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 April 19, 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 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 TRANSLATION 1108Translation rules modify either the source or destination address of the 1109packets associated with a stateful connection. 1110A stateful connection is automatically created to track packets matching 1111such a rule as long as they are not blocked by the filtering section of 1112.Nm pf.conf . 1113The translation engine modifies the specified address and/or port in the 1114packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to 1115the packet filter for evaluation. 1116.Pp 1117Since translation occurs before filtering the filter 1118engine will see packets as they look after any 1119addresses and ports have been translated. 1120Filter rules will therefore have to filter based on the translated 1121address and port number. 1122Packets that match a translation rule are only automatically passed if 1123the 1124.Ar pass 1125modifier is given, otherwise they are 1126still subject to 1127.Ar block 1128and 1129.Ar pass 1130rules. 1131.Pp 1132The state entry created permits 1133.Xr pf 4 1134to keep track of the original address for traffic associated with that state 1135and correctly direct return traffic for that connection. 1136.Pp 1137Various types of translation are possible with pf: 1138.Bl -tag -width xxxx 1139.It Ar binat 1140A 1141.Ar binat 1142rule specifies a bidirectional mapping between an external IP netblock 1143and an internal IP netblock. 1144.It Ar nat 1145A 1146.Ar nat 1147rule specifies that IP addresses are to be changed as the packet 1148traverses the given interface. 1149This technique allows one or more IP addresses 1150on the translating host to support network traffic for a larger range of 1151machines on an "inside" network. 1152Although in theory any IP address can be used on the inside, it is strongly 1153recommended that one of the address ranges defined by RFC 1918 be used. 1154These netblocks are: 1155.Bd -literal 115610.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8) 1157172.16.0.0 - 172.31.255.255 (i.e., 172.16/12) 1158192.168.0.0 - 192.168.255.255 (i.e., 192.168/16) 1159.Ed 1160.It Pa rdr 1161The packet is redirected to another destination and possibly a 1162different port. 1163.Ar rdr 1164rules can optionally specify port ranges instead of single ports. 1165rdr ... port 2000:2999 -\*(Gt ... port 4000 1166redirects ports 2000 to 2999 (inclusive) to port 4000. 1167rdr ... port 2000:2999 -\*(Gt ... port 4000:* 1168redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999. 1169.El 1170.Pp 1171In addition to modifying the address, some translation rules may modify 1172source or destination ports for 1173.Xr tcp 4 1174or 1175.Xr udp 4 1176connections; implicitly in the case of 1177.Ar nat 1178rules and explicitly in the case of 1179.Ar rdr 1180rules. 1181Port numbers are never translated with a 1182.Ar binat 1183rule. 1184.Pp 1185Evaluation order of the translation rules is dependent on the type 1186of the translation rules and of the direction of a packet. 1187.Ar binat 1188rules are always evaluated first. 1189Then either the 1190.Ar rdr 1191rules are evaluated on an inbound packet or the 1192.Ar nat 1193rules on an outbound packet. 1194Rules of the same type are evaluated in the same order in which they 1195appear in the ruleset. 1196The first matching rule decides what action is taken. 1197.Pp 1198The 1199.Ar no 1200option prefixed to a translation rule causes packets to remain untranslated, 1201much in the same way as 1202.Ar drop quick 1203works in the packet filter (see below). 1204If no rule matches the packet it is passed to the filter engine unmodified. 1205.Pp 1206Translation rules apply only to packets that pass through 1207the specified interface, and if no interface is specified, 1208translation is applied to packets on all interfaces. 1209For instance, redirecting port 80 on an external interface to an internal 1210web server will only work for connections originating from the outside. 1211Connections to the address of the external interface from local hosts will 1212not be redirected, since such packets do not actually pass through the 1213external interface. 1214Redirections cannot reflect packets back through the interface they arrive 1215on, they can only be redirected to hosts connected to different interfaces 1216or to the firewall itself. 1217.Pp 1218Note that redirecting external incoming connections to the loopback 1219address, as in 1220.Bd -literal -offset indent 1221rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd 1222.Ed 1223.Pp 1224will effectively allow an external host to connect to daemons 1225bound solely to the loopback address, circumventing the traditional 1226blocking of such connections on a real interface. 1227Unless this effect is desired, any of the local non-loopback addresses 1228should be used as redirection target instead, which allows external 1229connections only to daemons bound to this address or not bound to 1230any address. 1231.Pp 1232See 1233.Sx TRANSLATION EXAMPLES 1234below. 1235.Sh PACKET FILTERING 1236.Xr pf 4 1237has the ability to 1238.Ar block 1239, 1240.Ar pass 1241and 1242.Ar match 1243packets based on attributes of their layer 3 (see 1244.Xr ip 4 1245and 1246.Xr ip6 4 ) 1247and layer 4 (see 1248.Xr icmp 4 , 1249.Xr icmp6 4 , 1250.Xr tcp 4 , 1251.Xr udp 4 ) 1252headers. 1253In addition, packets may also be 1254assigned to queues for the purpose of bandwidth control. 1255.Pp 1256For each packet processed by the packet filter, the filter rules are 1257evaluated in sequential order, from first to last. 1258For 1259.Ar block 1260and 1261.Ar pass 1262, the last matching rule decides what action is taken. 1263For 1264.Ar match 1265, rules are evaulated every time they match; the pass/block state of a packet 1266remains unchanged. 1267If no rule matches the packet, the default action is to pass 1268the packet. 1269.Pp 1270The following actions can be used in the filter: 1271.Bl -tag -width xxxx 1272.It Ar block 1273The packet is blocked. 1274There are a number of ways in which a 1275.Ar block 1276rule can behave when blocking a packet. 1277The default behaviour is to 1278.Ar drop 1279packets silently, however this can be overridden or made 1280explicit either globally, by setting the 1281.Ar block-policy 1282option, or on a per-rule basis with one of the following options: 1283.Pp 1284.Bl -tag -width xxxx -compact 1285.It Ar drop 1286The packet is silently dropped. 1287.It Ar return-rst 1288This applies only to 1289.Xr tcp 4 1290packets, and issues a TCP RST which closes the 1291connection. 1292.It Ar return-icmp 1293.It Ar return-icmp6 1294This causes ICMP messages to be returned for packets which match the rule. 1295By default this is an ICMP UNREACHABLE message, however this 1296can be overridden by specifying a message as a code or number. 1297.It Ar return 1298This causes a TCP RST to be returned for 1299.Xr tcp 4 1300packets and an ICMP UNREACHABLE for UDP and other packets. 1301.El 1302.Pp 1303Options returning ICMP packets currently have no effect if 1304.Xr pf 4 1305operates on a 1306.Xr if_bridge 4 , 1307as the code to support this feature has not yet been implemented. 1308.Pp 1309The simplest mechanism to block everything by default and only pass 1310packets that match explicit rules is specify a first filter rule of: 1311.Bd -literal -offset indent 1312block all 1313.Ed 1314.It Ar match 1315The packet is matched. 1316This mechanism is used to provide fine grained filtering without altering the 1317block/pass state of a packet. 1318.Ar match 1319rules differ from 1320.Ar block 1321and 1322.Ar pass 1323rules in that parameters are set every time a packet matches the rule, not only 1324on the last matching rule. 1325For the following parameters, this means that the parameter effectively becomes 1326"sticky" until explicitly overridden: 1327.Ar queue 1328. 1329.It Ar pass 1330The packet is passed; 1331state is created unless the 1332.Ar no state 1333option is specified. 1334.El 1335.Pp 1336By default 1337.Xr pf 4 1338filters packets statefully; the first time a packet matches a 1339.Ar pass 1340rule, a state entry is created; for subsequent packets the filter checks 1341whether the packet matches any state. 1342If it does, the packet is passed without evaluation of any rules. 1343After the connection is closed or times out, the state entry is automatically 1344removed. 1345.Pp 1346This has several advantages. 1347For TCP connections, comparing a packet to a state involves checking 1348its sequence numbers, as well as TCP timestamps if a 1349.Ar scrub reassemble tcp 1350rule applies to the connection. 1351If these values are outside the narrow windows of expected 1352values, the packet is dropped. 1353This prevents spoofing attacks, such as when an attacker sends packets with 1354a fake source address/port but does not know the connection's sequence 1355numbers. 1356Similarly, 1357.Xr pf 4 1358knows how to match ICMP replies to states. 1359For example, 1360.Bd -literal -offset indent 1361pass out inet proto icmp all icmp-type echoreq 1362.Ed 1363.Pp 1364allows echo requests (such as those created by 1365.Xr ping 8 ) 1366out statefully, and matches incoming echo replies correctly to states. 1367.Pp 1368Also, looking up states is usually faster than evaluating rules. 1369If there are 50 rules, all of them are evaluated sequentially in O(n). 1370Even with 50000 states, only 16 comparisons are needed to match a 1371state, since states are stored in a binary search tree that allows 1372searches in O(log2 n). 1373.Pp 1374Furthermore, correct handling of ICMP error messages is critical to 1375many protocols, particularly TCP. 1376.Xr pf 4 1377matches ICMP error messages to the correct connection, checks them against 1378connection parameters, and passes them if appropriate. 1379For example if an ICMP source quench message referring to a stateful TCP 1380connection arrives, it will be matched to the state and get passed. 1381.Pp 1382Finally, state tracking is required for 1383.Ar nat , binat No and Ar rdr 1384rules, in order to track address and port translations and reverse the 1385translation on returning packets. 1386.Pp 1387.Xr pf 4 1388will also create state for other protocols which are effectively stateless by 1389nature. 1390UDP packets are matched to states using only host addresses and ports, 1391and other protocols are matched to states using only the host addresses. 1392.Pp 1393If stateless filtering of individual packets is desired, 1394the 1395.Ar no state 1396keyword can be used to specify that state will not be created 1397if this is the last matching rule. 1398A number of parameters can also be set to affect how 1399.Xr pf 4 1400handles state tracking. 1401See 1402.Sx STATEFUL TRACKING OPTIONS 1403below for further details. 1404.Sh PARAMETERS 1405The rule parameters specify the packets to which a rule applies. 1406A packet always comes in on, or goes out through, one interface. 1407Most parameters are optional. 1408If a parameter is specified, the rule only applies to packets with 1409matching attributes. 1410Certain parameters can be expressed as lists, in which case 1411.Xr pfctl 8 1412generates all needed rule combinations. 1413.Bl -tag -width xxxx 1414.It Ar in No or Ar out 1415This rule applies to incoming or outgoing packets. 1416If neither 1417.Ar in 1418nor 1419.Ar out 1420are specified, the rule will match packets in both directions. 1421.It Ar log 1422In addition to the action specified, a log message is generated. 1423Only the packet that establishes the state is logged, 1424unless the 1425.Ar no state 1426option is specified. 1427The logged packets are sent to a 1428.Xr pflog 4 1429interface, by default 1430.Ar pflog0 . 1431This interface is monitored by the 1432.Xr pflogd 8 1433logging daemon, which dumps the logged packets to the file 1434.Pa /var/log/pflog 1435in 1436.Xr pcap 3 1437binary format. 1438.It Ar log (all) 1439Used to force logging of all packets for a connection. 1440This is not necessary when 1441.Ar no state 1442is explicitly specified. 1443As with 1444.Ar log , 1445packets are logged to 1446.Xr pflog 4 . 1447.It Ar log (user) 1448Logs the 1449.Ux 1450user ID of the user that owns the socket and the PID of the process that 1451has the socket open where the packet is sourced from or destined to 1452(depending on which socket is local). 1453This is in addition to the normal information logged. 1454.Pp 1455Only the first packet 1456logged via 1457.Ar log (all, user) 1458will have the user credentials logged when using stateful matching. 1459.It Ar log (to Aq Ar interface ) 1460Send logs to the specified 1461.Xr pflog 4 1462interface instead of 1463.Ar pflog0 . 1464.It Ar quick 1465If a packet matches a rule which has the 1466.Ar quick 1467option set, this rule 1468is considered the last matching rule, and evaluation of subsequent rules 1469is skipped. 1470.It Ar on Aq Ar interface 1471This rule applies only to packets coming in on, or going out through, this 1472particular interface or interface group. 1473For more information on interface groups, 1474see the 1475.Ic group 1476keyword in 1477.Xr ifconfig 8 . 1478.It Aq Ar af 1479This rule applies only to packets of this address family. 1480Supported values are 1481.Ar inet 1482and 1483.Ar inet6 . 1484.It Ar proto Aq Ar protocol 1485This rule applies only to packets of this protocol. 1486Common protocols are 1487.Xr icmp 4 , 1488.Xr icmp6 4 , 1489.Xr tcp 4 , 1490and 1491.Xr udp 4 . 1492For a list of all the protocol name to number mappings used by 1493.Xr pfctl 8 , 1494see the file 1495.Pa /etc/protocols . 1496.It Xo 1497.Ar from Aq Ar source 1498.Ar port Aq Ar source 1499.Ar os Aq Ar source 1500.Ar to Aq Ar dest 1501.Ar port Aq Ar dest 1502.Xc 1503This rule applies only to packets with the specified source and destination 1504addresses and ports. 1505.Pp 1506Addresses can be specified in CIDR notation (matching netblocks), as 1507symbolic host names, interface names or interface group names, or as any 1508of the following keywords: 1509.Pp 1510.Bl -tag -width xxxxxxxxxxxxxx -compact 1511.It Ar any 1512Any address. 1513.It Ar no-route 1514Any address which is not currently routable. 1515.It Ar urpf-failed 1516Any source address that fails a unicast reverse path forwarding (URPF) 1517check, i.e. packets coming in on an interface other than that which holds 1518the route back to the packet's source address. 1519.It Aq Ar table 1520Any address that matches the given table. 1521.El 1522.Pp 1523Ranges of addresses are specified by using the 1524.Sq - 1525operator. 1526For instance: 1527.Dq 10.1.1.10 - 10.1.1.12 1528means all addresses from 10.1.1.10 to 10.1.1.12, 1529hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12. 1530.Pp 1531Interface names and interface group names can have modifiers appended: 1532.Pp 1533.Bl -tag -width xxxxxxxxxxxx -compact 1534.It Ar :network 1535Translates to the network(s) attached to the interface. 1536.It Ar :broadcast 1537Translates to the interface's broadcast address(es). 1538.It Ar :peer 1539Translates to the point-to-point interface's peer address(es). 1540.It Ar :0 1541Do not include interface aliases. 1542.El 1543.Pp 1544Host names may also have the 1545.Ar :0 1546option appended to restrict the name resolution to the first of each 1547v4 and non-link-local v6 address found. 1548.Pp 1549Host name resolution and interface to address translation are done at 1550ruleset load-time. 1551When the address of an interface (or host name) changes (under DHCP or PPP, 1552for instance), the ruleset must be reloaded for the change to be reflected 1553in the kernel. 1554Surrounding the interface name (and optional modifiers) in parentheses 1555changes this behaviour. 1556When the interface name is surrounded by parentheses, the rule is 1557automatically updated whenever the interface changes its address. 1558The ruleset does not need to be reloaded. 1559This is especially useful with 1560.Ar nat . 1561.Pp 1562Ports can be specified either by number or by name. 1563For example, port 80 can be specified as 1564.Em www . 1565For a list of all port name to number mappings used by 1566.Xr pfctl 8 , 1567see the file 1568.Pa /etc/services . 1569.Pp 1570Ports and ranges of ports are specified by using these operators: 1571.Bd -literal -offset indent 1572= (equal) 1573!= (unequal) 1574\*(Lt (less than) 1575\*(Le (less than or equal) 1576\*(Gt (greater than) 1577\*(Ge (greater than or equal) 1578: (range including boundaries) 1579\*(Gt\*(Lt (range excluding boundaries) 1580\*(Lt\*(Gt (except range) 1581.Ed 1582.Pp 1583.Sq \*(Gt\*(Lt , 1584.Sq \*(Lt\*(Gt 1585and 1586.Sq \&: 1587are binary operators (they take two arguments). 1588For instance: 1589.Bl -tag -width Fl 1590.It Ar port 2000:2004 1591means 1592.Sq all ports \*(Ge 2000 and \*(Le 2004 , 1593hence ports 2000, 2001, 2002, 2003 and 2004. 1594.It Ar port 2000 \*(Gt\*(Lt 2004 1595means 1596.Sq all ports \*(Gt 2000 and \*(Lt 2004 , 1597hence ports 2001, 2002 and 2003. 1598.It Ar port 2000 \*(Lt\*(Gt 2004 1599means 1600.Sq all ports \*(Lt 2000 or \*(Gt 2004 , 1601hence ports 1-1999 and 2005-65535. 1602.El 1603.Pp 1604The operating system of the source host can be specified in the case of TCP 1605rules with the 1606.Ar OS 1607modifier. 1608See the 1609.Sx OPERATING SYSTEM FINGERPRINTING 1610section for more information. 1611.Pp 1612The host, port and OS specifications are optional, as in the following examples: 1613.Bd -literal -offset indent 1614pass in all 1615pass in from any to any 1616pass in proto tcp from any port \*(Le 1024 to any 1617pass in proto tcp from any to any port 25 1618pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e 1619 to ! 10.1.2.3 port != ssh 1620pass in proto tcp from any os "OpenBSD" 1621.Ed 1622.It Ar all 1623This is equivalent to "from any to any". 1624.It Ar group Aq Ar group 1625Similar to 1626.Ar user , 1627this rule only applies to packets of sockets owned by the specified group. 1628.It Ar user Aq Ar user 1629This rule only applies to packets of sockets owned by the specified user. 1630For outgoing connections initiated from the firewall, this is the user 1631that opened the connection. 1632For incoming connections to the firewall itself, this is the user that 1633listens on the destination port. 1634For forwarded connections, where the firewall is not a connection endpoint, 1635the user and group are 1636.Em unknown . 1637.Pp 1638All packets, both outgoing and incoming, of one connection are associated 1639with the same user and group. 1640Only TCP and UDP packets can be associated with users; for other protocols 1641these parameters are ignored. 1642.Pp 1643User and group refer to the effective (as opposed to the real) IDs, in 1644case the socket is created by a setuid/setgid process. 1645User and group IDs are stored when a socket is created; 1646when a process creates a listening socket as root (for instance, by 1647binding to a privileged port) and subsequently changes to another 1648user ID (to drop privileges), the credentials will remain root. 1649.Pp 1650User and group IDs can be specified as either numbers or names. 1651The syntax is similar to the one for ports. 1652The value 1653.Em unknown 1654matches packets of forwarded connections. 1655.Em unknown 1656can only be used with the operators 1657.Cm = 1658and 1659.Cm != . 1660Other constructs like 1661.Cm user \*(Ge unknown 1662are invalid. 1663Forwarded packets with unknown user and group ID match only rules 1664that explicitly compare against 1665.Em unknown 1666with the operators 1667.Cm = 1668or 1669.Cm != . 1670For instance 1671.Cm user \*(Ge 0 1672does not match forwarded packets. 1673The following example allows only selected users to open outgoing 1674connections: 1675.Bd -literal -offset indent 1676block out proto { tcp, udp } all 1677pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei } 1678.Ed 1679.It Xo Ar flags Aq Ar a 1680.Pf / Ns Aq Ar b 1681.No \*(Ba / Ns Aq Ar b 1682.No \*(Ba any 1683.Xc 1684This rule only applies to TCP packets that have the flags 1685.Aq Ar a 1686set out of set 1687.Aq Ar b . 1688Flags not specified in 1689.Aq Ar b 1690are ignored. 1691For stateful connections, the default is 1692.Ar flags S/SA . 1693To indicate that flags should not be checked at all, specify 1694.Ar flags any . 1695The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R. 1696.Bl -tag -width Fl 1697.It Ar flags S/S 1698Flag SYN is set. 1699The other flags are ignored. 1700.It Ar flags S/SA 1701This is the default setting for stateful connections. 1702Out of SYN and ACK, exactly SYN may be set. 1703SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not. 1704This is more restrictive than the previous example. 1705.It Ar flags /SFRA 1706If the first set is not specified, it defaults to none. 1707All of SYN, FIN, RST and ACK must be unset. 1708.El 1709.Pp 1710Because 1711.Ar flags S/SA 1712is applied by default (unless 1713.Ar no state 1714is specified), only the initial SYN packet of a TCP handshake will create 1715a state for a TCP connection. 1716It is possible to be less restrictive, and allow state creation from 1717intermediate 1718.Pq non-SYN 1719packets, by specifying 1720.Ar flags any . 1721This will cause 1722.Xr pf 4 1723to synchronize to existing connections, for instance 1724if one flushes the state table. 1725However, states created from such intermediate packets may be missing 1726connection details such as the TCP window scaling factor. 1727States which modify the packet flow, such as those affected by 1728.Ar nat , binat No or Ar rdr 1729rules, 1730.Ar modulate No or Ar synproxy state 1731options, or scrubbed with 1732.Ar reassemble tcp 1733will also not be recoverable from intermediate packets. 1734Such connections will stall and time out. 1735.It Xo Ar icmp-type Aq Ar type 1736.Ar code Aq Ar code 1737.Xc 1738.It Xo Ar icmp6-type Aq Ar type 1739.Ar code Aq Ar code 1740.Xc 1741This rule only applies to ICMP or ICMPv6 packets with the specified type 1742and code. 1743Text names for ICMP types and codes are listed in 1744.Xr icmp 4 1745and 1746.Xr icmp6 4 . 1747This parameter is only valid for rules that cover protocols ICMP or 1748ICMP6. 1749The protocol and the ICMP type indicator 1750.Po 1751.Ar icmp-type 1752or 1753.Ar icmp6-type 1754.Pc 1755must match. 1756.It Xo Ar tos Aq Ar string 1757.No \*(Ba Aq Ar number 1758.Xc 1759This rule applies to packets with the specified 1760.Em TOS 1761bits set. 1762.Em TOS 1763may be 1764given as one of 1765.Ar critical , 1766.Ar inetcontrol , 1767.Ar lowdelay , 1768.Ar netcontrol , 1769.Ar throughput , 1770.Ar reliability , 1771or one of the DiffServ Code Points: 1772.Ar ef , 1773.Ar va , 1774.Ar af11 No ... Ar af43 , 1775.Ar cs0 No ... Ar cs7 ; 1776or as either hex or decimal. 1777.Pp 1778For example, the following rules are identical: 1779.Bd -literal -offset indent 1780pass all tos lowdelay 1781pass all tos 0x10 1782pass all tos 16 1783.Ed 1784.It Ar allow-opts 1785By default, IPv4 packets with IP options or IPv6 packets with routing 1786extension headers are blocked. 1787When 1788.Ar allow-opts 1789is specified for a 1790.Ar pass 1791rule, packets that pass the filter based on that rule (last matching) 1792do so even if they contain IP options or routing extension headers. 1793For packets that match state, the rule that initially created the 1794state is used. 1795The implicit 1796.Ar pass 1797rule that is used when a packet does not match any rules does not 1798allow IP options. 1799.It Ar label Aq Ar string 1800Adds a label (name) to the rule, which can be used to identify the rule. 1801For instance, 1802pfctl -s labels 1803shows per-rule statistics for rules that have labels. 1804.Pp 1805The following macros can be used in labels: 1806.Pp 1807.Bl -tag -width $srcaddr -compact -offset indent 1808.It Ar $if 1809The interface. 1810.It Ar $srcaddr 1811The source IP address. 1812.It Ar $dstaddr 1813The destination IP address. 1814.It Ar $srcport 1815The source port specification. 1816.It Ar $dstport 1817The destination port specification. 1818.It Ar $proto 1819The protocol name. 1820.It Ar $nr 1821The rule number. 1822.El 1823.Pp 1824For example: 1825.Bd -literal -offset indent 1826ips = \&"{ 1.2.3.4, 1.2.3.5 }\&" 1827pass in proto tcp from any to $ips \e 1828 port \*(Gt 1023 label \&"$dstaddr:$dstport\&" 1829.Ed 1830.Pp 1831expands to 1832.Bd -literal -offset indent 1833pass in inet proto tcp from any to 1.2.3.4 \e 1834 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&" 1835pass in inet proto tcp from any to 1.2.3.5 \e 1836 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&" 1837.Ed 1838.Pp 1839The macro expansion for the 1840.Ar label 1841directive occurs only at configuration file parse time, not during runtime. 1842.It Xo Ar queue Aq Ar queue 1843.No \*(Ba ( Aq Ar queue , 1844.Aq Ar queue ) 1845.Xc 1846Packets matching this rule will be assigned to the specified queue. 1847If two queues are given, packets which have a 1848.Em TOS 1849of 1850.Em lowdelay 1851and TCP ACKs with no data payload will be assigned to the second one. 1852See 1853.Sx QUEUEING 1854for setup details. 1855.Pp 1856For example: 1857.Bd -literal -offset indent 1858pass in proto tcp to port 25 queue mail 1859pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio) 1860.Ed 1861.Pp 1862.It Cm set prio Ar priority | Pq Ar priority , priority 1863Packets matching this rule will be assigned a specific queueing priority. 1864Priorities are assigned as integers 0 through 7. 1865If the packet is transmitted on a 1866.Xr vlan 4 1867interface, the queueing priority will be written as the priority 1868code point in the 802.1Q VLAN header. 1869If two priorities are given, packets which have a TOS of 1870.Cm lowdelay 1871and TCP ACKs with no data payload will be assigned to the second one. 1872.Pp 1873For example: 1874.Bd -literal -offset indent 1875pass in proto tcp to port 25 set prio 2 1876pass in proto tcp to port 22 set prio (2, 5) 1877.Ed 1878.Pp 1879.It Ar tag Aq Ar string 1880Packets matching this rule will be tagged with the 1881specified string. 1882The tag acts as an internal marker that can be used to 1883identify these packets later on. 1884This can be used, for example, to provide trust between 1885interfaces and to determine if packets have been 1886processed by translation rules. 1887Tags are 1888.Qq sticky , 1889meaning that the packet will be tagged even if the rule 1890is not the last matching rule. 1891Further matching rules can replace the tag with a 1892new one but will not remove a previously applied tag. 1893A packet is only ever assigned one tag at a time. 1894Packet tagging can be done during 1895.Ar nat , 1896.Ar rdr , 1897or 1898.Ar binat 1899rules in addition to filter rules. 1900Tags take the same macros as labels (see above). 1901.It Ar tagged Aq Ar string 1902Used with filter, translation or scrub rules 1903to specify that packets must already 1904be tagged with the given tag in order to match the rule. 1905Inverse tag matching can also be done 1906by specifying the 1907.Cm !\& 1908operator before the 1909.Ar tagged 1910keyword. 1911.It Ar rtable Aq Ar number 1912Used to select an alternate routing table for the routing lookup. 1913Only effective before the route lookup happened, i.e. when filtering inbound. 1914.It Xo Ar divert-to Aq Ar host 1915.Ar port Aq Ar port 1916.Xc 1917Used to redirect packets to a local socket bound to 1918.Ar host 1919and 1920.Ar port . 1921The packets will not be modified, so 1922.Xr getsockname 2 1923on the socket will return the original destination address of the packet. 1924.It Ar divert-reply 1925Used to receive replies for sockets that are bound to addresses 1926which are not local to the machine. 1927See 1928.Xr setsockopt 2 1929for information on how to bind these sockets. 1930.It Ar probability Aq Ar number 1931A probability attribute can be attached to a rule, with a value set between 19320 and 1, bounds not included. 1933In that case, the rule will be honoured using the given probability value 1934only. 1935For example, the following rule will drop 20% of incoming ICMP packets: 1936.Bd -literal -offset indent 1937block in proto icmp probability 20% 1938.Ed 1939.It Ar prio Aq Ar number 1940Only match packets which have the given queueing priority assigned. 1941.Pp 1942.El 1943.Sh ROUTING 1944If a packet matches a rule with a route option set, the packet filter will 1945route the packet according to the type of route option. 1946When such a rule creates state, the route option is also applied to all 1947packets matching the same connection. 1948.Bl -tag -width xxxx 1949.It Ar route-to 1950The 1951.Ar route-to 1952option routes the packet to the specified interface with an optional address 1953for the next hop. 1954When a 1955.Ar route-to 1956rule creates state, only packets that pass in the same direction as the 1957filter rule specifies will be routed in this way. 1958Packets passing in the opposite direction (replies) are not affected 1959and are routed normally. 1960.It Ar reply-to 1961The 1962.Ar reply-to 1963option is similar to 1964.Ar route-to , 1965but routes packets that pass in the opposite direction (replies) to the 1966specified interface. 1967Opposite direction is only defined in the context of a state entry, and 1968.Ar reply-to 1969is useful only in rules that create state. 1970It can be used on systems with multiple external connections to 1971route all outgoing packets of a connection through the interface 1972the incoming connection arrived through (symmetric routing enforcement). 1973.It Ar dup-to 1974The 1975.Ar dup-to 1976option creates a duplicate of the packet and routes it like 1977.Ar route-to . 1978The original packet gets routed as it normally would. 1979.El 1980.Sh POOL OPTIONS 1981For 1982.Ar nat 1983and 1984.Ar rdr 1985rules, (as well as for the 1986.Ar route-to , 1987.Ar reply-to 1988and 1989.Ar dup-to 1990rule options) for which there is a single redirection address which has a 1991subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP 1992address), a variety of different methods for assigning this address can be 1993used: 1994.Bl -tag -width xxxx 1995.It Ar bitmask 1996The 1997.Ar bitmask 1998option applies the network portion of the redirection address to the address 1999to be modified (source with 2000.Ar nat , 2001destination with 2002.Ar rdr ) . 2003.It Ar random 2004The 2005.Ar random 2006option selects an address at random within the defined block of addresses. 2007.It Ar source-hash 2008The 2009.Ar source-hash 2010option uses a hash of the source address to determine the redirection address, 2011ensuring that the redirection address is always the same for a given source. 2012An optional key can be specified after this keyword either in hex or as a 2013string; by default 2014.Xr pfctl 8 2015randomly generates a key for source-hash every time the 2016ruleset is reloaded. 2017.It Ar round-robin 2018The 2019.Ar round-robin 2020option loops through the redirection address(es). 2021.Pp 2022When more than one redirection address is specified, 2023.Ar round-robin 2024is the only permitted pool type. 2025.It Ar static-port 2026With 2027.Ar nat 2028rules, the 2029.Ar static-port 2030option prevents 2031.Xr pf 4 2032from modifying the source port on TCP and UDP packets. 2033.It Xo Ar map-e-portset Aq Ar psid-offset 2034.No / Aq Ar psid-len 2035.No / Aq Ar psid 2036.Xc 2037With 2038.Ar nat 2039rules, the 2040.Ar map-e-portset 2041option enables the source port translation of MAP-E (RFC 7597) Customer Edge. 2042In order to make the host act as a MAP-E Customer Edge, setting up a tunneling 2043interface and pass rules for encapsulated packets are required in addition 2044to the map-e-portset nat rule. 2045.Pp 2046For example: 2047.Bd -literal -offset indent 2048nat on $gif_mape_if from $int_if:network to any \e 2049 -> $ipv4_mape_src map-e-portset 6/8/0x34 2050.Ed 2051.Pp 2052sets PSID offset 6, PSID length 8, PSID 0x34. 2053.Ed 2054.El 2055.Pp 2056Additionally, the 2057.Ar sticky-address 2058option can be specified to help ensure that multiple connections from the 2059same source are mapped to the same redirection address. 2060This option can be used with the 2061.Ar random 2062and 2063.Ar round-robin 2064pool options. 2065Note that by default these associations are destroyed as soon as there are 2066no longer states which refer to them; in order to make the mappings last 2067beyond the lifetime of the states, increase the global options with 2068.Ar set timeout src.track . 2069See 2070.Sx STATEFUL TRACKING OPTIONS 2071for more ways to control the source tracking. 2072.Sh STATE MODULATION 2073Much of the security derived from TCP is attributable to how well the 2074initial sequence numbers (ISNs) are chosen. 2075Some popular stack implementations choose 2076.Em very 2077poor ISNs and thus are normally susceptible to ISN prediction exploits. 2078By applying a 2079.Ar modulate state 2080rule to a TCP connection, 2081.Xr pf 4 2082will create a high quality random sequence number for each connection 2083endpoint. 2084.Pp 2085The 2086.Ar modulate state 2087directive implicitly keeps state on the rule and is 2088only applicable to TCP connections. 2089.Pp 2090For instance: 2091.Bd -literal -offset indent 2092block all 2093pass out proto tcp from any to any modulate state 2094pass in proto tcp from any to any port 25 flags S/SFRA modulate state 2095.Ed 2096.Pp 2097Note that modulated connections will not recover when the state table 2098is lost (firewall reboot, flushing the state table, etc...). 2099.Xr pf 4 2100will not be able to infer a connection again after the state table flushes 2101the connection's modulator. 2102When the state is lost, the connection may be left dangling until the 2103respective endpoints time out the connection. 2104It is possible on a fast local network for the endpoints to start an ACK 2105storm while trying to resynchronize after the loss of the modulator. 2106The default 2107.Ar flags 2108settings (or a more strict equivalent) should be used on 2109.Ar modulate state 2110rules to prevent ACK storms. 2111.Pp 2112Note that alternative methods are available 2113to prevent loss of the state table 2114and allow for firewall failover. 2115See 2116.Xr carp 4 2117and 2118.Xr pfsync 4 2119for further information. 2120.Sh SYN PROXY 2121By default, 2122.Xr pf 4 2123passes packets that are part of a 2124.Xr tcp 4 2125handshake between the endpoints. 2126The 2127.Ar synproxy state 2128option can be used to cause 2129.Xr pf 4 2130itself to complete the handshake with the active endpoint, perform a handshake 2131with the passive endpoint, and then forward packets between the endpoints. 2132.Pp 2133No packets are sent to the passive endpoint before the active endpoint has 2134completed the handshake, hence so-called SYN floods with spoofed source 2135addresses will not reach the passive endpoint, as the sender can't complete the 2136handshake. 2137.Pp 2138The proxy is transparent to both endpoints, they each see a single 2139connection from/to the other endpoint. 2140.Xr pf 4 2141chooses random initial sequence numbers for both handshakes. 2142Once the handshakes are completed, the sequence number modulators 2143(see previous section) are used to translate further packets of the 2144connection. 2145.Ar synproxy state 2146includes 2147.Ar modulate state . 2148.Pp 2149Rules with 2150.Ar synproxy 2151will not work if 2152.Xr pf 4 2153operates on a 2154.Xr bridge 4 . 2155.Pp 2156Example: 2157.Bd -literal -offset indent 2158pass in proto tcp from any to any port www synproxy state 2159.Ed 2160.Sh STATEFUL TRACKING OPTIONS 2161A number of options related to stateful tracking can be applied on a 2162per-rule basis. 2163.Ar keep state , 2164.Ar modulate state 2165and 2166.Ar synproxy state 2167support these options, and 2168.Ar keep state 2169must be specified explicitly to apply options to a rule. 2170.Pp 2171.Bl -tag -width xxxx -compact 2172.It Ar max Aq Ar number 2173Limits the number of concurrent states the rule may create. 2174When this limit is reached, further packets that would create 2175state will not match this rule until existing states time out. 2176.It Ar no-sync 2177Prevent state changes for states created by this rule from appearing on the 2178.Xr pfsync 4 2179interface. 2180.It Xo Aq Ar timeout 2181.Aq Ar seconds 2182.Xc 2183Changes the timeout values used for states created by this rule. 2184For a list of all valid timeout names, see 2185.Sx OPTIONS 2186above. 2187.It Ar sloppy 2188Uses a sloppy TCP connection tracker that does not check sequence 2189numbers at all, which makes insertion and ICMP teardown attacks way 2190easier. 2191This is intended to be used in situations where one does not see all 2192packets of a connection, e.g. in asymmetric routing situations. 2193Cannot be used with modulate or synproxy state. 2194.El 2195.Pp 2196Multiple options can be specified, separated by commas: 2197.Bd -literal -offset indent 2198pass in proto tcp from any to any \e 2199 port www keep state \e 2200 (max 100, source-track rule, max-src-nodes 75, \e 2201 max-src-states 3, tcp.established 60, tcp.closing 5) 2202.Ed 2203.Pp 2204When the 2205.Ar source-track 2206keyword is specified, the number of states per source IP is tracked. 2207.Pp 2208.Bl -tag -width xxxx -compact 2209.It Ar source-track rule 2210The maximum number of states created by this rule is limited by the rule's 2211.Ar max-src-nodes 2212and 2213.Ar max-src-states 2214options. 2215Only state entries created by this particular rule count toward the rule's 2216limits. 2217.It Ar source-track global 2218The number of states created by all rules that use this option is limited. 2219Each rule can specify different 2220.Ar max-src-nodes 2221and 2222.Ar max-src-states 2223options, however state entries created by any participating rule count towards 2224each individual rule's limits. 2225.El 2226.Pp 2227The following limits can be set: 2228.Pp 2229.Bl -tag -width xxxx -compact 2230.It Ar max-src-nodes Aq Ar number 2231Limits the maximum number of source addresses which can simultaneously 2232have state table entries. 2233.It Ar max-src-states Aq Ar number 2234Limits the maximum number of simultaneous state entries that a single 2235source address can create with this rule. 2236.El 2237.Pp 2238For stateful TCP connections, limits on established connections (connections 2239which have completed the TCP 3-way handshake) can also be enforced 2240per source IP. 2241.Pp 2242.Bl -tag -width xxxx -compact 2243.It Ar max-src-conn Aq Ar number 2244Limits the maximum number of simultaneous TCP connections which have 2245completed the 3-way handshake that a single host can make. 2246.It Xo Ar max-src-conn-rate Aq Ar number 2247.No / Aq Ar seconds 2248.Xc 2249Limit the rate of new connections over a time interval. 2250The connection rate is an approximation calculated as a moving average. 2251.El 2252.Pp 2253Because the 3-way handshake ensures that the source address is not being 2254spoofed, more aggressive action can be taken based on these limits. 2255With the 2256.Ar overload Aq Ar table 2257state option, source IP addresses which hit either of the limits on 2258established connections will be added to the named table. 2259This table can be used in the ruleset to block further activity from 2260the offending host, redirect it to a tarpit process, or restrict its 2261bandwidth. 2262.Pp 2263The optional 2264.Ar flush 2265keyword kills all states created by the matching rule which originate 2266from the host which exceeds these limits. 2267The 2268.Ar global 2269modifier to the flush command kills all states originating from the 2270offending host, regardless of which rule created the state. 2271.Pp 2272For example, the following rules will protect the webserver against 2273hosts making more than 100 connections in 10 seconds. 2274Any host which connects faster than this rate will have its address added 2275to the 2276.Aq bad_hosts 2277table and have all states originating from it flushed. 2278Any new packets arriving from this host will be dropped unconditionally 2279by the block rule. 2280.Bd -literal -offset indent 2281block quick from \*(Ltbad_hosts\*(Gt 2282pass in on $ext_if proto tcp to $webserver port www keep state \e 2283 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global) 2284.Ed 2285.Sh OPERATING SYSTEM FINGERPRINTING 2286Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP 2287connection's initial SYN packet and guess at the host's operating system. 2288Unfortunately these nuances are easily spoofed by an attacker so the 2289fingerprint is not useful in making security decisions. 2290But the fingerprint is typically accurate enough to make policy decisions 2291upon. 2292.Pp 2293The fingerprints may be specified by operating system class, by 2294version, or by subtype/patchlevel. 2295The class of an operating system is typically the vendor or genre 2296and would be 2297.Ox 2298for the 2299.Xr pf 4 2300firewall itself. 2301The version of the oldest available 2302.Ox 2303release on the main FTP site 2304would be 2.6 and the fingerprint would be written 2305.Pp 2306.Dl \&"OpenBSD 2.6\&" 2307.Pp 2308The subtype of an operating system is typically used to describe the 2309patchlevel if that patch led to changes in the TCP stack behavior. 2310In the case of 2311.Ox , 2312the only subtype is for a fingerprint that was 2313normalized by the 2314.Ar no-df 2315scrub option and would be specified as 2316.Pp 2317.Dl \&"OpenBSD 3.3 no-df\&" 2318.Pp 2319Fingerprints for most popular operating systems are provided by 2320.Xr pf.os 5 . 2321Once 2322.Xr pf 4 2323is running, a complete list of known operating system fingerprints may 2324be listed by running: 2325.Pp 2326.Dl # pfctl -so 2327.Pp 2328Filter rules can enforce policy at any level of operating system specification 2329assuming a fingerprint is present. 2330Policy could limit traffic to approved operating systems or even ban traffic 2331from hosts that aren't at the latest service pack. 2332.Pp 2333The 2334.Ar unknown 2335class can also be used as the fingerprint which will match packets for 2336which no operating system fingerprint is known. 2337.Pp 2338Examples: 2339.Bd -literal -offset indent 2340pass out proto tcp from any os OpenBSD 2341block out proto tcp from any os Doors 2342block out proto tcp from any os "Doors PT" 2343block out proto tcp from any os "Doors PT SP3" 2344block out from any os "unknown" 2345pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" 2346.Ed 2347.Pp 2348Operating system fingerprinting is limited only to the TCP SYN packet. 2349This means that it will not work on other protocols and will not match 2350a currently established connection. 2351.Pp 2352Caveat: operating system fingerprints are occasionally wrong. 2353There are three problems: an attacker can trivially craft his packets to 2354appear as any operating system he chooses; 2355an operating system patch could change the stack behavior and no fingerprints 2356will match it until the database is updated; 2357and multiple operating systems may have the same fingerprint. 2358.Sh BLOCKING SPOOFED TRAFFIC 2359"Spoofing" is the faking of IP addresses, typically for malicious 2360purposes. 2361The 2362.Ar antispoof 2363directive expands to a set of filter rules which will block all 2364traffic with a source IP from the network(s) directly connected 2365to the specified interface(s) from entering the system through 2366any other interface. 2367.Pp 2368For example, the line 2369.Bd -literal -offset indent 2370antispoof for lo0 2371.Ed 2372.Pp 2373expands to 2374.Bd -literal -offset indent 2375block drop in on ! lo0 inet from 127.0.0.1/8 to any 2376block drop in on ! lo0 inet6 from ::1 to any 2377.Ed 2378.Pp 2379For non-loopback interfaces, there are additional rules to block incoming 2380packets with a source IP address identical to the interface's IP(s). 2381For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a 2382netmask of 255.255.255.0, 2383the line 2384.Bd -literal -offset indent 2385antispoof for wi0 inet 2386.Ed 2387.Pp 2388expands to 2389.Bd -literal -offset indent 2390block drop in on ! wi0 inet from 10.0.0.0/24 to any 2391block drop in inet from 10.0.0.1 to any 2392.Ed 2393.Pp 2394Caveat: Rules created by the 2395.Ar antispoof 2396directive interfere with packets sent over loopback interfaces 2397to local addresses. 2398One should pass these explicitly. 2399.Sh FRAGMENT HANDLING 2400The size of IP datagrams (packets) can be significantly larger than the 2401maximum transmission unit (MTU) of the network. 2402In cases when it is necessary or more efficient to send such large packets, 2403the large packet will be fragmented into many smaller packets that will each 2404fit onto the wire. 2405Unfortunately for a firewalling device, only the first logical fragment will 2406contain the necessary header information for the subprotocol that allows 2407.Xr pf 4 2408to filter on things such as TCP ports or to perform NAT. 2409.Pp 2410Besides the use of 2411.Ar scrub 2412rules as described in 2413.Sx TRAFFIC NORMALIZATION 2414above, there are three options for handling fragments in the packet filter. 2415.Pp 2416One alternative is to filter individual fragments with filter rules. 2417If no 2418.Ar scrub 2419rule applies to a fragment, it is passed to the filter. 2420Filter rules with matching IP header parameters decide whether the 2421fragment is passed or blocked, in the same way as complete packets 2422are filtered. 2423Without reassembly, fragments can only be filtered based on IP header 2424fields (source/destination address, protocol), since subprotocol header 2425fields are not available (TCP/UDP port numbers, ICMP code/type). 2426The 2427.Ar fragment 2428option can be used to restrict filter rules to apply only to 2429fragments, but not complete packets. 2430Filter rules without the 2431.Ar fragment 2432option still apply to fragments, if they only specify IP header fields. 2433For instance, the rule 2434.Bd -literal -offset indent 2435pass in proto tcp from any to any port 80 2436.Ed 2437.Pp 2438never applies to a fragment, even if the fragment is part of a TCP 2439packet with destination port 80, because without reassembly this information 2440is not available for each fragment. 2441This also means that fragments cannot create new or match existing 2442state table entries, which makes stateful filtering and address 2443translation (NAT, redirection) for fragments impossible. 2444.Pp 2445It's also possible to reassemble only certain fragments by specifying 2446source or destination addresses or protocols as parameters in 2447.Ar scrub 2448rules. 2449.Pp 2450In most cases, the benefits of reassembly outweigh the additional 2451memory cost, and it's recommended to use 2452.Ar scrub 2453rules to reassemble 2454all fragments via the 2455.Ar fragment reassemble 2456modifier. 2457.Pp 2458The memory allocated for fragment caching can be limited using 2459.Xr pfctl 8 . 2460Once this limit is reached, fragments that would have to be cached 2461are dropped until other entries time out. 2462The timeout value can also be adjusted. 2463.Pp 2464When forwarding reassembled IPv6 packets, pf refragments them with 2465the original maximum fragment size. 2466This allows the sender to determine the optimal fragment size by 2467path MTU discovery. 2468.Sh ANCHORS 2469Besides the main ruleset, 2470.Xr pfctl 8 2471can load rulesets into 2472.Ar anchor 2473attachment points. 2474An 2475.Ar anchor 2476is a container that can hold rules, address tables, and other anchors. 2477.Pp 2478An 2479.Ar anchor 2480has a name which specifies the path where 2481.Xr pfctl 8 2482can be used to access the anchor to perform operations on it, such as 2483attaching child anchors to it or loading rules into it. 2484Anchors may be nested, with components separated by 2485.Sq / 2486characters, similar to how file system hierarchies are laid out. 2487The main ruleset is actually the default anchor, so filter and 2488translation rules, for example, may also be contained in any anchor. 2489.Pp 2490An anchor can reference another 2491.Ar anchor 2492attachment point 2493using the following kinds 2494of rules: 2495.Bl -tag -width xxxx 2496.It Ar nat-anchor Aq Ar name 2497Evaluates the 2498.Ar nat 2499rules in the specified 2500.Ar anchor . 2501.It Ar rdr-anchor Aq Ar name 2502Evaluates the 2503.Ar rdr 2504rules in the specified 2505.Ar anchor . 2506.It Ar binat-anchor Aq Ar name 2507Evaluates the 2508.Ar binat 2509rules in the specified 2510.Ar anchor . 2511.It Ar anchor Aq Ar name 2512Evaluates the filter rules in the specified 2513.Ar anchor . 2514.It Xo Ar load anchor 2515.Aq Ar name 2516.Ar from Aq Ar file 2517.Xc 2518Loads the rules from the specified file into the 2519anchor 2520.Ar name . 2521.El 2522.Pp 2523When evaluation of the main ruleset reaches an 2524.Ar anchor 2525rule, 2526.Xr pf 4 2527will proceed to evaluate all rules specified in that anchor. 2528.Pp 2529Matching filter and translation rules marked with the 2530.Ar quick 2531option are final and abort the evaluation of the rules in other 2532anchors and the main ruleset. 2533If the 2534.Ar anchor 2535itself is marked with the 2536.Ar quick 2537option, 2538ruleset evaluation will terminate when the anchor is exited if the packet is 2539matched by any rule within the anchor. 2540.Pp 2541.Ar anchor 2542rules are evaluated relative to the anchor in which they are contained. 2543For example, all 2544.Ar anchor 2545rules specified in the main ruleset will reference anchor 2546attachment points underneath the main ruleset, and 2547.Ar anchor 2548rules specified in a file loaded from a 2549.Ar load anchor 2550rule will be attached under that anchor point. 2551.Pp 2552Rules may be contained in 2553.Ar anchor 2554attachment points which do not contain any rules when the main ruleset 2555is loaded, and later such anchors can be manipulated through 2556.Xr pfctl 8 2557without reloading the main ruleset or other anchors. 2558For example, 2559.Bd -literal -offset indent 2560ext_if = \&"kue0\&" 2561block on $ext_if all 2562anchor spam 2563pass out on $ext_if all 2564pass in on $ext_if proto tcp from any \e 2565 to $ext_if port smtp 2566.Ed 2567.Pp 2568blocks all packets on the external interface by default, then evaluates 2569all rules in the 2570.Ar anchor 2571named "spam", and finally passes all outgoing connections and 2572incoming connections to port 25. 2573.Bd -literal -offset indent 2574# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e 2575 pfctl -a spam -f - 2576.Ed 2577.Pp 2578This loads a single rule into the 2579.Ar anchor , 2580which blocks all packets from a specific address. 2581.Pp 2582The anchor can also be populated by adding a 2583.Ar load anchor 2584rule after the 2585.Ar anchor 2586rule: 2587.Bd -literal -offset indent 2588anchor spam 2589load anchor spam from "/etc/pf-spam.conf" 2590.Ed 2591.Pp 2592When 2593.Xr pfctl 8 2594loads 2595.Nm pf.conf , 2596it will also load all the rules from the file 2597.Pa /etc/pf-spam.conf 2598into the anchor. 2599.Pp 2600Optionally, 2601.Ar anchor 2602rules can specify packet filtering parameters using the same syntax as 2603filter rules. 2604When parameters are used, the 2605.Ar anchor 2606rule is only evaluated for matching packets. 2607This allows conditional evaluation of anchors, like: 2608.Bd -literal -offset indent 2609block on $ext_if all 2610anchor spam proto tcp from any to any port smtp 2611pass out on $ext_if all 2612pass in on $ext_if proto tcp from any to $ext_if port smtp 2613.Ed 2614.Pp 2615The rules inside 2616.Ar anchor 2617spam are only evaluated for 2618.Ar tcp 2619packets with destination port 25. 2620Hence, 2621.Bd -literal -offset indent 2622# echo \&"block in quick from 1.2.3.4 to any" \&| \e 2623 pfctl -a spam -f - 2624.Ed 2625.Pp 2626will only block connections from 1.2.3.4 to port 25. 2627.Pp 2628Anchors may end with the asterisk 2629.Pq Sq * 2630character, which signifies that all anchors attached at that point 2631should be evaluated in the alphabetical ordering of their anchor name. 2632For example, 2633.Bd -literal -offset indent 2634anchor "spam/*" 2635.Ed 2636.Pp 2637will evaluate each rule in each anchor attached to the 2638.Li spam 2639anchor. 2640Note that it will only evaluate anchors that are directly attached to the 2641.Li spam 2642anchor, and will not descend to evaluate anchors recursively. 2643.Pp 2644Since anchors are evaluated relative to the anchor in which they are 2645contained, there is a mechanism for accessing the parent and ancestor 2646anchors of a given anchor. 2647Similar to file system path name resolution, if the sequence 2648.Dq .. 2649appears as an anchor path component, the parent anchor of the current 2650anchor in the path evaluation at that point will become the new current 2651anchor. 2652As an example, consider the following: 2653.Bd -literal -offset indent 2654# echo ' anchor "spam/allowed" ' | pfctl -f - 2655# echo -e ' anchor "../banned" \en pass' | \e 2656 pfctl -a spam/allowed -f - 2657.Ed 2658.Pp 2659Evaluation of the main ruleset will lead into the 2660.Li spam/allowed 2661anchor, which will evaluate the rules in the 2662.Li spam/banned 2663anchor, if any, before finally evaluating the 2664.Ar pass 2665rule. 2666.Pp 2667Filter rule 2668.Ar anchors 2669can also be loaded inline in the ruleset within a brace ('{' '}') delimited 2670block. 2671Brace delimited blocks may contain rules or other brace-delimited blocks. 2672When anchors are loaded this way the anchor name becomes optional. 2673.Bd -literal -offset indent 2674anchor "external" on $ext_if { 2675 block 2676 anchor out { 2677 pass proto tcp from any to port { 25, 80, 443 } 2678 } 2679 pass in proto tcp to any port 22 2680} 2681.Ed 2682.Pp 2683Since the parser specification for anchor names is a string, any 2684reference to an anchor name containing 2685.Sq / 2686characters will require double quote 2687.Pq Sq \&" 2688characters around the anchor name. 2689.Sh TRANSLATION EXAMPLES 2690This example maps incoming requests on port 80 to port 8080, on 2691which a daemon is running (because, for example, it is not run as root, 2692and therefore lacks permission to bind to port 80). 2693.Bd -literal 2694# use a macro for the interface name, so it can be changed easily 2695ext_if = \&"ne3\&" 2696 2697# map daemon on 8080 to appear to be on 80 2698rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080 2699.Ed 2700.Pp 2701If the 2702.Ar pass 2703modifier is given, packets matching the translation rule are passed without 2704inspecting the filter rules: 2705.Bd -literal 2706rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e 2707 port 8080 2708.Ed 2709.Pp 2710In the example below, vlan12 is configured as 192.168.168.1; 2711the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111 2712when they are going out any interface except vlan12. 2713This has the net effect of making traffic from the 192.168.168.0/24 2714network appear as though it is the Internet routable address 2715204.92.77.111 to nodes behind any interface on the router except 2716for the nodes on vlan12. 2717(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.) 2718.Bd -literal 2719nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111 2720.Ed 2721.Pp 2722In the example below, the machine sits between a fake internal 144.19.74.* 2723network, and a routable external IP of 204.92.77.100. 2724The 2725.Ar no nat 2726rule excludes protocol AH from being translated. 2727.Bd -literal 2728# NO NAT 2729no nat on $ext_if proto ah from 144.19.74.0/24 to any 2730nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100 2731.Ed 2732.Pp 2733In the example below, packets bound for one specific server, as well as those 2734generated by the sysadmins are not proxied; all other connections are. 2735.Bd -literal 2736# NO RDR 2737no rdr on $int_if proto { tcp, udp } from any to $server port 80 2738no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80 2739rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e 2740 port 80 2741.Ed 2742.Pp 2743This longer example uses both a NAT and a redirection. 2744The external interface has the address 157.161.48.183. 2745On localhost, we are running 2746.Xr ftp-proxy 8 , 2747waiting for FTP sessions to be redirected to it. 2748The three mandatory anchors for 2749.Xr ftp-proxy 8 2750are omitted from this example; see the 2751.Xr ftp-proxy 8 2752manpage. 2753.Bd -literal 2754# NAT 2755# Translate outgoing packets' source addresses (any protocol). 2756# In this case, any address but the gateway's external address is mapped. 2757nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if) 2758 2759# NAT PROXYING 2760# Map outgoing packets' source port to an assigned proxy port instead of 2761# an arbitrary port. 2762# In this case, proxy outgoing isakmp with port 500 on the gateway. 2763nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e 2764 port 500 2765 2766# BINAT 2767# Translate outgoing packets' source address (any protocol). 2768# Translate incoming packets' destination address to an internal machine 2769# (bidirectional). 2770binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if 2771 2772# RDR 2773# Translate incoming packets' destination addresses. 2774# As an example, redirect a TCP and UDP port to an internal machine. 2775rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e 2776 -\*(Gt 10.1.2.151 port 22 2777rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e 2778 -\*(Gt 10.1.2.151 port 53 2779 2780# RDR 2781# Translate outgoing ftp control connections to send them to localhost 2782# for proxying with ftp-proxy(8) running on port 8021. 2783rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021 2784.Ed 2785.Pp 2786In this example, a NAT gateway is set up to translate internal addresses 2787using a pool of public addresses (192.0.2.16/28) and to redirect 2788incoming web server connections to a group of web servers on the internal 2789network. 2790.Bd -literal 2791# NAT LOAD BALANCE 2792# Translate outgoing packets' source addresses using an address pool. 2793# A given source address is always translated to the same pool address by 2794# using the source-hash keyword. 2795nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash 2796 2797# RDR ROUND ROBIN 2798# Translate incoming web server connections to a group of web servers on 2799# the internal network. 2800rdr on $ext_if proto tcp from any to any port 80 \e 2801 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin 2802.Ed 2803.Sh FILTER EXAMPLES 2804.Bd -literal 2805# The external interface is kue0 2806# (157.161.48.183, the only routable address) 2807# and the private network is 10.0.0.0/8, for which we are doing NAT. 2808 2809# use a macro for the interface name, so it can be changed easily 2810ext_if = \&"kue0\&" 2811 2812# normalize all incoming traffic 2813scrub in on $ext_if all fragment reassemble 2814 2815# block and log everything by default 2816block return log on $ext_if all 2817 2818# block anything coming from source we have no back routes for 2819block in from no-route to any 2820 2821# block packets whose ingress interface does not match the one in 2822# the route back to their source address 2823block in from urpf-failed to any 2824 2825# block and log outgoing packets that do not have our address as source, 2826# they are either spoofed or something is misconfigured (NAT disabled, 2827# for instance), we want to be nice and do not send out garbage. 2828block out log quick on $ext_if from ! 157.161.48.183 to any 2829 2830# silently drop broadcasts (cable modem noise) 2831block in quick on $ext_if from any to 255.255.255.255 2832 2833# block and log incoming packets from reserved address space and invalid 2834# addresses, they are either spoofed or misconfigured, we cannot reply to 2835# them anyway (hence, no return-rst). 2836block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e 2837 192.168.0.0/16, 255.255.255.255/32 } to any 2838 2839# ICMP 2840 2841# pass out/in certain ICMP queries and keep state (ping) 2842# state matching is done on host addresses and ICMP id (not type/code), 2843# so replies (like 0/0 for 8/0) will match queries 2844# ICMP error messages (which always refer to a TCP/UDP packet) are 2845# handled by the TCP/UDP states 2846pass on $ext_if inet proto icmp all icmp-type 8 code 0 2847 2848# UDP 2849 2850# pass out all UDP connections and keep state 2851pass out on $ext_if proto udp all 2852 2853# pass in certain UDP connections and keep state (DNS) 2854pass in on $ext_if proto udp from any to any port domain 2855 2856# TCP 2857 2858# pass out all TCP connections and modulate state 2859pass out on $ext_if proto tcp all modulate state 2860 2861# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT) 2862pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e 2863 auth } 2864 2865# Do not allow Windows 9x SMTP connections since they are typically 2866# a viral worm. Alternately we could limit these OSes to 1 connection each. 2867block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e 2868 to any port smtp 2869 2870# IPv6 2871# pass in/out all IPv6 traffic: note that we have to enable this in two 2872# different ways, on both our physical interface and our tunnel 2873pass quick on gif0 inet6 2874pass quick on $ext_if proto ipv6 2875 2876# Packet Tagging 2877 2878# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is 2879# being done on $ext_if for all outgoing packets. tag packets in on 2880# $int_if and pass those tagged packets out on $ext_if. all other 2881# outgoing packets (i.e., packets from the wireless network) are only 2882# permitted to access port 80. 2883 2884pass in on $int_if from any to any tag INTNET 2885pass in on $wifi_if from any to any 2886 2887block out on $ext_if from any to any 2888pass out quick on $ext_if tagged INTNET 2889pass out on $ext_if proto tcp from any to any port 80 2890 2891# tag incoming packets as they are redirected to spamd(8). use the tag 2892# to pass those packets through the packet filter. 2893 2894rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e 2895 tag SPAMD -\*(Gt 127.0.0.1 port spamd 2896 2897block in on $ext_if 2898pass in on $ext_if inet proto tcp tagged SPAMD 2899.Ed 2900.Sh GRAMMAR 2901Syntax for 2902.Nm 2903in BNF: 2904.Bd -literal 2905line = ( option | pf-rule | nat-rule | binat-rule | rdr-rule | 2906 antispoof-rule | altq-rule | queue-rule | trans-anchors | 2907 anchor-rule | anchor-close | load-anchor | table-rule | 2908 include ) 2909 2910option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] | 2911 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] | 2912 [ "optimization" [ "default" | "normal" | 2913 "high-latency" | "satellite" | 2914 "aggressive" | "conservative" ] ] 2915 [ "limit" ( limit-item | "{" limit-list "}" ) ] | 2916 [ "loginterface" ( interface-name | "none" ) ] | 2917 [ "block-policy" ( "drop" | "return" ) ] | 2918 [ "state-policy" ( "if-bound" | "floating" ) ] 2919 [ "state-defaults" state-opts ] 2920 [ "require-order" ( "yes" | "no" ) ] 2921 [ "fingerprints" filename ] | 2922 [ "skip on" ifspec ] | 2923 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] 2924 [ "keepcounters" ] ) 2925 2926pf-rule = action [ ( "in" | "out" ) ] 2927 [ "log" [ "(" logopts ")"] ] [ "quick" ] 2928 [ "on" ifspec ] [ route ] [ af ] [ protospec ] 2929 hosts [ filteropt-list ] 2930 2931logopts = logopt [ "," logopts ] 2932logopt = "all" | "user" | "to" interface-name 2933 2934filteropt-list = filteropt-list filteropt | filteropt 2935filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos | 2936 ( "no" | "keep" | "modulate" | "synproxy" ) "state" 2937 [ "(" state-opts ")" ] | 2938 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos | 2939 "max-mss" number | "random-id" | "reassemble tcp" | 2940 fragmentation | "allow-opts" | 2941 "label" string | "tag" string | [ ! ] "tagged" string | 2942 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) | 2943 "queue" ( string | "(" string [ [ "," ] string ] ")" ) | 2944 "rtable" number | "probability" number"%" | "prio" number 2945 2946nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 2947 [ "on" ifspec ] [ af ] 2948 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 2949 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 2950 [ portspec ] [ pooltype ] [ "static-port" ] 2951 [ "map-e-portset" number "/" number "/" number ] ] 2952 2953binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 2954 [ "on" interface-name ] [ af ] 2955 [ "proto" ( proto-name | proto-number ) ] 2956 "from" address [ "/" mask-bits ] "to" ipspec 2957 [ "tag" string ] [ "tagged" string ] 2958 [ "-\*(Gt" address [ "/" mask-bits ] ] 2959 2960rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 2961 [ "on" ifspec ] [ af ] 2962 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 2963 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 2964 [ portspec ] [ pooltype ] ] 2965 2966antispoof-rule = "antispoof" [ "log" ] [ "quick" ] 2967 "for" ifspec [ af ] [ "label" string ] 2968 2969table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ] 2970tableopts-list = tableopts-list tableopts | tableopts 2971tableopts = "persist" | "const" | "counters" | "file" string | 2972 "{" [ tableaddr-list ] "}" 2973tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec 2974tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ] 2975tableaddr = hostname | ifspec | "self" | 2976 ipv4-dotted-quad | ipv6-coloned-hex 2977 2978altq-rule = "altq on" interface-name queueopts-list 2979 "queue" subqueue 2980queue-rule = "queue" string [ "on" interface-name ] queueopts-list 2981 subqueue 2982 2983anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ] 2984 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ] 2985 2986anchor-close = "}" 2987 2988trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string 2989 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ] 2990 2991load-anchor = "load anchor" string "from" filename 2992 2993queueopts-list = queueopts-list queueopts | queueopts 2994queueopts = [ "bandwidth" bandwidth-spec ] | 2995 [ "qlimit" number ] | [ "tbrsize" number ] | 2996 [ "priority" number ] | [ schedulers ] 2997schedulers = ( cbq-def | priq-def | hfsc-def ) 2998bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" ) 2999 3000action = "pass" | "block" [ return ] | [ "no" ] "scrub" 3001return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] | 3002 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] | 3003 "return-icmp6" [ "(" icmp6code ")" ] 3004icmpcode = ( icmp-code-name | icmp-code-number ) 3005icmp6code = ( icmp6-code-name | icmp6-code-number ) 3006 3007ifspec = ( [ "!" ] ( interface-name | interface-group ) ) | 3008 "{" interface-list "}" 3009interface-list = [ "!" ] ( interface-name | interface-group ) 3010 [ [ "," ] interface-list ] 3011route = ( "route-to" | "reply-to" | "dup-to" ) 3012 ( routehost | "{" routehost-list "}" ) 3013 [ pooltype ] 3014af = "inet" | "inet6" 3015 3016protospec = "proto" ( proto-name | proto-number | 3017 "{" proto-list "}" ) 3018proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ] 3019 3020hosts = "all" | 3021 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host | 3022 "{" host-list "}" ) [ port ] [ os ] 3023 "to" ( "any" | "no-route" | "self" | host | 3024 "{" host-list "}" ) [ port ] 3025 3026ipspec = "any" | host | "{" host-list "}" 3027host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" ) 3028redirhost = address [ "/" mask-bits ] 3029routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")" 3030address = ( interface-name | interface-group | 3031 "(" ( interface-name | interface-group ) ")" | 3032 hostname | ipv4-dotted-quad | ipv6-coloned-hex ) 3033host-list = host [ [ "," ] host-list ] 3034redirhost-list = redirhost [ [ "," ] redirhost-list ] 3035routehost-list = routehost [ [ "," ] routehost-list ] 3036 3037port = "port" ( unary-op | binary-op | "{" op-list "}" ) 3038portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ] 3039os = "os" ( os-name | "{" os-list "}" ) 3040user = "user" ( unary-op | binary-op | "{" op-list "}" ) 3041group = "group" ( unary-op | binary-op | "{" op-list "}" ) 3042 3043unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ] 3044 ( name | number ) 3045binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number 3046op-list = ( unary-op | binary-op ) [ [ "," ] op-list ] 3047 3048os-name = operating-system-name 3049os-list = os-name [ [ "," ] os-list ] 3050 3051flags = "flags" ( [ flag-set ] "/" flag-set | "any" ) 3052flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ] 3053 [ "W" ] 3054 3055icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" ) 3056icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" ) 3057icmp-type-code = ( icmp-type-name | icmp-type-number ) 3058 [ "code" ( icmp-code-name | icmp-code-number ) ] 3059icmp-list = icmp-type-code [ [ "," ] icmp-list ] 3060 3061tos = ( "lowdelay" | "throughput" | "reliability" | 3062 [ "0x" ] number ) 3063 3064state-opts = state-opt [ [ "," ] state-opts ] 3065state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | 3066 "source-track" [ ( "rule" | "global" ) ] | 3067 "max-src-nodes" number | "max-src-states" number | 3068 "max-src-conn" number | 3069 "max-src-conn-rate" number "/" number | 3070 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] | 3071 "if-bound" | "floating" ) 3072 3073fragmentation = [ "fragment reassemble" ] 3074 3075timeout-list = timeout [ [ "," ] timeout-list ] 3076timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" | 3077 "tcp.closing" | "tcp.finwait" | "tcp.closed" | 3078 "udp.first" | "udp.single" | "udp.multiple" | 3079 "icmp.first" | "icmp.error" | 3080 "other.first" | "other.single" | "other.multiple" | 3081 "frag" | "interval" | "src.track" | 3082 "adaptive.start" | "adaptive.end" ) number 3083 3084limit-list = limit-item [ [ "," ] limit-list ] 3085limit-item = ( "states" | "frags" | "src-nodes" ) number 3086 3087pooltype = ( "bitmask" | "random" | 3088 "source-hash" [ ( hex-key | string-key ) ] | 3089 "round-robin" ) [ sticky-address ] 3090 3091subqueue = string | "{" queue-list "}" 3092queue-list = string [ [ "," ] string ] 3093cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ] 3094priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ] 3095hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ] 3096cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" ) 3097priq-opt = ( "default" | "red" | "ecn" | "rio" ) 3098hfsc-opt = ( "default" | "red" | "ecn" | "rio" | 3099 linkshare-sc | realtime-sc | upperlimit-sc ) 3100linkshare-sc = "linkshare" sc-spec 3101realtime-sc = "realtime" sc-spec 3102upperlimit-sc = "upperlimit" sc-spec 3103sc-spec = ( bandwidth-spec | 3104 "(" bandwidth-spec number bandwidth-spec ")" ) 3105include = "include" filename 3106.Ed 3107.Sh FILES 3108.Bl -tag -width "/etc/protocols" -compact 3109.It Pa /etc/hosts 3110Host name database. 3111.It Pa /etc/pf.conf 3112Default location of the ruleset file. 3113The file has to be created manually as it is not installed with a 3114standard installation. 3115.It Pa /etc/pf.os 3116Default location of OS fingerprints. 3117.It Pa /etc/protocols 3118Protocol name database. 3119.It Pa /etc/services 3120Service name database. 3121.El 3122.Sh SEE ALSO 3123.Xr altq 4 , 3124.Xr carp 4 , 3125.Xr icmp 4 , 3126.Xr icmp6 4 , 3127.Xr ip 4 , 3128.Xr ip6 4 , 3129.Xr pf 4 , 3130.Xr pfsync 4 , 3131.Xr tcp 4 , 3132.Xr udp 4 , 3133.Xr hosts 5 , 3134.Xr pf.os 5 , 3135.Xr protocols 5 , 3136.Xr services 5 , 3137.Xr ftp-proxy 8 , 3138.Xr pfctl 8 , 3139.Xr pflogd 8 3140.Sh HISTORY 3141The 3142.Nm 3143file format first appeared in 3144.Ox 3.0 . 3145