughly, 200-250ns per packet). 2180.El 2181.El 2182.Pp 2183In addition to the type, all parameters allowed for a pipe can also 2184be specified for a scheduler. 2185.Pp 2186Finally, the following parameters can be configured for both 2187pipes and queues: 2188.Pp 2189.Bl -tag -width XXXX -compact 2190.It Cm buckets Ar hash-table-size 2191Specifies the size of the hash table used for storing the 2192various queues. 2193Default value is 64 controlled by the 2194.Xr sysctl 8 2195variable 2196.Va net.inet.ip.dummynet.hash_size , 2197allowed range is 16 to 65536. 2198.Pp 2199.It Cm mask Ar mask-specifier 2200Packets sent to a given pipe or queue by an 2201.Nm 2202rule can be further classified into multiple flows, each of which is then 2203sent to a different 2204.Em dynamic 2205pipe or queue. 2206A flow identifier is constructed by masking the IP addresses, 2207ports and protocol types as specified with the 2208.Cm mask 2209options in the configuration of the pipe or queue. 2210For each different flow identifier, a new pipe or queue is created 2211with the same parameters as the original object, and matching packets 2212are sent to it. 2213.Pp 2214Thus, when 2215.Em dynamic pipes 2216are used, each flow will get the same bandwidth as defined by the pipe, 2217whereas when 2218.Em dynamic queues 2219are used, each flow will share the parent's pipe bandwidth evenly 2220with other flows generated by the same queue (note that other queues 2221with different weights might be connected to the same pipe). 2222.br 2223Available mask specifiers are a combination of one or more of the following: 2224.Pp 2225.Cm dst-ip Ar mask , 2226.Cm dst-ip6 Ar mask , 2227.Cm src-ip Ar mask , 2228.Cm src-ip6 Ar mask , 2229.Cm dst-port Ar mask , 2230.Cm src-port Ar mask , 2231.Cm flow-id Ar mask , 2232.Cm proto Ar mask 2233or 2234.Cm all , 2235.Pp 2236where the latter means all bits in all fields are significant. 2237.Pp 2238.It Cm noerror 2239When a packet is dropped by a 2240.Nm dummynet 2241queue or pipe, the error 2242is normally reported to the caller routine in the kernel, in the 2243same way as it happens when a device queue fills up. 2244Setting this 2245option reports the packet as successfully delivered, which can be 2246needed for some experimental setups where you want to simulate 2247loss or congestion at a remote router. 2248.Pp 2249.It Cm plr Ar packet-loss-rate 2250Packet loss rate. 2251Argument 2252.Ar packet-loss-rate 2253is a floating-point number between 0 and 1, with 0 meaning no 2254loss, 1 meaning 100% loss. 2255The loss rate is internally represented on 31 bits. 2256.Pp 2257.It Cm queue Brq Ar slots | size Ns Cm Kbytes 2258Queue size, in 2259.Ar slots 2260or 2261.Cm KBytes . 2262Default value is 50 slots, which 2263is the typical queue size for Ethernet devices. 2264Note that for slow speed links you should keep the queue 2265size short or your traffic might be affected by a significant 2266queueing delay. 2267E.g., 50 max-sized ethernet packets (1500 bytes) mean 600Kbit 2268or 20s of queue on a 30Kbit/s pipe. 2269Even worse effects can result if you get packets from an 2270interface with a much larger MTU, e.g.\& the loopback interface 2271with its 16KB packets. 2272The 2273.Xr sysctl 8 2274variables 2275.Em net.inet.ip.dummynet.pipe_byte_limit 2276and 2277.Em net.inet.ip.dummynet.pipe_slot_limit 2278control the maximum lengths that can be specified. 2279.Pp 2280.It Cm red | gred Ar w_q Ns / Ns Ar min_th Ns / Ns Ar max_th Ns / Ns Ar max_p 2281Make use of the RED (Random Early Detection) queue management algorithm. 2282.Ar w_q 2283and 2284.Ar max_p 2285are floating 2286point numbers between 0 and 1 (0 not included), while 2287.Ar min_th 2288and 2289.Ar max_th 2290are integer numbers specifying thresholds for queue management 2291(thresholds are computed in bytes if the queue has been defined 2292in bytes, in slots otherwise). 2293The 2294.Nm dummynet 2295also supports the gentle RED variant (gred). 2296Three 2297.Xr sysctl 8 2298variables can be used to control the RED behaviour: 2299.Bl -tag -width indent 2300.It Va net.inet.ip.dummynet.red_lookup_depth 2301specifies the accuracy in computing the average queue 2302when the link is idle (defaults to 256, must be greater than zero) 2303.It Va net.inet.ip.dummynet.red_avg_pkt_size 2304specifies the expected average packet size (defaults to 512, must be 2305greater than zero) 2306.It Va net.inet.ip.dummynet.red_max_pkt_size 2307specifies the expected maximum packet size, only used when queue 2308thresholds are in bytes (defaults to 1500, must be greater than zero). 2309.El 2310.El 2311.Pp 2312When used with IPv6 data, 2313.Nm dummynet 2314currently has several limitations. 2315Information necessary to route link-local packets to an 2316interface is not available after processing by 2317.Nm dummynet 2318so those packets are dropped in the output path. 2319Care should be taken to ensure that link-local packets are not passed to 2320.Nm dummynet . 2321.Sh CHECKLIST 2322Here are some important points to consider when designing your 2323rules: 2324.Bl -bullet 2325.It 2326Remember that you filter both packets going 2327.Cm in 2328and 2329.Cm out . 2330Most connections need packets going in both directions. 2331.It 2332Remember to test very carefully. 2333It is a good idea to be near the console when doing this. 2334If you cannot be near the console, 2335use an auto-recovery script such as the one in 2336.Pa /usr/share/examples/ipfw/change_rules.sh . 2337.It 2338Do not forget the loopback interface. 2339.El 2340.Sh FINE POINTS 2341.Bl -bullet 2342.It 2343There are circumstances where fragmented datagrams are unconditionally 2344dropped. 2345TCP packets are dropped if they do not contain at least 20 bytes of 2346TCP header, UDP packets are dropped if they do not contain a full 8 2347byte UDP header, and ICMP packets are dropped if they do not contain 23484 bytes of ICMP header, enough to specify the ICMP type, code, and 2349checksum. 2350These packets are simply logged as 2351.Dq pullup failed 2352since there may not be enough good data in the packet to produce a 2353meaningful log entry. 2354.It 2355Another type of packet is unconditionally dropped, a TCP packet with a 2356fragment offset of one. 2357This is a valid packet, but it only has one use, to try 2358to circumvent firewalls. 2359When logging is enabled, these packets are 2360reported as being dropped by rule -1. 2361.It 2362If you are logged in over a network, loading the 2363.Xr kld 4 2364version of 2365.Nm 2366is probably not as straightforward as you would think. 2367The following command line is recommended: 2368.Bd -literal -offset indent 2369kldload ipfw && \e 2370ipfw add 32000 allow ip from any to any 2371.Ed 2372.Pp 2373Along the same lines, doing an 2374.Bd -literal -offset indent 2375ipfw flush 2376.Ed 2377.Pp 2378in similar surroundings is also a bad idea. 2379.It 2380The 2381.Nm 2382filter list may not be modified if the system security level 2383is set to 3 or higher 2384(see 2385.Xr init 8 2386for information on system security levels). 2387.El 2388.Sh PACKET DIVERSION 2389A 2390.Xr divert 4 2391socket bound to the specified port will receive all packets 2392diverted to that port. 2393If no socket is bound to the destination port, or if the divert module is 2394not loaded, or if the kernel was not compiled with divert socket support, 2395the packets are dropped. 2396.Sh NETWORK ADDRESS TRANSLATION (NAT) 2397.Pp 2398.Nm 2399support in-kernel NAT using the kernel version of 2400.Xr libalias 3 . 2401.Pp 2402The nat configuration command is the following: 2403.Bd -ragged -offset indent 2404.Bk -words 2405.Cm nat 2406.Ar nat_number 2407.Cm config 2408.Ar nat-configuration 2409.Ek 2410.Ed 2411.Pp 2412The following parameters can be configured: 2413.Bl -tag -width indent 2414.It Cm ip Ar ip_address 2415Define an ip address to use for aliasing. 2416.It Cm if Ar nic 2417Use ip address of NIC for aliasing, dynamically changing 2418it if NIC's ip address changes. 2419.It Cm log 2420Enable logging on this nat instance. 2421.It Cm deny_in 2422Deny any incoming connection from outside world. 2423.It Cm same_ports 2424Try to leave the alias port numbers unchanged from 2425the actual local port numbers. 2426.It Cm unreg_only 2427Traffic on the local network not originating from an 2428unregistered address spaces will be ignored. 2429.It Cm reset 2430Reset table of the packet aliasing engine on address change. 2431.It Cm reverse 2432Reverse the way libalias handles aliasing. 2433.It Cm proxy_only 2434Obey transparent proxy rules only, packet aliasing is not performed. 2435.El 2436.Pp 2437To let the packet continue after being (de)aliased, set the sysctl variable 2438.Va net.inet.ip.fw.one_pass 2439to 0. 2440For more information about aliasing modes, refer to 2441.Xr libalias 3 . 2442See Section 2443.Sx EXAMPLES 2444for some examples about nat usage. 2445.Ss REDIRECT AND LSNAT SUPPORT IN IPFW 2446Redirect and LSNAT support follow closely the syntax used in 2447.Xr natd 8 . 2448See Section 2449.Sx EXAMPLES 2450for some examples on how to do redirect and lsnat. 2451.Ss SCTP NAT SUPPORT 2452SCTP nat can be configured in a similar manner to TCP through the 2453.Nm 2454command line tool. 2455The main difference is that 2456.Nm sctp nat 2457does not do port translation. 2458Since the local and global side ports will be the same, 2459there is no need to specify both. 2460Ports are redirected as follows: 2461.Bd -ragged -offset indent 2462.Bk -words 2463.Cm nat 2464.Ar nat_number 2465.Cm config if 2466.Ar nic 2467.Cm redirect_port sctp 2468.Ar ip_address [,addr_list] {[port | port-port] [,ports]} 2469.Ek 2470.Ed 2471.Pp 2472Most 2473.Nm sctp nat 2474configuration can be done in real-time through the 2475.Xr sysctl 8 2476interface. 2477All may be changed dynamically, though the hash_table size will only 2478change for new 2479.Nm nat 2480instances. 2481See 2482.Sx SYSCTL VARIABLES 2483for more info. 2484.Sh SYSCTL VARIABLES 2485A set of 2486.Xr sysctl 8 2487variables controls the behaviour of the firewall and 2488associated modules 2489.Pq Nm dummynet , bridge , sctp nat . 2490These are shown below together with their default value 2491(but always check with the 2492.Xr sysctl 8 2493command what value is actually in use) and meaning: 2494.Bl -tag -width indent 2495.It Va net.inet.ip.alias.sctp.accept_global_ootb_addip: No 0 2496Defines how the 2497.Nm nat 2498responds to receipt of global OOTB ASCONF-AddIP: 2499.Bl -tag -width indent 2500.It Cm 0 2501No response (unless a partially matching association exists - 2502ports and vtags match but global address does not) 2503.It Cm 1 2504.Nm nat 2505will accept and process all OOTB global AddIP messages. 2506.El 2507.Pp 2508Option 1 should never be selected as this forms a security risk. 2509An attacker can 2510establish multiple fake associations by sending AddIP messages. 2511.It Va net.inet.ip.alias.sctp.chunk_proc_limit: No 5 2512Defines the maximum number of chunks in an SCTP packet that will be parsed for a 2513packet that matches an existing association. 2514This value is enforced to be greater or equal than 2515.Cm net.inet.ip.alias.sctp.initialising_chunk_proc_limit . 2516A high value is 2517a DoS risk yet setting too low a value may result in important control chunks in 2518the packet not being located and parsed. 2519.It Va net.inet.ip.alias.sctp.error_on_ootb: No 1 2520Defines when the 2521.Nm nat 2522responds to any Out-of-the-Blue (OOTB) packets with ErrorM packets. 2523An OOTB packet is a packet that arrives with no existing association 2524registered in the 2525.Nm nat 2526and is not an INIT or ASCONF-AddIP packet: 2527.Bl -tag -width indent 2528.It Cm 0 2529ErrorM is never sent in response to OOTB packets. 2530.It Cm 1 2531ErrorM is only sent to OOTB packets received on the local side. 2532.It Cm 2 2533ErrorM is sent to the local side and on the global side ONLY if there is a 2534partial match (ports and vtags match but the source global IP does not). 2535This value is only useful if the 2536.Nm nat 2537is tracking global IP addresses. 2538.It Cm 3 2539ErrorM is sent in response to all OOTB packets on both the local and global side 2540(DoS risk). 2541.El 2542.Pp 2543At the moment the default is 0, since the ErrorM packet is not yet 2544supported by most SCTP stacks. 2545When it is supported, and if not tracking 2546global addresses, we recommend setting this value to 1 to allow 2547multi-homed local hosts to function with the 2548.Nm nat . 2549To track global addresses, we recommend setting this value to 2 to 2550allow global hosts to be informed when they need to (re)send an 2551ASCONF-AddIP. 2552Value 3 should never be chosen (except for debugging) as the 2553.Nm nat 2554will respond to all OOTB global packets (a DoS risk). 2555.It Va net.inet.ip.alias.sctp.hashtable_size: No 2003 2556Size of hash tables used for 2557.Nm nat 2558lookups (100 < prime_number > 1000001). 2559This value sets the 2560.Nm hash table 2561size for any future created 2562.Nm nat 2563instance and therefore must be set prior to creating a 2564.Nm nat 2565instance. 2566The table sizes may be changed to suit specific needs. 2567If there will be few 2568concurrent associations, and memory is scarce, you may make these smaller. 2569If there will be many thousands (or millions) of concurrent associations, you 2570should make these larger. 2571A prime number is best for the table size. 2572The sysctl 2573update function will adjust your input value to the next highest prime number. 2574.It Va net.inet.ip.alias.sctp.holddown_time: No 0 2575Hold association in table for this many seconds after receiving a 2576SHUTDOWN-COMPLETE. 2577This allows endpoints to correct shutdown gracefully if a 2578shutdown_complete is lost and retransmissions are required. 2579.It Va net.inet.ip.alias.sctp.init_timer: No 15 2580Timeout value while waiting for (INIT-ACK|AddIP-ACK). 2581This value cannot be 0. 2582.It Va net.inet.ip.alias.sctp.initialising_chunk_proc_limit: No 2 2583Defines the maximum number of chunks in an SCTP packet that will be parsed when 2584no existing association exists that matches that packet. 2585Ideally this packet 2586will only be an INIT or ASCONF-AddIP packet. 2587A higher value may become a DoS 2588risk as malformed packets can consume processing resources. 2589.It Va net.inet.ip.alias.sctp.param_proc_limit: No 25 2590Defines the maximum number of parameters within a chunk that will be parsed in a 2591packet. 2592As for other similar sysctl variables, larger values pose a DoS risk. 2593.It Va net.inet.ip.alias.sctp.log_level: No 0 2594Level of detail in the system log messages (0 \- minimal, 1 \- event, 25952 \- info, 3 \- detail, 4 \- debug, 5 \- max debug). May be a good 2596option in high loss environments. 2597.It Va net.inet.ip.alias.sctp.shutdown_time: No 15 2598Timeout value while waiting for SHUTDOWN-COMPLETE. 2599This value cannot be 0. 2600.It Va net.inet.ip.alias.sctp.track_global_addresses: No 0 2601Enables/disables global IP address tracking within the 2602.Nm nat 2603and places an 2604upper limit on the number of addresses tracked for each association: 2605.Bl -tag -width indent 2606.It Cm 0 2607Global tracking is disabled 2608.It Cm >1 2609Enables tracking, the maximum number of addresses tracked for each 2610association is limited to this value 2611.El 2612.Pp 2613This variable is fully dynamic, the new value will be adopted for all newly 2614arriving associations, existing associations are treated as they were previously. 2615Global tracking will decrease the number of collisions within the 2616.Nm nat 2617at a cost 2618of increased processing load, memory usage, complexity, and possible 2619.Nm nat 2620state 2621problems in complex networks with multiple 2622.Nm nats . 2623We recommend not tracking 2624global IP addresses, this will still result in a fully functional 2625.Nm nat . 2626.It Va net.inet.ip.alias.sctp.up_timer: No 300 2627Timeout value to keep an association up with no traffic. 2628This value cannot be 0. 2629.It Va net.inet.ip.dummynet.expire : No 1 2630Lazily delete dynamic pipes/queue once they have no pending traffic. 2631You can disable this by setting the variable to 0, in which case 2632the pipes/queues will only be deleted when the threshold is reached. 2633.It Va net.inet.ip.dummynet.hash_size : No 64 2634Default size of the hash table used for dynamic pipes/queues. 2635This value is used when no 2636.Cm buckets 2637option is specified when configuring a pipe/queue. 2638.It Va net.inet.ip.dummynet.io_fast : No 0 2639If set to a non-zero value, 2640the 2641.Dq fast 2642mode of 2643.Nm dummynet 2644operation (see above) is enabled. 2645.It Va net.inet.ip.dummynet.io_pkt 2646Number of packets passed to 2647.Nm dummynet . 2648.It Va net.inet.ip.dummynet.io_pkt_drop 2649Number of packets dropped by 2650.Nm dummynet . 2651.It Va net.inet.ip.dummynet.io_pkt_fast 2652Number of packets bypassed by the 2653.Nm dummynet 2654scheduler. 2655.It Va net.inet.ip.dummynet.max_chain_len : No 16 2656Target value for the maximum number of pipes/queues in a hash bucket. 2657The product 2658.Cm max_chain_len*hash_size 2659is used to determine the threshold over which empty pipes/queues 2660will be expired even when 2661.Cm net.inet.ip.dummynet.expire=0 . 2662.It Va net.inet.ip.dummynet.red_lookup_depth : No 256 2663.It Va net.inet.ip.dummynet.red_avg_pkt_size : No 512 2664.It Va net.inet.ip.dummynet.red_max_pkt_size : No 1500 2665Parameters used in the computations of the drop probability 2666for the RED algorithm. 2667.It Va net.inet.ip.dummynet.pipe_byte_limit : No 1048576 2668.It Va net.inet.ip.dummynet.pipe_slot_limit : No 100 2669The maximum queue size that can be specified in bytes or packets. 2670These limits prevent accidental exhaustion of resources such as mbufs. 2671If you raise these limits, 2672you should make sure the system is configured so that sufficient resources 2673are available. 2674.It Va net.inet.ip.fw.autoinc_step : No 100 2675Delta between rule numbers when auto-generating them. 2676The value must be in the range 1..1000. 2677.It Va net.inet.ip.fw.curr_dyn_buckets : Va net.inet.ip.fw.dyn_buckets 2678The current number of buckets in the hash table for dynamic rules 2679(readonly). 2680.It Va net.inet.ip.fw.debug : No 1 2681Controls debugging messages produced by 2682.Nm . 2683.It Va net.inet.ip.fw.default_rule : No 65535 2684The default rule number (read-only). 2685By the design of 2686.Nm , the default rule is the last one, so its number 2687can also serve as the highest number allowed for a rule. 2688.It Va net.inet.ip.fw.dyn_buckets : No 256 2689The number of buckets in the hash table for dynamic rules. 2690Must be a power of 2, up to 65536. 2691It only takes effect when all dynamic rules have expired, so you 2692are advised to use a 2693.Cm flush 2694command to make sure that the hash table is resized. 2695.It Va net.inet.ip.fw.dyn_count : No 3 2696Current number of dynamic rules 2697(read-only). 2698.It Va net.inet.ip.fw.dyn_keepalive : No 1 2699Enables generation of keepalive packets for 2700.Cm keep-state 2701rules on TCP sessions. 2702A keepalive is generated to both 2703sides of the connection every 5 seconds for the last 20 2704seconds of the lifetime of the rule. 2705.It Va net.inet.ip.fw.dyn_max : No 8192 2706Maximum number of dynamic rules. 2707When you hit this limit, no more dynamic rules can be 2708installed until old ones expire. 2709.It Va net.inet.ip.fw.dyn_ack_lifetime : No 300 2710.It Va net.inet.ip.fw.dyn_syn_lifetime : No 20 2711.It Va net.inet.ip.fw.dyn_fin_lifetime : No 1 2712.It Va net.inet.ip.fw.dyn_rst_lifetime : No 1 2713.It Va net.inet.ip.fw.dyn_udp_lifetime : No 5 2714.It Va net.inet.ip.fw.dyn_short_lifetime : No 30 2715These variables control the lifetime, in seconds, of dynamic 2716rules. 2717Upon the initial SYN exchange the lifetime is kept short, 2718then increased after both SYN have been seen, then decreased 2719again during the final FIN exchange or when a RST is received. 2720Both 2721.Em dyn_fin_lifetime 2722and 2723.Em dyn_rst_lifetime 2724must be strictly lower than 5 seconds, the period of 2725repetition of keepalives. 2726The firewall enforces that. 2727.It Va net.inet.ip.fw.enable : No 1 2728Enables the firewall. 2729Setting this variable to 0 lets you run your machine without 2730firewall even if compiled in. 2731.It Va net.inet6.ip6.fw.enable : No 1 2732provides the same functionality as above for the IPv6 case. 2733.It Va net.inet.ip.fw.one_pass : No 1 2734When set, the packet exiting from the 2735.Nm dummynet 2736pipe or from 2737.Xr ng_ipfw 4 2738node is not passed though the firewall again. 2739Otherwise, after an action, the packet is 2740reinjected into the firewall at the next rule. 2741.It Va net.inet.ip.fw.tables_max : No 128 2742Maximum number of tables (read-only). 2743.It Va net.inet.ip.fw.verbose : No 1 2744Enables verbose messages. 2745.It Va net.inet.ip.fw.verbose_limit : No 0 2746Limits the number of messages produced by a verbose firewall. 2747.It Va net.inet6.ip6.fw.deny_unknown_exthdrs : No 1 2748If enabled packets with unknown IPv6 Extension Headers will be denied. 2749.It Va net.link.ether.ipfw : No 0 2750Controls whether layer-2 packets are passed to 2751.Nm . 2752Default is no. 2753.It Va net.link.bridge.ipfw : No 0 2754Controls whether bridged packets are passed to 2755.Nm . 2756Default is no. 2757.El 2758.Pp 2759.Sh EXAMPLES 2760There are far too many possible uses of 2761.Nm 2762so this Section will only give a small set of examples. 2763.Pp 2764.Ss BASIC PACKET FILTERING 2765This command adds an entry which denies all tcp packets from 2766.Em cracker.evil.org 2767to the telnet port of 2768.Em wolf.tambov.su 2769from being forwarded by the host: 2770.Pp 2771.Dl "ipfw add deny tcp from cracker.evil.org to wolf.tambov.su telnet" 2772.Pp 2773This one disallows any connection from the entire cracker's 2774network to my host: 2775.Pp 2776.Dl "ipfw add deny ip from 123.45.67.0/24 to my.host.org" 2777.Pp 2778A first and efficient way to limit access (not using dynamic rules) 2779is the use of the following rules: 2780.Pp 2781.Dl "ipfw add allow tcp from any to any established" 2782.Dl "ipfw add allow tcp from net1 portlist1 to net2 portlist2 setup" 2783.Dl "ipfw add allow tcp from net3 portlist3 to net3 portlist3 setup" 2784.Dl "..." 2785.Dl "ipfw add deny tcp from any to any" 2786.Pp 2787The first rule will be a quick match for normal TCP packets, 2788but it will not match the initial SYN packet, which will be 2789matched by the 2790.Cm setup 2791rules only for selected source/destination pairs. 2792All other SYN packets will be rejected by the final 2793.Cm deny 2794rule. 2795.Pp 2796If you administer one or more subnets, you can take advantage 2797of the address sets and or-blocks and write extremely 2798compact rulesets which selectively enable services to blocks 2799of clients, as below: 2800.Pp 2801.Dl "goodguys=\*q{ 10.1.2.0/24{20,35,66,18} or 10.2.3.0/28{6,3,11} }\*q" 2802.Dl "badguys=\*q10.1.2.0/24{8,38,60}\*q" 2803.Dl "" 2804.Dl "ipfw add allow ip from ${goodguys} to any" 2805.Dl "ipfw add deny ip from ${badguys} to any" 2806.Dl "... normal policies ..." 2807.Pp 2808The 2809.Cm verrevpath 2810option could be used to do automated anti-spoofing by adding the 2811following to the top of a ruleset: 2812.Pp 2813.Dl "ipfw add deny ip from any to any not verrevpath in" 2814.Pp 2815This rule drops all incoming packets that appear to be coming to the 2816system on the wrong interface. 2817For example, a packet with a source 2818address belonging to a host on a protected internal network would be 2819dropped if it tried to enter the system from an external interface. 2820.Pp 2821The 2822.Cm antispoof 2823option could be used to do similar but more restricted anti-spoofing 2824by adding the following to the top of a ruleset: 2825.Pp 2826.Dl "ipfw add deny ip from any to any not antispoof in" 2827.Pp 2828This rule drops all incoming packets that appear to be coming from another 2829directly connected system but on the wrong interface. 2830For example, a packet with a source address of 2831.Li 192.168.0.0/24 , 2832configured on 2833.Li fxp0 , 2834but coming in on 2835.Li fxp1 2836would be dropped. 2837.Ss DYNAMIC RULES 2838In order to protect a site from flood attacks involving fake 2839TCP packets, it is safer to use dynamic rules: 2840.Pp 2841.Dl "ipfw add check-state" 2842.Dl "ipfw add deny tcp from any to any established" 2843.Dl "ipfw add allow tcp from my-net to any setup keep-state" 2844.Pp 2845This will let the firewall install dynamic rules only for 2846those connection which start with a regular SYN packet coming 2847from the inside of our network. 2848Dynamic rules are checked when encountering the first 2849.Cm check-state 2850or 2851.Cm keep-state 2852rule. 2853A 2854.Cm check-state 2855rule should usually be placed near the beginning of the 2856ruleset to minimize the amount of work scanning the ruleset. 2857Your mileage may vary. 2858.Pp 2859To limit the number of connections a user can open 2860you can use the following type of rules: 2861.Pp 2862.Dl "ipfw add allow tcp from my-net/24 to any setup limit src-addr 10" 2863.Dl "ipfw add allow tcp from any to me setup limit src-addr 4" 2864.Pp 2865The former (assuming it runs on a gateway) will allow each host 2866on a /24 network to open at most 10 TCP connections. 2867The latter can be placed on a server to make sure that a single 2868client does not use more than 4 simultaneous connections. 2869.Pp 2870.Em BEWARE : 2871stateful rules can be subject to denial-of-service attacks 2872by a SYN-flood which opens a huge number of dynamic rules. 2873The effects of such attacks can be partially limited by 2874acting on a set of 2875.Xr sysctl 8 2876variables which control the operation of the firewall. 2877.Pp 2878Here is a good usage of the 2879.Cm list 2880command to see accounting records and timestamp information: 2881.Pp 2882.Dl ipfw -at list 2883.Pp 2884or in short form without timestamps: 2885.Pp 2886.Dl ipfw -a list 2887.Pp 2888which is equivalent to: 2889.Pp 2890.Dl ipfw show 2891.Pp 2892Next rule diverts all incoming packets from 192.168.2.0/24 2893to divert port 5000: 2894.Pp 2895.Dl ipfw divert 5000 ip from 192.168.2.0/24 to any in 2896.Pp 2897.Ss TRAFFIC SHAPING 2898The following rules show some of the applications of 2899.Nm 2900and 2901.Nm dummynet 2902for simulations and the like. 2903.Pp 2904This rule drops random incoming packets with a probability 2905of 5%: 2906.Pp 2907.Dl "ipfw add prob 0.05 deny ip from any to any in" 2908.Pp 2909A similar effect can be achieved making use of 2910.Nm dummynet 2911pipes: 2912.Pp 2913.Dl "ipfw add pipe 10 ip from any to any" 2914.Dl "ipfw pipe 10 config plr 0.05" 2915.Pp 2916We can use pipes to artificially limit bandwidth, e.g.\& on a 2917machine acting as a router, if we want to limit traffic from 2918local clients on 192.168.2.0/24 we do: 2919.Pp 2920.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 2921.Dl "ipfw pipe 1 config bw 300Kbit/s queue 50KBytes" 2922.Pp 2923note that we use the 2924.Cm out 2925modifier so that the rule is not used twice. 2926Remember in fact that 2927.Nm 2928rules are checked both on incoming and outgoing packets. 2929.Pp 2930Should we want to simulate a bidirectional link with bandwidth 2931limitations, the correct way is the following: 2932.Pp 2933.Dl "ipfw add pipe 1 ip from any to any out" 2934.Dl "ipfw add pipe 2 ip from any to any in" 2935.Dl "ipfw pipe 1 config bw 64Kbit/s queue 10Kbytes" 2936.Dl "ipfw pipe 2 config bw 64Kbit/s queue 10Kbytes" 2937.Pp 2938The above can be very useful, e.g.\& if you want to see how 2939your fancy Web page will look for a residential user who 2940is connected only through a slow link. 2941You should not use only one pipe for both directions, unless 2942you want to simulate a half-duplex medium (e.g.\& AppleTalk, 2943Ethernet, IRDA). 2944It is not necessary that both pipes have the same configuration, 2945so we can also simulate asymmetric links. 2946.Pp 2947Should we want to verify network performance with the RED queue 2948management algorithm: 2949.Pp 2950.Dl "ipfw add pipe 1 ip from any to any" 2951.Dl "ipfw pipe 1 config bw 500Kbit/s queue 100 red 0.002/30/80/0.1" 2952.Pp 2953Another typical application of the traffic shaper is to 2954introduce some delay in the communication. 2955This can significantly affect applications which do a lot of Remote 2956Procedure Calls, and where the round-trip-time of the 2957connection often becomes a limiting factor much more than 2958bandwidth: 2959.Pp 2960.Dl "ipfw add pipe 1 ip from any to any out" 2961.Dl "ipfw add pipe 2 ip from any to any in" 2962.Dl "ipfw pipe 1 config delay 250ms bw 1Mbit/s" 2963.Dl "ipfw pipe 2 config delay 250ms bw 1Mbit/s" 2964.Pp 2965Per-flow queueing can be useful for a variety of purposes. 2966A very simple one is counting traffic: 2967.Pp 2968.Dl "ipfw add pipe 1 tcp from any to any" 2969.Dl "ipfw add pipe 1 udp from any to any" 2970.Dl "ipfw add pipe 1 ip from any to any" 2971.Dl "ipfw pipe 1 config mask all" 2972.Pp 2973The above set of rules will create queues (and collect 2974statistics) for all traffic. 2975Because the pipes have no limitations, the only effect is 2976collecting statistics. 2977Note that we need 3 rules, not just the last one, because 2978when 2979.Nm 2980tries to match IP packets it will not consider ports, so we 2981would not see connections on separate ports as different 2982ones. 2983.Pp 2984A more sophisticated example is limiting the outbound traffic 2985on a net with per-host limits, rather than per-network limits: 2986.Pp 2987.Dl "ipfw add pipe 1 ip from 192.168.2.0/24 to any out" 2988.Dl "ipfw add pipe 2 ip from any to 192.168.2.0/24 in" 2989.Dl "ipfw pipe 1 config mask src-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 2990.Dl "ipfw pipe 2 config mask dst-ip 0x000000ff bw 200Kbit/s queue 20Kbytes" 2991.Ss LOOKUP TABLES 2992In the following example, we need to create several traffic bandwidth 2993classes and we need different hosts/networks to fall into different classes. 2994We create one pipe for each class and configure them accordingly. 2995Then we create a single table and fill it with IP subnets and addresses. 2996For each subnet/host we set the argument equal to the number of the pipe 2997that it should use. 2998Then we classify traffic using a single rule: 2999.Pp 3000.Dl "ipfw pipe 1 config bw 1000Kbyte/s" 3001.Dl "ipfw pipe 4 config bw 4000Kbyte/s" 3002.Dl "..." 3003.Dl "ipfw table 1 add 192.168.2.0/24 1" 3004.Dl "ipfw table 1 add 192.168.0.0/27 4" 3005.Dl "ipfw table 1 add 192.168.0.2 1" 3006.Dl "..." 3007.Dl "ipfw add pipe tablearg ip from table(1) to any" 3008.Pp 3009Using the 3010.Cm fwd 3011action, the table entries may include hostnames and IP addresses. 3012.Pp 3013.Dl "ipfw table 1 add 192.168.2.0/24 10.23.2.1" 3014.Dl "ipfw table 1 add 192.168.0.0/27 router1.dmz" 3015.Dl "..." 3016.Dl "ipfw add 100 fwd tablearg ip from any to table(1)" 3017.Ss SETS OF RULES 3018To add a set of rules atomically, e.g.\& set 18: 3019.Pp 3020.Dl "ipfw set disable 18" 3021.Dl "ipfw add NN set 18 ... # repeat as needed" 3022.Dl "ipfw set enable 18" 3023.Pp 3024To delete a set of rules atomically the command is simply: 3025.Pp 3026.Dl "ipfw delete set 18" 3027.Pp 3028To test a ruleset and disable it and regain control if something goes wrong: 3029.Pp 3030.Dl "ipfw set disable 18" 3031.Dl "ipfw add NN set 18 ... # repeat as needed" 3032.Dl "ipfw set enable 18; echo done; sleep 30 && ipfw set disable 18" 3033.Pp 3034Here if everything goes well, you press control-C before the "sleep" 3035terminates, and your ruleset will be left active. 3036Otherwise, e.g.\& if 3037you cannot access your box, the ruleset will be disabled after 3038the sleep terminates thus restoring the previous situation. 3039.Pp 3040To show rules of the specific set: 3041.Pp 3042.Dl "ipfw set 18 show" 3043.Pp 3044To show rules of the disabled set: 3045.Pp 3046.Dl "ipfw -S set 18 show" 3047.Pp 3048To clear a specific rule counters of the specific set: 3049.Pp 3050.Dl "ipfw set 18 zero NN" 3051.Pp 3052To delete a specific rule of the specific set: 3053.Pp 3054.Dl "ipfw set 18 delete NN" 3055.Ss NAT, REDIRECT AND LSNAT 3056First redirect all the traffic to nat instance 123: 3057.Pp 3058.Dl "ipfw add nat 123 all from any to any" 3059.Pp 3060Then to configure nat instance 123 to alias all the outgoing traffic with ip 3061192.168.0.123, blocking all incoming connections, trying to keep 3062same ports on both sides, clearing aliasing table on address change 3063and keeping a log of traffic/link statistics: 3064.Pp 3065.Dl "ipfw nat 123 config ip 192.168.0.123 log deny_in reset same_ports" 3066.Pp 3067Or to change address of instance 123, aliasing table will be cleared (see 3068reset option): 3069.Pp 3070.Dl "ipfw nat 123 config ip 10.0.0.1" 3071.Pp 3072To see configuration of nat instance 123: 3073.Pp 3074.Dl "ipfw nat 123 show config" 3075.Pp 3076To show logs of all the instances in range 111-999: 3077.Pp 3078.Dl "ipfw nat 111-999 show" 3079.Pp 3080To see configurations of all instances: 3081.Pp 3082.Dl "ipfw nat show config" 3083.Pp 3084Or a redirect rule with mixed modes could looks like: 3085.Pp 3086.Dl "ipfw nat 123 config redirect_addr 10.0.0.1 10.0.0.66" 3087.Dl " redirect_port tcp 192.168.0.1:80 500" 3088.Dl " redirect_proto udp 192.168.1.43 192.168.1.1" 3089.Dl " redirect_addr 192.168.0.10,192.168.0.11" 3090.Dl " 10.0.0.100 # LSNAT" 3091.Dl " redirect_port tcp 192.168.0.1:80,192.168.0.10:22" 3092.Dl " 500 # LSNAT" 3093.Pp 3094or it could be split in: 3095.Pp 3096.Dl "ipfw nat 1 config redirect_addr 10.0.0.1 10.0.0.66" 3097.Dl "ipfw nat 2 config redirect_port tcp 192.168.0.1:80 500" 3098.Dl "ipfw nat 3 config redirect_proto udp 192.168.1.43 192.168.1.1" 3099.Dl "ipfw nat 4 config redirect_addr 192.168.0.10,192.168.0.11,192.168.0.12" 3100.Dl " 10.0.0.100" 3101.Dl "ipfw nat 5 config redirect_port tcp" 3102.Dl " 192.168.0.1:80,192.168.0.10:22,192.168.0.20:25 500" 3103.Pp 3104.Sh SEE ALSO 3105.Xr cpp 1 , 3106.Xr m4 1 , 3107.Xr altq 4 , 3108.Xr divert 4 , 3109.Xr dummynet 4 , 3110.Xr if_bridge 4 , 3111.Xr ip 4 , 3112.Xr ipfirewall 4 , 3113.Xr ng_ipfw 4 , 3114.Xr protocols 5 , 3115.Xr services 5 , 3116.Xr init 8 , 3117.Xr kldload 8 , 3118.Xr reboot 8 , 3119.Xr sysctl 8 , 3120.Xr syslogd 8 3121.Sh HISTORY 3122The 3123.Nm 3124utility first appeared in 3125.Fx 2.0 . 3126.Nm dummynet 3127was introduced in 3128.Fx 2.2.8 . 3129Stateful extensions were introduced in 3130.Fx 4.0 . 3131.Nm ipfw2 3132was introduced in Summer 2002. 3133.Sh AUTHORS 3134.An Ugen J. S. Antsilevich , 3135.An Poul-Henning Kamp , 3136.An Alex Nash , 3137.An Archie Cobbs , 3138.An Luigi Rizzo . 3139.Pp 3140.An -nosplit 3141API based upon code written by 3142.An Daniel Boulet 3143for BSDI. 3144.Pp 3145Dummynet has been introduced by Luigi Rizzo in 1997-1998. 3146.Pp 3147Some early work (1999-2000) on the 3148.Nm dummynet 3149traffic shaper supported by Akamba Corp. 3150.Pp 3151The ipfw core (ipfw2) has been completely redesigned and 3152reimplemented by Luigi Rizzo in summer 2002. Further 3153actions and 3154options have been added by various developer over the years. 3155.Pp 3156.An -nosplit 3157In-kernel NAT support written by 3158.An Paolo Pisati Aq piso@FreeBSD.org 3159as part of a Summer of Code 2005 project. 3160.Pp 3161SCTP 3162.Nm nat 3163support has been developed by 3164.An The Centre for Advanced Internet Architectures (CAIA) Aq http://www.caia.swin.edu.au . 3165The primary developers and maintainers are David Hayes and Jason But. 3166For further information visit: 3167.Aq http://www.caia.swin.edu.au/urp/SONATA 3168.Pp 3169Delay profiles have been developed by Alessandro Cerri and 3170Luigi Rizzo, supported by the 3171European Commission within Projects Onelab and Onelab2. 3172.Sh BUGS 3173The syntax has grown over the years and sometimes it might be confusing. 3174Unfortunately, backward compatibility prevents cleaning up mistakes 3175made in the definition of the syntax. 3176.Pp 3177.Em !!! WARNING !!! 3178.Pp 3179Misconfiguring the firewall can put your computer in an unusable state, 3180possibly shutting down network services and requiring console access to 3181regain control of it. 3182.Pp 3183Incoming packet fragments diverted by 3184.Cm divert 3185are reassembled before delivery to the socket. 3186The action used on those packet is the one from the 3187rule which matches the first fragment of the packet. 3188.Pp 3189Packets diverted to userland, and then reinserted by a userland process 3190may lose various packet attributes. 3191The packet source interface name 3192will be preserved if it is shorter than 8 bytes and the userland process 3193saves and reuses the sockaddr_in 3194(as does 3195.Xr natd 8 ) ; 3196otherwise, it may be lost. 3197If a packet is reinserted in this manner, later rules may be incorrectly 3198applied, making the order of 3199.Cm divert 3200rules in the rule sequence very important. 3201.Pp 3202Dummynet drops all packets with IPv6 link-local addresses. 3203.Pp 3204Rules using 3205.Cm uid 3206or 3207.Cm gid 3208may not behave as expected. 3209In particular, incoming SYN packets may 3210have no uid or gid associated with them since they do not yet belong 3211to a TCP connection, and the uid/gid associated with a packet may not 3212be as expected if the associated process calls 3213.Xr setuid 2 3214or similar system calls. 3215.Pp 3216Rule syntax is subject to the command line environment and some patterns 3217may need to be escaped with the backslash character 3218or quoted appropriately. 3219.Pp 3220Due to the architecture of 3221.Xr libalias 3 , 3222ipfw nat is not compatible with the TCP segmentation offloading (TSO). 3223Thus, to reliably nat your network traffic, please disable TSO 3224on your NICs using 3225.Xr ifconfig 8 . 3226.Pp 3227ICMP error messages are not implicitly matched by dynamic rules 3228for the respective conversations. 3229To avoid failures of network error detection and path MTU discovery, 3230ICMP error messages may need to be allowed explicitly through static 3231rules. 3232