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 March 9, 2022 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 eight 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 Ethernet Filtering 58Ethernet filtering provides rule-based blocking or passing of Ethernet packets. 59.It Cm Traffic Normalization Li (e.g. Em scrub ) 60Traffic normalization protects internal machines against inconsistencies 61in Internet protocols and implementations. 62.It Cm Queueing 63Queueing provides rule-based bandwidth control. 64.It Cm Translation Li (Various forms of NAT) 65Translation rules specify how addresses are to be mapped or redirected to 66other addresses. 67.It Cm Packet Filtering 68Packet filtering provides rule-based blocking or passing of packets. 69.El 70.Pp 71With the exception of 72.Cm macros 73and 74.Cm tables , 75the types of statements should be grouped and appear in 76.Nm pf.conf 77in the order shown above, as this matches the operation of the underlying 78packet filtering engine. 79By default 80.Xr pfctl 8 81enforces this order (see 82.Ar set require-order 83below). 84.Pp 85Comments can be put anywhere in the file using a hash mark 86.Pq Sq # , 87and extend to the end of the current line. 88.Pp 89Additional configuration files can be included with the 90.Ic include 91keyword, for example: 92.Bd -literal -offset indent 93include "/etc/pf/sub.filter.conf" 94.Ed 95.Sh MACROS 96Macros can be defined that will later be expanded in context. 97Macro names must start with a letter, and may contain letters, digits 98and underscores. 99Macro names may not be reserved words (for example 100.Ar pass , 101.Ar in , 102.Ar out ) . 103Macros are not expanded inside quotes. 104.Pp 105For example, 106.Bd -literal -offset indent 107ext_if = \&"kue0\&" 108all_ifs = \&"{\&" $ext_if lo0 \&"}\&" 109pass out on $ext_if from any to any 110pass in on $ext_if proto tcp from any to any port 25 111.Ed 112.Sh TABLES 113Tables are named structures which can hold a collection of addresses and 114networks. 115Lookups against tables in 116.Xr pf 4 117are relatively fast, making a single rule with tables much more efficient, 118in terms of 119processor usage and memory consumption, than a large number of rules which 120differ only in IP address (either created explicitly or automatically by rule 121expansion). 122.Pp 123Tables can be used as the source or destination of filter rules, 124.Ar scrub 125rules 126or 127translation rules such as 128.Ar nat 129or 130.Ar rdr 131(see below for details on the various rule types). 132Tables can also be used for the redirect address of 133.Ar nat 134and 135.Ar rdr 136rules and in the routing options of filter rules, but only for 137.Ar round-robin 138pools. 139.Pp 140Tables can be defined with any of the following 141.Xr pfctl 8 142mechanisms. 143As with macros, reserved words may not be used as table names. 144.Bl -tag -width "manually" 145.It Ar manually 146Persistent tables can be manually created with the 147.Ar add 148or 149.Ar replace 150option of 151.Xr pfctl 8 , 152before or after the ruleset has been loaded. 153.It Pa pf.conf 154Table definitions can be placed directly in this file, and loaded at the 155same time as other rules are loaded, atomically. 156Table definitions inside 157.Nm pf.conf 158use the 159.Ar table 160statement, and are especially useful to define non-persistent tables. 161The contents of a pre-existing table defined without a list of addresses 162to initialize it is not altered when 163.Nm pf.conf 164is loaded. 165A table initialized with the empty list, 166.Li { } , 167will be cleared on load. 168.El 169.Pp 170Tables may be defined with the following attributes: 171.Bl -tag -width persist 172.It Ar persist 173The 174.Ar persist 175flag forces the kernel to keep the table even when no rules refer to it. 176If the flag is not set, the kernel will automatically remove the table 177when the last rule referring to it is flushed. 178.It Ar const 179The 180.Ar const 181flag prevents the user from altering the contents of the table once it 182has been created. 183Without that flag, 184.Xr pfctl 8 185can be used to add or remove addresses from the table at any time, even 186when running with 187.Xr securelevel 7 188= 2. 189.It Ar counters 190The 191.Ar counters 192flag enables per-address packet and byte counters which can be displayed with 193.Xr pfctl 8 . 194Note that this feature carries significant memory overhead for large tables. 195.El 196.Pp 197For example, 198.Bd -literal -offset indent 199table \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 } 200table \*(Ltbadhosts\*(Gt persist 201block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } to any 202.Ed 203.Pp 204creates a table called private, to hold RFC 1918 private network 205blocks, and a table called badhosts, which is initially empty. 206A filter rule is set up to block all traffic coming from addresses listed in 207either table. 208The private table cannot have its contents changed and the badhosts table 209will exist even when no active filter rules reference it. 210Addresses may later be added to the badhosts table, so that traffic from 211these hosts can be blocked by using 212.Bd -literal -offset indent 213# pfctl -t badhosts -Tadd 204.92.77.111 214.Ed 215.Pp 216A table can also be initialized with an address list specified in one or more 217external files, using the following syntax: 218.Bd -literal -offset indent 219table \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&" 220block on fxp0 from \*(Ltspam\*(Gt to any 221.Ed 222.Pp 223The files 224.Pa /etc/spammers 225and 226.Pa /etc/openrelays 227list IP addresses, one per line. 228Any lines beginning with a # are treated as comments and ignored. 229In addition to being specified by IP address, hosts may also be 230specified by their hostname. 231When the resolver is called to add a hostname to a table, 232.Em all 233resulting IPv4 and IPv6 addresses are placed into the table. 234IP addresses can also be entered in a table by specifying a valid interface 235name, a valid interface group or the 236.Em self 237keyword, in which case all addresses assigned to the interface(s) will be 238added to the table. 239.Sh OPTIONS 240.Xr pf 4 241may be tuned for various situations using the 242.Ar set 243command. 244.Bl -tag -width xxxx 245.It Ar set timeout 246.Pp 247.Bl -tag -width "src.track" -compact 248.It Ar interval 249Interval between purging expired states and fragments. 250.It Ar frag 251Seconds before an unassembled fragment is expired. 252.It Ar src.track 253Length of time to retain a source tracking entry after the last state 254expires. 255.El 256.Pp 257When a packet matches a stateful connection, the seconds to live for the 258connection will be updated to that of the 259.Ar proto.modifier 260which corresponds to the connection state. 261Each packet which matches this state will reset the TTL. 262Tuning these values may improve the performance of the 263firewall at the risk of dropping valid idle connections. 264.Pp 265.Bl -tag -width xxxx -compact 266.It Ar tcp.first 267The state after the first packet. 268.It Ar tcp.opening 269The state before the destination host ever sends a packet. 270.It Ar tcp.established 271The fully established state. 272.It Ar tcp.closing 273The state after the first FIN has been sent. 274.It Ar tcp.finwait 275The state after both FINs have been exchanged and the connection is closed. 276Some hosts (notably web servers on Solaris) send TCP packets even after closing 277the connection. 278Increasing 279.Ar tcp.finwait 280(and possibly 281.Ar tcp.closing ) 282can prevent blocking of such packets. 283.It Ar tcp.closed 284The state after one endpoint sends an RST. 285.El 286.Pp 287ICMP and UDP are handled in a fashion similar to TCP, but with a much more 288limited set of states: 289.Pp 290.Bl -tag -width xxxx -compact 291.It Ar udp.first 292The state after the first packet. 293.It Ar udp.single 294The state if the source host sends more than one packet but the destination 295host has never sent one back. 296.It Ar udp.multiple 297The state if both hosts have sent packets. 298.It Ar icmp.first 299The state after the first packet. 300.It Ar icmp.error 301The state after an ICMP error came back in response to an ICMP packet. 302.El 303.Pp 304Other protocols are handled similarly to UDP: 305.Pp 306.Bl -tag -width xxxx -compact 307.It Ar other.first 308.It Ar other.single 309.It Ar other.multiple 310.El 311.Pp 312Timeout values can be reduced adaptively as the number of state table 313entries grows. 314.Pp 315.Bl -tag -width xxxx -compact 316.It Ar adaptive.start 317When the number of state entries exceeds this value, adaptive scaling 318begins. 319All timeout values are scaled linearly with factor 320(adaptive.end - number of states) / (adaptive.end - adaptive.start). 321.It Ar adaptive.end 322When reaching this number of state entries, all timeout values become 323zero, effectively purging all state entries immediately. 324This value is used to define the scale factor, it should not actually 325be reached (set a lower state limit, see below). 326.El 327.Pp 328Adaptive timeouts are enabled by default, with an adaptive.start value 329equal to 60% of the state limit, and an adaptive.end value equal to 330120% of the state limit. 331They can be disabled by setting both adaptive.start and adaptive.end to 0. 332.Pp 333The adaptive timeout values can be defined both globally and for each rule. 334When used on a per-rule basis, the values relate to the number of 335states created by the rule, otherwise to the total number of 336states. 337.Pp 338For example: 339.Bd -literal -offset indent 340set timeout tcp.first 120 341set timeout tcp.established 86400 342set timeout { adaptive.start 6000, adaptive.end 12000 } 343set limit states 10000 344.Ed 345.Pp 346With 9000 state table entries, the timeout values are scaled to 50% 347(tcp.first 60, tcp.established 43200). 348.It Ar set loginterface 349Enable collection of packet and byte count statistics for the given 350interface or interface group. 351These statistics can be viewed using 352.Bd -literal -offset indent 353# pfctl -s info 354.Ed 355.Pp 356In this example 357.Xr pf 4 358collects statistics on the interface named dc0: 359.Bd -literal -offset indent 360set loginterface dc0 361.Ed 362.Pp 363One can disable the loginterface using: 364.Bd -literal -offset indent 365set loginterface none 366.Ed 367.It Ar set limit 368Sets hard limits on the memory pools used by the packet filter. 369See 370.Xr zone 9 371for an explanation of memory pools. 372.Pp 373For example, 374.Bd -literal -offset indent 375set limit states 20000 376.Ed 377.Pp 378sets the maximum number of entries in the memory pool used by state table 379entries (generated by 380.Ar pass 381rules which do not specify 382.Ar no state ) 383to 20000. 384Using 385.Bd -literal -offset indent 386set limit frags 20000 387.Ed 388.Pp 389sets the maximum number of entries in the memory pool used for fragment 390reassembly (generated by 391.Ar scrub 392rules) to 20000. 393Using 394.Bd -literal -offset indent 395set limit src-nodes 2000 396.Ed 397.Pp 398sets the maximum number of entries in the memory pool used for tracking 399source IP addresses (generated by the 400.Ar sticky-address 401and 402.Ar src.track 403options) to 2000. 404Using 405.Bd -literal -offset indent 406set limit tables 1000 407set limit table-entries 100000 408.Ed 409.Pp 410sets limits on the memory pools used by tables. 411The first limits the number of tables that can exist to 1000. 412The second limits the overall number of addresses that can be stored 413in tables to 100000. 414.Pp 415Various limits can be combined on a single line: 416.Bd -literal -offset indent 417set limit { states 20000, frags 20000, src-nodes 2000 } 418.Ed 419.It Ar set ruleset-optimization 420.Bl -tag -width xxxxxxxx -compact 421.It Ar none 422Disable the ruleset optimizer. 423.It Ar basic 424Enable basic ruleset optimization. 425This is the default behaviour. 426Basic ruleset optimization does four things to improve the 427performance of ruleset evaluations: 428.Pp 429.Bl -enum -compact 430.It 431remove duplicate rules 432.It 433remove rules that are a subset of another rule 434.It 435combine multiple rules into a table when advantageous 436.It 437re-order the rules to improve evaluation performance 438.El 439.Pp 440.It Ar profile 441Uses the currently loaded ruleset as a feedback profile to tailor the 442ordering of quick rules to actual network traffic. 443.El 444.Pp 445It is important to note that the ruleset optimizer will modify the ruleset 446to improve performance. 447A side effect of the ruleset modification is that per-rule accounting 448statistics will have different meanings than before. 449If per-rule accounting is important for billing purposes or whatnot, 450either the ruleset optimizer should not be used or a label field should 451be added to all of the accounting rules to act as optimization barriers. 452.Pp 453Optimization can also be set as a command-line argument to 454.Xr pfctl 8 , 455overriding the settings in 456.Nm . 457.It Ar set optimization 458Optimize state timeouts for one of the following network environments: 459.Pp 460.Bl -tag -width xxxx -compact 461.It Ar normal 462A normal network environment. 463Suitable for almost all networks. 464.It Ar high-latency 465A high-latency environment (such as a satellite connection). 466.It Ar satellite 467Alias for 468.Ar high-latency . 469.It Ar aggressive 470Aggressively expire connections. 471This can greatly reduce the memory usage of the firewall at the cost of 472dropping idle connections early. 473.It Ar conservative 474Extremely conservative settings. 475Avoid dropping legitimate connections at the 476expense of greater memory utilization (possibly much greater on a busy 477network) and slightly increased processor utilization. 478.El 479.Pp 480For example: 481.Bd -literal -offset indent 482set optimization aggressive 483.Ed 484.It Ar set block-policy 485The 486.Ar block-policy 487option sets the default behaviour for the packet 488.Ar block 489action: 490.Pp 491.Bl -tag -width xxxxxxxx -compact 492.It Ar drop 493Packet is silently dropped. 494.It Ar return 495A TCP RST is returned for blocked TCP packets, 496an ICMP UNREACHABLE is returned for blocked UDP packets, 497and all other packets are silently dropped. 498.El 499.Pp 500For example: 501.Bd -literal -offset indent 502set block-policy return 503.Ed 504.It Ar set fail-policy 505The 506.Ar fail-policy 507option sets the behaviour of rules which should pass a packet but were 508unable to do so. 509This might happen when a nat or route-to rule uses an empty table as list 510of targets or if a rule fails to create state or source node. 511The following 512.Ar block 513actions are possible: 514.Pp 515.Bl -tag -width xxxxxxxx -compact 516.It Ar drop 517Incoming packet is silently dropped. 518.It Ar return 519Incoming packet is dropped and TCP RST is returned for TCP packets, 520an ICMP UNREACHABLE is returned for UDP packets, 521and no response is sent for other packets. 522.El 523.Pp 524For example: 525.Bd -literal -offset indent 526set fail-policy return 527.Ed 528.It Ar set state-policy 529The 530.Ar state-policy 531option sets the default behaviour for states: 532.Pp 533.Bl -tag -width group-bound -compact 534.It Ar if-bound 535States are bound to interface. 536.It Ar floating 537States can match packets on any interfaces (the default). 538.El 539.Pp 540For example: 541.Bd -literal -offset indent 542set state-policy if-bound 543.Ed 544.It Ar set syncookies never | always | adaptive 545When 546.Cm syncookies 547are active, pf will answer each incoming TCP SYN with a syncookie SYNACK, 548without allocating any resources. 549Upon reception of the client's ACK in response to the syncookie 550SYNACK, pf will evaluate the ruleset and create state if the ruleset 551permits it, complete the three way handshake with the target host and 552continue the connection with synproxy in place. 553This allows pf to be resilient against large synflood attacks which would 554run the state table against its limits otherwise. 555Due to the blind answers to every incoming SYN syncookies share the caveats of 556synproxy, namely seemingly accepting connections that will be dropped later on. 557.Pp 558.Bl -tag -width adaptive -compact 559.It Cm never 560pf will never send syncookie SYNACKs (the default). 561.It Cm always 562pf will always send syncookie SYNACKs. 563.It Cm adaptive 564pf will enable syncookie mode when a given percentage of the state table 565is used up by half-open TCP connections, as in, those that saw the initial 566SYN but didn't finish the three way handshake. 567The thresholds for entering and leaving syncookie mode can be specified using 568.Bd -literal -offset indent 569set syncookies adaptive (start 25%, end 12%) 570.Ed 571.El 572.It Ar set state-defaults 573The 574.Ar state-defaults 575option sets the state options for states created from rules 576without an explicit 577.Ar keep state . 578For example: 579.Bd -literal -offset indent 580set state-defaults no-sync 581.Ed 582.It Ar set hostid 583The 32-bit 584.Ar hostid 585identifies this firewall's state table entries to other firewalls 586in a 587.Xr pfsync 4 588failover cluster. 589By default the hostid is set to a pseudo-random value, however it may be 590desirable to manually configure it, for example to more easily identify the 591source of state table entries. 592.Bd -literal -offset indent 593set hostid 1 594.Ed 595.Pp 596The hostid may be specified in either decimal or hexadecimal. 597.It Ar set require-order 598By default 599.Xr pfctl 8 600enforces an ordering of the statement types in the ruleset to: 601.Em options , 602.Em normalization , 603.Em queueing , 604.Em translation , 605.Em filtering . 606Setting this option to 607.Ar no 608disables this enforcement. 609There may be non-trivial and non-obvious implications to an out of 610order ruleset. 611Consider carefully before disabling the order enforcement. 612.It Ar set fingerprints 613Load fingerprints of known operating systems from the given filename. 614By default fingerprints of known operating systems are automatically 615loaded from 616.Xr pf.os 5 617in 618.Pa /etc 619but can be overridden via this option. 620Setting this option may leave a small period of time where the fingerprints 621referenced by the currently active ruleset are inconsistent until the new 622ruleset finishes loading. 623.Pp 624For example: 625.Pp 626.Dl set fingerprints \&"/etc/pf.os.devel\&" 627.It Ar set skip on Aq Ar ifspec 628List interfaces for which packets should not be filtered. 629Packets passing in or out on such interfaces are passed as if pf was 630disabled, i.e. pf does not process them in any way. 631This can be useful on loopback and other virtual interfaces, when 632packet filtering is not desired and can have unexpected effects. 633For example: 634.Pp 635.Dl set skip on lo0 636.It Ar set debug 637Set the debug 638.Ar level 639to one of the following: 640.Pp 641.Bl -tag -width xxxxxxxxxxxx -compact 642.It Ar none 643Don't generate debug messages. 644.It Ar urgent 645Generate debug messages only for serious errors. 646.It Ar misc 647Generate debug messages for various errors. 648.It Ar loud 649Generate debug messages for common conditions. 650.El 651.It Ar set keepcounters 652Preserve rule counters across rule updates. 653Usually rule counters are reset to zero on every update of the ruleset. 654With 655.Ar keepcounters 656set pf will attempt to find matching rules between old and new rulesets 657and preserve the rule counters. 658.El 659.Sh ETHERNET FILTERING 660.Xr pf 4 661has the ability to 662.Ar block 663and 664.Ar pass 665packets based on attributes of their Ethernet (layer 2) header. 666.Pp 667For each packet processed by the packet filter, the filter rules are 668evaluated in sequential order, from first to last. 669The last matching rule decides what action is taken. 670If no rule matches the packet, the default action is to pass 671the packet. 672.Pp 673The folliwing actions can be used in the filter: 674.Bl -tag -width xxxx 675.It Ar block 676The packet is blocked. 677Unlike for layer 3 traffic the packet is always silently dropped. 678.It Ar pass 679The packet is passed; 680no state is created for layer 2 traffic. 681.El 682.Sh PARAMETERS 683The rule parameters specify the packets to which a rule applies. 684A packet always comes in on, or goes out through, one interface. 685Most parameters are optional. 686If a parameter is specified, the rule only applies to packets with 687matching attributes. 688Certain parameters can be expressed as lists, in which case 689.Xr pfctl 8 690generates all needed rule combinations. 691.Bl -tag -width xxxx 692.It Ar in No or Ar out 693This rule applies to incoming or outgoing packets. 694If neither 695.Ar in 696nor 697.Ar out 698are specified, the rule will match packets in both directions. 699.It Ar quick 700If a packet matches a rule which has the 701.Ar quick 702option set, this rule 703is considered the last matching rule, and evaluation of subsequent rules 704is skipped. 705.It Ar on Aq Ar interface 706This rule applies only to packets coming in on, or going out through, this 707particular interface or interface group. 708For more information on interface groups, 709see the 710.Ic group 711keyword in 712.Xr ifconfig 8 . 713.It Ar proto Aq Ar protocol 714This rule applies only to packets of this protocol. 715Note that Ethernet protocol numbers are different from those used in 716.Xr ip 4 717and 718.Xr ip6 4 . 719.It Xo 720.Ar from Aq Ar source 721.Ar to Aq Ar dest 722.Xc 723This rule applies only to packets with the specified source and destination 724MAC addresses. 725.It Xo Ar queue Aq Ar queue 726.Xc 727Packets matching this rule will be assigned to the specified queue. 728See 729.Sx QUEUEING 730for setup details. 731.Pp 732.It Ar tag Aq Ar string 733Packets matching this rule will be tagged with the 734specified string. 735The tag acts as an internal marker that can be used to 736identify these packets later on. 737This can be used, for example, to provide trust between 738interfaces and to determine if packets have been 739processed by translation rules. 740Tags are 741.Qq sticky , 742meaning that the packet will be tagged even if the rule 743is not the last matching rule. 744Further matching rules can replace the tag with a 745new one but will not remove a previously applied tag. 746A packet is only ever assigned one tag at a time. 747.It Ar tagged Aq Ar string 748Used to specify that packets must already be tagged with the given tag in order 749to match the rule. 750Inverse tag matching can also be done by specifying the ! operator before the 751tagged keyword. 752.Sh TRAFFIC NORMALIZATION 753Traffic normalization is used to sanitize packet content in such 754a way that there are no ambiguities in packet interpretation on 755the receiving side. 756The normalizer does IP fragment reassembly to prevent attacks 757that confuse intrusion detection systems by sending overlapping 758IP fragments. 759Packet normalization is invoked with the 760.Ar scrub 761directive. 762.Pp 763.Ar scrub 764has the following options: 765.Bl -tag -width xxxx 766.It Ar no-df 767Clears the 768.Ar dont-fragment 769bit from a matching IP packet. 770Some operating systems are known to generate fragmented packets with the 771.Ar dont-fragment 772bit set. 773This is particularly true with NFS. 774.Ar Scrub 775will drop such fragmented 776.Ar dont-fragment 777packets unless 778.Ar no-df 779is specified. 780.Pp 781Unfortunately some operating systems also generate their 782.Ar dont-fragment 783packets with a zero IP identification field. 784Clearing the 785.Ar dont-fragment 786bit on packets with a zero IP ID may cause deleterious results if an 787upstream router later fragments the packet. 788Using the 789.Ar random-id 790modifier (see below) is recommended in combination with the 791.Ar no-df 792modifier to ensure unique IP identifiers. 793.It Ar min-ttl Aq Ar number 794Enforces a minimum TTL for matching IP packets. 795.It Ar max-mss Aq Ar number 796Enforces a maximum MSS for matching TCP packets. 797.It Xo Ar set-tos Aq Ar string 798.No \*(Ba Aq Ar number 799.Xc 800Enforces a 801.Em TOS 802for matching IP packets. 803.Em TOS 804may be 805given as one of 806.Ar critical , 807.Ar inetcontrol , 808.Ar lowdelay , 809.Ar netcontrol , 810.Ar throughput , 811.Ar reliability , 812or one of the DiffServ Code Points: 813.Ar ef , 814.Ar va , 815.Ar af11 No ... Ar af43 , 816.Ar cs0 No ... Ar cs7 ; 817or as either hex or decimal. 818.It Ar random-id 819Replaces the IP identification field with random values to compensate 820for predictable values generated by many hosts. 821This option only applies to packets that are not fragmented 822after the optional fragment reassembly. 823.It Ar fragment reassemble 824Using 825.Ar scrub 826rules, fragments can be reassembled by normalization. 827In this case, fragments are buffered until they form a complete 828packet, and only the completed packet is passed on to the filter. 829The advantage is that filter rules have to deal only with complete 830packets, and can ignore fragments. 831The drawback of caching fragments is the additional memory cost. 832.It Ar reassemble tcp 833Statefully normalizes TCP connections. 834.Ar scrub reassemble tcp 835rules may not have the direction (in/out) specified. 836.Ar reassemble tcp 837performs the following normalizations: 838.Pp 839.Bl -tag -width timeout -compact 840.It ttl 841Neither side of the connection is allowed to reduce their IP TTL. 842An attacker may send a packet such that it reaches the firewall, affects 843the firewall state, and expires before reaching the destination host. 844.Ar reassemble tcp 845will raise the TTL of all packets back up to the highest value seen on 846the connection. 847.It timestamp modulation 848Modern TCP stacks will send a timestamp on every TCP packet and echo 849the other endpoint's timestamp back to them. 850Many operating systems will merely start the timestamp at zero when 851first booted, and increment it several times a second. 852The uptime of the host can be deduced by reading the timestamp and multiplying 853by a constant. 854Also observing several different timestamps can be used to count hosts 855behind a NAT device. 856And spoofing TCP packets into a connection requires knowing or guessing 857valid timestamps. 858Timestamps merely need to be monotonically increasing and not derived off a 859guessable base time. 860.Ar reassemble tcp 861will cause 862.Ar scrub 863to modulate the TCP timestamps with a random number. 864.It extended PAWS checks 865There is a problem with TCP on long fat pipes, in that a packet might get 866delayed for longer than it takes the connection to wrap its 32-bit sequence 867space. 868In such an occurrence, the old packet would be indistinguishable from a 869new packet and would be accepted as such. 870The solution to this is called PAWS: Protection Against Wrapped Sequence 871numbers. 872It protects against it by making sure the timestamp on each packet does 873not go backwards. 874.Ar reassemble tcp 875also makes sure the timestamp on the packet does not go forward more 876than the RFC allows. 877By doing this, 878.Xr pf 4 879artificially extends the security of TCP sequence numbers by 10 to 18 880bits when the host uses appropriately randomized timestamps, since a 881blind attacker would have to guess the timestamp as well. 882.El 883.El 884.Pp 885For example, 886.Bd -literal -offset indent 887scrub in on $ext_if all fragment reassemble 888.Ed 889.Pp 890The 891.Ar no 892option prefixed to a scrub rule causes matching packets to remain unscrubbed, 893much in the same way as 894.Ar drop quick 895works in the packet filter (see below). 896This mechanism should be used when it is necessary to exclude specific packets 897from broader scrub rules. 898.Sh QUEUEING with ALTQ 899The ALTQ system is currently not available in the GENERIC kernel nor as 900loadable modules. 901In order to use the herein after called queueing options one has to use a 902custom built kernel. 903Please refer to 904.Xr altq 4 905to learn about the related kernel options. 906.Pp 907Packets can be assigned to queues for the purpose of bandwidth 908control. 909At least two declarations are required to configure queues, and later 910any packet filtering rule can reference the defined queues by name. 911During the filtering component of 912.Nm pf.conf , 913the last referenced 914.Ar queue 915name is where any packets from 916.Ar pass 917rules will be queued, while for 918.Ar block 919rules it specifies where any resulting ICMP or TCP RST 920packets should be queued. 921The 922.Ar scheduler 923defines the algorithm used to decide which packets get delayed, dropped, or 924sent out immediately. 925There are three 926.Ar schedulers 927currently supported. 928.Bl -tag -width xxxx 929.It Ar cbq 930Class Based Queueing. 931.Ar Queues 932attached to an interface build a tree, thus each 933.Ar queue 934can have further child 935.Ar queues . 936Each queue can have a 937.Ar priority 938and a 939.Ar bandwidth 940assigned. 941.Ar Priority 942mainly controls the time packets take to get sent out, while 943.Ar bandwidth 944has primarily effects on throughput. 945.Ar cbq 946achieves both partitioning and sharing of link bandwidth 947by hierarchically structured classes. 948Each class has its own 949.Ar queue 950and is assigned its share of 951.Ar bandwidth . 952A child class can borrow bandwidth from its parent class 953as long as excess bandwidth is available 954(see the option 955.Ar borrow , 956below). 957.It Ar priq 958Priority Queueing. 959.Ar Queues 960are flat attached to the interface, thus, 961.Ar queues 962cannot have further child 963.Ar queues . 964Each 965.Ar queue 966has a unique 967.Ar priority 968assigned, ranging from 0 to 15. 969Packets in the 970.Ar queue 971with the highest 972.Ar priority 973are processed first. 974.It Ar hfsc 975Hierarchical Fair Service Curve. 976.Ar Queues 977attached to an interface build a tree, thus each 978.Ar queue 979can have further child 980.Ar queues . 981Each queue can have a 982.Ar priority 983and a 984.Ar bandwidth 985assigned. 986.Ar Priority 987mainly controls the time packets take to get sent out, while 988.Ar bandwidth 989primarily affects throughput. 990.Ar hfsc 991supports both link-sharing and guaranteed real-time services. 992It employs a service curve based QoS model, 993and its unique feature is an ability to decouple 994.Ar delay 995and 996.Ar bandwidth 997allocation. 998.El 999.Pp 1000The interfaces on which queueing should be activated are declared using 1001the 1002.Ar altq on 1003declaration. 1004.Ar altq on 1005has the following keywords: 1006.Bl -tag -width xxxx 1007.It Aq Ar interface 1008Queueing is enabled on the named interface. 1009.It Aq Ar scheduler 1010Specifies which queueing scheduler to use. 1011Currently supported values 1012are 1013.Ar cbq 1014for Class Based Queueing, 1015.Ar priq 1016for Priority Queueing and 1017.Ar hfsc 1018for the Hierarchical Fair Service Curve scheduler. 1019.It Ar bandwidth Aq Ar bw 1020The maximum bitrate for all queues on an 1021interface may be specified using the 1022.Ar bandwidth 1023keyword. 1024The value can be specified as an absolute value or as a 1025percentage of the interface bandwidth. 1026When using an absolute value, the suffixes 1027.Ar b , 1028.Ar Kb , 1029.Ar Mb , 1030and 1031.Ar Gb 1032are used to represent bits, kilobits, megabits, and 1033gigabits per second, respectively. 1034The value must not exceed the interface bandwidth. 1035If 1036.Ar bandwidth 1037is not specified, the interface bandwidth is used 1038(but take note that some interfaces do not know their bandwidth, 1039or can adapt their bandwidth rates). 1040.It Ar qlimit Aq Ar limit 1041The maximum number of packets held in the queue. 1042The default is 50. 1043.It Ar tbrsize Aq Ar size 1044Adjusts the size, in bytes, of the token bucket regulator. 1045If not specified, heuristics based on the 1046interface bandwidth are used to determine the size. 1047.It Ar queue Aq Ar list 1048Defines a list of subqueues to create on an interface. 1049.El 1050.Pp 1051In the following example, the interface dc0 1052should queue up to 5Mbps in four second-level queues using 1053Class Based Queueing. 1054Those four queues will be shown in a later example. 1055.Bd -literal -offset indent 1056altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh } 1057.Ed 1058.Pp 1059Once interfaces are activated for queueing using the 1060.Ar altq 1061directive, a sequence of 1062.Ar queue 1063directives may be defined. 1064The name associated with a 1065.Ar queue 1066must match a queue defined in the 1067.Ar altq 1068directive (e.g. mail), or, except for the 1069.Ar priq 1070.Ar scheduler , 1071in a parent 1072.Ar queue 1073declaration. 1074The following keywords can be used: 1075.Bl -tag -width xxxx 1076.It Ar on Aq Ar interface 1077Specifies the interface the queue operates on. 1078If not given, it operates on all matching interfaces. 1079.It Ar bandwidth Aq Ar bw 1080Specifies the maximum bitrate to be processed by the queue. 1081This value must not exceed the value of the parent 1082.Ar queue 1083and can be specified as an absolute value or a percentage of the parent 1084queue's bandwidth. 1085If not specified, defaults to 100% of the parent queue's bandwidth. 1086The 1087.Ar priq 1088scheduler does not support bandwidth specification. 1089.It Ar priority Aq Ar level 1090Between queues a priority level can be set. 1091For 1092.Ar cbq 1093and 1094.Ar hfsc , 1095the range is 0 to 7 and for 1096.Ar priq , 1097the range is 0 to 15. 1098The default for all is 1. 1099.Ar Priq 1100queues with a higher priority are always served first. 1101.Ar Cbq 1102and 1103.Ar Hfsc 1104queues with a higher priority are preferred in the case of overload. 1105.It Ar qlimit Aq Ar limit 1106The maximum number of packets held in the queue. 1107The default is 50. 1108.El 1109.Pp 1110The 1111.Ar scheduler 1112can get additional parameters with 1113.Xo Aq Ar scheduler 1114.Pf ( Aq Ar parameters ) . 1115.Xc 1116Parameters are as follows: 1117.Bl -tag -width Fl 1118.It Ar default 1119Packets not matched by another queue are assigned to this one. 1120Exactly one default queue is required. 1121.It Ar red 1122Enable RED (Random Early Detection) on this queue. 1123RED drops packets with a probability proportional to the average 1124queue length. 1125.It Ar rio 1126Enables RIO on this queue. 1127RIO is RED with IN/OUT, thus running 1128RED two times more than RIO would achieve the same effect. 1129RIO is currently not supported in the GENERIC kernel. 1130.It Ar ecn 1131Enables ECN (Explicit Congestion Notification) on this queue. 1132ECN implies RED. 1133.El 1134.Pp 1135The 1136.Ar cbq 1137.Ar scheduler 1138supports an additional option: 1139.Bl -tag -width Fl 1140.It Ar borrow 1141The queue can borrow bandwidth from the parent. 1142.El 1143.Pp 1144The 1145.Ar hfsc 1146.Ar scheduler 1147supports some additional options: 1148.Bl -tag -width Fl 1149.It Ar realtime Aq Ar sc 1150The minimum required bandwidth for the queue. 1151.It Ar upperlimit Aq Ar sc 1152The maximum allowed bandwidth for the queue. 1153.It Ar linkshare Aq Ar sc 1154The bandwidth share of a backlogged queue. 1155.El 1156.Pp 1157.Aq Ar sc 1158is an acronym for 1159.Ar service curve . 1160.Pp 1161The format for service curve specifications is 1162.Ar ( m1 , d , m2 ) . 1163.Ar m2 1164controls the bandwidth assigned to the queue. 1165.Ar m1 1166and 1167.Ar d 1168are optional and can be used to control the initial bandwidth assignment. 1169For the first 1170.Ar d 1171milliseconds the queue gets the bandwidth given as 1172.Ar m1 , 1173afterwards the value given in 1174.Ar m2 . 1175.Pp 1176Furthermore, with 1177.Ar cbq 1178and 1179.Ar hfsc , 1180child queues can be specified as in an 1181.Ar altq 1182declaration, thus building a tree of queues using a part of 1183their parent's bandwidth. 1184.Pp 1185Packets can be assigned to queues based on filter rules by using the 1186.Ar queue 1187keyword. 1188Normally only one 1189.Ar queue 1190is specified; when a second one is specified it will instead be used for 1191packets which have a 1192.Em TOS 1193of 1194.Em lowdelay 1195and for TCP ACKs with no data payload. 1196.Pp 1197To continue the previous example, the examples below would specify the 1198four referenced 1199queues, plus a few child queues. 1200Interactive 1201.Xr ssh 1 1202sessions get priority over bulk transfers like 1203.Xr scp 1 1204and 1205.Xr sftp 1 . 1206The queues may then be referenced by filtering rules (see 1207.Sx PACKET FILTERING 1208below). 1209.Bd -literal 1210queue std bandwidth 10% cbq(default) 1211queue http bandwidth 60% priority 2 cbq(borrow red) \e 1212 { employees, developers } 1213queue developers bandwidth 75% cbq(borrow) 1214queue employees bandwidth 15% 1215queue mail bandwidth 10% priority 0 cbq(borrow ecn) 1216queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk } 1217queue ssh_interactive bandwidth 50% priority 7 cbq(borrow) 1218queue ssh_bulk bandwidth 50% priority 0 cbq(borrow) 1219 1220block return out on dc0 inet all queue std 1221pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e 1222 queue developers 1223pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e 1224 queue employees 1225pass out on dc0 inet proto tcp from any to any port 22 \e 1226 queue(ssh_bulk, ssh_interactive) 1227pass out on dc0 inet proto tcp from any to any port 25 \e 1228 queue mail 1229.Ed 1230.Sh QUEUEING with dummynet 1231Queueing can also be done with 1232.Xr dummynet 4 . 1233Queues and pipes can be created with 1234.Xr dnctl 8 . 1235.Pp 1236Packets can be assigned to queues and pipes using 1237.Ar dnqueue 1238and 1239.Ar dnpipe 1240respectively. 1241.Pp 1242Both 1243.Ar dnqueue 1244and 1245.Ar dnpipe 1246take either a single pipe or queue number or two numbers as arguments. 1247The first pipe or queue number will be used to shape the traffic in the rule 1248direction, the second will be used to shape the traffic in the reverse 1249direction. 1250If the rule does not specify a direction the first packet to create state will 1251be shaped according to the first number, and the response traffic according to 1252the second. 1253.Pp 1254If the 1255.Xr dummynet 4 1256module is not loaded any traffic sent into a queue or pipe will be dropped. 1257.Sh TRANSLATION 1258Translation rules modify either the source or destination address of the 1259packets associated with a stateful connection. 1260A stateful connection is automatically created to track packets matching 1261such a rule as long as they are not blocked by the filtering section of 1262.Nm pf.conf . 1263The translation engine modifies the specified address and/or port in the 1264packet, recalculates IP, TCP and UDP checksums as necessary, and passes it to 1265the packet filter for evaluation. 1266.Pp 1267Since translation occurs before filtering the filter 1268engine will see packets as they look after any 1269addresses and ports have been translated. 1270Filter rules will therefore have to filter based on the translated 1271address and port number. 1272Packets that match a translation rule are only automatically passed if 1273the 1274.Ar pass 1275modifier is given, otherwise they are 1276still subject to 1277.Ar block 1278and 1279.Ar pass 1280rules. 1281.Pp 1282The state entry created permits 1283.Xr pf 4 1284to keep track of the original address for traffic associated with that state 1285and correctly direct return traffic for that connection. 1286.Pp 1287Various types of translation are possible with pf: 1288.Bl -tag -width xxxx 1289.It Ar binat 1290A 1291.Ar binat 1292rule specifies a bidirectional mapping between an external IP netblock 1293and an internal IP netblock. 1294.It Ar nat 1295A 1296.Ar nat 1297rule specifies that IP addresses are to be changed as the packet 1298traverses the given interface. 1299This technique allows one or more IP addresses 1300on the translating host to support network traffic for a larger range of 1301machines on an "inside" network. 1302Although in theory any IP address can be used on the inside, it is strongly 1303recommended that one of the address ranges defined by RFC 1918 be used. 1304These netblocks are: 1305.Bd -literal 130610.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8) 1307172.16.0.0 - 172.31.255.255 (i.e., 172.16/12) 1308192.168.0.0 - 192.168.255.255 (i.e., 192.168/16) 1309.Ed 1310.It Pa rdr 1311The packet is redirected to another destination and possibly a 1312different port. 1313.Ar rdr 1314rules can optionally specify port ranges instead of single ports. 1315rdr ... port 2000:2999 -\*(Gt ... port 4000 1316redirects ports 2000 to 2999 (inclusive) to port 4000. 1317rdr ... port 2000:2999 -\*(Gt ... port 4000:* 1318redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999. 1319.El 1320.Pp 1321In addition to modifying the address, some translation rules may modify 1322source or destination ports for 1323.Xr tcp 4 1324or 1325.Xr udp 4 1326connections; implicitly in the case of 1327.Ar nat 1328rules and explicitly in the case of 1329.Ar rdr 1330rules. 1331Port numbers are never translated with a 1332.Ar binat 1333rule. 1334.Pp 1335Evaluation order of the translation rules is dependent on the type 1336of the translation rules and of the direction of a packet. 1337.Ar binat 1338rules are always evaluated first. 1339Then either the 1340.Ar rdr 1341rules are evaluated on an inbound packet or the 1342.Ar nat 1343rules on an outbound packet. 1344Rules of the same type are evaluated in the same order in which they 1345appear in the ruleset. 1346The first matching rule decides what action is taken. 1347.Pp 1348The 1349.Ar no 1350option prefixed to a translation rule causes packets to remain untranslated, 1351much in the same way as 1352.Ar drop quick 1353works in the packet filter (see below). 1354If no rule matches the packet it is passed to the filter engine unmodified. 1355.Pp 1356Translation rules apply only to packets that pass through 1357the specified interface, and if no interface is specified, 1358translation is applied to packets on all interfaces. 1359For instance, redirecting port 80 on an external interface to an internal 1360web server will only work for connections originating from the outside. 1361Connections to the address of the external interface from local hosts will 1362not be redirected, since such packets do not actually pass through the 1363external interface. 1364Redirections cannot reflect packets back through the interface they arrive 1365on, they can only be redirected to hosts connected to different interfaces 1366or to the firewall itself. 1367.Pp 1368Note that redirecting external incoming connections to the loopback 1369address, as in 1370.Bd -literal -offset indent 1371rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd 1372.Ed 1373.Pp 1374will effectively allow an external host to connect to daemons 1375bound solely to the loopback address, circumventing the traditional 1376blocking of such connections on a real interface. 1377Unless this effect is desired, any of the local non-loopback addresses 1378should be used as redirection target instead, which allows external 1379connections only to daemons bound to this address or not bound to 1380any address. 1381.Pp 1382See 1383.Sx TRANSLATION EXAMPLES 1384below. 1385.Sh PACKET FILTERING 1386.Xr pf 4 1387has the ability to 1388.Ar block 1389, 1390.Ar pass 1391and 1392.Ar match 1393packets based on attributes of their layer 3 (see 1394.Xr ip 4 1395and 1396.Xr ip6 4 ) 1397and layer 4 (see 1398.Xr icmp 4 , 1399.Xr icmp6 4 , 1400.Xr tcp 4 , 1401.Xr udp 4 ) 1402headers. 1403In addition, packets may also be 1404assigned to queues for the purpose of bandwidth control. 1405.Pp 1406For each packet processed by the packet filter, the filter rules are 1407evaluated in sequential order, from first to last. 1408For 1409.Ar block 1410and 1411.Ar pass 1412, the last matching rule decides what action is taken. 1413For 1414.Ar match 1415, rules are evaulated every time they match; the pass/block state of a packet 1416remains unchanged. 1417If no rule matches the packet, the default action is to pass 1418the packet. 1419.Pp 1420The following actions can be used in the filter: 1421.Bl -tag -width xxxx 1422.It Ar block 1423The packet is blocked. 1424There are a number of ways in which a 1425.Ar block 1426rule can behave when blocking a packet. 1427The default behaviour is to 1428.Ar drop 1429packets silently, however this can be overridden or made 1430explicit either globally, by setting the 1431.Ar block-policy 1432option, or on a per-rule basis with one of the following options: 1433.Pp 1434.Bl -tag -width xxxx -compact 1435.It Ar drop 1436The packet is silently dropped. 1437.It Ar return-rst 1438This applies only to 1439.Xr tcp 4 1440packets, and issues a TCP RST which closes the 1441connection. 1442.It Ar return-icmp 1443.It Ar return-icmp6 1444This causes ICMP messages to be returned for packets which match the rule. 1445By default this is an ICMP UNREACHABLE message, however this 1446can be overridden by specifying a message as a code or number. 1447.It Ar return 1448This causes a TCP RST to be returned for 1449.Xr tcp 4 1450packets and an ICMP UNREACHABLE for UDP and other packets. 1451.El 1452.Pp 1453Options returning ICMP packets currently have no effect if 1454.Xr pf 4 1455operates on a 1456.Xr if_bridge 4 , 1457as the code to support this feature has not yet been implemented. 1458.Pp 1459The simplest mechanism to block everything by default and only pass 1460packets that match explicit rules is specify a first filter rule of: 1461.Bd -literal -offset indent 1462block all 1463.Ed 1464.It Ar match 1465The packet is matched. 1466This mechanism is used to provide fine grained filtering without altering the 1467block/pass state of a packet. 1468.Ar match 1469rules differ from 1470.Ar block 1471and 1472.Ar pass 1473rules in that parameters are set every time a packet matches the rule, not only 1474on the last matching rule. 1475For the following parameters, this means that the parameter effectively becomes 1476"sticky" until explicitly overridden: 1477.Ar queue , 1478.Ar dnpipe , 1479.Ar dnqueue 1480. 1481.It Ar pass 1482The packet is passed; 1483state is created unless the 1484.Ar no state 1485option is specified. 1486.El 1487.Pp 1488By default 1489.Xr pf 4 1490filters packets statefully; the first time a packet matches a 1491.Ar pass 1492rule, a state entry is created; for subsequent packets the filter checks 1493whether the packet matches any state. 1494If it does, the packet is passed without evaluation of any rules. 1495After the connection is closed or times out, the state entry is automatically 1496removed. 1497.Pp 1498This has several advantages. 1499For TCP connections, comparing a packet to a state involves checking 1500its sequence numbers, as well as TCP timestamps if a 1501.Ar scrub reassemble tcp 1502rule applies to the connection. 1503If these values are outside the narrow windows of expected 1504values, the packet is dropped. 1505This prevents spoofing attacks, such as when an attacker sends packets with 1506a fake source address/port but does not know the connection's sequence 1507numbers. 1508Similarly, 1509.Xr pf 4 1510knows how to match ICMP replies to states. 1511For example, 1512.Bd -literal -offset indent 1513pass out inet proto icmp all icmp-type echoreq 1514.Ed 1515.Pp 1516allows echo requests (such as those created by 1517.Xr ping 8 ) 1518out statefully, and matches incoming echo replies correctly to states. 1519.Pp 1520Also, looking up states is usually faster than evaluating rules. 1521If there are 50 rules, all of them are evaluated sequentially in O(n). 1522Even with 50000 states, only 16 comparisons are needed to match a 1523state, since states are stored in a binary search tree that allows 1524searches in O(log2 n). 1525.Pp 1526Furthermore, correct handling of ICMP error messages is critical to 1527many protocols, particularly TCP. 1528.Xr pf 4 1529matches ICMP error messages to the correct connection, checks them against 1530connection parameters, and passes them if appropriate. 1531For example if an ICMP source quench message referring to a stateful TCP 1532connection arrives, it will be matched to the state and get passed. 1533.Pp 1534Finally, state tracking is required for 1535.Ar nat , binat No and Ar rdr 1536rules, in order to track address and port translations and reverse the 1537translation on returning packets. 1538.Pp 1539.Xr pf 4 1540will also create state for other protocols which are effectively stateless by 1541nature. 1542UDP packets are matched to states using only host addresses and ports, 1543and other protocols are matched to states using only the host addresses. 1544.Pp 1545If stateless filtering of individual packets is desired, 1546the 1547.Ar no state 1548keyword can be used to specify that state will not be created 1549if this is the last matching rule. 1550A number of parameters can also be set to affect how 1551.Xr pf 4 1552handles state tracking. 1553See 1554.Sx STATEFUL TRACKING OPTIONS 1555below for further details. 1556.Sh PARAMETERS 1557The rule parameters specify the packets to which a rule applies. 1558A packet always comes in on, or goes out through, one interface. 1559Most parameters are optional. 1560If a parameter is specified, the rule only applies to packets with 1561matching attributes. 1562Certain parameters can be expressed as lists, in which case 1563.Xr pfctl 8 1564generates all needed rule combinations. 1565.Bl -tag -width xxxx 1566.It Ar in No or Ar out 1567This rule applies to incoming or outgoing packets. 1568If neither 1569.Ar in 1570nor 1571.Ar out 1572are specified, the rule will match packets in both directions. 1573.It Ar log 1574In addition to the action specified, a log message is generated. 1575Only the packet that establishes the state is logged, 1576unless the 1577.Ar no state 1578option is specified. 1579The logged packets are sent to a 1580.Xr pflog 4 1581interface, by default 1582.Ar pflog0 . 1583This interface is monitored by the 1584.Xr pflogd 8 1585logging daemon, which dumps the logged packets to the file 1586.Pa /var/log/pflog 1587in 1588.Xr pcap 3 1589binary format. 1590.It Ar log (all) 1591Used to force logging of all packets for a connection. 1592This is not necessary when 1593.Ar no state 1594is explicitly specified. 1595As with 1596.Ar log , 1597packets are logged to 1598.Xr pflog 4 . 1599.It Ar log (user) 1600Logs the 1601.Ux 1602user ID of the user that owns the socket and the PID of the process that 1603has the socket open where the packet is sourced from or destined to 1604(depending on which socket is local). 1605This is in addition to the normal information logged. 1606.Pp 1607Only the first packet 1608logged via 1609.Ar log (all, user) 1610will have the user credentials logged when using stateful matching. 1611.It Ar log (to Aq Ar interface ) 1612Send logs to the specified 1613.Xr pflog 4 1614interface instead of 1615.Ar pflog0 . 1616.It Ar quick 1617If a packet matches a rule which has the 1618.Ar quick 1619option set, this rule 1620is considered the last matching rule, and evaluation of subsequent rules 1621is skipped. 1622.It Ar on Aq Ar interface 1623This rule applies only to packets coming in on, or going out through, this 1624particular interface or interface group. 1625For more information on interface groups, 1626see the 1627.Ic group 1628keyword in 1629.Xr ifconfig 8 . 1630.It Aq Ar af 1631This rule applies only to packets of this address family. 1632Supported values are 1633.Ar inet 1634and 1635.Ar inet6 . 1636.It Ar proto Aq Ar protocol 1637This rule applies only to packets of this protocol. 1638Common protocols are 1639.Xr icmp 4 , 1640.Xr icmp6 4 , 1641.Xr tcp 4 , 1642and 1643.Xr udp 4 . 1644For a list of all the protocol name to number mappings used by 1645.Xr pfctl 8 , 1646see the file 1647.Pa /etc/protocols . 1648.It Xo 1649.Ar from Aq Ar source 1650.Ar port Aq Ar source 1651.Ar os Aq Ar source 1652.Ar to Aq Ar dest 1653.Ar port Aq Ar dest 1654.Xc 1655This rule applies only to packets with the specified source and destination 1656addresses and ports. 1657.Pp 1658Addresses can be specified in CIDR notation (matching netblocks), as 1659symbolic host names, interface names or interface group names, or as any 1660of the following keywords: 1661.Pp 1662.Bl -tag -width xxxxxxxxxxxxxx -compact 1663.It Ar any 1664Any address. 1665.It Ar no-route 1666Any address which is not currently routable. 1667.It Ar urpf-failed 1668Any source address that fails a unicast reverse path forwarding (URPF) 1669check, i.e. packets coming in on an interface other than that which holds 1670the route back to the packet's source address. 1671.It Aq Ar table 1672Any address that matches the given table. 1673.El 1674.Pp 1675Ranges of addresses are specified by using the 1676.Sq - 1677operator. 1678For instance: 1679.Dq 10.1.1.10 - 10.1.1.12 1680means all addresses from 10.1.1.10 to 10.1.1.12, 1681hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12. 1682.Pp 1683Interface names and interface group names can have modifiers appended: 1684.Pp 1685.Bl -tag -width xxxxxxxxxxxx -compact 1686.It Ar :network 1687Translates to the network(s) attached to the interface. 1688.It Ar :broadcast 1689Translates to the interface's broadcast address(es). 1690.It Ar :peer 1691Translates to the point-to-point interface's peer address(es). 1692.It Ar :0 1693Do not include interface aliases. 1694.El 1695.Pp 1696Host names may also have the 1697.Ar :0 1698option appended to restrict the name resolution to the first of each 1699v4 and non-link-local v6 address found. 1700.Pp 1701Host name resolution and interface to address translation are done at 1702ruleset load-time. 1703When the address of an interface (or host name) changes (under DHCP or PPP, 1704for instance), the ruleset must be reloaded for the change to be reflected 1705in the kernel. 1706Surrounding the interface name (and optional modifiers) in parentheses 1707changes this behaviour. 1708When the interface name is surrounded by parentheses, the rule is 1709automatically updated whenever the interface changes its address. 1710The ruleset does not need to be reloaded. 1711This is especially useful with 1712.Ar nat . 1713.Pp 1714Ports can be specified either by number or by name. 1715For example, port 80 can be specified as 1716.Em www . 1717For a list of all port name to number mappings used by 1718.Xr pfctl 8 , 1719see the file 1720.Pa /etc/services . 1721.Pp 1722Ports and ranges of ports are specified by using these operators: 1723.Bd -literal -offset indent 1724= (equal) 1725!= (unequal) 1726\*(Lt (less than) 1727\*(Le (less than or equal) 1728\*(Gt (greater than) 1729\*(Ge (greater than or equal) 1730: (range including boundaries) 1731\*(Gt\*(Lt (range excluding boundaries) 1732\*(Lt\*(Gt (except range) 1733.Ed 1734.Pp 1735.Sq \*(Gt\*(Lt , 1736.Sq \*(Lt\*(Gt 1737and 1738.Sq \&: 1739are binary operators (they take two arguments). 1740For instance: 1741.Bl -tag -width Fl 1742.It Ar port 2000:2004 1743means 1744.Sq all ports \*(Ge 2000 and \*(Le 2004 , 1745hence ports 2000, 2001, 2002, 2003 and 2004. 1746.It Ar port 2000 \*(Gt\*(Lt 2004 1747means 1748.Sq all ports \*(Gt 2000 and \*(Lt 2004 , 1749hence ports 2001, 2002 and 2003. 1750.It Ar port 2000 \*(Lt\*(Gt 2004 1751means 1752.Sq all ports \*(Lt 2000 or \*(Gt 2004 , 1753hence ports 1-1999 and 2005-65535. 1754.El 1755.Pp 1756The operating system of the source host can be specified in the case of TCP 1757rules with the 1758.Ar OS 1759modifier. 1760See the 1761.Sx OPERATING SYSTEM FINGERPRINTING 1762section for more information. 1763.Pp 1764The host, port and OS specifications are optional, as in the following examples: 1765.Bd -literal -offset indent 1766pass in all 1767pass in from any to any 1768pass in proto tcp from any port \*(Le 1024 to any 1769pass in proto tcp from any to any port 25 1770pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e 1771 to ! 10.1.2.3 port != ssh 1772pass in proto tcp from any os "OpenBSD" 1773.Ed 1774.It Ar all 1775This is equivalent to "from any to any". 1776.It Ar group Aq Ar group 1777Similar to 1778.Ar user , 1779this rule only applies to packets of sockets owned by the specified group. 1780.It Ar user Aq Ar user 1781This rule only applies to packets of sockets owned by the specified user. 1782For outgoing connections initiated from the firewall, this is the user 1783that opened the connection. 1784For incoming connections to the firewall itself, this is the user that 1785listens on the destination port. 1786For forwarded connections, where the firewall is not a connection endpoint, 1787the user and group are 1788.Em unknown . 1789.Pp 1790All packets, both outgoing and incoming, of one connection are associated 1791with the same user and group. 1792Only TCP and UDP packets can be associated with users; for other protocols 1793these parameters are ignored. 1794.Pp 1795User and group refer to the effective (as opposed to the real) IDs, in 1796case the socket is created by a setuid/setgid process. 1797User and group IDs are stored when a socket is created; 1798when a process creates a listening socket as root (for instance, by 1799binding to a privileged port) and subsequently changes to another 1800user ID (to drop privileges), the credentials will remain root. 1801.Pp 1802User and group IDs can be specified as either numbers or names. 1803The syntax is similar to the one for ports. 1804The value 1805.Em unknown 1806matches packets of forwarded connections. 1807.Em unknown 1808can only be used with the operators 1809.Cm = 1810and 1811.Cm != . 1812Other constructs like 1813.Cm user \*(Ge unknown 1814are invalid. 1815Forwarded packets with unknown user and group ID match only rules 1816that explicitly compare against 1817.Em unknown 1818with the operators 1819.Cm = 1820or 1821.Cm != . 1822For instance 1823.Cm user \*(Ge 0 1824does not match forwarded packets. 1825The following example allows only selected users to open outgoing 1826connections: 1827.Bd -literal -offset indent 1828block out proto { tcp, udp } all 1829pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei } 1830.Ed 1831.It Xo Ar flags Aq Ar a 1832.Pf / Ns Aq Ar b 1833.No \*(Ba / Ns Aq Ar b 1834.No \*(Ba any 1835.Xc 1836This rule only applies to TCP packets that have the flags 1837.Aq Ar a 1838set out of set 1839.Aq Ar b . 1840Flags not specified in 1841.Aq Ar b 1842are ignored. 1843For stateful connections, the default is 1844.Ar flags S/SA . 1845To indicate that flags should not be checked at all, specify 1846.Ar flags any . 1847The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R. 1848.Bl -tag -width Fl 1849.It Ar flags S/S 1850Flag SYN is set. 1851The other flags are ignored. 1852.It Ar flags S/SA 1853This is the default setting for stateful connections. 1854Out of SYN and ACK, exactly SYN may be set. 1855SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not. 1856This is more restrictive than the previous example. 1857.It Ar flags /SFRA 1858If the first set is not specified, it defaults to none. 1859All of SYN, FIN, RST and ACK must be unset. 1860.El 1861.Pp 1862Because 1863.Ar flags S/SA 1864is applied by default (unless 1865.Ar no state 1866is specified), only the initial SYN packet of a TCP handshake will create 1867a state for a TCP connection. 1868It is possible to be less restrictive, and allow state creation from 1869intermediate 1870.Pq non-SYN 1871packets, by specifying 1872.Ar flags any . 1873This will cause 1874.Xr pf 4 1875to synchronize to existing connections, for instance 1876if one flushes the state table. 1877However, states created from such intermediate packets may be missing 1878connection details such as the TCP window scaling factor. 1879States which modify the packet flow, such as those affected by 1880.Ar nat , binat No or Ar rdr 1881rules, 1882.Ar modulate No or Ar synproxy state 1883options, or scrubbed with 1884.Ar reassemble tcp 1885will also not be recoverable from intermediate packets. 1886Such connections will stall and time out. 1887.It Xo Ar icmp-type Aq Ar type 1888.Ar code Aq Ar code 1889.Xc 1890.It Xo Ar icmp6-type Aq Ar type 1891.Ar code Aq Ar code 1892.Xc 1893This rule only applies to ICMP or ICMPv6 packets with the specified type 1894and code. 1895Text names for ICMP types and codes are listed in 1896.Xr icmp 4 1897and 1898.Xr icmp6 4 . 1899This parameter is only valid for rules that cover protocols ICMP or 1900ICMP6. 1901The protocol and the ICMP type indicator 1902.Po 1903.Ar icmp-type 1904or 1905.Ar icmp6-type 1906.Pc 1907must match. 1908.It Xo Ar tos Aq Ar string 1909.No \*(Ba Aq Ar number 1910.Xc 1911This rule applies to packets with the specified 1912.Em TOS 1913bits set. 1914.Em TOS 1915may be 1916given as one of 1917.Ar critical , 1918.Ar inetcontrol , 1919.Ar lowdelay , 1920.Ar netcontrol , 1921.Ar throughput , 1922.Ar reliability , 1923or one of the DiffServ Code Points: 1924.Ar ef , 1925.Ar va , 1926.Ar af11 No ... Ar af43 , 1927.Ar cs0 No ... Ar cs7 ; 1928or as either hex or decimal. 1929.Pp 1930For example, the following rules are identical: 1931.Bd -literal -offset indent 1932pass all tos lowdelay 1933pass all tos 0x10 1934pass all tos 16 1935.Ed 1936.It Ar allow-opts 1937By default, IPv4 packets with IP options or IPv6 packets with routing 1938extension headers are blocked. 1939When 1940.Ar allow-opts 1941is specified for a 1942.Ar pass 1943rule, packets that pass the filter based on that rule (last matching) 1944do so even if they contain IP options or routing extension headers. 1945For packets that match state, the rule that initially created the 1946state is used. 1947The implicit 1948.Ar pass 1949rule that is used when a packet does not match any rules does not 1950allow IP options. 1951.It Ar label Aq Ar string 1952Adds a label (name) to the rule, which can be used to identify the rule. 1953For instance, 1954pfctl -s labels 1955shows per-rule statistics for rules that have labels. 1956.Pp 1957The following macros can be used in labels: 1958.Pp 1959.Bl -tag -width $srcaddr -compact -offset indent 1960.It Ar $if 1961The interface. 1962.It Ar $srcaddr 1963The source IP address. 1964.It Ar $dstaddr 1965The destination IP address. 1966.It Ar $srcport 1967The source port specification. 1968.It Ar $dstport 1969The destination port specification. 1970.It Ar $proto 1971The protocol name. 1972.It Ar $nr 1973The rule number. 1974.El 1975.Pp 1976For example: 1977.Bd -literal -offset indent 1978ips = \&"{ 1.2.3.4, 1.2.3.5 }\&" 1979pass in proto tcp from any to $ips \e 1980 port \*(Gt 1023 label \&"$dstaddr:$dstport\&" 1981.Ed 1982.Pp 1983expands to 1984.Bd -literal -offset indent 1985pass in inet proto tcp from any to 1.2.3.4 \e 1986 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&" 1987pass in inet proto tcp from any to 1.2.3.5 \e 1988 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&" 1989.Ed 1990.Pp 1991The macro expansion for the 1992.Ar label 1993directive occurs only at configuration file parse time, not during runtime. 1994.It Ar ridentifier Aq Ar number 1995Add an identifier (number) to the rule, which can be used to correlate the rule 1996to pflog entries, even after ruleset updates. 1997.It Xo Ar queue Aq Ar queue 1998.No \*(Ba ( Aq Ar queue , 1999.Aq Ar queue ) 2000.Xc 2001Packets matching this rule will be assigned to the specified queue. 2002If two queues are given, packets which have a 2003.Em TOS 2004of 2005.Em lowdelay 2006and TCP ACKs with no data payload will be assigned to the second one. 2007See 2008.Sx QUEUEING 2009for setup details. 2010.Pp 2011For example: 2012.Bd -literal -offset indent 2013pass in proto tcp to port 25 queue mail 2014pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio) 2015.Ed 2016.It Cm set prio Ar priority | Pq Ar priority , priority 2017Packets matching this rule will be assigned a specific queueing priority. 2018Priorities are assigned as integers 0 through 7. 2019If the packet is transmitted on a 2020.Xr vlan 4 2021interface, the queueing priority will be written as the priority 2022code point in the 802.1Q VLAN header. 2023If two priorities are given, packets which have a TOS of 2024.Cm lowdelay 2025and TCP ACKs with no data payload will be assigned to the second one. 2026.Pp 2027For example: 2028.Bd -literal -offset indent 2029pass in proto tcp to port 25 set prio 2 2030pass in proto tcp to port 22 set prio (2, 5) 2031.Ed 2032.It Ar tag Aq Ar string 2033Packets matching this rule will be tagged with the 2034specified string. 2035The tag acts as an internal marker that can be used to 2036identify these packets later on. 2037This can be used, for example, to provide trust between 2038interfaces and to determine if packets have been 2039processed by translation rules. 2040Tags are 2041.Qq sticky , 2042meaning that the packet will be tagged even if the rule 2043is not the last matching rule. 2044Further matching rules can replace the tag with a 2045new one but will not remove a previously applied tag. 2046A packet is only ever assigned one tag at a time. 2047Packet tagging can be done during 2048.Ar nat , 2049.Ar rdr , 2050.Ar binat 2051or 2052.Ar ether 2053rules in addition to filter rules. 2054Tags take the same macros as labels (see above). 2055.It Ar tagged Aq Ar string 2056Used with filter, translation or scrub rules 2057to specify that packets must already 2058be tagged with the given tag in order to match the rule. 2059Inverse tag matching can also be done 2060by specifying the 2061.Cm !\& 2062operator before the 2063.Ar tagged 2064keyword. 2065.It Ar rtable Aq Ar number 2066Used to select an alternate routing table for the routing lookup. 2067Only effective before the route lookup happened, i.e. when filtering inbound. 2068.It Xo Ar divert-to Aq Ar host 2069.Ar port Aq Ar port 2070.Xc 2071Used to redirect packets to a local socket bound to 2072.Ar host 2073and 2074.Ar port . 2075The packets will not be modified, so 2076.Xr getsockname 2 2077on the socket will return the original destination address of the packet. 2078.It Ar divert-reply 2079Used to receive replies for sockets that are bound to addresses 2080which are not local to the machine. 2081See 2082.Xr setsockopt 2 2083for information on how to bind these sockets. 2084.It Ar probability Aq Ar number 2085A probability attribute can be attached to a rule, with a value set between 20860 and 1, bounds not included. 2087In that case, the rule will be honoured using the given probability value 2088only. 2089For example, the following rule will drop 20% of incoming ICMP packets: 2090.Bd -literal -offset indent 2091block in proto icmp probability 20% 2092.Ed 2093.It Ar prio Aq Ar number 2094Only match packets which have the given queueing priority assigned. 2095.El 2096.Sh ROUTING 2097If a packet matches a rule with a route option set, the packet filter will 2098route the packet according to the type of route option. 2099When such a rule creates state, the route option is also applied to all 2100packets matching the same connection. 2101.Bl -tag -width xxxx 2102.It Ar route-to 2103The 2104.Ar route-to 2105option routes the packet to the specified interface with an optional address 2106for the next hop. 2107When a 2108.Ar route-to 2109rule creates state, only packets that pass in the same direction as the 2110filter rule specifies will be routed in this way. 2111Packets passing in the opposite direction (replies) are not affected 2112and are routed normally. 2113.It Ar reply-to 2114The 2115.Ar reply-to 2116option is similar to 2117.Ar route-to , 2118but routes packets that pass in the opposite direction (replies) to the 2119specified interface. 2120Opposite direction is only defined in the context of a state entry, and 2121.Ar reply-to 2122is useful only in rules that create state. 2123It can be used on systems with multiple external connections to 2124route all outgoing packets of a connection through the interface 2125the incoming connection arrived through (symmetric routing enforcement). 2126.It Ar dup-to 2127The 2128.Ar dup-to 2129option creates a duplicate of the packet and routes it like 2130.Ar route-to . 2131The original packet gets routed as it normally would. 2132.El 2133.Sh POOL OPTIONS 2134For 2135.Ar nat 2136and 2137.Ar rdr 2138rules, (as well as for the 2139.Ar route-to , 2140.Ar reply-to 2141and 2142.Ar dup-to 2143rule options) for which there is a single redirection address which has a 2144subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP 2145address), a variety of different methods for assigning this address can be 2146used: 2147.Bl -tag -width xxxx 2148.It Ar bitmask 2149The 2150.Ar bitmask 2151option applies the network portion of the redirection address to the address 2152to be modified (source with 2153.Ar nat , 2154destination with 2155.Ar rdr ) . 2156.It Ar random 2157The 2158.Ar random 2159option selects an address at random within the defined block of addresses. 2160.It Ar source-hash 2161The 2162.Ar source-hash 2163option uses a hash of the source address to determine the redirection address, 2164ensuring that the redirection address is always the same for a given source. 2165An optional key can be specified after this keyword either in hex or as a 2166string; by default 2167.Xr pfctl 8 2168randomly generates a key for source-hash every time the 2169ruleset is reloaded. 2170.It Ar round-robin 2171The 2172.Ar round-robin 2173option loops through the redirection address(es). 2174.Pp 2175When more than one redirection address is specified, 2176.Ar round-robin 2177is the only permitted pool type. 2178.It Ar static-port 2179With 2180.Ar nat 2181rules, the 2182.Ar static-port 2183option prevents 2184.Xr pf 4 2185from modifying the source port on TCP and UDP packets. 2186.It Xo Ar map-e-portset Aq Ar psid-offset 2187.No / Aq Ar psid-len 2188.No / Aq Ar psid 2189.Xc 2190With 2191.Ar nat 2192rules, the 2193.Ar map-e-portset 2194option enables the source port translation of MAP-E (RFC 7597) Customer Edge. 2195In order to make the host act as a MAP-E Customer Edge, setting up a tunneling 2196interface and pass rules for encapsulated packets are required in addition 2197to the map-e-portset nat rule. 2198.Pp 2199For example: 2200.Bd -literal -offset indent 2201nat on $gif_mape_if from $int_if:network to any \e 2202 -> $ipv4_mape_src map-e-portset 6/8/0x34 2203.Ed 2204.Pp 2205sets PSID offset 6, PSID length 8, PSID 0x34. 2206.El 2207.Pp 2208Additionally, the 2209.Ar sticky-address 2210option can be specified to help ensure that multiple connections from the 2211same source are mapped to the same redirection address. 2212This option can be used with the 2213.Ar random 2214and 2215.Ar round-robin 2216pool options. 2217Note that by default these associations are destroyed as soon as there are 2218no longer states which refer to them; in order to make the mappings last 2219beyond the lifetime of the states, increase the global options with 2220.Ar set timeout src.track . 2221See 2222.Sx STATEFUL TRACKING OPTIONS 2223for more ways to control the source tracking. 2224.Sh STATE MODULATION 2225Much of the security derived from TCP is attributable to how well the 2226initial sequence numbers (ISNs) are chosen. 2227Some popular stack implementations choose 2228.Em very 2229poor ISNs and thus are normally susceptible to ISN prediction exploits. 2230By applying a 2231.Ar modulate state 2232rule to a TCP connection, 2233.Xr pf 4 2234will create a high quality random sequence number for each connection 2235endpoint. 2236.Pp 2237The 2238.Ar modulate state 2239directive implicitly keeps state on the rule and is 2240only applicable to TCP connections. 2241.Pp 2242For instance: 2243.Bd -literal -offset indent 2244block all 2245pass out proto tcp from any to any modulate state 2246pass in proto tcp from any to any port 25 flags S/SFRA modulate state 2247.Ed 2248.Pp 2249Note that modulated connections will not recover when the state table 2250is lost (firewall reboot, flushing the state table, etc...). 2251.Xr pf 4 2252will not be able to infer a connection again after the state table flushes 2253the connection's modulator. 2254When the state is lost, the connection may be left dangling until the 2255respective endpoints time out the connection. 2256It is possible on a fast local network for the endpoints to start an ACK 2257storm while trying to resynchronize after the loss of the modulator. 2258The default 2259.Ar flags 2260settings (or a more strict equivalent) should be used on 2261.Ar modulate state 2262rules to prevent ACK storms. 2263.Pp 2264Note that alternative methods are available 2265to prevent loss of the state table 2266and allow for firewall failover. 2267See 2268.Xr carp 4 2269and 2270.Xr pfsync 4 2271for further information. 2272.Sh SYN PROXY 2273By default, 2274.Xr pf 4 2275passes packets that are part of a 2276.Xr tcp 4 2277handshake between the endpoints. 2278The 2279.Ar synproxy state 2280option can be used to cause 2281.Xr pf 4 2282itself to complete the handshake with the active endpoint, perform a handshake 2283with the passive endpoint, and then forward packets between the endpoints. 2284.Pp 2285No packets are sent to the passive endpoint before the active endpoint has 2286completed the handshake, hence so-called SYN floods with spoofed source 2287addresses will not reach the passive endpoint, as the sender can't complete the 2288handshake. 2289.Pp 2290The proxy is transparent to both endpoints, they each see a single 2291connection from/to the other endpoint. 2292.Xr pf 4 2293chooses random initial sequence numbers for both handshakes. 2294Once the handshakes are completed, the sequence number modulators 2295(see previous section) are used to translate further packets of the 2296connection. 2297.Ar synproxy state 2298includes 2299.Ar modulate state . 2300.Pp 2301Rules with 2302.Ar synproxy 2303will not work if 2304.Xr pf 4 2305operates on a 2306.Xr bridge 4 . 2307.Pp 2308Example: 2309.Bd -literal -offset indent 2310pass in proto tcp from any to any port www synproxy state 2311.Ed 2312.Sh STATEFUL TRACKING OPTIONS 2313A number of options related to stateful tracking can be applied on a 2314per-rule basis. 2315.Ar keep state , 2316.Ar modulate state 2317and 2318.Ar synproxy state 2319support these options, and 2320.Ar keep state 2321must be specified explicitly to apply options to a rule. 2322.Pp 2323.Bl -tag -width xxxx -compact 2324.It Ar max Aq Ar number 2325Limits the number of concurrent states the rule may create. 2326When this limit is reached, further packets that would create 2327state will not match this rule until existing states time out. 2328.It Ar no-sync 2329Prevent state changes for states created by this rule from appearing on the 2330.Xr pfsync 4 2331interface. 2332.It Xo Aq Ar timeout 2333.Aq Ar seconds 2334.Xc 2335Changes the timeout values used for states created by this rule. 2336For a list of all valid timeout names, see 2337.Sx OPTIONS 2338above. 2339.It Ar sloppy 2340Uses a sloppy TCP connection tracker that does not check sequence 2341numbers at all, which makes insertion and ICMP teardown attacks way 2342easier. 2343This is intended to be used in situations where one does not see all 2344packets of a connection, e.g. in asymmetric routing situations. 2345Cannot be used with modulate or synproxy state. 2346.El 2347.Pp 2348Multiple options can be specified, separated by commas: 2349.Bd -literal -offset indent 2350pass in proto tcp from any to any \e 2351 port www keep state \e 2352 (max 100, source-track rule, max-src-nodes 75, \e 2353 max-src-states 3, tcp.established 60, tcp.closing 5) 2354.Ed 2355.Pp 2356When the 2357.Ar source-track 2358keyword is specified, the number of states per source IP is tracked. 2359.Pp 2360.Bl -tag -width xxxx -compact 2361.It Ar source-track rule 2362The maximum number of states created by this rule is limited by the rule's 2363.Ar max-src-nodes 2364and 2365.Ar max-src-states 2366options. 2367Only state entries created by this particular rule count toward the rule's 2368limits. 2369.It Ar source-track global 2370The number of states created by all rules that use this option is limited. 2371Each rule can specify different 2372.Ar max-src-nodes 2373and 2374.Ar max-src-states 2375options, however state entries created by any participating rule count towards 2376each individual rule's limits. 2377.El 2378.Pp 2379The following limits can be set: 2380.Pp 2381.Bl -tag -width xxxx -compact 2382.It Ar max-src-nodes Aq Ar number 2383Limits the maximum number of source addresses which can simultaneously 2384have state table entries. 2385.It Ar max-src-states Aq Ar number 2386Limits the maximum number of simultaneous state entries that a single 2387source address can create with this rule. 2388.El 2389.Pp 2390For stateful TCP connections, limits on established connections (connections 2391which have completed the TCP 3-way handshake) can also be enforced 2392per source IP. 2393.Pp 2394.Bl -tag -width xxxx -compact 2395.It Ar max-src-conn Aq Ar number 2396Limits the maximum number of simultaneous TCP connections which have 2397completed the 3-way handshake that a single host can make. 2398.It Xo Ar max-src-conn-rate Aq Ar number 2399.No / Aq Ar seconds 2400.Xc 2401Limit the rate of new connections over a time interval. 2402The connection rate is an approximation calculated as a moving average. 2403.El 2404.Pp 2405Because the 3-way handshake ensures that the source address is not being 2406spoofed, more aggressive action can be taken based on these limits. 2407With the 2408.Ar overload Aq Ar table 2409state option, source IP addresses which hit either of the limits on 2410established connections will be added to the named table. 2411This table can be used in the ruleset to block further activity from 2412the offending host, redirect it to a tarpit process, or restrict its 2413bandwidth. 2414.Pp 2415The optional 2416.Ar flush 2417keyword kills all states created by the matching rule which originate 2418from the host which exceeds these limits. 2419The 2420.Ar global 2421modifier to the flush command kills all states originating from the 2422offending host, regardless of which rule created the state. 2423.Pp 2424For example, the following rules will protect the webserver against 2425hosts making more than 100 connections in 10 seconds. 2426Any host which connects faster than this rate will have its address added 2427to the 2428.Aq bad_hosts 2429table and have all states originating from it flushed. 2430Any new packets arriving from this host will be dropped unconditionally 2431by the block rule. 2432.Bd -literal -offset indent 2433block quick from \*(Ltbad_hosts\*(Gt 2434pass in on $ext_if proto tcp to $webserver port www keep state \e 2435 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global) 2436.Ed 2437.Sh OPERATING SYSTEM FINGERPRINTING 2438Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP 2439connection's initial SYN packet and guess at the host's operating system. 2440Unfortunately these nuances are easily spoofed by an attacker so the 2441fingerprint is not useful in making security decisions. 2442But the fingerprint is typically accurate enough to make policy decisions 2443upon. 2444.Pp 2445The fingerprints may be specified by operating system class, by 2446version, or by subtype/patchlevel. 2447The class of an operating system is typically the vendor or genre 2448and would be 2449.Ox 2450for the 2451.Xr pf 4 2452firewall itself. 2453The version of the oldest available 2454.Ox 2455release on the main FTP site 2456would be 2.6 and the fingerprint would be written 2457.Pp 2458.Dl \&"OpenBSD 2.6\&" 2459.Pp 2460The subtype of an operating system is typically used to describe the 2461patchlevel if that patch led to changes in the TCP stack behavior. 2462In the case of 2463.Ox , 2464the only subtype is for a fingerprint that was 2465normalized by the 2466.Ar no-df 2467scrub option and would be specified as 2468.Pp 2469.Dl \&"OpenBSD 3.3 no-df\&" 2470.Pp 2471Fingerprints for most popular operating systems are provided by 2472.Xr pf.os 5 . 2473Once 2474.Xr pf 4 2475is running, a complete list of known operating system fingerprints may 2476be listed by running: 2477.Pp 2478.Dl # pfctl -so 2479.Pp 2480Filter rules can enforce policy at any level of operating system specification 2481assuming a fingerprint is present. 2482Policy could limit traffic to approved operating systems or even ban traffic 2483from hosts that aren't at the latest service pack. 2484.Pp 2485The 2486.Ar unknown 2487class can also be used as the fingerprint which will match packets for 2488which no operating system fingerprint is known. 2489.Pp 2490Examples: 2491.Bd -literal -offset indent 2492pass out proto tcp from any os OpenBSD 2493block out proto tcp from any os Doors 2494block out proto tcp from any os "Doors PT" 2495block out proto tcp from any os "Doors PT SP3" 2496block out from any os "unknown" 2497pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" 2498.Ed 2499.Pp 2500Operating system fingerprinting is limited only to the TCP SYN packet. 2501This means that it will not work on other protocols and will not match 2502a currently established connection. 2503.Pp 2504Caveat: operating system fingerprints are occasionally wrong. 2505There are three problems: an attacker can trivially craft his packets to 2506appear as any operating system he chooses; 2507an operating system patch could change the stack behavior and no fingerprints 2508will match it until the database is updated; 2509and multiple operating systems may have the same fingerprint. 2510.Sh BLOCKING SPOOFED TRAFFIC 2511"Spoofing" is the faking of IP addresses, typically for malicious 2512purposes. 2513The 2514.Ar antispoof 2515directive expands to a set of filter rules which will block all 2516traffic with a source IP from the network(s) directly connected 2517to the specified interface(s) from entering the system through 2518any other interface. 2519.Pp 2520For example, the line 2521.Bd -literal -offset indent 2522antispoof for lo0 2523.Ed 2524.Pp 2525expands to 2526.Bd -literal -offset indent 2527block drop in on ! lo0 inet from 127.0.0.1/8 to any 2528block drop in on ! lo0 inet6 from ::1 to any 2529.Ed 2530.Pp 2531For non-loopback interfaces, there are additional rules to block incoming 2532packets with a source IP address identical to the interface's IP(s). 2533For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a 2534netmask of 255.255.255.0, 2535the line 2536.Bd -literal -offset indent 2537antispoof for wi0 inet 2538.Ed 2539.Pp 2540expands to 2541.Bd -literal -offset indent 2542block drop in on ! wi0 inet from 10.0.0.0/24 to any 2543block drop in inet from 10.0.0.1 to any 2544.Ed 2545.Pp 2546Caveat: Rules created by the 2547.Ar antispoof 2548directive interfere with packets sent over loopback interfaces 2549to local addresses. 2550One should pass these explicitly. 2551.Sh FRAGMENT HANDLING 2552The size of IP datagrams (packets) can be significantly larger than the 2553maximum transmission unit (MTU) of the network. 2554In cases when it is necessary or more efficient to send such large packets, 2555the large packet will be fragmented into many smaller packets that will each 2556fit onto the wire. 2557Unfortunately for a firewalling device, only the first logical fragment will 2558contain the necessary header information for the subprotocol that allows 2559.Xr pf 4 2560to filter on things such as TCP ports or to perform NAT. 2561.Pp 2562Besides the use of 2563.Ar scrub 2564rules as described in 2565.Sx TRAFFIC NORMALIZATION 2566above, there are three options for handling fragments in the packet filter. 2567.Pp 2568One alternative is to filter individual fragments with filter rules. 2569If no 2570.Ar scrub 2571rule applies to a fragment, it is passed to the filter. 2572Filter rules with matching IP header parameters decide whether the 2573fragment is passed or blocked, in the same way as complete packets 2574are filtered. 2575Without reassembly, fragments can only be filtered based on IP header 2576fields (source/destination address, protocol), since subprotocol header 2577fields are not available (TCP/UDP port numbers, ICMP code/type). 2578The 2579.Ar fragment 2580option can be used to restrict filter rules to apply only to 2581fragments, but not complete packets. 2582Filter rules without the 2583.Ar fragment 2584option still apply to fragments, if they only specify IP header fields. 2585For instance, the rule 2586.Bd -literal -offset indent 2587pass in proto tcp from any to any port 80 2588.Ed 2589.Pp 2590never applies to a fragment, even if the fragment is part of a TCP 2591packet with destination port 80, because without reassembly this information 2592is not available for each fragment. 2593This also means that fragments cannot create new or match existing 2594state table entries, which makes stateful filtering and address 2595translation (NAT, redirection) for fragments impossible. 2596.Pp 2597It's also possible to reassemble only certain fragments by specifying 2598source or destination addresses or protocols as parameters in 2599.Ar scrub 2600rules. 2601.Pp 2602In most cases, the benefits of reassembly outweigh the additional 2603memory cost, and it's recommended to use 2604.Ar scrub 2605rules to reassemble 2606all fragments via the 2607.Ar fragment reassemble 2608modifier. 2609.Pp 2610The memory allocated for fragment caching can be limited using 2611.Xr pfctl 8 . 2612Once this limit is reached, fragments that would have to be cached 2613are dropped until other entries time out. 2614The timeout value can also be adjusted. 2615.Pp 2616When forwarding reassembled IPv6 packets, pf refragments them with 2617the original maximum fragment size. 2618This allows the sender to determine the optimal fragment size by 2619path MTU discovery. 2620.Sh ANCHORS 2621Besides the main ruleset, 2622.Xr pfctl 8 2623can load rulesets into 2624.Ar anchor 2625attachment points. 2626An 2627.Ar anchor 2628is a container that can hold rules, address tables, and other anchors. 2629.Pp 2630An 2631.Ar anchor 2632has a name which specifies the path where 2633.Xr pfctl 8 2634can be used to access the anchor to perform operations on it, such as 2635attaching child anchors to it or loading rules into it. 2636Anchors may be nested, with components separated by 2637.Sq / 2638characters, similar to how file system hierarchies are laid out. 2639The main ruleset is actually the default anchor, so filter and 2640translation rules, for example, may also be contained in any anchor. 2641.Pp 2642An anchor can reference another 2643.Ar anchor 2644attachment point 2645using the following kinds 2646of rules: 2647.Bl -tag -width xxxx 2648.It Ar nat-anchor Aq Ar name 2649Evaluates the 2650.Ar nat 2651rules in the specified 2652.Ar anchor . 2653.It Ar rdr-anchor Aq Ar name 2654Evaluates the 2655.Ar rdr 2656rules in the specified 2657.Ar anchor . 2658.It Ar binat-anchor Aq Ar name 2659Evaluates the 2660.Ar binat 2661rules in the specified 2662.Ar anchor . 2663.It Ar anchor Aq Ar name 2664Evaluates the filter rules in the specified 2665.Ar anchor . 2666.It Xo Ar load anchor 2667.Aq Ar name 2668.Ar from Aq Ar file 2669.Xc 2670Loads the rules from the specified file into the 2671anchor 2672.Ar name . 2673.El 2674.Pp 2675When evaluation of the main ruleset reaches an 2676.Ar anchor 2677rule, 2678.Xr pf 4 2679will proceed to evaluate all rules specified in that anchor. 2680.Pp 2681Matching filter and translation rules marked with the 2682.Ar quick 2683option are final and abort the evaluation of the rules in other 2684anchors and the main ruleset. 2685If the 2686.Ar anchor 2687itself is marked with the 2688.Ar quick 2689option, 2690ruleset evaluation will terminate when the anchor is exited if the packet is 2691matched by any rule within the anchor. 2692.Pp 2693.Ar anchor 2694rules are evaluated relative to the anchor in which they are contained. 2695For example, all 2696.Ar anchor 2697rules specified in the main ruleset will reference anchor 2698attachment points underneath the main ruleset, and 2699.Ar anchor 2700rules specified in a file loaded from a 2701.Ar load anchor 2702rule will be attached under that anchor point. 2703.Pp 2704Rules may be contained in 2705.Ar anchor 2706attachment points which do not contain any rules when the main ruleset 2707is loaded, and later such anchors can be manipulated through 2708.Xr pfctl 8 2709without reloading the main ruleset or other anchors. 2710For example, 2711.Bd -literal -offset indent 2712ext_if = \&"kue0\&" 2713block on $ext_if all 2714anchor spam 2715pass out on $ext_if all 2716pass in on $ext_if proto tcp from any \e 2717 to $ext_if port smtp 2718.Ed 2719.Pp 2720blocks all packets on the external interface by default, then evaluates 2721all rules in the 2722.Ar anchor 2723named "spam", and finally passes all outgoing connections and 2724incoming connections to port 25. 2725.Bd -literal -offset indent 2726# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e 2727 pfctl -a spam -f - 2728.Ed 2729.Pp 2730This loads a single rule into the 2731.Ar anchor , 2732which blocks all packets from a specific address. 2733.Pp 2734The anchor can also be populated by adding a 2735.Ar load anchor 2736rule after the 2737.Ar anchor 2738rule: 2739.Bd -literal -offset indent 2740anchor spam 2741load anchor spam from "/etc/pf-spam.conf" 2742.Ed 2743.Pp 2744When 2745.Xr pfctl 8 2746loads 2747.Nm pf.conf , 2748it will also load all the rules from the file 2749.Pa /etc/pf-spam.conf 2750into the anchor. 2751.Pp 2752Optionally, 2753.Ar anchor 2754rules can specify packet filtering parameters using the same syntax as 2755filter rules. 2756When parameters are used, the 2757.Ar anchor 2758rule is only evaluated for matching packets. 2759This allows conditional evaluation of anchors, like: 2760.Bd -literal -offset indent 2761block on $ext_if all 2762anchor spam proto tcp from any to any port smtp 2763pass out on $ext_if all 2764pass in on $ext_if proto tcp from any to $ext_if port smtp 2765.Ed 2766.Pp 2767The rules inside 2768.Ar anchor 2769spam are only evaluated for 2770.Ar tcp 2771packets with destination port 25. 2772Hence, 2773.Bd -literal -offset indent 2774# echo \&"block in quick from 1.2.3.4 to any" \&| \e 2775 pfctl -a spam -f - 2776.Ed 2777.Pp 2778will only block connections from 1.2.3.4 to port 25. 2779.Pp 2780Anchors may end with the asterisk 2781.Pq Sq * 2782character, which signifies that all anchors attached at that point 2783should be evaluated in the alphabetical ordering of their anchor name. 2784For example, 2785.Bd -literal -offset indent 2786anchor "spam/*" 2787.Ed 2788.Pp 2789will evaluate each rule in each anchor attached to the 2790.Li spam 2791anchor. 2792Note that it will only evaluate anchors that are directly attached to the 2793.Li spam 2794anchor, and will not descend to evaluate anchors recursively. 2795.Pp 2796Since anchors are evaluated relative to the anchor in which they are 2797contained, there is a mechanism for accessing the parent and ancestor 2798anchors of a given anchor. 2799Similar to file system path name resolution, if the sequence 2800.Dq .. 2801appears as an anchor path component, the parent anchor of the current 2802anchor in the path evaluation at that point will become the new current 2803anchor. 2804As an example, consider the following: 2805.Bd -literal -offset indent 2806# echo ' anchor "spam/allowed" ' | pfctl -f - 2807# echo -e ' anchor "../banned" \en pass' | \e 2808 pfctl -a spam/allowed -f - 2809.Ed 2810.Pp 2811Evaluation of the main ruleset will lead into the 2812.Li spam/allowed 2813anchor, which will evaluate the rules in the 2814.Li spam/banned 2815anchor, if any, before finally evaluating the 2816.Ar pass 2817rule. 2818.Pp 2819Filter rule 2820.Ar anchors 2821can also be loaded inline in the ruleset within a brace ('{' '}') delimited 2822block. 2823Brace delimited blocks may contain rules or other brace-delimited blocks. 2824When anchors are loaded this way the anchor name becomes optional. 2825.Bd -literal -offset indent 2826anchor "external" on $ext_if { 2827 block 2828 anchor out { 2829 pass proto tcp from any to port { 25, 80, 443 } 2830 } 2831 pass in proto tcp to any port 22 2832} 2833.Ed 2834.Pp 2835Since the parser specification for anchor names is a string, any 2836reference to an anchor name containing 2837.Sq / 2838characters will require double quote 2839.Pq Sq \&" 2840characters around the anchor name. 2841.Sh TRANSLATION EXAMPLES 2842This example maps incoming requests on port 80 to port 8080, on 2843which a daemon is running (because, for example, it is not run as root, 2844and therefore lacks permission to bind to port 80). 2845.Bd -literal 2846# use a macro for the interface name, so it can be changed easily 2847ext_if = \&"ne3\&" 2848 2849# map daemon on 8080 to appear to be on 80 2850rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080 2851.Ed 2852.Pp 2853If the 2854.Ar pass 2855modifier is given, packets matching the translation rule are passed without 2856inspecting the filter rules: 2857.Bd -literal 2858rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e 2859 port 8080 2860.Ed 2861.Pp 2862In the example below, vlan12 is configured as 192.168.168.1; 2863the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111 2864when they are going out any interface except vlan12. 2865This has the net effect of making traffic from the 192.168.168.0/24 2866network appear as though it is the Internet routable address 2867204.92.77.111 to nodes behind any interface on the router except 2868for the nodes on vlan12. 2869(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.) 2870.Bd -literal 2871nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111 2872.Ed 2873.Pp 2874In the example below, the machine sits between a fake internal 144.19.74.* 2875network, and a routable external IP of 204.92.77.100. 2876The 2877.Ar no nat 2878rule excludes protocol AH from being translated. 2879.Bd -literal 2880# NO NAT 2881no nat on $ext_if proto ah from 144.19.74.0/24 to any 2882nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100 2883.Ed 2884.Pp 2885In the example below, packets bound for one specific server, as well as those 2886generated by the sysadmins are not proxied; all other connections are. 2887.Bd -literal 2888# NO RDR 2889no rdr on $int_if proto { tcp, udp } from any to $server port 80 2890no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80 2891rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e 2892 port 80 2893.Ed 2894.Pp 2895This longer example uses both a NAT and a redirection. 2896The external interface has the address 157.161.48.183. 2897On localhost, we are running 2898.Xr ftp-proxy 8 , 2899waiting for FTP sessions to be redirected to it. 2900The three mandatory anchors for 2901.Xr ftp-proxy 8 2902are omitted from this example; see the 2903.Xr ftp-proxy 8 2904manpage. 2905.Bd -literal 2906# NAT 2907# Translate outgoing packets' source addresses (any protocol). 2908# In this case, any address but the gateway's external address is mapped. 2909nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if) 2910 2911# NAT PROXYING 2912# Map outgoing packets' source port to an assigned proxy port instead of 2913# an arbitrary port. 2914# In this case, proxy outgoing isakmp with port 500 on the gateway. 2915nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e 2916 port 500 2917 2918# BINAT 2919# Translate outgoing packets' source address (any protocol). 2920# Translate incoming packets' destination address to an internal machine 2921# (bidirectional). 2922binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if 2923 2924# RDR 2925# Translate incoming packets' destination addresses. 2926# As an example, redirect a TCP and UDP port to an internal machine. 2927rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e 2928 -\*(Gt 10.1.2.151 port 22 2929rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e 2930 -\*(Gt 10.1.2.151 port 53 2931 2932# RDR 2933# Translate outgoing ftp control connections to send them to localhost 2934# for proxying with ftp-proxy(8) running on port 8021. 2935rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021 2936.Ed 2937.Pp 2938In this example, a NAT gateway is set up to translate internal addresses 2939using a pool of public addresses (192.0.2.16/28) and to redirect 2940incoming web server connections to a group of web servers on the internal 2941network. 2942.Bd -literal 2943# NAT LOAD BALANCE 2944# Translate outgoing packets' source addresses using an address pool. 2945# A given source address is always translated to the same pool address by 2946# using the source-hash keyword. 2947nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash 2948 2949# RDR ROUND ROBIN 2950# Translate incoming web server connections to a group of web servers on 2951# the internal network. 2952rdr on $ext_if proto tcp from any to any port 80 \e 2953 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin 2954.Ed 2955.Sh FILTER EXAMPLES 2956.Bd -literal 2957# The external interface is kue0 2958# (157.161.48.183, the only routable address) 2959# and the private network is 10.0.0.0/8, for which we are doing NAT. 2960 2961# use a macro for the interface name, so it can be changed easily 2962ext_if = \&"kue0\&" 2963 2964# normalize all incoming traffic 2965scrub in on $ext_if all fragment reassemble 2966 2967# block and log everything by default 2968block return log on $ext_if all 2969 2970# block anything coming from source we have no back routes for 2971block in from no-route to any 2972 2973# block packets whose ingress interface does not match the one in 2974# the route back to their source address 2975block in from urpf-failed to any 2976 2977# block and log outgoing packets that do not have our address as source, 2978# they are either spoofed or something is misconfigured (NAT disabled, 2979# for instance), we want to be nice and do not send out garbage. 2980block out log quick on $ext_if from ! 157.161.48.183 to any 2981 2982# silently drop broadcasts (cable modem noise) 2983block in quick on $ext_if from any to 255.255.255.255 2984 2985# block and log incoming packets from reserved address space and invalid 2986# addresses, they are either spoofed or misconfigured, we cannot reply to 2987# them anyway (hence, no return-rst). 2988block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e 2989 192.168.0.0/16, 255.255.255.255/32 } to any 2990 2991# ICMP 2992 2993# pass out/in certain ICMP queries and keep state (ping) 2994# state matching is done on host addresses and ICMP id (not type/code), 2995# so replies (like 0/0 for 8/0) will match queries 2996# ICMP error messages (which always refer to a TCP/UDP packet) are 2997# handled by the TCP/UDP states 2998pass on $ext_if inet proto icmp all icmp-type 8 code 0 2999 3000# UDP 3001 3002# pass out all UDP connections and keep state 3003pass out on $ext_if proto udp all 3004 3005# pass in certain UDP connections and keep state (DNS) 3006pass in on $ext_if proto udp from any to any port domain 3007 3008# TCP 3009 3010# pass out all TCP connections and modulate state 3011pass out on $ext_if proto tcp all modulate state 3012 3013# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT) 3014pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e 3015 auth } 3016 3017# Do not allow Windows 9x SMTP connections since they are typically 3018# a viral worm. Alternately we could limit these OSes to 1 connection each. 3019block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e 3020 to any port smtp 3021 3022# IPv6 3023# pass in/out all IPv6 traffic: note that we have to enable this in two 3024# different ways, on both our physical interface and our tunnel 3025pass quick on gif0 inet6 3026pass quick on $ext_if proto ipv6 3027 3028# Packet Tagging 3029 3030# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is 3031# being done on $ext_if for all outgoing packets. tag packets in on 3032# $int_if and pass those tagged packets out on $ext_if. all other 3033# outgoing packets (i.e., packets from the wireless network) are only 3034# permitted to access port 80. 3035 3036pass in on $int_if from any to any tag INTNET 3037pass in on $wifi_if from any to any 3038 3039block out on $ext_if from any to any 3040pass out quick on $ext_if tagged INTNET 3041pass out on $ext_if proto tcp from any to any port 80 3042 3043# tag incoming packets as they are redirected to spamd(8). use the tag 3044# to pass those packets through the packet filter. 3045 3046rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e 3047 tag SPAMD -\*(Gt 127.0.0.1 port spamd 3048 3049block in on $ext_if 3050pass in on $ext_if inet proto tcp tagged SPAMD 3051.Ed 3052.Sh GRAMMAR 3053Syntax for 3054.Nm 3055in BNF: 3056.Bd -literal 3057line = ( option | ether-rule | pf-rule | nat-rule | binat-rule | 3058 rdr-rule | antispoof-rule | altq-rule | queue-rule | 3059 trans-anchors | anchor-rule | anchor-close | load-anchor | 3060 table-rule | include ) 3061 3062option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] | 3063 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] | 3064 [ "optimization" [ "default" | "normal" | 3065 "high-latency" | "satellite" | 3066 "aggressive" | "conservative" ] ] 3067 [ "limit" ( limit-item | "{" limit-list "}" ) ] | 3068 [ "loginterface" ( interface-name | "none" ) ] | 3069 [ "block-policy" ( "drop" | "return" ) ] | 3070 [ "state-policy" ( "if-bound" | "floating" ) ] 3071 [ "state-defaults" state-opts ] 3072 [ "require-order" ( "yes" | "no" ) ] 3073 [ "fingerprints" filename ] | 3074 [ "skip on" ifspec ] | 3075 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] 3076 [ "keepcounters" ] ) 3077 3078ether-rule = "ether" etheraction [ ( "in" | "out" ) ] 3079 [ "quick" ] [ "on" ifspec ] [ etherprotospec ] 3080 etherhosts [ "l3" hosts ] [ etherfilteropt-list ] 3081 3082pf-rule = action [ ( "in" | "out" ) ] 3083 [ "log" [ "(" logopts ")"] ] [ "quick" ] 3084 [ "on" ifspec ] [ route ] [ af ] [ protospec ] 3085 hosts [ filteropt-list ] 3086 3087logopts = logopt [ "," logopts ] 3088logopt = "all" | "user" | "to" interface-name 3089 3090etherfilteropt-list = etherfilteropt-list etherfilteropt | etherfilteropt 3091etherfilteropt = "tag" string | "tagged" string | "queue" ( string ) 3092 3093filteropt-list = filteropt-list filteropt | filteropt 3094filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos | 3095 ( "no" | "keep" | "modulate" | "synproxy" ) "state" 3096 [ "(" state-opts ")" ] | 3097 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos | 3098 "max-mss" number | "random-id" | "reassemble tcp" | 3099 fragmentation | "allow-opts" | 3100 "label" string | "tag" string | [ ! ] "tagged" string | 3101 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) | 3102 "queue" ( string | "(" string [ [ "," ] string ] ")" ) | 3103 "rtable" number | "probability" number"%" | "prio" number | 3104 "dnpipe" ( number | "(" number "," number ")" ) | 3105 "dnqueue" ( number | "(" number "," number ")" ) | 3106 "ridentifier" number 3107 3108nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3109 [ "on" ifspec ] [ af ] 3110 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3111 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 3112 [ portspec ] [ pooltype ] [ "static-port" ] 3113 [ "map-e-portset" number "/" number "/" number ] ] 3114 3115binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3116 [ "on" interface-name ] [ af ] 3117 [ "proto" ( proto-name | proto-number ) ] 3118 "from" address [ "/" mask-bits ] "to" ipspec 3119 [ "tag" string ] [ "tagged" string ] 3120 [ "-\*(Gt" address [ "/" mask-bits ] ] 3121 3122rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3123 [ "on" ifspec ] [ af ] 3124 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3125 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 3126 [ portspec ] [ pooltype ] ] 3127 3128antispoof-rule = "antispoof" [ "log" ] [ "quick" ] 3129 "for" ifspec [ af ] [ "label" string ] 3130 [ "ridentifier" number ] 3131 3132table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ] 3133tableopts-list = tableopts-list tableopts | tableopts 3134tableopts = "persist" | "const" | "counters" | "file" string | 3135 "{" [ tableaddr-list ] "}" 3136tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec 3137tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ] 3138tableaddr = hostname | ifspec | "self" | 3139 ipv4-dotted-quad | ipv6-coloned-hex 3140 3141altq-rule = "altq on" interface-name queueopts-list 3142 "queue" subqueue 3143queue-rule = "queue" string [ "on" interface-name ] queueopts-list 3144 subqueue 3145 3146anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ] 3147 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ] 3148 3149anchor-close = "}" 3150 3151trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string 3152 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ] 3153 3154load-anchor = "load anchor" string "from" filename 3155 3156queueopts-list = queueopts-list queueopts | queueopts 3157queueopts = [ "bandwidth" bandwidth-spec ] | 3158 [ "qlimit" number ] | [ "tbrsize" number ] | 3159 [ "priority" number ] | [ schedulers ] 3160schedulers = ( cbq-def | priq-def | hfsc-def ) 3161bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" ) 3162 3163etheraction = "pass" | "block" 3164action = "pass" | "block" [ return ] | [ "no" ] "scrub" 3165return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] | 3166 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] | 3167 "return-icmp6" [ "(" icmp6code ")" ] 3168icmpcode = ( icmp-code-name | icmp-code-number ) 3169icmp6code = ( icmp6-code-name | icmp6-code-number ) 3170 3171ifspec = ( [ "!" ] ( interface-name | interface-group ) ) | 3172 "{" interface-list "}" 3173interface-list = [ "!" ] ( interface-name | interface-group ) 3174 [ [ "," ] interface-list ] 3175route = ( "route-to" | "reply-to" | "dup-to" ) 3176 ( routehost | "{" routehost-list "}" ) 3177 [ pooltype ] 3178af = "inet" | "inet6" 3179 3180etherprotospec = "proto" ( proto-number | "{" proto-list "}" ) 3181protospec = "proto" ( proto-name | proto-number | 3182 "{" proto-list "}" ) 3183proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ] 3184 3185etherhosts = "from" macaddress "to" macaddress 3186macaddress = mac | mac "/" masklen | mac "&" mask 3187 3188hosts = "all" | 3189 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host | 3190 "{" host-list "}" ) [ port ] [ os ] 3191 "to" ( "any" | "no-route" | "self" | host | 3192 "{" host-list "}" ) [ port ] 3193 3194ipspec = "any" | host | "{" host-list "}" 3195host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" ) 3196redirhost = address [ "/" mask-bits ] 3197routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")" 3198address = ( interface-name | interface-group | 3199 "(" ( interface-name | interface-group ) ")" | 3200 hostname | ipv4-dotted-quad | ipv6-coloned-hex ) 3201host-list = host [ [ "," ] host-list ] 3202redirhost-list = redirhost [ [ "," ] redirhost-list ] 3203routehost-list = routehost [ [ "," ] routehost-list ] 3204 3205port = "port" ( unary-op | binary-op | "{" op-list "}" ) 3206portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ] 3207os = "os" ( os-name | "{" os-list "}" ) 3208user = "user" ( unary-op | binary-op | "{" op-list "}" ) 3209group = "group" ( unary-op | binary-op | "{" op-list "}" ) 3210 3211unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ] 3212 ( name | number ) 3213binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number 3214op-list = ( unary-op | binary-op ) [ [ "," ] op-list ] 3215 3216os-name = operating-system-name 3217os-list = os-name [ [ "," ] os-list ] 3218 3219flags = "flags" ( [ flag-set ] "/" flag-set | "any" ) 3220flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ] 3221 [ "W" ] 3222 3223icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" ) 3224icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" ) 3225icmp-type-code = ( icmp-type-name | icmp-type-number ) 3226 [ "code" ( icmp-code-name | icmp-code-number ) ] 3227icmp-list = icmp-type-code [ [ "," ] icmp-list ] 3228 3229tos = ( "lowdelay" | "throughput" | "reliability" | 3230 [ "0x" ] number ) 3231 3232state-opts = state-opt [ [ "," ] state-opts ] 3233state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | 3234 "source-track" [ ( "rule" | "global" ) ] | 3235 "max-src-nodes" number | "max-src-states" number | 3236 "max-src-conn" number | 3237 "max-src-conn-rate" number "/" number | 3238 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] | 3239 "if-bound" | "floating" ) 3240 3241fragmentation = [ "fragment reassemble" ] 3242 3243timeout-list = timeout [ [ "," ] timeout-list ] 3244timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" | 3245 "tcp.closing" | "tcp.finwait" | "tcp.closed" | 3246 "udp.first" | "udp.single" | "udp.multiple" | 3247 "icmp.first" | "icmp.error" | 3248 "other.first" | "other.single" | "other.multiple" | 3249 "frag" | "interval" | "src.track" | 3250 "adaptive.start" | "adaptive.end" ) number 3251 3252limit-list = limit-item [ [ "," ] limit-list ] 3253limit-item = ( "states" | "frags" | "src-nodes" ) number 3254 3255pooltype = ( "bitmask" | "random" | 3256 "source-hash" [ ( hex-key | string-key ) ] | 3257 "round-robin" ) [ sticky-address ] 3258 3259subqueue = string | "{" queue-list "}" 3260queue-list = string [ [ "," ] string ] 3261cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ] 3262priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ] 3263hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ] 3264cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" ) 3265priq-opt = ( "default" | "red" | "ecn" | "rio" ) 3266hfsc-opt = ( "default" | "red" | "ecn" | "rio" | 3267 linkshare-sc | realtime-sc | upperlimit-sc ) 3268linkshare-sc = "linkshare" sc-spec 3269realtime-sc = "realtime" sc-spec 3270upperlimit-sc = "upperlimit" sc-spec 3271sc-spec = ( bandwidth-spec | 3272 "(" bandwidth-spec number bandwidth-spec ")" ) 3273include = "include" filename 3274.Ed 3275.Sh FILES 3276.Bl -tag -width "/etc/protocols" -compact 3277.It Pa /etc/hosts 3278Host name database. 3279.It Pa /etc/pf.conf 3280Default location of the ruleset file. 3281The file has to be created manually as it is not installed with a 3282standard installation. 3283.It Pa /etc/pf.os 3284Default location of OS fingerprints. 3285.It Pa /etc/protocols 3286Protocol name database. 3287.It Pa /etc/services 3288Service name database. 3289.El 3290.Sh SEE ALSO 3291.Xr altq 4 , 3292.Xr carp 4 , 3293.Xr icmp 4 , 3294.Xr icmp6 4 , 3295.Xr ip 4 , 3296.Xr ip6 4 , 3297.Xr pf 4 , 3298.Xr pfsync 4 , 3299.Xr tcp 4 , 3300.Xr udp 4 , 3301.Xr hosts 5 , 3302.Xr pf.os 5 , 3303.Xr protocols 5 , 3304.Xr services 5 , 3305.Xr ftp-proxy 8 , 3306.Xr pfctl 8 , 3307.Xr pflogd 8 3308.Sh HISTORY 3309The 3310.Nm 3311file format first appeared in 3312.Ox 3.0 . 3313