1.\" $FreeBSD$ 2.\" $OpenBSD: pf.conf.5,v 1.406 2009/01/31 19:37:12 sobrado Exp $ 3.\" 4.\" Copyright (c) 2002, Daniel Hartmeier 5.\" All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" - Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" - Redistributions in binary form must reproduce the above 14.\" copyright notice, this list of conditions and the following 15.\" disclaimer in the documentation and/or other materials provided 16.\" with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 21.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 22.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 23.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 24.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 25.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 26.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 28.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29.\" POSSIBILITY OF SUCH DAMAGE. 30.\" 31.Dd September 10, 2021 32.Dt PF.CONF 5 33.Os 34.Sh NAME 35.Nm pf.conf 36.Nd packet filter configuration file 37.Sh DESCRIPTION 38The 39.Xr pf 4 40packet filter modifies, drops or passes packets according to rules or 41definitions specified in 42.Nm pf.conf . 43.Sh STATEMENT ORDER 44There are seven types of statements in 45.Nm pf.conf : 46.Bl -tag -width xxxx 47.It Cm Macros 48User-defined variables may be defined and used later, simplifying 49the configuration file. 50Macros must be defined before they are referenced in 51.Nm pf.conf . 52.It Cm Tables 53Tables provide a mechanism for increasing the performance and flexibility of 54rules with large numbers of source or destination addresses. 55.It Cm Options 56Options tune the behaviour of the packet filtering engine. 57.It Cm Traffic Normalization Li (e.g. Em scrub ) 58Traffic normalization protects internal machines against inconsistencies 59in Internet protocols and implementations. 60.It Cm Queueing 61Queueing provides rule-based bandwidth control. 62.It Cm Translation Li (Various forms of NAT) 63Translation rules specify how addresses are to be mapped or redirected to 64other addresses. 65.It Cm Packet Filtering 66Packet filtering provides rule-based blocking or passing of packets. 67.El 68.Pp 69With the exception of 70.Cm macros 71and 72.Cm tables , 73the types of statements should be grouped and appear in 74.Nm pf.conf 75in the order shown above, as this matches the operation of the underlying 76packet filtering engine. 77By default 78.Xr pfctl 8 79enforces this order (see 80.Ar set require-order 81below). 82.Pp 83Comments can be put anywhere in the file using a hash mark 84.Pq Sq # , 85and extend to the end of the current line. 86.Pp 87Additional configuration files can be included with the 88.Ic include 89keyword, for example: 90.Bd -literal -offset indent 91include "/etc/pf/sub.filter.conf" 92.Ed 93.Sh MACROS 94Macros can be defined that will later be expanded in context. 95Macro names must start with a letter, and may contain letters, digits 96and underscores. 97Macro names may not be reserved words (for example 98.Ar pass , 99.Ar in , 100.Ar out ) . 101Macros are not expanded inside quotes. 102.Pp 103For example, 104.Bd -literal -offset indent 105ext_if = \&"kue0\&" 106all_ifs = \&"{\&" $ext_if lo0 \&"}\&" 107pass out on $ext_if from any to any 108pass in on $ext_if proto tcp from any to any port 25 109.Ed 110.Sh TABLES 111Tables are named structures which can hold a collection of addresses and 112networks. 113Lookups against tables in 114.Xr pf 4 115are relatively fast, making a single rule with tables much more efficient, 116in terms of 117processor usage and memory consumption, than a large number of rules which 118differ only in IP address (either created explicitly or automatically by rule 119expansion). 120.Pp 121Tables can be used as the source or destination of filter rules, 122.Ar scrub 123rules 124or 125translation rules such as 126.Ar nat 127or 128.Ar rdr 129(see below for details on the various rule types). 130Tables can also be used for the redirect address of 131.Ar nat 132and 133.Ar rdr 134rules and in the routing options of filter rules, but only for 135.Ar round-robin 136pools. 137.Pp 138Tables can be defined with any of the following 139.Xr pfctl 8 140mechanisms. 141As with macros, reserved words may not be used as table names. 142.Bl -tag -width "manually" 143.It Ar manually 144Persistent tables can be manually created with the 145.Ar add 146or 147.Ar replace 148option of 149.Xr pfctl 8 , 150before or after the ruleset has been loaded. 151.It Pa pf.conf 152Table definitions can be placed directly in this file, and loaded at the 153same time as other rules are loaded, atomically. 154Table definitions inside 155.Nm pf.conf 156use the 157.Ar table 158statement, and are especially useful to define non-persistent tables. 159The contents of a pre-existing table defined without a list of addresses 160to initialize it is not altered when 161.Nm pf.conf 162is loaded. 163A table initialized with the empty list, 164.Li { } , 165will be cleared on load. 166.El 167.Pp 168Tables may be defined with the following attributes: 169.Bl -tag -width persist 170.It Ar persist 171The 172.Ar persist 173flag forces the kernel to keep the table even when no rules refer to it. 174If the flag is not set, the kernel will automatically remove the table 175when the last rule referring to it is flushed. 176.It Ar const 177The 178.Ar const 179flag prevents the user from altering the contents of the table once it 180has been created. 181Without that flag, 182.Xr pfctl 8 183can be used to add or remove addresses from the table at any time, even 184when running with 185.Xr securelevel 7 186= 2. 187.It Ar counters 188The 189.Ar counters 190flag enables per-address packet and byte counters which can be displayed with 191.Xr pfctl 8 . 192Note that this feature carries significant memory overhead for large tables. 193.El 194.Pp 195For example, 196.Bd -literal -offset indent 197table \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 } 198table \*(Ltbadhosts\*(Gt persist 199block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } to any 200.Ed 201.Pp 202creates a table called private, to hold RFC 1918 private network 203blocks, and a table called badhosts, which is initially empty. 204A filter rule is set up to block all traffic coming from addresses listed in 205either table. 206The private table cannot have its contents changed and the badhosts table 207will exist even when no active filter rules reference it. 208Addresses may later be added to the badhosts table, so that traffic from 209these hosts can be blocked by using 210.Bd -literal -offset indent 211# pfctl -t badhosts -Tadd 204.92.77.111 212.Ed 213.Pp 214A table can also be initialized with an address list specified in one or more 215external files, using the following syntax: 216.Bd -literal -offset indent 217table \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&" 218block on fxp0 from \*(Ltspam\*(Gt to any 219.Ed 220.Pp 221The files 222.Pa /etc/spammers 223and 224.Pa /etc/openrelays 225list IP addresses, one per line. 226Any lines beginning with a # are treated as comments and ignored. 227In addition to being specified by IP address, hosts may also be 228specified by their hostname. 229When the resolver is called to add a hostname to a table, 230.Em all 231resulting IPv4 and IPv6 addresses are placed into the table. 232IP addresses can also be entered in a table by specifying a valid interface 233name, a valid interface group or the 234.Em self 235keyword, in which case all addresses assigned to the interface(s) will be 236added to the table. 237.Sh OPTIONS 238.Xr pf 4 239may be tuned for various situations using the 240.Ar set 241command. 242.Bl -tag -width xxxx 243.It Ar set timeout 244.Pp 245.Bl -tag -width "src.track" -compact 246.It Ar interval 247Interval between purging expired states and fragments. 248.It Ar frag 249Seconds before an unassembled fragment is expired. 250.It Ar src.track 251Length of time to retain a source tracking entry after the last state 252expires. 253.El 254.Pp 255When a packet matches a stateful connection, the seconds to live for the 256connection will be updated to that of the 257.Ar proto.modifier 258which corresponds to the connection state. 259Each packet which matches this state will reset the TTL. 260Tuning these values may improve the performance of the 261firewall at the risk of dropping valid idle connections. 262.Pp 263.Bl -tag -width xxxx -compact 264.It Ar tcp.first 265The state after the first packet. 266.It Ar tcp.opening 267The state before the destination host ever sends a packet. 268.It Ar tcp.established 269The fully established state. 270.It Ar tcp.closing 271The state after the first FIN has been sent. 272.It Ar tcp.finwait 273The state after both FINs have been exchanged and the connection is closed. 274Some hosts (notably web servers on Solaris) send TCP packets even after closing 275the connection. 276Increasing 277.Ar tcp.finwait 278(and possibly 279.Ar tcp.closing ) 280can prevent blocking of such packets. 281.It Ar tcp.closed 282The state after one endpoint sends an RST. 283.El 284.Pp 285ICMP and UDP are handled in a fashion similar to TCP, but with a much more 286limited set of states: 287.Pp 288.Bl -tag -width xxxx -compact 289.It Ar udp.first 290The state after the first packet. 291.It Ar udp.single 292The state if the source host sends more than one packet but the destination 293host has never sent one back. 294.It Ar udp.multiple 295The state if both hosts have sent packets. 296.It Ar icmp.first 297The state after the first packet. 298.It Ar icmp.error 299The state after an ICMP error came back in response to an ICMP packet. 300.El 301.Pp 302Other protocols are handled similarly to UDP: 303.Pp 304.Bl -tag -width xxxx -compact 305.It Ar other.first 306.It Ar other.single 307.It Ar other.multiple 308.El 309.Pp 310Timeout values can be reduced adaptively as the number of state table 311entries grows. 312.Pp 313.Bl -tag -width xxxx -compact 314.It Ar adaptive.start 315When the number of state entries exceeds this value, adaptive scaling 316begins. 317All timeout values are scaled linearly with factor 318(adaptive.end - number of states) / (adaptive.end - adaptive.start). 319.It Ar adaptive.end 320When reaching this number of state entries, all timeout values become 321zero, effectively purging all state entries immediately. 322This value is used to define the scale factor, it should not actually 323be reached (set a lower state limit, see below). 324.El 325.Pp 326Adaptive timeouts are enabled by default, with an adaptive.start value 327equal to 60% of the state limit, and an adaptive.end value equal to 328120% of the state limit. 329They can be disabled by setting both adaptive.start and adaptive.end to 0. 330.Pp 331The adaptive timeout values can be defined both globally and for each rule. 332When used on a per-rule basis, the values relate to the number of 333states created by the rule, otherwise to the total number of 334states. 335.Pp 336For example: 337.Bd -literal -offset indent 338set timeout tcp.first 120 339set timeout tcp.established 86400 340set timeout { adaptive.start 6000, adaptive.end 12000 } 341set limit states 10000 342.Ed 343.Pp 344With 9000 state table entries, the timeout values are scaled to 50% 345(tcp.first 60, tcp.established 43200). 346.It Ar set loginterface 347Enable collection of packet and byte count statistics for the given 348interface or interface group. 349These statistics can be viewed using 350.Bd -literal -offset indent 351# pfctl -s info 352.Ed 353.Pp 354In this example 355.Xr pf 4 356collects statistics on the interface named dc0: 357.Bd -literal -offset indent 358set loginterface dc0 359.Ed 360.Pp 361One can disable the loginterface using: 362.Bd -literal -offset indent 363set loginterface none 364.Ed 365.It Ar set limit 366Sets hard limits on the memory pools used by the packet filter. 367See 368.Xr zone 9 369for an explanation of memory pools. 370.Pp 371For example, 372.Bd -literal -offset indent 373set limit states 20000 374.Ed 375.Pp 376sets the maximum number of entries in the memory pool used by state table 377entries (generated by 378.Ar pass 379rules which do not specify 380.Ar no state ) 381to 20000. 382Using 383.Bd -literal -offset indent 384set limit frags 20000 385.Ed 386.Pp 387sets the maximum number of entries in the memory pool used for fragment 388reassembly (generated by 389.Ar scrub 390rules) to 20000. 391Using 392.Bd -literal -offset indent 393set limit src-nodes 2000 394.Ed 395.Pp 396sets the maximum number of entries in the memory pool used for tracking 397source IP addresses (generated by the 398.Ar sticky-address 399and 400.Ar src.track 401options) to 2000. 402Using 403.Bd -literal -offset indent 404set limit tables 1000 405set limit table-entries 100000 406.Ed 407.Pp 408sets limits on the memory pools used by tables. 409The first limits the number of tables that can exist to 1000. 410The second limits the overall number of addresses that can be stored 411in tables to 100000. 412.Pp 413Various limits can be combined on a single line: 414.Bd -literal -offset indent 415set limit { states 20000, frags 20000, src-nodes 2000 } 416.Ed 417.It Ar set ruleset-optimization 418.Bl -tag -width xxxxxxxx -compact 419.It Ar none 420Disable the ruleset optimizer. 421.It Ar basic 422Enable basic ruleset optimization. 423This is the default behaviour. 424Basic ruleset optimization does four things to improve the 425performance of ruleset evaluations: 426.Pp 427.Bl -enum -compact 428.It 429remove duplicate rules 430.It 431remove rules that are a subset of another rule 432.It 433combine multiple rules into a table when advantageous 434.It 435re-order the rules to improve evaluation performance 436.El 437.Pp 438.It Ar profile 439Uses the currently loaded ruleset as a feedback profile to tailor the 440ordering of quick rules to actual network traffic. 441.El 442.Pp 443It is important to note that the ruleset optimizer will modify the ruleset 444to improve performance. 445A side effect of the ruleset modification is that per-rule accounting 446statistics will have different meanings than before. 447If per-rule accounting is important for billing purposes or whatnot, 448either the ruleset optimizer should not be used or a label field should 449be added to all of the accounting rules to act as optimization barriers. 450.Pp 451Optimization can also be set as a command-line argument to 452.Xr pfctl 8 , 453overriding the settings in 454.Nm . 455.It Ar set optimization 456Optimize state timeouts for one of the following network environments: 457.Pp 458.Bl -tag -width xxxx -compact 459.It Ar normal 460A normal network environment. 461Suitable for almost all networks. 462.It Ar high-latency 463A high-latency environment (such as a satellite connection). 464.It Ar satellite 465Alias for 466.Ar high-latency . 467.It Ar aggressive 468Aggressively expire connections. 469This can greatly reduce the memory usage of the firewall at the cost of 470dropping idle connections early. 471.It Ar conservative 472Extremely conservative settings. 473Avoid dropping legitimate connections at the 474expense of greater memory utilization (possibly much greater on a busy 475network) and slightly increased processor utilization. 476.El 477.Pp 478For example: 479.Bd -literal -offset indent 480set optimization aggressive 481.Ed 482.It Ar set block-policy 483The 484.Ar block-policy 485option sets the default behaviour for the packet 486.Ar block 487action: 488.Pp 489.Bl -tag -width xxxxxxxx -compact 490.It Ar drop 491Packet is silently dropped. 492.It Ar return 493A TCP RST is returned for blocked TCP packets, 494an ICMP UNREACHABLE is returned for blocked UDP packets, 495and all other packets are silently dropped. 496.El 497.Pp 498For example: 499.Bd -literal -offset indent 500set block-policy return 501.Ed 502.It Ar set fail-policy 503The 504.Ar fail-policy 505option sets the behaviour of rules which should pass a packet but were 506unable to do so. 507This might happen when a nat or route-to rule uses an empty table as list 508of targets or if a rule fails to create state or source node. 509The following 510.Ar block 511actions are possible: 512.Pp 513.Bl -tag -width xxxxxxxx -compact 514.It Ar drop 515Incoming packet is silently dropped. 516.It Ar return 517Incoming packet is dropped and TCP RST is returned for TCP packets, 518an ICMP UNREACHABLE is returned for UDP packets, 519and no response is sent for other packets. 520.El 521.Pp 522For example: 523.Bd -literal -offset indent 524set fail-policy return 525.Ed 526.It Ar set state-policy 527The 528.Ar state-policy 529option sets the default behaviour for states: 530.Pp 531.Bl -tag -width group-bound -compact 532.It Ar if-bound 533States are bound to interface. 534.It Ar floating 535States can match packets on any interfaces (the default). 536.El 537.Pp 538For example: 539.Bd -literal -offset indent 540set state-policy if-bound 541.Ed 542.It Ar set state-defaults 543The 544.Ar state-defaults 545option sets the state options for states created from rules 546without an explicit 547.Ar keep state . 548For example: 549.Bd -literal -offset indent 550set state-defaults no-sync 551.Ed 552.It Ar set hostid 553The 32-bit 554.Ar hostid 555identifies this firewall's state table entries to other firewalls 556in a 557.Xr pfsync 4 558failover cluster. 559By default the hostid is set to a pseudo-random value, however it may be 560desirable to manually configure it, for example to more easily identify the 561source of state table entries. 562.Bd -literal -offset indent 563set hostid 1 564.Ed 565.Pp 566The hostid may be specified in either decimal or hexadecimal. 567.It Ar set require-order 568By default 569.Xr pfctl 8 570enforces an ordering of the statement types in the ruleset to: 571.Em options , 572.Em normalization , 573.Em queueing , 574.Em translation , 575.Em filtering . 576Setting this option to 577.Ar no 578disables this enforcement. 579There may be non-trivial and non-obvious implications to an out of 580order ruleset. 581Consider carefully before disabling the order enforcement. 582.It Ar set fingerprints 583Load fingerprints of known operating systems from the given filename. 584By default fingerprints of known operating systems are automatically 585loaded from 586.Xr pf.os 5 587in 588.Pa /etc 589but can be overridden via this option. 590Setting this option may leave a small period of time where the fingerprints 591referenced by the currently active ruleset are inconsistent until the new 592ruleset finishes loading. 593.Pp 594For example: 595.Pp 596.Dl set fingerprints \&"/etc/pf.os.devel\&" 597.It Ar set skip on Aq Ar ifspec 598List interfaces for which packets should not be filtered. 599Packets passing in or out on such interfaces are passed as if pf was 600disabled, i.e. pf does not process them in any way. 601This can be useful on loopback and other virtual interfaces, when 602packet filtering is not desired and can have unexpected effects. 603For example: 604.Pp 605.Dl set skip on lo0 606.It Ar set debug 607Set the debug 608.Ar level 609to one of the following: 610.Pp 611.Bl -tag -width xxxxxxxxxxxx -compact 612.It Ar none 613Don't generate debug messages. 614.It Ar urgent 615Generate debug messages only for serious errors. 616.It Ar misc 617Generate debug messages for various errors. 618.It Ar loud 619Generate debug messages for common conditions. 620.El 621.It Ar set keepcounters 622Preserve rule counters across rule updates. 623Usually rule counters are reset to zero on every update of the ruleset. 624With 625.Ar keepcounters 626set pf will attempt to find matching rules between old and new rulesets 627and preserve the rule counters. 628.El 629.Sh TRAFFIC NORMALIZATION 630Traffic normalization is used to sanitize packet content in such 631a way that there are no ambiguities in packet interpretation on 632the receiving side. 633The normalizer does IP fragment reassembly to prevent attacks 634that confuse intrusion detection systems by sending overlapping 635IP fragments. 636Packet normalization is invoked with the 637.Ar scrub 638directive. 639.Pp 640.Ar scrub 641has the following options: 642.Bl -tag -width xxxx 643.It Ar no-df 644Clears the 645.Ar dont-fragment 646bit from a matching IP packet. 647Some operating systems are known to generate fragmented packets with the 648.Ar dont-fragment 649bit set. 650This is particularly true with NFS. 651.Ar Scrub 652will drop such fragmented 653.Ar dont-fragment 654packets unless 655.Ar no-df 656is specified. 657.Pp 658Unfortunately some operating systems also generate their 659.Ar dont-fragment 660packets with a zero IP identification field. 661Clearing the 662.Ar dont-fragment 663bit on packets with a zero IP ID may cause deleterious results if an 664upstream router later fragments the packet. 665Using the 666.Ar random-id 667modifier (see below) is recommended in combination with the 668.Ar no-df 669modifier to ensure unique IP identifiers. 670.It Ar min-ttl Aq Ar number 671Enforces a minimum TTL for matching IP packets. 672.It Ar max-mss Aq Ar number 673Enforces a maximum MSS for matching TCP packets. 674.It Xo Ar set-tos Aq Ar string 675.No \*(Ba Aq Ar number 676.Xc 677Enforces a 678.Em TOS 679for matching IP packets. 680.Em TOS 681may be 682given as one of 683.Ar critical , 684.Ar inetcontrol , 685.Ar lowdelay , 686.Ar netcontrol , 687.Ar throughput , 688.Ar reliability , 689or one of the DiffServ Code Points: 690.Ar ef , 691.Ar va , 692.Ar af11 No ... Ar af43 , 693.Ar cs0 No ... Ar cs7 ; 694or as either hex or decimal. 695.It Ar random-id 696Replaces the IP identification field with random values to compensate 697for predictable values generated by many hosts. 698This option only applies to packets that are not fragmented 699after the optional fragment reassembly. 700.It Ar fragment reassemble 701Using 702.Ar scrub 703rules, fragments can be reassembled by normalization. 704In this case, fragments are buffered until they form a complete 705packet, and only the completed packet is passed on to the filter. 706The advantage is that filter rules have to deal only with complete 707packets, and can ignore fragments. 708The drawback of caching fragments is the additional memory cost. 709.It Ar reassemble tcp 710Statefully normalizes TCP connections. 711.Ar scrub reassemble tcp 712rules may not have the direction (in/out) specified. 713.Ar reassemble tcp 714performs the following normalizations: 715.Pp 716.Bl -tag -width timeout -compact 717.It ttl 718Neither side of the connection is allowed to reduce their IP TTL. 719An attacker may send a packet such that it reaches the firewall, affects 720the firewall state, and expires before reaching the destination host. 721.Ar reassemble tcp 722will raise the TTL of all packets back up to the highest value seen on 723the connection. 724.It timestamp modulation 725Modern TCP stacks will send a timestamp on every TCP packet and echo 726the other endpoint's timestamp back to them. 727Many operating systems will merely start the timestamp at zero when 728first booted, and increment it several times a second. 729The uptime of the host can be deduced by reading the timestamp and multiplying 730by a constant. 731Also observing several different timestamps can be used to count hosts 732behind a NAT device. 733And spoofing TCP packets into a connection requires knowing or guessing 734valid timestamps. 735Timestamps merely need to be monotonically increasing and not derived off a 736guessable base time. 737.Ar reassemble tcp 738will cause 739.Ar scrub 740to modulate the TCP timestamps with a random number. 741.It extended PAWS checks 742There is a problem with TCP on long fat pipes, in that a packet might get 743delayed for longer than it takes the connection to wrap its 32-bit sequence 744space. 745In such an occurrence, the old packet would be indistinguishable from a 746new packet and would be accepted as such. 747The solution to this is called PAWS: Protection Against Wrapped Sequence 748numbers. 749It protects against it by making sure the timestamp on each packet does 750not go backwards. 751.Ar reassemble tcp 752also makes sure the timestamp on the packet does not go forward more 753than the RFC allows. 754By doing this, 755.Xr pf 4 756artificially extends the security of TCP sequence numbers by 10 to 18 757bits when the host uses appropriately randomized timestamps, since a 758blind attacker would have to guess the timestamp as well. 759.El 760.El 761.Pp 762For example, 763.Bd -literal -offset indent 764scrub in on $ext_if all fragment reassemble 765.Ed 766.Pp 767The 768.Ar no 769option prefixed to a scrub rule causes matching packets to remain unscrubbed, 770much in the same way as 771.Ar drop quick 772works in the packet filter (see below). 773This mechanism should be used when it is necessary to exclude specific packets 774from broader scrub rules. 775.Sh QUEUEING with ALTQ 776The ALTQ system is currently not available in the GENERIC kernel nor as 777loadable modules. 778In order to use the herein after called queueing options one has to use a 779custom built kernel. 780Please refer to 781.Xr altq 4 782to learn about the related kernel options. 783.Pp 784Packets can be assigned to queues for the purpose of bandwidth 785control. 786At least two declarations are required to configure queues, and later 787any packet filtering rule can reference the defined queues by name. 788During the filtering component of 789.Nm pf.conf , 790the last referenced 791.Ar queue 792name is where any packets from 793.Ar pass 794rules will be queued, while for 795.Ar block 796rules it specifies where any resulting ICMP or TCP RST 797packets should be queued. 798The 799.Ar scheduler 800defines the algorithm used to decide which packets get delayed, dropped, or 801sent out immediately. 802There are three 803.Ar schedulers 804currently supported. 805.Bl -tag -width xxxx 806.It Ar cbq 807Class Based Queueing. 808.Ar Queues 809attached to an interface build a tree, thus each 810.Ar queue 811can have further child 812.Ar queues . 813Each queue can have a 814.Ar priority 815and a 816.Ar bandwidth 817assigned. 818.Ar Priority 819mainly controls the time packets take to get sent out, while 820.Ar bandwidth 821has primarily effects on throughput. 822.Ar cbq 823achieves both partitioning and sharing of link bandwidth 824by hierarchically structured classes. 825Each class has its own 826.Ar queue 827and is assigned its share of 828.Ar bandwidth . 829A child class can borrow bandwidth from its parent class 830as long as excess bandwidth is available 831(see the option 832.Ar borrow , 833below). 834.It Ar priq 835Priority Queueing. 836.Ar Queues 837are flat attached to the interface, thus, 838.Ar queues 839cannot have further child 840.Ar queues . 841Each 842.Ar queue 843has a unique 844.Ar priority 845assigned, ranging from 0 to 15. 846Packets in the 847.Ar queue 848with the highest 849.Ar priority 850are processed first. 851.It Ar hfsc 852Hierarchical Fair Service Curve. 853.Ar Queues 854attached to an interface build a tree, thus each 855.Ar queue 856can have further child 857.Ar queues . 858Each queue can have a 859.Ar priority 860and a 861.Ar bandwidth 862assigned. 863.Ar Priority 864mainly controls the time packets take to get sent out, while 865.Ar bandwidth 866primarily affects throughput. 867.Ar hfsc 868supports both link-sharing and guaranteed real-time services. 869It employs a service curve based QoS model, 870and its unique feature is an ability to decouple 871.Ar delay 872and 873.Ar bandwidth 874allocation. 875.El 876.Pp 877The interfaces on which queueing should be activated are declared using 878the 879.Ar altq on 880declaration. 881.Ar altq on 882has the following keywords: 883.Bl -tag -width xxxx 884.It Aq Ar interface 885Queueing is enabled on the named interface. 886.It Aq Ar scheduler 887Specifies which queueing scheduler to use. 888Currently supported values 889are 890.Ar cbq 891for Class Based Queueing, 892.Ar priq 893for Priority Queueing and 894.Ar hfsc 895for the Hierarchical Fair Service Curve scheduler. 896.It Ar bandwidth Aq Ar bw 897The maximum bitrate for all queues on an 898interface may be specified using the 899.Ar bandwidth 900keyword. 901The value can be specified as an absolute value or as a 902percentage of the interface bandwidth. 903When using an absolute value, the suffixes 904.Ar b , 905.Ar Kb , 906.Ar Mb , 907and 908.Ar Gb 909are used to represent bits, kilobits, megabits, and 910gigabits per second, respectively. 911The value must not exceed the interface bandwidth. 912If 913.Ar bandwidth 914is not specified, the interface bandwidth is used 915(but take note that some interfaces do not know their bandwidth, 916or can adapt their bandwidth rates). 917.It Ar qlimit Aq Ar limit 918The maximum number of packets held in the queue. 919The default is 50. 920.It Ar tbrsize Aq Ar size 921Adjusts the size, in bytes, of the token bucket regulator. 922If not specified, heuristics based on the 923interface bandwidth are used to determine the size. 924.It Ar queue Aq Ar list 925Defines a list of subqueues to create on an interface. 926.El 927.Pp 928In the following example, the interface dc0 929should queue up to 5Mbps in four second-level queues using 930Class Based Queueing. 931Those four queues will be shown in a later example. 932.Bd -literal -offset indent 933altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh } 934.Ed 935.Pp 936Once interfaces are activated for queueing using the 937.Ar altq 938directive, a sequence of 939.Ar queue 940directives may be defined. 941The name associated with a 942.Ar queue 943must match a queue defined in the 944.Ar altq 945directive (e.g. mail), or, except for the 946.Ar priq 947.Ar scheduler , 948in a parent 949.Ar queue 950declaration. 951The following keywords can be used: 952.Bl -tag -width xxxx 953.It Ar on Aq Ar interface 954Specifies the interface the queue operates on. 955If not given, it operates on all matching interfaces. 956.It Ar bandwidth Aq Ar bw 957Specifies the maximum bitrate to be processed by the queue. 958This value must not exceed the value of the parent 959.Ar queue 960and can be specified as an absolute value or a percentage of the parent 961queue's bandwidth. 962If not specified, defaults to 100% of the parent queue's bandwidth. 963The 964.Ar priq 965scheduler does not support bandwidth specification. 966.It Ar priority Aq Ar level 967Between queues a priority level can be set. 968For 969.Ar cbq 970and 971.Ar hfsc , 972the range is 0 to 7 and for 973.Ar priq , 974the range is 0 to 15. 975The default for all is 1. 976.Ar Priq 977queues with a higher priority are always served first. 978.Ar Cbq 979and 980.Ar Hfsc 981queues with a higher priority are preferred in the case of overload. 982.It Ar qlimit Aq Ar limit 983The maximum number of packets held in the queue. 984The default is 50. 985.El 986.Pp 987The 988.Ar scheduler 989can get additional parameters with 990.Xo Aq Ar scheduler 991.Pf ( Aq Ar parameters ) . 992.Xc 993Parameters are as follows: 994.Bl -tag -width Fl 995.It Ar default 996Packets not matched by another queue are assigned to this one. 997Exactly one default queue is required. 998.It Ar red 999Enable RED (Random Early Detection) on this queue. 1000RED drops packets with a probability proportional to the average 1001queue length. 1002.It Ar rio 1003Enables RIO on this queue. 1004RIO is RED with IN/OUT, thus running 1005RED two times more than RIO would achieve the same effect. 1006RIO is currently not supported in the GENERIC kernel. 1007.It Ar ecn 1008Enables ECN (Explicit Congestion Notification) on this queue. 1009ECN implies RED. 1010.El 1011.Pp 1012The 1013.Ar cbq 1014.Ar scheduler 1015supports an additional option: 1016.Bl -tag -width Fl 1017.It Ar borrow 1018The queue can borrow bandwidth from the parent. 1019.El 1020.Pp 1021The 1022.Ar hfsc 1023.Ar scheduler 1024supports some additional options: 1025.Bl -tag -width Fl 1026.It Ar realtime Aq Ar sc 1027The minimum required bandwidth for the queue. 1028.It Ar upperlimit Aq Ar sc 1029The maximum allowed bandwidth for the queue. 1030.It Ar linkshare Aq Ar sc 1031The bandwidth share of a backlogged queue. 1032.El 1033.Pp 1034.Aq Ar sc 1035is an acronym for 1036.Ar service curve . 1037.Pp 1038The format for service curve specifications is 1039.Ar ( m1 , d , m2 ) . 1040.Ar m2 1041controls the bandwidth assigned to the queue. 1042.Ar m1 1043and 1044.Ar d 1045are optional and can be used to control the initial bandwidth assignment. 1046For the first 1047.Ar d 1048milliseconds the queue gets the bandwidth given as 1049.Ar m1 , 1050afterwards the value given in 1051.Ar m2 . 1052.Pp 1053Furthermore, with 1054.Ar cbq 1055and 1056.Ar hfsc , 1057child queues can be specified as in an 1058.Ar altq 1059declaration, thus building a tree of queues using a part of 1060their parent's bandwidth. 1061.Pp 1062Packets can be assigned to queues based on filter rules by using the 1063.Ar queue 1064keyword. 1065Normally only one 1066.Ar queue 1067is specified; when a second one is specified it will instead be used for 1068packets which have a 1069.Em TOS 1070of 1071.Em lowdelay 1072and for TCP ACKs with no data payload. 1073.Pp 1074To continue the previous example, the examples below would specify the 1075four referenced 1076queues, plus a few child queues. 1077Interactive 1078.Xr ssh 1 1079sessions get priority over bulk transfers like 1080.Xr scp 1 1081and 1082.Xr sftp 1 . 1083The queues may then be referenced by filtering rules (see 1084.Sx PACKET FILTERING 1085below). 1086.Bd -literal 1087queue std bandwidth 10% cbq(default) 1088queue http bandwidth 60% priority 2 cbq(borrow red) \e 1089 { employees, developers } 1090queue developers bandwidth 75% cbq(borrow) 1091queue employees bandwidth 15% 1092queue mail bandwidth 10% priority 0 cbq(borrow ecn) 1093queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk } 1094queue ssh_interactive bandwidth 50% priority 7 cbq(borrow) 1095queue ssh_bulk bandwidth 50% priority 0 cbq(borrow) 1096 1097block return out on dc0 inet all queue std 1098pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e 1099 queue developers 1100pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e 1101 queue employees 1102pass out on dc0 inet proto tcp from any to any port 22 \e 1103 queue(ssh_bulk, ssh_interactive) 1104pass out on dc0 inet proto tcp from any to any port 25 \e 1105 queue mail 1106.Ed 1107.Sh QUEUEING with dummynet 1108Queueing can also be done with 1109.Xr dummynet 4 . 1110Queues and pipes can be created with 1111.Xr dnctl 8 . 1112.Pp 1113Packets can be assigned to queues and pipes using 1114.Ar dnqueue 1115and 1116.Ar dnpipe 1117respectively. 1118.Pp 1119Both 1120.Ar dnqueue 1121and 1122.Ar dnpipe 1123take either a single pipe or queue number or two numbers as arguments. 1124The first pipe or queue number will be used to shape the traffic in the rule 1125direction, the second will be used to shape the traffic in the reverse 1126direction. 1127If the rule does not specify a direction the first packet to create state will 1128be shaped according to the first number, and the response traffic according to 1129the second. 1130.Pp 1131If the 1132.Xr dummynet 4 1133module is not loaded any traffic sent into a queue or pipe will be dropped. 1134.Sh TRANSLATION 1135Translation rules modify either the source or destination address of the 1136packets associated with a stateful connection. 1137A stateful connection is automatically created to track packets matching 1138such a rule as long as they are not blocked by the filtering section of 1139.Nm pf.conf . 1140The translation engine modifies the specified address and/or port in the 1141packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to 1142the packet filter for evaluation. 1143.Pp 1144Since translation occurs before filtering the filter 1145engine will see packets as they look after any 1146addresses and ports have been translated. 1147Filter rules will therefore have to filter based on the translated 1148address and port number. 1149Packets that match a translation rule are only automatically passed if 1150the 1151.Ar pass 1152modifier is given, otherwise they are 1153still subject to 1154.Ar block 1155and 1156.Ar pass 1157rules. 1158.Pp 1159The state entry created permits 1160.Xr pf 4 1161to keep track of the original address for traffic associated with that state 1162and correctly direct return traffic for that connection. 1163.Pp 1164Various types of translation are possible with pf: 1165.Bl -tag -width xxxx 1166.It Ar binat 1167A 1168.Ar binat 1169rule specifies a bidirectional mapping between an external IP netblock 1170and an internal IP netblock. 1171.It Ar nat 1172A 1173.Ar nat 1174rule specifies that IP addresses are to be changed as the packet 1175traverses the given interface. 1176This technique allows one or more IP addresses 1177on the translating host to support network traffic for a larger range of 1178machines on an "inside" network. 1179Although in theory any IP address can be used on the inside, it is strongly 1180recommended that one of the address ranges defined by RFC 1918 be used. 1181These netblocks are: 1182.Bd -literal 118310.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8) 1184172.16.0.0 - 172.31.255.255 (i.e., 172.16/12) 1185192.168.0.0 - 192.168.255.255 (i.e., 192.168/16) 1186.Ed 1187.It Pa rdr 1188The packet is redirected to another destination and possibly a 1189different port. 1190.Ar rdr 1191rules can optionally specify port ranges instead of single ports. 1192rdr ... port 2000:2999 -\*(Gt ... port 4000 1193redirects ports 2000 to 2999 (inclusive) to port 4000. 1194rdr ... port 2000:2999 -\*(Gt ... port 4000:* 1195redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999. 1196.El 1197.Pp 1198In addition to modifying the address, some translation rules may modify 1199source or destination ports for 1200.Xr tcp 4 1201or 1202.Xr udp 4 1203connections; implicitly in the case of 1204.Ar nat 1205rules and explicitly in the case of 1206.Ar rdr 1207rules. 1208Port numbers are never translated with a 1209.Ar binat 1210rule. 1211.Pp 1212Evaluation order of the translation rules is dependent on the type 1213of the translation rules and of the direction of a packet. 1214.Ar binat 1215rules are always evaluated first. 1216Then either the 1217.Ar rdr 1218rules are evaluated on an inbound packet or the 1219.Ar nat 1220rules on an outbound packet. 1221Rules of the same type are evaluated in the same order in which they 1222appear in the ruleset. 1223The first matching rule decides what action is taken. 1224.Pp 1225The 1226.Ar no 1227option prefixed to a translation rule causes packets to remain untranslated, 1228much in the same way as 1229.Ar drop quick 1230works in the packet filter (see below). 1231If no rule matches the packet it is passed to the filter engine unmodified. 1232.Pp 1233Translation rules apply only to packets that pass through 1234the specified interface, and if no interface is specified, 1235translation is applied to packets on all interfaces. 1236For instance, redirecting port 80 on an external interface to an internal 1237web server will only work for connections originating from the outside. 1238Connections to the address of the external interface from local hosts will 1239not be redirected, since such packets do not actually pass through the 1240external interface. 1241Redirections cannot reflect packets back through the interface they arrive 1242on, they can only be redirected to hosts connected to different interfaces 1243or to the firewall itself. 1244.Pp 1245Note that redirecting external incoming connections to the loopback 1246address, as in 1247.Bd -literal -offset indent 1248rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd 1249.Ed 1250.Pp 1251will effectively allow an external host to connect to daemons 1252bound solely to the loopback address, circumventing the traditional 1253blocking of such connections on a real interface. 1254Unless this effect is desired, any of the local non-loopback addresses 1255should be used as redirection target instead, which allows external 1256connections only to daemons bound to this address or not bound to 1257any address. 1258.Pp 1259See 1260.Sx TRANSLATION EXAMPLES 1261below. 1262.Sh PACKET FILTERING 1263.Xr pf 4 1264has the ability to 1265.Ar block 1266, 1267.Ar pass 1268and 1269.Ar match 1270packets based on attributes of their layer 3 (see 1271.Xr ip 4 1272and 1273.Xr ip6 4 ) 1274and layer 4 (see 1275.Xr icmp 4 , 1276.Xr icmp6 4 , 1277.Xr tcp 4 , 1278.Xr udp 4 ) 1279headers. 1280In addition, packets may also be 1281assigned to queues for the purpose of bandwidth control. 1282.Pp 1283For each packet processed by the packet filter, the filter rules are 1284evaluated in sequential order, from first to last. 1285For 1286.Ar block 1287and 1288.Ar pass 1289, the last matching rule decides what action is taken. 1290For 1291.Ar match 1292, rules are evaulated every time they match; the pass/block state of a packet 1293remains unchanged. 1294If no rule matches the packet, the default action is to pass 1295the packet. 1296.Pp 1297The following actions can be used in the filter: 1298.Bl -tag -width xxxx 1299.It Ar block 1300The packet is blocked. 1301There are a number of ways in which a 1302.Ar block 1303rule can behave when blocking a packet. 1304The default behaviour is to 1305.Ar drop 1306packets silently, however this can be overridden or made 1307explicit either globally, by setting the 1308.Ar block-policy 1309option, or on a per-rule basis with one of the following options: 1310.Pp 1311.Bl -tag -width xxxx -compact 1312.It Ar drop 1313The packet is silently dropped. 1314.It Ar return-rst 1315This applies only to 1316.Xr tcp 4 1317packets, and issues a TCP RST which closes the 1318connection. 1319.It Ar return-icmp 1320.It Ar return-icmp6 1321This causes ICMP messages to be returned for packets which match the rule. 1322By default this is an ICMP UNREACHABLE message, however this 1323can be overridden by specifying a message as a code or number. 1324.It Ar return 1325This causes a TCP RST to be returned for 1326.Xr tcp 4 1327packets and an ICMP UNREACHABLE for UDP and other packets. 1328.El 1329.Pp 1330Options returning ICMP packets currently have no effect if 1331.Xr pf 4 1332operates on a 1333.Xr if_bridge 4 , 1334as the code to support this feature has not yet been implemented. 1335.Pp 1336The simplest mechanism to block everything by default and only pass 1337packets that match explicit rules is specify a first filter rule of: 1338.Bd -literal -offset indent 1339block all 1340.Ed 1341.It Ar match 1342The packet is matched. 1343This mechanism is used to provide fine grained filtering without altering the 1344block/pass state of a packet. 1345.Ar match 1346rules differ from 1347.Ar block 1348and 1349.Ar pass 1350rules in that parameters are set every time a packet matches the rule, not only 1351on the last matching rule. 1352For the following parameters, this means that the parameter effectively becomes 1353"sticky" until explicitly overridden: 1354.Ar queue , 1355.Ar dnpipe , 1356.Ar dnqueue 1357. 1358.It Ar pass 1359The packet is passed; 1360state is created unless the 1361.Ar no state 1362option is specified. 1363.El 1364.Pp 1365By default 1366.Xr pf 4 1367filters packets statefully; the first time a packet matches a 1368.Ar pass 1369rule, a state entry is created; for subsequent packets the filter checks 1370whether the packet matches any state. 1371If it does, the packet is passed without evaluation of any rules. 1372After the connection is closed or times out, the state entry is automatically 1373removed. 1374.Pp 1375This has several advantages. 1376For TCP connections, comparing a packet to a state involves checking 1377its sequence numbers, as well as TCP timestamps if a 1378.Ar scrub reassemble tcp 1379rule applies to the connection. 1380If these values are outside the narrow windows of expected 1381values, the packet is dropped. 1382This prevents spoofing attacks, such as when an attacker sends packets with 1383a fake source address/port but does not know the connection's sequence 1384numbers. 1385Similarly, 1386.Xr pf 4 1387knows how to match ICMP replies to states. 1388For example, 1389.Bd -literal -offset indent 1390pass out inet proto icmp all icmp-type echoreq 1391.Ed 1392.Pp 1393allows echo requests (such as those created by 1394.Xr ping 8 ) 1395out statefully, and matches incoming echo replies correctly to states. 1396.Pp 1397Also, looking up states is usually faster than evaluating rules. 1398If there are 50 rules, all of them are evaluated sequentially in O(n). 1399Even with 50000 states, only 16 comparisons are needed to match a 1400state, since states are stored in a binary search tree that allows 1401searches in O(log2 n). 1402.Pp 1403Furthermore, correct handling of ICMP error messages is critical to 1404many protocols, particularly TCP. 1405.Xr pf 4 1406matches ICMP error messages to the correct connection, checks them against 1407connection parameters, and passes them if appropriate. 1408For example if an ICMP source quench message referring to a stateful TCP 1409connection arrives, it will be matched to the state and get passed. 1410.Pp 1411Finally, state tracking is required for 1412.Ar nat , binat No and Ar rdr 1413rules, in order to track address and port translations and reverse the 1414translation on returning packets. 1415.Pp 1416.Xr pf 4 1417will also create state for other protocols which are effectively stateless by 1418nature. 1419UDP packets are matched to states using only host addresses and ports, 1420and other protocols are matched to states using only the host addresses. 1421.Pp 1422If stateless filtering of individual packets is desired, 1423the 1424.Ar no state 1425keyword can be used to specify that state will not be created 1426if this is the last matching rule. 1427A number of parameters can also be set to affect how 1428.Xr pf 4 1429handles state tracking. 1430See 1431.Sx STATEFUL TRACKING OPTIONS 1432below for further details. 1433.Sh PARAMETERS 1434The rule parameters specify the packets to which a rule applies. 1435A packet always comes in on, or goes out through, one interface. 1436Most parameters are optional. 1437If a parameter is specified, the rule only applies to packets with 1438matching attributes. 1439Certain parameters can be expressed as lists, in which case 1440.Xr pfctl 8 1441generates all needed rule combinations. 1442.Bl -tag -width xxxx 1443.It Ar in No or Ar out 1444This rule applies to incoming or outgoing packets. 1445If neither 1446.Ar in 1447nor 1448.Ar out 1449are specified, the rule will match packets in both directions. 1450.It Ar log 1451In addition to the action specified, a log message is generated. 1452Only the packet that establishes the state is logged, 1453unless the 1454.Ar no state 1455option is specified. 1456The logged packets are sent to a 1457.Xr pflog 4 1458interface, by default 1459.Ar pflog0 . 1460This interface is monitored by the 1461.Xr pflogd 8 1462logging daemon, which dumps the logged packets to the file 1463.Pa /var/log/pflog 1464in 1465.Xr pcap 3 1466binary format. 1467.It Ar log (all) 1468Used to force logging of all packets for a connection. 1469This is not necessary when 1470.Ar no state 1471is explicitly specified. 1472As with 1473.Ar log , 1474packets are logged to 1475.Xr pflog 4 . 1476.It Ar log (user) 1477Logs the 1478.Ux 1479user ID of the user that owns the socket and the PID of the process that 1480has the socket open where the packet is sourced from or destined to 1481(depending on which socket is local). 1482This is in addition to the normal information logged. 1483.Pp 1484Only the first packet 1485logged via 1486.Ar log (all, user) 1487will have the user credentials logged when using stateful matching. 1488.It Ar log (to Aq Ar interface ) 1489Send logs to the specified 1490.Xr pflog 4 1491interface instead of 1492.Ar pflog0 . 1493.It Ar quick 1494If a packet matches a rule which has the 1495.Ar quick 1496option set, this rule 1497is considered the last matching rule, and evaluation of subsequent rules 1498is skipped. 1499.It Ar on Aq Ar interface 1500This rule applies only to packets coming in on, or going out through, this 1501particular interface or interface group. 1502For more information on interface groups, 1503see the 1504.Ic group 1505keyword in 1506.Xr ifconfig 8 . 1507.It Aq Ar af 1508This rule applies only to packets of this address family. 1509Supported values are 1510.Ar inet 1511and 1512.Ar inet6 . 1513.It Ar proto Aq Ar protocol 1514This rule applies only to packets of this protocol. 1515Common protocols are 1516.Xr icmp 4 , 1517.Xr icmp6 4 , 1518.Xr tcp 4 , 1519and 1520.Xr udp 4 . 1521For a list of all the protocol name to number mappings used by 1522.Xr pfctl 8 , 1523see the file 1524.Pa /etc/protocols . 1525.It Xo 1526.Ar from Aq Ar source 1527.Ar port Aq Ar source 1528.Ar os Aq Ar source 1529.Ar to Aq Ar dest 1530.Ar port Aq Ar dest 1531.Xc 1532This rule applies only to packets with the specified source and destination 1533addresses and ports. 1534.Pp 1535Addresses can be specified in CIDR notation (matching netblocks), as 1536symbolic host names, interface names or interface group names, or as any 1537of the following keywords: 1538.Pp 1539.Bl -tag -width xxxxxxxxxxxxxx -compact 1540.It Ar any 1541Any address. 1542.It Ar no-route 1543Any address which is not currently routable. 1544.It Ar urpf-failed 1545Any source address that fails a unicast reverse path forwarding (URPF) 1546check, i.e. packets coming in on an interface other than that which holds 1547the route back to the packet's source address. 1548.It Aq Ar table 1549Any address that matches the given table. 1550.El 1551.Pp 1552Ranges of addresses are specified by using the 1553.Sq - 1554operator. 1555For instance: 1556.Dq 10.1.1.10 - 10.1.1.12 1557means all addresses from 10.1.1.10 to 10.1.1.12, 1558hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12. 1559.Pp 1560Interface names and interface group names can have modifiers appended: 1561.Pp 1562.Bl -tag -width xxxxxxxxxxxx -compact 1563.It Ar :network 1564Translates to the network(s) attached to the interface. 1565.It Ar :broadcast 1566Translates to the interface's broadcast address(es). 1567.It Ar :peer 1568Translates to the point-to-point interface's peer address(es). 1569.It Ar :0 1570Do not include interface aliases. 1571.El 1572.Pp 1573Host names may also have the 1574.Ar :0 1575option appended to restrict the name resolution to the first of each 1576v4 and non-link-local v6 address found. 1577.Pp 1578Host name resolution and interface to address translation are done at 1579ruleset load-time. 1580When the address of an interface (or host name) changes (under DHCP or PPP, 1581for instance), the ruleset must be reloaded for the change to be reflected 1582in the kernel. 1583Surrounding the interface name (and optional modifiers) in parentheses 1584changes this behaviour. 1585When the interface name is surrounded by parentheses, the rule is 1586automatically updated whenever the interface changes its address. 1587The ruleset does not need to be reloaded. 1588This is especially useful with 1589.Ar nat . 1590.Pp 1591Ports can be specified either by number or by name. 1592For example, port 80 can be specified as 1593.Em www . 1594For a list of all port name to number mappings used by 1595.Xr pfctl 8 , 1596see the file 1597.Pa /etc/services . 1598.Pp 1599Ports and ranges of ports are specified by using these operators: 1600.Bd -literal -offset indent 1601= (equal) 1602!= (unequal) 1603\*(Lt (less than) 1604\*(Le (less than or equal) 1605\*(Gt (greater than) 1606\*(Ge (greater than or equal) 1607: (range including boundaries) 1608\*(Gt\*(Lt (range excluding boundaries) 1609\*(Lt\*(Gt (except range) 1610.Ed 1611.Pp 1612.Sq \*(Gt\*(Lt , 1613.Sq \*(Lt\*(Gt 1614and 1615.Sq \&: 1616are binary operators (they take two arguments). 1617For instance: 1618.Bl -tag -width Fl 1619.It Ar port 2000:2004 1620means 1621.Sq all ports \*(Ge 2000 and \*(Le 2004 , 1622hence ports 2000, 2001, 2002, 2003 and 2004. 1623.It Ar port 2000 \*(Gt\*(Lt 2004 1624means 1625.Sq all ports \*(Gt 2000 and \*(Lt 2004 , 1626hence ports 2001, 2002 and 2003. 1627.It Ar port 2000 \*(Lt\*(Gt 2004 1628means 1629.Sq all ports \*(Lt 2000 or \*(Gt 2004 , 1630hence ports 1-1999 and 2005-65535. 1631.El 1632.Pp 1633The operating system of the source host can be specified in the case of TCP 1634rules with the 1635.Ar OS 1636modifier. 1637See the 1638.Sx OPERATING SYSTEM FINGERPRINTING 1639section for more information. 1640.Pp 1641The host, port and OS specifications are optional, as in the following examples: 1642.Bd -literal -offset indent 1643pass in all 1644pass in from any to any 1645pass in proto tcp from any port \*(Le 1024 to any 1646pass in proto tcp from any to any port 25 1647pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e 1648 to ! 10.1.2.3 port != ssh 1649pass in proto tcp from any os "OpenBSD" 1650.Ed 1651.It Ar all 1652This is equivalent to "from any to any". 1653.It Ar group Aq Ar group 1654Similar to 1655.Ar user , 1656this rule only applies to packets of sockets owned by the specified group. 1657.It Ar user Aq Ar user 1658This rule only applies to packets of sockets owned by the specified user. 1659For outgoing connections initiated from the firewall, this is the user 1660that opened the connection. 1661For incoming connections to the firewall itself, this is the user that 1662listens on the destination port. 1663For forwarded connections, where the firewall is not a connection endpoint, 1664the user and group are 1665.Em unknown . 1666.Pp 1667All packets, both outgoing and incoming, of one connection are associated 1668with the same user and group. 1669Only TCP and UDP packets can be associated with users; for other protocols 1670these parameters are ignored. 1671.Pp 1672User and group refer to the effective (as opposed to the real) IDs, in 1673case the socket is created by a setuid/setgid process. 1674User and group IDs are stored when a socket is created; 1675when a process creates a listening socket as root (for instance, by 1676binding to a privileged port) and subsequently changes to another 1677user ID (to drop privileges), the credentials will remain root. 1678.Pp 1679User and group IDs can be specified as either numbers or names. 1680The syntax is similar to the one for ports. 1681The value 1682.Em unknown 1683matches packets of forwarded connections. 1684.Em unknown 1685can only be used with the operators 1686.Cm = 1687and 1688.Cm != . 1689Other constructs like 1690.Cm user \*(Ge unknown 1691are invalid. 1692Forwarded packets with unknown user and group ID match only rules 1693that explicitly compare against 1694.Em unknown 1695with the operators 1696.Cm = 1697or 1698.Cm != . 1699For instance 1700.Cm user \*(Ge 0 1701does not match forwarded packets. 1702The following example allows only selected users to open outgoing 1703connections: 1704.Bd -literal -offset indent 1705block out proto { tcp, udp } all 1706pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei } 1707.Ed 1708.It Xo Ar flags Aq Ar a 1709.Pf / Ns Aq Ar b 1710.No \*(Ba / Ns Aq Ar b 1711.No \*(Ba any 1712.Xc 1713This rule only applies to TCP packets that have the flags 1714.Aq Ar a 1715set out of set 1716.Aq Ar b . 1717Flags not specified in 1718.Aq Ar b 1719are ignored. 1720For stateful connections, the default is 1721.Ar flags S/SA . 1722To indicate that flags should not be checked at all, specify 1723.Ar flags any . 1724The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R. 1725.Bl -tag -width Fl 1726.It Ar flags S/S 1727Flag SYN is set. 1728The other flags are ignored. 1729.It Ar flags S/SA 1730This is the default setting for stateful connections. 1731Out of SYN and ACK, exactly SYN may be set. 1732SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not. 1733This is more restrictive than the previous example. 1734.It Ar flags /SFRA 1735If the first set is not specified, it defaults to none. 1736All of SYN, FIN, RST and ACK must be unset. 1737.El 1738.Pp 1739Because 1740.Ar flags S/SA 1741is applied by default (unless 1742.Ar no state 1743is specified), only the initial SYN packet of a TCP handshake will create 1744a state for a TCP connection. 1745It is possible to be less restrictive, and allow state creation from 1746intermediate 1747.Pq non-SYN 1748packets, by specifying 1749.Ar flags any . 1750This will cause 1751.Xr pf 4 1752to synchronize to existing connections, for instance 1753if one flushes the state table. 1754However, states created from such intermediate packets may be missing 1755connection details such as the TCP window scaling factor. 1756States which modify the packet flow, such as those affected by 1757.Ar nat , binat No or Ar rdr 1758rules, 1759.Ar modulate No or Ar synproxy state 1760options, or scrubbed with 1761.Ar reassemble tcp 1762will also not be recoverable from intermediate packets. 1763Such connections will stall and time out. 1764.It Xo Ar icmp-type Aq Ar type 1765.Ar code Aq Ar code 1766.Xc 1767.It Xo Ar icmp6-type Aq Ar type 1768.Ar code Aq Ar code 1769.Xc 1770This rule only applies to ICMP or ICMPv6 packets with the specified type 1771and code. 1772Text names for ICMP types and codes are listed in 1773.Xr icmp 4 1774and 1775.Xr icmp6 4 . 1776This parameter is only valid for rules that cover protocols ICMP or 1777ICMP6. 1778The protocol and the ICMP type indicator 1779.Po 1780.Ar icmp-type 1781or 1782.Ar icmp6-type 1783.Pc 1784must match. 1785.It Xo Ar tos Aq Ar string 1786.No \*(Ba Aq Ar number 1787.Xc 1788This rule applies to packets with the specified 1789.Em TOS 1790bits set. 1791.Em TOS 1792may be 1793given as one of 1794.Ar critical , 1795.Ar inetcontrol , 1796.Ar lowdelay , 1797.Ar netcontrol , 1798.Ar throughput , 1799.Ar reliability , 1800or one of the DiffServ Code Points: 1801.Ar ef , 1802.Ar va , 1803.Ar af11 No ... Ar af43 , 1804.Ar cs0 No ... Ar cs7 ; 1805or as either hex or decimal. 1806.Pp 1807For example, the following rules are identical: 1808.Bd -literal -offset indent 1809pass all tos lowdelay 1810pass all tos 0x10 1811pass all tos 16 1812.Ed 1813.It Ar allow-opts 1814By default, IPv4 packets with IP options or IPv6 packets with routing 1815extension headers are blocked. 1816When 1817.Ar allow-opts 1818is specified for a 1819.Ar pass 1820rule, packets that pass the filter based on that rule (last matching) 1821do so even if they contain IP options or routing extension headers. 1822For packets that match state, the rule that initially created the 1823state is used. 1824The implicit 1825.Ar pass 1826rule that is used when a packet does not match any rules does not 1827allow IP options. 1828.It Ar label Aq Ar string 1829Adds a label (name) to the rule, which can be used to identify the rule. 1830For instance, 1831pfctl -s labels 1832shows per-rule statistics for rules that have labels. 1833.Pp 1834The following macros can be used in labels: 1835.Pp 1836.Bl -tag -width $srcaddr -compact -offset indent 1837.It Ar $if 1838The interface. 1839.It Ar $srcaddr 1840The source IP address. 1841.It Ar $dstaddr 1842The destination IP address. 1843.It Ar $srcport 1844The source port specification. 1845.It Ar $dstport 1846The destination port specification. 1847.It Ar $proto 1848The protocol name. 1849.It Ar $nr 1850The rule number. 1851.El 1852.Pp 1853For example: 1854.Bd -literal -offset indent 1855ips = \&"{ 1.2.3.4, 1.2.3.5 }\&" 1856pass in proto tcp from any to $ips \e 1857 port \*(Gt 1023 label \&"$dstaddr:$dstport\&" 1858.Ed 1859.Pp 1860expands to 1861.Bd -literal -offset indent 1862pass in inet proto tcp from any to 1.2.3.4 \e 1863 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&" 1864pass in inet proto tcp from any to 1.2.3.5 \e 1865 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&" 1866.Ed 1867.Pp 1868The macro expansion for the 1869.Ar label 1870directive occurs only at configuration file parse time, not during runtime. 1871.It Xo Ar queue Aq Ar queue 1872.No \*(Ba ( Aq Ar queue , 1873.Aq Ar queue ) 1874.Xc 1875Packets matching this rule will be assigned to the specified queue. 1876If two queues are given, packets which have a 1877.Em TOS 1878of 1879.Em lowdelay 1880and TCP ACKs with no data payload will be assigned to the second one. 1881See 1882.Sx QUEUEING 1883for setup details. 1884.Pp 1885For example: 1886.Bd -literal -offset indent 1887pass in proto tcp to port 25 queue mail 1888pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio) 1889.Ed 1890.Pp 1891.It Cm set prio Ar priority | Pq Ar priority , priority 1892Packets matching this rule will be assigned a specific queueing priority. 1893Priorities are assigned as integers 0 through 7. 1894If the packet is transmitted on a 1895.Xr vlan 4 1896interface, the queueing priority will be written as the priority 1897code point in the 802.1Q VLAN header. 1898If two priorities are given, packets which have a TOS of 1899.Cm lowdelay 1900and TCP ACKs with no data payload will be assigned to the second one. 1901.Pp 1902For example: 1903.Bd -literal -offset indent 1904pass in proto tcp to port 25 set prio 2 1905pass in proto tcp to port 22 set prio (2, 5) 1906.Ed 1907.Pp 1908.It Ar tag Aq Ar string 1909Packets matching this rule will be tagged with the 1910specified string. 1911The tag acts as an internal marker that can be used to 1912identify these packets later on. 1913This can be used, for example, to provide trust between 1914interfaces and to determine if packets have been 1915processed by translation rules. 1916Tags are 1917.Qq sticky , 1918meaning that the packet will be tagged even if the rule 1919is not the last matching rule. 1920Further matching rules can replace the tag with a 1921new one but will not remove a previously applied tag. 1922A packet is only ever assigned one tag at a time. 1923Packet tagging can be done during 1924.Ar nat , 1925.Ar rdr , 1926or 1927.Ar binat 1928rules in addition to filter rules. 1929Tags take the same macros as labels (see above). 1930.It Ar tagged Aq Ar string 1931Used with filter, translation or scrub rules 1932to specify that packets must already 1933be tagged with the given tag in order to match the rule. 1934Inverse tag matching can also be done 1935by specifying the 1936.Cm !\& 1937operator before the 1938.Ar tagged 1939keyword. 1940.It Ar rtable Aq Ar number 1941Used to select an alternate routing table for the routing lookup. 1942Only effective before the route lookup happened, i.e. when filtering inbound. 1943.It Xo Ar divert-to Aq Ar host 1944.Ar port Aq Ar port 1945.Xc 1946Used to redirect packets to a local socket bound to 1947.Ar host 1948and 1949.Ar port . 1950The packets will not be modified, so 1951.Xr getsockname 2 1952on the socket will return the original destination address of the packet. 1953.It Ar divert-reply 1954Used to receive replies for sockets that are bound to addresses 1955which are not local to the machine. 1956See 1957.Xr setsockopt 2 1958for information on how to bind these sockets. 1959.It Ar probability Aq Ar number 1960A probability attribute can be attached to a rule, with a value set between 19610 and 1, bounds not included. 1962In that case, the rule will be honoured using the given probability value 1963only. 1964For example, the following rule will drop 20% of incoming ICMP packets: 1965.Bd -literal -offset indent 1966block in proto icmp probability 20% 1967.Ed 1968.It Ar prio Aq Ar number 1969Only match packets which have the given queueing priority assigned. 1970.Pp 1971.El 1972.Sh ROUTING 1973If a packet matches a rule with a route option set, the packet filter will 1974route the packet according to the type of route option. 1975When such a rule creates state, the route option is also applied to all 1976packets matching the same connection. 1977.Bl -tag -width xxxx 1978.It Ar route-to 1979The 1980.Ar route-to 1981option routes the packet to the specified interface with an optional address 1982for the next hop. 1983When a 1984.Ar route-to 1985rule creates state, only packets that pass in the same direction as the 1986filter rule specifies will be routed in this way. 1987Packets passing in the opposite direction (replies) are not affected 1988and are routed normally. 1989.It Ar reply-to 1990The 1991.Ar reply-to 1992option is similar to 1993.Ar route-to , 1994but routes packets that pass in the opposite direction (replies) to the 1995specified interface. 1996Opposite direction is only defined in the context of a state entry, and 1997.Ar reply-to 1998is useful only in rules that create state. 1999It can be used on systems with multiple external connections to 2000route all outgoing packets of a connection through the interface 2001the incoming connection arrived through (symmetric routing enforcement). 2002.It Ar dup-to 2003The 2004.Ar dup-to 2005option creates a duplicate of the packet and routes it like 2006.Ar route-to . 2007The original packet gets routed as it normally would. 2008.El 2009.Sh POOL OPTIONS 2010For 2011.Ar nat 2012and 2013.Ar rdr 2014rules, (as well as for the 2015.Ar route-to , 2016.Ar reply-to 2017and 2018.Ar dup-to 2019rule options) for which there is a single redirection address which has a 2020subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP 2021address), a variety of different methods for assigning this address can be 2022used: 2023.Bl -tag -width xxxx 2024.It Ar bitmask 2025The 2026.Ar bitmask 2027option applies the network portion of the redirection address to the address 2028to be modified (source with 2029.Ar nat , 2030destination with 2031.Ar rdr ) . 2032.It Ar random 2033The 2034.Ar random 2035option selects an address at random within the defined block of addresses. 2036.It Ar source-hash 2037The 2038.Ar source-hash 2039option uses a hash of the source address to determine the redirection address, 2040ensuring that the redirection address is always the same for a given source. 2041An optional key can be specified after this keyword either in hex or as a 2042string; by default 2043.Xr pfctl 8 2044randomly generates a key for source-hash every time the 2045ruleset is reloaded. 2046.It Ar round-robin 2047The 2048.Ar round-robin 2049option loops through the redirection address(es). 2050.Pp 2051When more than one redirection address is specified, 2052.Ar round-robin 2053is the only permitted pool type. 2054.It Ar static-port 2055With 2056.Ar nat 2057rules, the 2058.Ar static-port 2059option prevents 2060.Xr pf 4 2061from modifying the source port on TCP and UDP packets. 2062.It Xo Ar map-e-portset Aq Ar psid-offset 2063.No / Aq Ar psid-len 2064.No / Aq Ar psid 2065.Xc 2066With 2067.Ar nat 2068rules, the 2069.Ar map-e-portset 2070option enables the source port translation of MAP-E (RFC 7597) Customer Edge. 2071In order to make the host act as a MAP-E Customer Edge, setting up a tunneling 2072interface and pass rules for encapsulated packets are required in addition 2073to the map-e-portset nat rule. 2074.Pp 2075For example: 2076.Bd -literal -offset indent 2077nat on $gif_mape_if from $int_if:network to any \e 2078 -> $ipv4_mape_src map-e-portset 6/8/0x34 2079.Ed 2080.Pp 2081sets PSID offset 6, PSID length 8, PSID 0x34. 2082.Ed 2083.El 2084.Pp 2085Additionally, the 2086.Ar sticky-address 2087option can be specified to help ensure that multiple connections from the 2088same source are mapped to the same redirection address. 2089This option can be used with the 2090.Ar random 2091and 2092.Ar round-robin 2093pool options. 2094Note that by default these associations are destroyed as soon as there are 2095no longer states which refer to them; in order to make the mappings last 2096beyond the lifetime of the states, increase the global options with 2097.Ar set timeout src.track . 2098See 2099.Sx STATEFUL TRACKING OPTIONS 2100for more ways to control the source tracking. 2101.Sh STATE MODULATION 2102Much of the security derived from TCP is attributable to how well the 2103initial sequence numbers (ISNs) are chosen. 2104Some popular stack implementations choose 2105.Em very 2106poor ISNs and thus are normally susceptible to ISN prediction exploits. 2107By applying a 2108.Ar modulate state 2109rule to a TCP connection, 2110.Xr pf 4 2111will create a high quality random sequence number for each connection 2112endpoint. 2113.Pp 2114The 2115.Ar modulate state 2116directive implicitly keeps state on the rule and is 2117only applicable to TCP connections. 2118.Pp 2119For instance: 2120.Bd -literal -offset indent 2121block all 2122pass out proto tcp from any to any modulate state 2123pass in proto tcp from any to any port 25 flags S/SFRA modulate state 2124.Ed 2125.Pp 2126Note that modulated connections will not recover when the state table 2127is lost (firewall reboot, flushing the state table, etc...). 2128.Xr pf 4 2129will not be able to infer a connection again after the state table flushes 2130the connection's modulator. 2131When the state is lost, the connection may be left dangling until the 2132respective endpoints time out the connection. 2133It is possible on a fast local network for the endpoints to start an ACK 2134storm while trying to resynchronize after the loss of the modulator. 2135The default 2136.Ar flags 2137settings (or a more strict equivalent) should be used on 2138.Ar modulate state 2139rules to prevent ACK storms. 2140.Pp 2141Note that alternative methods are available 2142to prevent loss of the state table 2143and allow for firewall failover. 2144See 2145.Xr carp 4 2146and 2147.Xr pfsync 4 2148for further information. 2149.Sh SYN PROXY 2150By default, 2151.Xr pf 4 2152passes packets that are part of a 2153.Xr tcp 4 2154handshake between the endpoints. 2155The 2156.Ar synproxy state 2157option can be used to cause 2158.Xr pf 4 2159itself to complete the handshake with the active endpoint, perform a handshake 2160with the passive endpoint, and then forward packets between the endpoints. 2161.Pp 2162No packets are sent to the passive endpoint before the active endpoint has 2163completed the handshake, hence so-called SYN floods with spoofed source 2164addresses will not reach the passive endpoint, as the sender can't complete the 2165handshake. 2166.Pp 2167The proxy is transparent to both endpoints, they each see a single 2168connection from/to the other endpoint. 2169.Xr pf 4 2170chooses random initial sequence numbers for both handshakes. 2171Once the handshakes are completed, the sequence number modulators 2172(see previous section) are used to translate further packets of the 2173connection. 2174.Ar synproxy state 2175includes 2176.Ar modulate state . 2177.Pp 2178Rules with 2179.Ar synproxy 2180will not work if 2181.Xr pf 4 2182operates on a 2183.Xr bridge 4 . 2184.Pp 2185Example: 2186.Bd -literal -offset indent 2187pass in proto tcp from any to any port www synproxy state 2188.Ed 2189.Sh STATEFUL TRACKING OPTIONS 2190A number of options related to stateful tracking can be applied on a 2191per-rule basis. 2192.Ar keep state , 2193.Ar modulate state 2194and 2195.Ar synproxy state 2196support these options, and 2197.Ar keep state 2198must be specified explicitly to apply options to a rule. 2199.Pp 2200.Bl -tag -width xxxx -compact 2201.It Ar max Aq Ar number 2202Limits the number of concurrent states the rule may create. 2203When this limit is reached, further packets that would create 2204state will not match this rule until existing states time out. 2205.It Ar no-sync 2206Prevent state changes for states created by this rule from appearing on the 2207.Xr pfsync 4 2208interface. 2209.It Xo Aq Ar timeout 2210.Aq Ar seconds 2211.Xc 2212Changes the timeout values used for states created by this rule. 2213For a list of all valid timeout names, see 2214.Sx OPTIONS 2215above. 2216.It Ar sloppy 2217Uses a sloppy TCP connection tracker that does not check sequence 2218numbers at all, which makes insertion and ICMP teardown attacks way 2219easier. 2220This is intended to be used in situations where one does not see all 2221packets of a connection, e.g. in asymmetric routing situations. 2222Cannot be used with modulate or synproxy state. 2223.El 2224.Pp 2225Multiple options can be specified, separated by commas: 2226.Bd -literal -offset indent 2227pass in proto tcp from any to any \e 2228 port www keep state \e 2229 (max 100, source-track rule, max-src-nodes 75, \e 2230 max-src-states 3, tcp.established 60, tcp.closing 5) 2231.Ed 2232.Pp 2233When the 2234.Ar source-track 2235keyword is specified, the number of states per source IP is tracked. 2236.Pp 2237.Bl -tag -width xxxx -compact 2238.It Ar source-track rule 2239The maximum number of states created by this rule is limited by the rule's 2240.Ar max-src-nodes 2241and 2242.Ar max-src-states 2243options. 2244Only state entries created by this particular rule count toward the rule's 2245limits. 2246.It Ar source-track global 2247The number of states created by all rules that use this option is limited. 2248Each rule can specify different 2249.Ar max-src-nodes 2250and 2251.Ar max-src-states 2252options, however state entries created by any participating rule count towards 2253each individual rule's limits. 2254.El 2255.Pp 2256The following limits can be set: 2257.Pp 2258.Bl -tag -width xxxx -compact 2259.It Ar max-src-nodes Aq Ar number 2260Limits the maximum number of source addresses which can simultaneously 2261have state table entries. 2262.It Ar max-src-states Aq Ar number 2263Limits the maximum number of simultaneous state entries that a single 2264source address can create with this rule. 2265.El 2266.Pp 2267For stateful TCP connections, limits on established connections (connections 2268which have completed the TCP 3-way handshake) can also be enforced 2269per source IP. 2270.Pp 2271.Bl -tag -width xxxx -compact 2272.It Ar max-src-conn Aq Ar number 2273Limits the maximum number of simultaneous TCP connections which have 2274completed the 3-way handshake that a single host can make. 2275.It Xo Ar max-src-conn-rate Aq Ar number 2276.No / Aq Ar seconds 2277.Xc 2278Limit the rate of new connections over a time interval. 2279The connection rate is an approximation calculated as a moving average. 2280.El 2281.Pp 2282Because the 3-way handshake ensures that the source address is not being 2283spoofed, more aggressive action can be taken based on these limits. 2284With the 2285.Ar overload Aq Ar table 2286state option, source IP addresses which hit either of the limits on 2287established connections will be added to the named table. 2288This table can be used in the ruleset to block further activity from 2289the offending host, redirect it to a tarpit process, or restrict its 2290bandwidth. 2291.Pp 2292The optional 2293.Ar flush 2294keyword kills all states created by the matching rule which originate 2295from the host which exceeds these limits. 2296The 2297.Ar global 2298modifier to the flush command kills all states originating from the 2299offending host, regardless of which rule created the state. 2300.Pp 2301For example, the following rules will protect the webserver against 2302hosts making more than 100 connections in 10 seconds. 2303Any host which connects faster than this rate will have its address added 2304to the 2305.Aq bad_hosts 2306table and have all states originating from it flushed. 2307Any new packets arriving from this host will be dropped unconditionally 2308by the block rule. 2309.Bd -literal -offset indent 2310block quick from \*(Ltbad_hosts\*(Gt 2311pass in on $ext_if proto tcp to $webserver port www keep state \e 2312 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global) 2313.Ed 2314.Sh OPERATING SYSTEM FINGERPRINTING 2315Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP 2316connection's initial SYN packet and guess at the host's operating system. 2317Unfortunately these nuances are easily spoofed by an attacker so the 2318fingerprint is not useful in making security decisions. 2319But the fingerprint is typically accurate enough to make policy decisions 2320upon. 2321.Pp 2322The fingerprints may be specified by operating system class, by 2323version, or by subtype/patchlevel. 2324The class of an operating system is typically the vendor or genre 2325and would be 2326.Ox 2327for the 2328.Xr pf 4 2329firewall itself. 2330The version of the oldest available 2331.Ox 2332release on the main FTP site 2333would be 2.6 and the fingerprint would be written 2334.Pp 2335.Dl \&"OpenBSD 2.6\&" 2336.Pp 2337The subtype of an operating system is typically used to describe the 2338patchlevel if that patch led to changes in the TCP stack behavior. 2339In the case of 2340.Ox , 2341the only subtype is for a fingerprint that was 2342normalized by the 2343.Ar no-df 2344scrub option and would be specified as 2345.Pp 2346.Dl \&"OpenBSD 3.3 no-df\&" 2347.Pp 2348Fingerprints for most popular operating systems are provided by 2349.Xr pf.os 5 . 2350Once 2351.Xr pf 4 2352is running, a complete list of known operating system fingerprints may 2353be listed by running: 2354.Pp 2355.Dl # pfctl -so 2356.Pp 2357Filter rules can enforce policy at any level of operating system specification 2358assuming a fingerprint is present. 2359Policy could limit traffic to approved operating systems or even ban traffic 2360from hosts that aren't at the latest service pack. 2361.Pp 2362The 2363.Ar unknown 2364class can also be used as the fingerprint which will match packets for 2365which no operating system fingerprint is known. 2366.Pp 2367Examples: 2368.Bd -literal -offset indent 2369pass out proto tcp from any os OpenBSD 2370block out proto tcp from any os Doors 2371block out proto tcp from any os "Doors PT" 2372block out proto tcp from any os "Doors PT SP3" 2373block out from any os "unknown" 2374pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" 2375.Ed 2376.Pp 2377Operating system fingerprinting is limited only to the TCP SYN packet. 2378This means that it will not work on other protocols and will not match 2379a currently established connection. 2380.Pp 2381Caveat: operating system fingerprints are occasionally wrong. 2382There are three problems: an attacker can trivially craft his packets to 2383appear as any operating system he chooses; 2384an operating system patch could change the stack behavior and no fingerprints 2385will match it until the database is updated; 2386and multiple operating systems may have the same fingerprint. 2387.Sh BLOCKING SPOOFED TRAFFIC 2388"Spoofing" is the faking of IP addresses, typically for malicious 2389purposes. 2390The 2391.Ar antispoof 2392directive expands to a set of filter rules which will block all 2393traffic with a source IP from the network(s) directly connected 2394to the specified interface(s) from entering the system through 2395any other interface. 2396.Pp 2397For example, the line 2398.Bd -literal -offset indent 2399antispoof for lo0 2400.Ed 2401.Pp 2402expands to 2403.Bd -literal -offset indent 2404block drop in on ! lo0 inet from 127.0.0.1/8 to any 2405block drop in on ! lo0 inet6 from ::1 to any 2406.Ed 2407.Pp 2408For non-loopback interfaces, there are additional rules to block incoming 2409packets with a source IP address identical to the interface's IP(s). 2410For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a 2411netmask of 255.255.255.0, 2412the line 2413.Bd -literal -offset indent 2414antispoof for wi0 inet 2415.Ed 2416.Pp 2417expands to 2418.Bd -literal -offset indent 2419block drop in on ! wi0 inet from 10.0.0.0/24 to any 2420block drop in inet from 10.0.0.1 to any 2421.Ed 2422.Pp 2423Caveat: Rules created by the 2424.Ar antispoof 2425directive interfere with packets sent over loopback interfaces 2426to local addresses. 2427One should pass these explicitly. 2428.Sh FRAGMENT HANDLING 2429The size of IP datagrams (packets) can be significantly larger than the 2430maximum transmission unit (MTU) of the network. 2431In cases when it is necessary or more efficient to send such large packets, 2432the large packet will be fragmented into many smaller packets that will each 2433fit onto the wire. 2434Unfortunately for a firewalling device, only the first logical fragment will 2435contain the necessary header information for the subprotocol that allows 2436.Xr pf 4 2437to filter on things such as TCP ports or to perform NAT. 2438.Pp 2439Besides the use of 2440.Ar scrub 2441rules as described in 2442.Sx TRAFFIC NORMALIZATION 2443above, there are three options for handling fragments in the packet filter. 2444.Pp 2445One alternative is to filter individual fragments with filter rules. 2446If no 2447.Ar scrub 2448rule applies to a fragment, it is passed to the filter. 2449Filter rules with matching IP header parameters decide whether the 2450fragment is passed or blocked, in the same way as complete packets 2451are filtered. 2452Without reassembly, fragments can only be filtered based on IP header 2453fields (source/destination address, protocol), since subprotocol header 2454fields are not available (TCP/UDP port numbers, ICMP code/type). 2455The 2456.Ar fragment 2457option can be used to restrict filter rules to apply only to 2458fragments, but not complete packets. 2459Filter rules without the 2460.Ar fragment 2461option still apply to fragments, if they only specify IP header fields. 2462For instance, the rule 2463.Bd -literal -offset indent 2464pass in proto tcp from any to any port 80 2465.Ed 2466.Pp 2467never applies to a fragment, even if the fragment is part of a TCP 2468packet with destination port 80, because without reassembly this information 2469is not available for each fragment. 2470This also means that fragments cannot create new or match existing 2471state table entries, which makes stateful filtering and address 2472translation (NAT, redirection) for fragments impossible. 2473.Pp 2474It's also possible to reassemble only certain fragments by specifying 2475source or destination addresses or protocols as parameters in 2476.Ar scrub 2477rules. 2478.Pp 2479In most cases, the benefits of reassembly outweigh the additional 2480memory cost, and it's recommended to use 2481.Ar scrub 2482rules to reassemble 2483all fragments via the 2484.Ar fragment reassemble 2485modifier. 2486.Pp 2487The memory allocated for fragment caching can be limited using 2488.Xr pfctl 8 . 2489Once this limit is reached, fragments that would have to be cached 2490are dropped until other entries time out. 2491The timeout value can also be adjusted. 2492.Pp 2493When forwarding reassembled IPv6 packets, pf refragments them with 2494the original maximum fragment size. 2495This allows the sender to determine the optimal fragment size by 2496path MTU discovery. 2497.Sh ANCHORS 2498Besides the main ruleset, 2499.Xr pfctl 8 2500can load rulesets into 2501.Ar anchor 2502attachment points. 2503An 2504.Ar anchor 2505is a container that can hold rules, address tables, and other anchors. 2506.Pp 2507An 2508.Ar anchor 2509has a name which specifies the path where 2510.Xr pfctl 8 2511can be used to access the anchor to perform operations on it, such as 2512attaching child anchors to it or loading rules into it. 2513Anchors may be nested, with components separated by 2514.Sq / 2515characters, similar to how file system hierarchies are laid out. 2516The main ruleset is actually the default anchor, so filter and 2517translation rules, for example, may also be contained in any anchor. 2518.Pp 2519An anchor can reference another 2520.Ar anchor 2521attachment point 2522using the following kinds 2523of rules: 2524.Bl -tag -width xxxx 2525.It Ar nat-anchor Aq Ar name 2526Evaluates the 2527.Ar nat 2528rules in the specified 2529.Ar anchor . 2530.It Ar rdr-anchor Aq Ar name 2531Evaluates the 2532.Ar rdr 2533rules in the specified 2534.Ar anchor . 2535.It Ar binat-anchor Aq Ar name 2536Evaluates the 2537.Ar binat 2538rules in the specified 2539.Ar anchor . 2540.It Ar anchor Aq Ar name 2541Evaluates the filter rules in the specified 2542.Ar anchor . 2543.It Xo Ar load anchor 2544.Aq Ar name 2545.Ar from Aq Ar file 2546.Xc 2547Loads the rules from the specified file into the 2548anchor 2549.Ar name . 2550.El 2551.Pp 2552When evaluation of the main ruleset reaches an 2553.Ar anchor 2554rule, 2555.Xr pf 4 2556will proceed to evaluate all rules specified in that anchor. 2557.Pp 2558Matching filter and translation rules marked with the 2559.Ar quick 2560option are final and abort the evaluation of the rules in other 2561anchors and the main ruleset. 2562If the 2563.Ar anchor 2564itself is marked with the 2565.Ar quick 2566option, 2567ruleset evaluation will terminate when the anchor is exited if the packet is 2568matched by any rule within the anchor. 2569.Pp 2570.Ar anchor 2571rules are evaluated relative to the anchor in which they are contained. 2572For example, all 2573.Ar anchor 2574rules specified in the main ruleset will reference anchor 2575attachment points underneath the main ruleset, and 2576.Ar anchor 2577rules specified in a file loaded from a 2578.Ar load anchor 2579rule will be attached under that anchor point. 2580.Pp 2581Rules may be contained in 2582.Ar anchor 2583attachment points which do not contain any rules when the main ruleset 2584is loaded, and later such anchors can be manipulated through 2585.Xr pfctl 8 2586without reloading the main ruleset or other anchors. 2587For example, 2588.Bd -literal -offset indent 2589ext_if = \&"kue0\&" 2590block on $ext_if all 2591anchor spam 2592pass out on $ext_if all 2593pass in on $ext_if proto tcp from any \e 2594 to $ext_if port smtp 2595.Ed 2596.Pp 2597blocks all packets on the external interface by default, then evaluates 2598all rules in the 2599.Ar anchor 2600named "spam", and finally passes all outgoing connections and 2601incoming connections to port 25. 2602.Bd -literal -offset indent 2603# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e 2604 pfctl -a spam -f - 2605.Ed 2606.Pp 2607This loads a single rule into the 2608.Ar anchor , 2609which blocks all packets from a specific address. 2610.Pp 2611The anchor can also be populated by adding a 2612.Ar load anchor 2613rule after the 2614.Ar anchor 2615rule: 2616.Bd -literal -offset indent 2617anchor spam 2618load anchor spam from "/etc/pf-spam.conf" 2619.Ed 2620.Pp 2621When 2622.Xr pfctl 8 2623loads 2624.Nm pf.conf , 2625it will also load all the rules from the file 2626.Pa /etc/pf-spam.conf 2627into the anchor. 2628.Pp 2629Optionally, 2630.Ar anchor 2631rules can specify packet filtering parameters using the same syntax as 2632filter rules. 2633When parameters are used, the 2634.Ar anchor 2635rule is only evaluated for matching packets. 2636This allows conditional evaluation of anchors, like: 2637.Bd -literal -offset indent 2638block on $ext_if all 2639anchor spam proto tcp from any to any port smtp 2640pass out on $ext_if all 2641pass in on $ext_if proto tcp from any to $ext_if port smtp 2642.Ed 2643.Pp 2644The rules inside 2645.Ar anchor 2646spam are only evaluated for 2647.Ar tcp 2648packets with destination port 25. 2649Hence, 2650.Bd -literal -offset indent 2651# echo \&"block in quick from 1.2.3.4 to any" \&| \e 2652 pfctl -a spam -f - 2653.Ed 2654.Pp 2655will only block connections from 1.2.3.4 to port 25. 2656.Pp 2657Anchors may end with the asterisk 2658.Pq Sq * 2659character, which signifies that all anchors attached at that point 2660should be evaluated in the alphabetical ordering of their anchor name. 2661For example, 2662.Bd -literal -offset indent 2663anchor "spam/*" 2664.Ed 2665.Pp 2666will evaluate each rule in each anchor attached to the 2667.Li spam 2668anchor. 2669Note that it will only evaluate anchors that are directly attached to the 2670.Li spam 2671anchor, and will not descend to evaluate anchors recursively. 2672.Pp 2673Since anchors are evaluated relative to the anchor in which they are 2674contained, there is a mechanism for accessing the parent and ancestor 2675anchors of a given anchor. 2676Similar to file system path name resolution, if the sequence 2677.Dq .. 2678appears as an anchor path component, the parent anchor of the current 2679anchor in the path evaluation at that point will become the new current 2680anchor. 2681As an example, consider the following: 2682.Bd -literal -offset indent 2683# echo ' anchor "spam/allowed" ' | pfctl -f - 2684# echo -e ' anchor "../banned" \en pass' | \e 2685 pfctl -a spam/allowed -f - 2686.Ed 2687.Pp 2688Evaluation of the main ruleset will lead into the 2689.Li spam/allowed 2690anchor, which will evaluate the rules in the 2691.Li spam/banned 2692anchor, if any, before finally evaluating the 2693.Ar pass 2694rule. 2695.Pp 2696Filter rule 2697.Ar anchors 2698can also be loaded inline in the ruleset within a brace ('{' '}') delimited 2699block. 2700Brace delimited blocks may contain rules or other brace-delimited blocks. 2701When anchors are loaded this way the anchor name becomes optional. 2702.Bd -literal -offset indent 2703anchor "external" on $ext_if { 2704 block 2705 anchor out { 2706 pass proto tcp from any to port { 25, 80, 443 } 2707 } 2708 pass in proto tcp to any port 22 2709} 2710.Ed 2711.Pp 2712Since the parser specification for anchor names is a string, any 2713reference to an anchor name containing 2714.Sq / 2715characters will require double quote 2716.Pq Sq \&" 2717characters around the anchor name. 2718.Sh TRANSLATION EXAMPLES 2719This example maps incoming requests on port 80 to port 8080, on 2720which a daemon is running (because, for example, it is not run as root, 2721and therefore lacks permission to bind to port 80). 2722.Bd -literal 2723# use a macro for the interface name, so it can be changed easily 2724ext_if = \&"ne3\&" 2725 2726# map daemon on 8080 to appear to be on 80 2727rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080 2728.Ed 2729.Pp 2730If the 2731.Ar pass 2732modifier is given, packets matching the translation rule are passed without 2733inspecting the filter rules: 2734.Bd -literal 2735rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e 2736 port 8080 2737.Ed 2738.Pp 2739In the example below, vlan12 is configured as 192.168.168.1; 2740the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111 2741when they are going out any interface except vlan12. 2742This has the net effect of making traffic from the 192.168.168.0/24 2743network appear as though it is the Internet routable address 2744204.92.77.111 to nodes behind any interface on the router except 2745for the nodes on vlan12. 2746(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.) 2747.Bd -literal 2748nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111 2749.Ed 2750.Pp 2751In the example below, the machine sits between a fake internal 144.19.74.* 2752network, and a routable external IP of 204.92.77.100. 2753The 2754.Ar no nat 2755rule excludes protocol AH from being translated. 2756.Bd -literal 2757# NO NAT 2758no nat on $ext_if proto ah from 144.19.74.0/24 to any 2759nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100 2760.Ed 2761.Pp 2762In the example below, packets bound for one specific server, as well as those 2763generated by the sysadmins are not proxied; all other connections are. 2764.Bd -literal 2765# NO RDR 2766no rdr on $int_if proto { tcp, udp } from any to $server port 80 2767no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80 2768rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e 2769 port 80 2770.Ed 2771.Pp 2772This longer example uses both a NAT and a redirection. 2773The external interface has the address 157.161.48.183. 2774On localhost, we are running 2775.Xr ftp-proxy 8 , 2776waiting for FTP sessions to be redirected to it. 2777The three mandatory anchors for 2778.Xr ftp-proxy 8 2779are omitted from this example; see the 2780.Xr ftp-proxy 8 2781manpage. 2782.Bd -literal 2783# NAT 2784# Translate outgoing packets' source addresses (any protocol). 2785# In this case, any address but the gateway's external address is mapped. 2786nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if) 2787 2788# NAT PROXYING 2789# Map outgoing packets' source port to an assigned proxy port instead of 2790# an arbitrary port. 2791# In this case, proxy outgoing isakmp with port 500 on the gateway. 2792nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e 2793 port 500 2794 2795# BINAT 2796# Translate outgoing packets' source address (any protocol). 2797# Translate incoming packets' destination address to an internal machine 2798# (bidirectional). 2799binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if 2800 2801# RDR 2802# Translate incoming packets' destination addresses. 2803# As an example, redirect a TCP and UDP port to an internal machine. 2804rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e 2805 -\*(Gt 10.1.2.151 port 22 2806rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e 2807 -\*(Gt 10.1.2.151 port 53 2808 2809# RDR 2810# Translate outgoing ftp control connections to send them to localhost 2811# for proxying with ftp-proxy(8) running on port 8021. 2812rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021 2813.Ed 2814.Pp 2815In this example, a NAT gateway is set up to translate internal addresses 2816using a pool of public addresses (192.0.2.16/28) and to redirect 2817incoming web server connections to a group of web servers on the internal 2818network. 2819.Bd -literal 2820# NAT LOAD BALANCE 2821# Translate outgoing packets' source addresses using an address pool. 2822# A given source address is always translated to the same pool address by 2823# using the source-hash keyword. 2824nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash 2825 2826# RDR ROUND ROBIN 2827# Translate incoming web server connections to a group of web servers on 2828# the internal network. 2829rdr on $ext_if proto tcp from any to any port 80 \e 2830 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin 2831.Ed 2832.Sh FILTER EXAMPLES 2833.Bd -literal 2834# The external interface is kue0 2835# (157.161.48.183, the only routable address) 2836# and the private network is 10.0.0.0/8, for which we are doing NAT. 2837 2838# use a macro for the interface name, so it can be changed easily 2839ext_if = \&"kue0\&" 2840 2841# normalize all incoming traffic 2842scrub in on $ext_if all fragment reassemble 2843 2844# block and log everything by default 2845block return log on $ext_if all 2846 2847# block anything coming from source we have no back routes for 2848block in from no-route to any 2849 2850# block packets whose ingress interface does not match the one in 2851# the route back to their source address 2852block in from urpf-failed to any 2853 2854# block and log outgoing packets that do not have our address as source, 2855# they are either spoofed or something is misconfigured (NAT disabled, 2856# for instance), we want to be nice and do not send out garbage. 2857block out log quick on $ext_if from ! 157.161.48.183 to any 2858 2859# silently drop broadcasts (cable modem noise) 2860block in quick on $ext_if from any to 255.255.255.255 2861 2862# block and log incoming packets from reserved address space and invalid 2863# addresses, they are either spoofed or misconfigured, we cannot reply to 2864# them anyway (hence, no return-rst). 2865block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e 2866 192.168.0.0/16, 255.255.255.255/32 } to any 2867 2868# ICMP 2869 2870# pass out/in certain ICMP queries and keep state (ping) 2871# state matching is done on host addresses and ICMP id (not type/code), 2872# so replies (like 0/0 for 8/0) will match queries 2873# ICMP error messages (which always refer to a TCP/UDP packet) are 2874# handled by the TCP/UDP states 2875pass on $ext_if inet proto icmp all icmp-type 8 code 0 2876 2877# UDP 2878 2879# pass out all UDP connections and keep state 2880pass out on $ext_if proto udp all 2881 2882# pass in certain UDP connections and keep state (DNS) 2883pass in on $ext_if proto udp from any to any port domain 2884 2885# TCP 2886 2887# pass out all TCP connections and modulate state 2888pass out on $ext_if proto tcp all modulate state 2889 2890# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT) 2891pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e 2892 auth } 2893 2894# Do not allow Windows 9x SMTP connections since they are typically 2895# a viral worm. Alternately we could limit these OSes to 1 connection each. 2896block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e 2897 to any port smtp 2898 2899# IPv6 2900# pass in/out all IPv6 traffic: note that we have to enable this in two 2901# different ways, on both our physical interface and our tunnel 2902pass quick on gif0 inet6 2903pass quick on $ext_if proto ipv6 2904 2905# Packet Tagging 2906 2907# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is 2908# being done on $ext_if for all outgoing packets. tag packets in on 2909# $int_if and pass those tagged packets out on $ext_if. all other 2910# outgoing packets (i.e., packets from the wireless network) are only 2911# permitted to access port 80. 2912 2913pass in on $int_if from any to any tag INTNET 2914pass in on $wifi_if from any to any 2915 2916block out on $ext_if from any to any 2917pass out quick on $ext_if tagged INTNET 2918pass out on $ext_if proto tcp from any to any port 80 2919 2920# tag incoming packets as they are redirected to spamd(8). use the tag 2921# to pass those packets through the packet filter. 2922 2923rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e 2924 tag SPAMD -\*(Gt 127.0.0.1 port spamd 2925 2926block in on $ext_if 2927pass in on $ext_if inet proto tcp tagged SPAMD 2928.Ed 2929.Sh GRAMMAR 2930Syntax for 2931.Nm 2932in BNF: 2933.Bd -literal 2934line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule | 2935 antispoof-rule | altq-rule | queue-rule | trans-anchors | 2936 anchor-rule | anchor-close | load-anchor | table-rule | 2937 include ) 2938 2939option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] | 2940 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] | 2941 [ "optimization" [ "default" | "normal" | 2942 "high-latency" | "satellite" | 2943 "aggressive" | "conservative" ] ] 2944 [ "limit" ( limit-item | "{" limit-list "}" ) ] | 2945 [ "loginterface" ( interface-name | "none" ) ] | 2946 [ "block-policy" ( "drop" | "return" ) ] | 2947 [ "state-policy" ( "if-bound" | "floating" ) ] 2948 [ "state-defaults" state-opts ] 2949 [ "require-order" ( "yes" | "no" ) ] 2950 [ "fingerprints" filename ] | 2951 [ "skip on" ifspec ] | 2952 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] 2953 [ "keepcounters" ] ) 2954 2955pf-rule = action [ ( "in" | "out" ) ] 2956 [ "log" [ "(" logopts ")"] ] [ "quick" ] 2957 [ "on" ifspec ] [ route ] [ af ] [ protospec ] 2958 hosts [ filteropt-list ] 2959 2960logopts = logopt [ "," logopts ] 2961logopt = "all" | "user" | "to" interface-name 2962 2963filteropt-list = filteropt-list filteropt | filteropt 2964filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos | 2965 ( "no" | "keep" | "modulate" | "synproxy" ) "state" 2966 [ "(" state-opts ")" ] | 2967 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos | 2968 "max-mss" number | "random-id" | "reassemble tcp" | 2969 fragmentation | "allow-opts" | 2970 "label" string | "tag" string | [ ! ] "tagged" string | 2971 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) | 2972 "queue" ( string | "(" string [ [ "," ] string ] ")" ) | 2973 "rtable" number | "probability" number"%" | "prio" number | 2974 "dnpipe" ( number | "(" number "," number ")" ) | 2975 "dnqueue" ( number | "(" number "," number ")" ) 2976 2977nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 2978 [ "on" ifspec ] [ af ] 2979 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 2980 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 2981 [ portspec ] [ pooltype ] [ "static-port" ] 2982 [ "map-e-portset" number "/" number "/" number ] ] 2983 2984binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 2985 [ "on" interface-name ] [ af ] 2986 [ "proto" ( proto-name | proto-number ) ] 2987 "from" address [ "/" mask-bits ] "to" ipspec 2988 [ "tag" string ] [ "tagged" string ] 2989 [ "-\*(Gt" address [ "/" mask-bits ] ] 2990 2991rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 2992 [ "on" ifspec ] [ af ] 2993 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 2994 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 2995 [ portspec ] [ pooltype ] ] 2996 2997antispoof-rule = "antispoof" [ "log" ] [ "quick" ] 2998 "for" ifspec [ af ] [ "label" string ] 2999 3000table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ] 3001tableopts-list = tableopts-list tableopts | tableopts 3002tableopts = "persist" | "const" | "counters" | "file" string | 3003 "{" [ tableaddr-list ] "}" 3004tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec 3005tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ] 3006tableaddr = hostname | ifspec | "self" | 3007 ipv4-dotted-quad | ipv6-coloned-hex 3008 3009altq-rule = "altq on" interface-name queueopts-list 3010 "queue" subqueue 3011queue-rule = "queue" string [ "on" interface-name ] queueopts-list 3012 subqueue 3013 3014anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ] 3015 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ] 3016 3017anchor-close = "}" 3018 3019trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string 3020 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ] 3021 3022load-anchor = "load anchor" string "from" filename 3023 3024queueopts-list = queueopts-list queueopts | queueopts 3025queueopts = [ "bandwidth" bandwidth-spec ] | 3026 [ "qlimit" number ] | [ "tbrsize" number ] | 3027 [ "priority" number ] | [ schedulers ] 3028schedulers = ( cbq-def | priq-def | hfsc-def ) 3029bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" ) 3030 3031action = "pass" | "block" [ return ] | [ "no" ] "scrub" 3032return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] | 3033 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] | 3034 "return-icmp6" [ "(" icmp6code ")" ] 3035icmpcode = ( icmp-code-name | icmp-code-number ) 3036icmp6code = ( icmp6-code-name | icmp6-code-number ) 3037 3038ifspec = ( [ "!" ] ( interface-name | interface-group ) ) | 3039 "{" interface-list "}" 3040interface-list = [ "!" ] ( interface-name | interface-group ) 3041 [ [ "," ] interface-list ] 3042route = ( "route-to" | "reply-to" | "dup-to" ) 3043 ( routehost | "{" routehost-list "}" ) 3044 [ pooltype ] 3045af = "inet" | "inet6" 3046 3047protospec = "proto" ( proto-name | proto-number | 3048 "{" proto-list "}" ) 3049proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ] 3050 3051hosts = "all" | 3052 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host | 3053 "{" host-list "}" ) [ port ] [ os ] 3054 "to" ( "any" | "no-route" | "self" | host | 3055 "{" host-list "}" ) [ port ] 3056 3057ipspec = "any" | host | "{" host-list "}" 3058host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" ) 3059redirhost = address [ "/" mask-bits ] 3060routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")" 3061address = ( interface-name | interface-group | 3062 "(" ( interface-name | interface-group ) ")" | 3063 hostname | ipv4-dotted-quad | ipv6-coloned-hex ) 3064host-list = host [ [ "," ] host-list ] 3065redirhost-list = redirhost [ [ "," ] redirhost-list ] 3066routehost-list = routehost [ [ "," ] routehost-list ] 3067 3068port = "port" ( unary-op | binary-op | "{" op-list "}" ) 3069portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ] 3070os = "os" ( os-name | "{" os-list "}" ) 3071user = "user" ( unary-op | binary-op | "{" op-list "}" ) 3072group = "group" ( unary-op | binary-op | "{" op-list "}" ) 3073 3074unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ] 3075 ( name | number ) 3076binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number 3077op-list = ( unary-op | binary-op ) [ [ "," ] op-list ] 3078 3079os-name = operating-system-name 3080os-list = os-name [ [ "," ] os-list ] 3081 3082flags = "flags" ( [ flag-set ] "/" flag-set | "any" ) 3083flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ] 3084 [ "W" ] 3085 3086icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" ) 3087icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" ) 3088icmp-type-code = ( icmp-type-name | icmp-type-number ) 3089 [ "code" ( icmp-code-name | icmp-code-number ) ] 3090icmp-list = icmp-type-code [ [ "," ] icmp-list ] 3091 3092tos = ( "lowdelay" | "throughput" | "reliability" | 3093 [ "0x" ] number ) 3094 3095state-opts = state-opt [ [ "," ] state-opts ] 3096state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | 3097 "source-track" [ ( "rule" | "global" ) ] | 3098 "max-src-nodes" number | "max-src-states" number | 3099 "max-src-conn" number | 3100 "max-src-conn-rate" number "/" number | 3101 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] | 3102 "if-bound" | "floating" ) 3103 3104fragmentation = [ "fragment reassemble" ] 3105 3106timeout-list = timeout [ [ "," ] timeout-list ] 3107timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" | 3108 "tcp.closing" | "tcp.finwait" | "tcp.closed" | 3109 "udp.first" | "udp.single" | "udp.multiple" | 3110 "icmp.first" | "icmp.error" | 3111 "other.first" | "other.single" | "other.multiple" | 3112 "frag" | "interval" | "src.track" | 3113 "adaptive.start" | "adaptive.end" ) number 3114 3115limit-list = limit-item [ [ "," ] limit-list ] 3116limit-item = ( "states" | "frags" | "src-nodes" ) number 3117 3118pooltype = ( "bitmask" | "random" | 3119 "source-hash" [ ( hex-key | string-key ) ] | 3120 "round-robin" ) [ sticky-address ] 3121 3122subqueue = string | "{" queue-list "}" 3123queue-list = string [ [ "," ] string ] 3124cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ] 3125priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ] 3126hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ] 3127cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" ) 3128priq-opt = ( "default" | "red" | "ecn" | "rio" ) 3129hfsc-opt = ( "default" | "red" | "ecn" | "rio" | 3130 linkshare-sc | realtime-sc | upperlimit-sc ) 3131linkshare-sc = "linkshare" sc-spec 3132realtime-sc = "realtime" sc-spec 3133upperlimit-sc = "upperlimit" sc-spec 3134sc-spec = ( bandwidth-spec | 3135 "(" bandwidth-spec number bandwidth-spec ")" ) 3136include = "include" filename 3137.Ed 3138.Sh FILES 3139.Bl -tag -width "/etc/protocols" -compact 3140.It Pa /etc/hosts 3141Host name database. 3142.It Pa /etc/pf.conf 3143Default location of the ruleset file. 3144The file has to be created manually as it is not installed with a 3145standard installation. 3146.It Pa /etc/pf.os 3147Default location of OS fingerprints. 3148.It Pa /etc/protocols 3149Protocol name database. 3150.It Pa /etc/services 3151Service name database. 3152.El 3153.Sh SEE ALSO 3154.Xr altq 4 , 3155.Xr carp 4 , 3156.Xr icmp 4 , 3157.Xr icmp6 4 , 3158.Xr ip 4 , 3159.Xr ip6 4 , 3160.Xr pf 4 , 3161.Xr pfsync 4 , 3162.Xr tcp 4 , 3163.Xr udp 4 , 3164.Xr hosts 5 , 3165.Xr pf.os 5 , 3166.Xr protocols 5 , 3167.Xr services 5 , 3168.Xr ftp-proxy 8 , 3169.Xr pfctl 8 , 3170.Xr pflogd 8 3171.Sh HISTORY 3172The 3173.Nm 3174file format first appeared in 3175.Ox 3.0 . 3176