1.\" $OpenBSD: pf.conf.5,v 1.406 2009/01/31 19:37:12 sobrado Exp $ 2.\" 3.\" Copyright (c) 2002, Daniel Hartmeier 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 10.\" - Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" - Redistributions in binary form must reproduce the above 13.\" copyright notice, this list of conditions and the following 14.\" disclaimer in the documentation and/or other materials provided 15.\" with the distribution. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 20.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 21.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 23.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 24.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 25.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 27.\" ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd November 17, 2023 31.Dt PF.CONF 5 32.Os 33.Sh NAME 34.Nm pf.conf 35.Nd packet filter configuration file 36.Sh DESCRIPTION 37The 38.Xr pf 4 39packet filter modifies, drops or passes packets according to rules or 40definitions specified in 41.Nm pf.conf . 42.Sh STATEMENT ORDER 43There are eight types of statements in 44.Nm pf.conf : 45.Bl -tag -width xxxx 46.It Cm Macros 47User-defined variables may be defined and used later, simplifying 48the configuration file. 49Macros must be defined before they are referenced in 50.Nm pf.conf . 51.It Cm Tables 52Tables provide a mechanism for increasing the performance and flexibility of 53rules with large numbers of source or destination addresses. 54.It Cm Options 55Options tune the behaviour of the packet filtering engine. 56.It Cm Ethernet Filtering 57Ethernet filtering provides rule-based blocking or passing of Ethernet packets. 58.It Cm Traffic Normalization Li (e.g. Em scrub ) 59Traffic normalization protects internal machines against inconsistencies 60in Internet protocols and implementations. 61.It Cm Queueing 62Queueing provides rule-based bandwidth control. 63.It Cm Translation Li (Various forms of NAT) 64Translation rules specify how addresses are to be mapped or redirected to 65other addresses. 66.It Cm Packet Filtering 67Packet filtering provides rule-based blocking or passing of packets. 68.El 69.Pp 70With the exception of 71.Cm macros 72and 73.Cm tables , 74the types of statements should be grouped and appear in 75.Nm pf.conf 76in the order shown above, as this matches the operation of the underlying 77packet filtering engine. 78By default 79.Xr pfctl 8 80enforces this order (see 81.Ar set require-order 82below). 83.Pp 84Comments can be put anywhere in the file using a hash mark 85.Pq Sq # , 86and extend to the end of the current line. 87.Pp 88Additional configuration files can be included with the 89.Ic include 90keyword, for example: 91.Bd -literal -offset indent 92include "/etc/pf/sub.filter.conf" 93.Ed 94.Sh MACROS 95Macros can be defined that will later be expanded in context. 96Macro names must start with a letter, and may contain letters, digits 97and underscores. 98Macro names may not be reserved words (for example 99.Ar pass , 100.Ar in , 101.Ar out ) . 102Macros are not expanded inside quotes. 103.Pp 104For example, 105.Bd -literal -offset indent 106ext_if = \&"kue0\&" 107all_ifs = \&"{\&" $ext_if lo0 \&"}\&" 108pass out on $ext_if from any to any 109pass in on $ext_if proto tcp from any to any port 25 110.Ed 111.Sh TABLES 112Tables are named structures which can hold a collection of addresses and 113networks. 114Lookups against tables in 115.Xr pf 4 116are relatively fast, making a single rule with tables much more efficient, 117in terms of 118processor usage and memory consumption, than a large number of rules which 119differ only in IP address (either created explicitly or automatically by rule 120expansion). 121.Pp 122Tables can be used as the source or destination of filter rules, 123.Ar scrub 124rules 125or 126translation rules such as 127.Ar nat 128or 129.Ar rdr 130(see below for details on the various rule types). 131Tables can also be used for the redirect address of 132.Ar nat 133and 134.Ar rdr 135rules and in the routing options of filter rules, but only for 136.Ar round-robin 137pools. 138.Pp 139Tables can be defined with any of the following 140.Xr pfctl 8 141mechanisms. 142As with macros, reserved words may not be used as table names. 143.Bl -tag -width "manually" 144.It Ar manually 145Persistent tables can be manually created with the 146.Ar add 147or 148.Ar replace 149option of 150.Xr pfctl 8 , 151before or after the ruleset has been loaded. 152.It Pa pf.conf 153Table definitions can be placed directly in this file, and loaded at the 154same time as other rules are loaded, atomically. 155Table definitions inside 156.Nm pf.conf 157use the 158.Ar table 159statement, and are especially useful to define non-persistent tables. 160The contents of a pre-existing table defined without a list of addresses 161to initialize it is not altered when 162.Nm pf.conf 163is loaded. 164A table initialized with the empty list, 165.Li { } , 166will be cleared on load. 167.El 168.Pp 169Tables may be defined with the following attributes: 170.Bl -tag -width persist 171.It Ar persist 172The 173.Ar persist 174flag forces the kernel to keep the table even when no rules refer to it. 175If the flag is not set, the kernel will automatically remove the table 176when the last rule referring to it is flushed. 177.It Ar const 178The 179.Ar const 180flag prevents the user from altering the contents of the table once it 181has been created. 182Without that flag, 183.Xr pfctl 8 184can be used to add or remove addresses from the table at any time, even 185when running with 186.Xr securelevel 7 187= 2. 188.It Ar counters 189The 190.Ar counters 191flag enables per-address packet and byte counters which can be displayed with 192.Xr pfctl 8 . 193Note that this feature carries significant memory overhead for large tables. 194.El 195.Pp 196For example, 197.Bd -literal -offset indent 198table \*(Ltprivate\*(Gt const { 10/8, 172.16/12, 192.168/16 } 199table \*(Ltbadhosts\*(Gt persist 200block on fxp0 from { \*(Ltprivate\*(Gt, \*(Ltbadhosts\*(Gt } to any 201.Ed 202.Pp 203creates a table called private, to hold RFC 1918 private network 204blocks, and a table called badhosts, which is initially empty. 205A filter rule is set up to block all traffic coming from addresses listed in 206either table. 207The private table cannot have its contents changed and the badhosts table 208will exist even when no active filter rules reference it. 209Addresses may later be added to the badhosts table, so that traffic from 210these hosts can be blocked by using 211.Bd -literal -offset indent 212# pfctl -t badhosts -Tadd 204.92.77.111 213.Ed 214.Pp 215A table can also be initialized with an address list specified in one or more 216external files, using the following syntax: 217.Bd -literal -offset indent 218table \*(Ltspam\*(Gt persist file \&"/etc/spammers\&" file \&"/etc/openrelays\&" 219block on fxp0 from \*(Ltspam\*(Gt to any 220.Ed 221.Pp 222The files 223.Pa /etc/spammers 224and 225.Pa /etc/openrelays 226list IP addresses, one per line. 227Any lines beginning with a # are treated as comments and ignored. 228In addition to being specified by IP address, hosts may also be 229specified by their hostname. 230When the resolver is called to add a hostname to a table, 231.Em all 232resulting IPv4 and IPv6 addresses are placed into the table. 233IP addresses can also be entered in a table by specifying a valid interface 234name, a valid interface group or the 235.Em self 236keyword, in which case all addresses assigned to the interface(s) will be 237added to the table. 238.Sh OPTIONS 239.Xr pf 4 240may be tuned for various situations using the 241.Ar set 242command. 243.Bl -tag -width xxxx 244.It Ar set timeout 245.Pp 246.Bl -tag -width "src.track" -compact 247.It Ar interval 248Interval between purging expired states and fragments. 249.It Ar frag 250Seconds before an unassembled fragment is expired. 251.It Ar src.track 252Length of time to retain a source tracking entry after the last state 253expires. 254.El 255.Pp 256When a packet matches a stateful connection, the seconds to live for the 257connection will be updated to that of the 258.Ar proto.modifier 259which corresponds to the connection state. 260Each packet which matches this state will reset the TTL. 261Tuning these values may improve the performance of the 262firewall at the risk of dropping valid idle connections. 263.Pp 264.Bl -tag -width xxxx -compact 265.It Ar tcp.first 266The state after the first packet. 267.It Ar tcp.opening 268The state before the destination host ever sends a packet. 269.It Ar tcp.established 270The fully established state. 271.It Ar tcp.closing 272The state after the first FIN has been sent. 273.It Ar tcp.finwait 274The state after both FINs have been exchanged and the connection is closed. 275Some hosts (notably web servers on Solaris) send TCP packets even after closing 276the connection. 277Increasing 278.Ar tcp.finwait 279(and possibly 280.Ar tcp.closing ) 281can prevent blocking of such packets. 282.It Ar tcp.closed 283The state after one endpoint sends an RST. 284.El 285.Pp 286SCTP timeout are handled similar to TCP, but with its own set of states: 287.Pp 288.Bl -tag -width xxxx -compact 289.It Ar sctp.first 290The state after the first packet. 291.It Ar sctp.opening 292The state before the destination host ever sends a packet. 293.It Ar sctp.established 294The fully established state. 295.It Ar sctp.closing 296The state after the first SHUTDOWN chunk has been sent. 297.It Ar sctp.closed 298The state after SHUTDOWN_ACK has been exchanged and the connection is closed. 299.El 300.Pp 301ICMP and UDP are handled in a fashion similar to TCP, but with a much more 302limited set of states: 303.Pp 304.Bl -tag -width xxxx -compact 305.It Ar udp.first 306The state after the first packet. 307.It Ar udp.single 308The state if the source host sends more than one packet but the destination 309host has never sent one back. 310.It Ar udp.multiple 311The state if both hosts have sent packets. 312.It Ar icmp.first 313The state after the first packet. 314.It Ar icmp.error 315The state after an ICMP error came back in response to an ICMP packet. 316.El 317.Pp 318Other protocols are handled similarly to UDP: 319.Pp 320.Bl -tag -width xxxx -compact 321.It Ar other.first 322.It Ar other.single 323.It Ar other.multiple 324.El 325.Pp 326Timeout values can be reduced adaptively as the number of state table 327entries grows. 328.Pp 329.Bl -tag -width xxxx -compact 330.It Ar adaptive.start 331When the number of state entries exceeds this value, adaptive scaling 332begins. 333All timeout values are scaled linearly with factor 334(adaptive.end - number of states) / (adaptive.end - adaptive.start). 335.It Ar adaptive.end 336When reaching this number of state entries, all timeout values become 337zero, effectively purging all state entries immediately. 338This value is used to define the scale factor, it should not actually 339be reached (set a lower state limit, see below). 340.El 341.Pp 342Adaptive timeouts are enabled by default, with an adaptive.start value 343equal to 60% of the state limit, and an adaptive.end value equal to 344120% of the state limit. 345They can be disabled by setting both adaptive.start and adaptive.end to 0. 346.Pp 347The adaptive timeout values can be defined both globally and for each rule. 348When used on a per-rule basis, the values relate to the number of 349states created by the rule, otherwise to the total number of 350states. 351.Pp 352For example: 353.Bd -literal -offset indent 354set timeout tcp.first 120 355set timeout tcp.established 86400 356set timeout { adaptive.start 6000, adaptive.end 12000 } 357set limit states 10000 358.Ed 359.Pp 360With 9000 state table entries, the timeout values are scaled to 50% 361(tcp.first 60, tcp.established 43200). 362.It Ar set loginterface 363Enable collection of packet and byte count statistics for the given 364interface or interface group. 365These statistics can be viewed using 366.Bd -literal -offset indent 367# pfctl -s info 368.Ed 369.Pp 370In this example 371.Xr pf 4 372collects statistics on the interface named dc0: 373.Bd -literal -offset indent 374set loginterface dc0 375.Ed 376.Pp 377One can disable the loginterface using: 378.Bd -literal -offset indent 379set loginterface none 380.Ed 381.It Ar set limit 382Sets hard limits on the memory pools used by the packet filter. 383See 384.Xr zone 9 385for an explanation of memory pools. 386.Pp 387For example, 388.Bd -literal -offset indent 389set limit states 20000 390.Ed 391.Pp 392sets the maximum number of entries in the memory pool used by state table 393entries (generated by 394.Ar pass 395rules which do not specify 396.Ar no state ) 397to 20000. 398Using 399.Bd -literal -offset indent 400set limit frags 20000 401.Ed 402.Pp 403sets the maximum number of entries in the memory pool used for fragment 404reassembly (generated by the 405.Ar set reassemble 406option or 407.Ar scrub 408rules) to 20000. 409Using 410.Bd -literal -offset indent 411set limit src-nodes 2000 412.Ed 413.Pp 414sets the maximum number of entries in the memory pool used for tracking 415source IP addresses (generated by the 416.Ar sticky-address 417and 418.Ar src.track 419options) to 2000. 420Using 421.Bd -literal -offset indent 422set limit tables 1000 423set limit table-entries 100000 424.Ed 425.Pp 426sets limits on the memory pools used by tables. 427The first limits the number of tables that can exist to 1000. 428The second limits the overall number of addresses that can be stored 429in tables to 100000. 430.Pp 431Various limits can be combined on a single line: 432.Bd -literal -offset indent 433set limit { states 20000, frags 20000, src-nodes 2000 } 434.Ed 435.It Ar set ruleset-optimization 436.Bl -tag -width xxxxxxxx -compact 437.It Ar none 438Disable the ruleset optimizer. 439.It Ar basic 440Enable basic ruleset optimization. 441This is the default behaviour. 442Basic ruleset optimization does four things to improve the 443performance of ruleset evaluations: 444.Pp 445.Bl -enum -compact 446.It 447remove duplicate rules 448.It 449remove rules that are a subset of another rule 450.It 451combine multiple rules into a table when advantageous 452.It 453re-order the rules to improve evaluation performance 454.El 455.Pp 456.It Ar profile 457Uses the currently loaded ruleset as a feedback profile to tailor the 458ordering of quick rules to actual network traffic. 459.El 460.Pp 461It is important to note that the ruleset optimizer will modify the ruleset 462to improve performance. 463A side effect of the ruleset modification is that per-rule accounting 464statistics will have different meanings than before. 465If per-rule accounting is important for billing purposes or whatnot, 466either the ruleset optimizer should not be used or a label field should 467be added to all of the accounting rules to act as optimization barriers. 468.Pp 469Optimization can also be set as a command-line argument to 470.Xr pfctl 8 , 471overriding the settings in 472.Nm . 473.It Ar set optimization 474Optimize state timeouts for one of the following network environments: 475.Pp 476.Bl -tag -width xxxx -compact 477.It Ar normal 478A normal network environment. 479Suitable for almost all networks. 480.It Ar high-latency 481A high-latency environment (such as a satellite connection). 482.It Ar satellite 483Alias for 484.Ar high-latency . 485.It Ar aggressive 486Aggressively expire connections. 487This can greatly reduce the memory usage of the firewall at the cost of 488dropping idle connections early. 489.It Ar conservative 490Extremely conservative settings. 491Avoid dropping legitimate connections at the 492expense of greater memory utilization (possibly much greater on a busy 493network) and slightly increased processor utilization. 494.El 495.Pp 496For example: 497.Bd -literal -offset indent 498set optimization aggressive 499.Ed 500.It Ar set reassemble yes | no Op Cm no-df 501The 502.Cm reassemble 503option is used to enable or disable the reassembly of fragmented packets, 504and can be set to 505.Cm yes 506or 507.Cm no . 508If 509.Cm no-df 510is also specified, fragments with the 511.Dq dont-fragment 512bit set are reassembled too, 513instead of being dropped; 514the reassembled packet will have the 515.Dq dont-fragment 516bit cleared. 517The default value is 518.Cm no . 519.Pp 520This option is ignored if there are pre-FreeBSD 14 521.Cm scrub 522rules present. 523.It Ar set block-policy 524The 525.Ar block-policy 526option sets the default behaviour for the packet 527.Ar block 528action: 529.Pp 530.Bl -tag -width xxxxxxxx -compact 531.It Ar drop 532Packet is silently dropped. 533.It Ar return 534A TCP RST is returned for blocked TCP packets, 535an SCTP ABORT chunk is returned for blocked SCTP packets, 536an ICMP UNREACHABLE is returned for blocked UDP packets, 537and all other packets are silently dropped. 538.El 539.Pp 540For example: 541.Bd -literal -offset indent 542set block-policy return 543.Ed 544.It Ar set fail-policy 545The 546.Ar fail-policy 547option sets the behaviour of rules which should pass a packet but were 548unable to do so. 549This might happen when a nat or route-to rule uses an empty table as list 550of targets or if a rule fails to create state or source node. 551The following 552.Ar block 553actions are possible: 554.Pp 555.Bl -tag -width xxxxxxxx -compact 556.It Ar drop 557Incoming packet is silently dropped. 558.It Ar return 559Incoming packet is dropped and TCP RST is returned for TCP packets, 560an SCTP ABORT chunk is returned for blocked SCTP packets, 561an ICMP UNREACHABLE is returned for UDP packets, 562and no response is sent for other packets. 563.El 564.Pp 565For example: 566.Bd -literal -offset indent 567set fail-policy return 568.Ed 569.It Ar set state-policy 570The 571.Ar state-policy 572option sets the default behaviour for states: 573.Pp 574.Bl -tag -width group-bound -compact 575.It Ar if-bound 576States are bound to interface. 577.It Ar floating 578States can match packets on any interfaces (the default). 579.El 580.Pp 581For example: 582.Bd -literal -offset indent 583set state-policy if-bound 584.Ed 585.It Ar set syncookies never | always | adaptive 586When 587.Cm syncookies 588are active, pf will answer each incoming TCP SYN with a syncookie SYNACK, 589without allocating any resources. 590Upon reception of the client's ACK in response to the syncookie 591SYNACK, pf will evaluate the ruleset and create state if the ruleset 592permits it, complete the three way handshake with the target host and 593continue the connection with synproxy in place. 594This allows pf to be resilient against large synflood attacks which would 595run the state table against its limits otherwise. 596Due to the blind answers to every incoming SYN syncookies share the caveats of 597synproxy, namely seemingly accepting connections that will be dropped later on. 598.Pp 599.Bl -tag -width adaptive -compact 600.It Cm never 601pf will never send syncookie SYNACKs (the default). 602.It Cm always 603pf will always send syncookie SYNACKs. 604.It Cm adaptive 605pf will enable syncookie mode when a given percentage of the state table 606is used up by half-open TCP connections, as in, those that saw the initial 607SYN but didn't finish the three way handshake. 608The thresholds for entering and leaving syncookie mode can be specified using 609.Bd -literal -offset indent 610set syncookies adaptive (start 25%, end 12%) 611.Ed 612.El 613.It Ar set state-defaults 614The 615.Ar state-defaults 616option sets the state options for states created from rules 617without an explicit 618.Ar keep state . 619For example: 620.Bd -literal -offset indent 621set state-defaults no-sync 622.Ed 623.It Ar set hostid 624The 32-bit 625.Ar hostid 626identifies this firewall's state table entries to other firewalls 627in a 628.Xr pfsync 4 629failover cluster. 630By default the hostid is set to a pseudo-random value, however it may be 631desirable to manually configure it, for example to more easily identify the 632source of state table entries. 633.Bd -literal -offset indent 634set hostid 1 635.Ed 636.Pp 637The hostid may be specified in either decimal or hexadecimal. 638.It Ar set require-order 639By default 640.Xr pfctl 8 641enforces an ordering of the statement types in the ruleset to: 642.Em options , 643.Em normalization , 644.Em queueing , 645.Em translation , 646.Em filtering . 647Setting this option to 648.Ar no 649disables this enforcement. 650There may be non-trivial and non-obvious implications to an out of 651order ruleset. 652Consider carefully before disabling the order enforcement. 653.It Ar set fingerprints 654Load fingerprints of known operating systems from the given filename. 655By default fingerprints of known operating systems are automatically 656loaded from 657.Xr pf.os 5 658in 659.Pa /etc 660but can be overridden via this option. 661Setting this option may leave a small period of time where the fingerprints 662referenced by the currently active ruleset are inconsistent until the new 663ruleset finishes loading. 664.Pp 665For example: 666.Pp 667.Dl set fingerprints \&"/etc/pf.os.devel\&" 668.It Ar set skip on Aq Ar ifspec 669List interfaces for which packets should not be filtered. 670Packets passing in or out on such interfaces are passed as if pf was 671disabled, i.e. pf does not process them in any way. 672This can be useful on loopback and other virtual interfaces, when 673packet filtering is not desired and can have unexpected effects. 674For example: 675.Pp 676.Dl set skip on lo0 677.It Ar set debug 678Set the debug 679.Ar level 680to one of the following: 681.Pp 682.Bl -tag -width xxxxxxxxxxxx -compact 683.It Ar none 684Don't generate debug messages. 685.It Ar urgent 686Generate debug messages only for serious errors. 687.It Ar misc 688Generate debug messages for various errors. 689.It Ar loud 690Generate debug messages for common conditions. 691.El 692.It Ar set keepcounters 693Preserve rule counters across rule updates. 694Usually rule counters are reset to zero on every update of the ruleset. 695With 696.Ar keepcounters 697set pf will attempt to find matching rules between old and new rulesets 698and preserve the rule counters. 699.El 700.Sh ETHERNET FILTERING 701.Xr pf 4 702has the ability to 703.Ar block 704and 705.Ar pass 706packets based on attributes of their Ethernet (layer 2) header. 707.Pp 708For each packet processed by the packet filter, the filter rules are 709evaluated in sequential order, from first to last. 710The last matching rule decides what action is taken. 711If no rule matches the packet, the default action is to pass 712the packet. 713.Pp 714The following actions can be used in the filter: 715.Bl -tag -width xxxx 716.It Ar block 717The packet is blocked. 718Unlike for layer 3 traffic the packet is always silently dropped. 719.It Ar pass 720The packet is passed; 721no state is created for layer 2 traffic. 722.El 723.Sh PARAMETERS 724The rule parameters specify the packets to which a rule applies. 725A packet always comes in on, or goes out through, one interface. 726Most parameters are optional. 727If a parameter is specified, the rule only applies to packets with 728matching attributes. 729Certain parameters can be expressed as lists, in which case 730.Xr pfctl 8 731generates all needed rule combinations. 732.Bl -tag -width xxxx 733.It Ar in No or Ar out 734This rule applies to incoming or outgoing packets. 735If neither 736.Ar in 737nor 738.Ar out 739are specified, the rule will match packets in both directions. 740.It Ar quick 741If a packet matches a rule which has the 742.Ar quick 743option set, this rule 744is considered the last matching rule, and evaluation of subsequent rules 745is skipped. 746.It Ar on Aq Ar ifspec 747This rule applies only to packets coming in on, or going out through, this 748particular interface or interface group. 749For more information on interface groups, 750see the 751.Ic group 752keyword in 753.Xr ifconfig 8 . 754.It Ar bridge-to Aq interface 755Packets matching this rule will be sent out of the specified interface without 756further processing. 757.It Ar proto Aq Ar protocol 758This rule applies only to packets of this protocol. 759Note that Ethernet protocol numbers are different from those used in 760.Xr ip 4 761and 762.Xr ip6 4 . 763.It Xo 764.Ar from Aq Ar source 765.Ar to Aq Ar dest 766.Xc 767This rule applies only to packets with the specified source and destination 768MAC addresses. 769.It Xo Ar queue Aq Ar queue 770.Xc 771Packets matching this rule will be assigned to the specified queue. 772See 773.Sx QUEUEING 774for setup details. 775.Pp 776.It Ar tag Aq Ar string 777Packets matching this rule will be tagged with the 778specified string. 779The tag acts as an internal marker that can be used to 780identify these packets later on. 781This can be used, for example, to provide trust between 782interfaces and to determine if packets have been 783processed by translation rules. 784Tags are 785.Qq sticky , 786meaning that the packet will be tagged even if the rule 787is not the last matching rule. 788Further matching rules can replace the tag with a 789new one but will not remove a previously applied tag. 790A packet is only ever assigned one tag at a time. 791.It Ar tagged Aq Ar string 792Used to specify that packets must already be tagged with the given tag in order 793to match the rule. 794Inverse tag matching can also be done by specifying the ! operator before the 795tagged keyword. 796.El 797.Sh TRAFFIC NORMALIZATION 798Traffic normalization is a broad umbrella term 799for aspects of the packet filter which deal with 800verifying packets, packet fragments, spoofed traffic, 801and other irregularities. 802.Ss Scrub 803Scrub involves sanitising packet content in such a way 804that there are no ambiguities in packet interpretation on the receiving side. 805It is invoked with the 806.Cm scrub 807option, added to filter rules. 808.Pp 809Parameters are specified enclosed in parentheses. 810At least one of the following parameters must be specified: 811.Bl -tag -width xxxx 812.It Ar no-df 813Clears the 814.Ar dont-fragment 815bit from a matching IP packet. 816Some operating systems are known to generate fragmented packets with the 817.Ar dont-fragment 818bit set. 819This is particularly true with NFS. 820.Ar Scrub 821will drop such fragmented 822.Ar dont-fragment 823packets unless 824.Ar no-df 825is specified. 826.Pp 827Unfortunately some operating systems also generate their 828.Ar dont-fragment 829packets with a zero IP identification field. 830Clearing the 831.Ar dont-fragment 832bit on packets with a zero IP ID may cause deleterious results if an 833upstream router later fragments the packet. 834Using the 835.Ar random-id 836modifier (see below) is recommended in combination with the 837.Ar no-df 838modifier to ensure unique IP identifiers. 839.It Ar min-ttl Aq Ar number 840Enforces a minimum TTL for matching IP packets. 841.It Ar max-mss Aq Ar number 842Enforces a maximum MSS for matching TCP packets. 843.It Xo Ar set-tos Aq Ar string 844.No \*(Ba Aq Ar number 845.Xc 846Enforces a 847.Em TOS 848for matching IP packets. 849.Em TOS 850may be 851given as one of 852.Ar critical , 853.Ar inetcontrol , 854.Ar lowdelay , 855.Ar netcontrol , 856.Ar throughput , 857.Ar reliability , 858or one of the DiffServ Code Points: 859.Ar ef , 860.Ar va , 861.Ar af11 No ... Ar af43 , 862.Ar cs0 No ... Ar cs7 ; 863or as either hex or decimal. 864.It Ar random-id 865Replaces the IP identification field with random values to compensate 866for predictable values generated by many hosts. 867This option only applies to packets that are not fragmented 868after the optional fragment reassembly. 869.It Ar reassemble tcp 870Statefully normalizes TCP connections. 871.Ar reassemble tcp 872performs the following normalizations: 873.Pp 874.Bl -tag -width timeout -compact 875.It ttl 876Neither side of the connection is allowed to reduce their IP TTL. 877An attacker may send a packet such that it reaches the firewall, affects 878the firewall state, and expires before reaching the destination host. 879.Ar reassemble tcp 880will raise the TTL of all packets back up to the highest value seen on 881the connection. 882.It timestamp modulation 883Modern TCP stacks will send a timestamp on every TCP packet and echo 884the other endpoint's timestamp back to them. 885Many operating systems will merely start the timestamp at zero when 886first booted, and increment it several times a second. 887The uptime of the host can be deduced by reading the timestamp and multiplying 888by a constant. 889Also observing several different timestamps can be used to count hosts 890behind a NAT device. 891And spoofing TCP packets into a connection requires knowing or guessing 892valid timestamps. 893Timestamps merely need to be monotonically increasing and not derived off a 894guessable base time. 895.Ar reassemble tcp 896will cause 897.Ar scrub 898to modulate the TCP timestamps with a random number. 899.It extended PAWS checks 900There is a problem with TCP on long fat pipes, in that a packet might get 901delayed for longer than it takes the connection to wrap its 32-bit sequence 902space. 903In such an occurrence, the old packet would be indistinguishable from a 904new packet and would be accepted as such. 905The solution to this is called PAWS: Protection Against Wrapped Sequence 906numbers. 907It protects against it by making sure the timestamp on each packet does 908not go backwards. 909.Ar reassemble tcp 910also makes sure the timestamp on the packet does not go forward more 911than the RFC allows. 912By doing this, 913.Xr pf 4 914artificially extends the security of TCP sequence numbers by 10 to 18 915bits when the host uses appropriately randomized timestamps, since a 916blind attacker would have to guess the timestamp as well. 917.El 918.El 919.Pp 920For example, 921.Bd -literal -offset indent 922match in all scrub (no-df random-id max-mss 1440) 923.Ed 924.Ss Scrub ruleset (pre-FreeBSD 14) 925In order to maintain compatibility with older releases of FreeBSD 926.Ar scrub 927rules can also be specified in their own ruleset. 928In such case they are invoked with the 929.Ar scrub 930directive. 931If there are such rules present they determine packet reassembly behaviour. 932When no such rules are present the option 933.Ar set reassembly 934takes precedence. 935The 936.Ar scrub 937rules can take all parameters specified above for a 938.Ar scrub 939option of filter rules and 2 more parameters controlling fragment reassembly: 940.Bl -tag -width xxxx 941.It Ar fragment reassemble 942Using 943.Ar scrub 944rules, fragments can be reassembled by normalization. 945In this case, fragments are buffered until they form a complete 946packet, and only the completed packet is passed on to the filter. 947The advantage is that filter rules have to deal only with complete 948packets, and can ignore fragments. 949The drawback of caching fragments is the additional memory cost. 950This is the default behaviour unless no fragment reassemble is specified. 951.It Ar no fragment reassemble 952Do not reassemble fragments. 953.El 954.Pp 955For example, 956.Bd -literal -offset indent 957scrub in on $ext_if all fragment reassemble 958.Ed 959.Pp 960The 961.Ar no 962option prefixed to a scrub rule causes matching packets to remain unscrubbed, 963much in the same way as 964.Ar drop quick 965works in the packet filter (see below). 966This mechanism should be used when it is necessary to exclude specific packets 967from broader scrub rules. 968.Pp 969.Ar scrub 970rules in the 971.Ar scrub 972ruleset are evaluated for every packet before stateful filtering. 973This means excessive usage of them will cause performance penalty. 974.Ar scrub reassemble tcp 975rules must not have the direction (in/out) specified. 976.Sh QUEUEING with ALTQ 977The ALTQ system is currently not available in the GENERIC kernel nor as 978loadable modules. 979In order to use the herein after called queueing options one has to use a 980custom built kernel. 981Please refer to 982.Xr altq 4 983to learn about the related kernel options. 984.Pp 985Packets can be assigned to queues for the purpose of bandwidth 986control. 987At least two declarations are required to configure queues, and later 988any packet filtering rule can reference the defined queues by name. 989During the filtering component of 990.Nm pf.conf , 991the last referenced 992.Ar queue 993name is where any packets from 994.Ar pass 995rules will be queued, while for 996.Ar block 997rules it specifies where any resulting ICMP or TCP RST 998packets should be queued. 999The 1000.Ar scheduler 1001defines the algorithm used to decide which packets get delayed, dropped, or 1002sent out immediately. 1003There are three 1004.Ar schedulers 1005currently supported. 1006.Bl -tag -width xxxx 1007.It Ar cbq 1008Class Based Queueing. 1009.Ar Queues 1010attached to an interface build a tree, thus each 1011.Ar queue 1012can have further child 1013.Ar queues . 1014Each queue can have a 1015.Ar priority 1016and a 1017.Ar bandwidth 1018assigned. 1019.Ar Priority 1020mainly controls the time packets take to get sent out, while 1021.Ar bandwidth 1022has primarily effects on throughput. 1023.Ar cbq 1024achieves both partitioning and sharing of link bandwidth 1025by hierarchically structured classes. 1026Each class has its own 1027.Ar queue 1028and is assigned its share of 1029.Ar bandwidth . 1030A child class can borrow bandwidth from its parent class 1031as long as excess bandwidth is available 1032(see the option 1033.Ar borrow , 1034below). 1035.It Ar priq 1036Priority Queueing. 1037.Ar Queues 1038are flat attached to the interface, thus, 1039.Ar queues 1040cannot have further child 1041.Ar queues . 1042Each 1043.Ar queue 1044has a unique 1045.Ar priority 1046assigned, ranging from 0 to 15. 1047Packets in the 1048.Ar queue 1049with the highest 1050.Ar priority 1051are processed first. 1052.It Ar hfsc 1053Hierarchical Fair Service Curve. 1054.Ar Queues 1055attached to an interface build a tree, thus each 1056.Ar queue 1057can have further child 1058.Ar queues . 1059Each queue can have a 1060.Ar priority 1061and a 1062.Ar bandwidth 1063assigned. 1064.Ar Priority 1065mainly controls the time packets take to get sent out, while 1066.Ar bandwidth 1067primarily affects throughput. 1068.Ar hfsc 1069supports both link-sharing and guaranteed real-time services. 1070It employs a service curve based QoS model, 1071and its unique feature is an ability to decouple 1072.Ar delay 1073and 1074.Ar bandwidth 1075allocation. 1076.El 1077.Pp 1078The interfaces on which queueing should be activated are declared using 1079the 1080.Ar altq on 1081declaration. 1082.Ar altq on 1083has the following keywords: 1084.Bl -tag -width xxxx 1085.It Aq Ar interface 1086Queueing is enabled on the named interface. 1087.It Aq Ar scheduler 1088Specifies which queueing scheduler to use. 1089Currently supported values 1090are 1091.Ar cbq 1092for Class Based Queueing, 1093.Ar priq 1094for Priority Queueing and 1095.Ar hfsc 1096for the Hierarchical Fair Service Curve scheduler. 1097.It Ar bandwidth Aq Ar bw 1098The maximum bitrate for all queues on an 1099interface may be specified using the 1100.Ar bandwidth 1101keyword. 1102The value can be specified as an absolute value or as a 1103percentage of the interface bandwidth. 1104When using an absolute value, the suffixes 1105.Ar b , 1106.Ar Kb , 1107.Ar Mb , 1108and 1109.Ar Gb 1110are used to represent bits, kilobits, megabits, and 1111gigabits per second, respectively. 1112The value must not exceed the interface bandwidth. 1113If 1114.Ar bandwidth 1115is not specified, the interface bandwidth is used 1116(but take note that some interfaces do not know their bandwidth, 1117or can adapt their bandwidth rates). 1118.It Ar qlimit Aq Ar limit 1119The maximum number of packets held in the queue. 1120The default is 50. 1121.It Ar tbrsize Aq Ar size 1122Adjusts the size, in bytes, of the token bucket regulator. 1123If not specified, heuristics based on the 1124interface bandwidth are used to determine the size. 1125.It Ar queue Aq Ar list 1126Defines a list of subqueues to create on an interface. 1127.El 1128.Pp 1129In the following example, the interface dc0 1130should queue up to 5Mbps in four second-level queues using 1131Class Based Queueing. 1132Those four queues will be shown in a later example. 1133.Bd -literal -offset indent 1134altq on dc0 cbq bandwidth 5Mb queue { std, http, mail, ssh } 1135.Ed 1136.Pp 1137Once interfaces are activated for queueing using the 1138.Ar altq 1139directive, a sequence of 1140.Ar queue 1141directives may be defined. 1142The name associated with a 1143.Ar queue 1144must match a queue defined in the 1145.Ar altq 1146directive (e.g. mail), or, except for the 1147.Ar priq 1148.Ar scheduler , 1149in a parent 1150.Ar queue 1151declaration. 1152The following keywords can be used: 1153.Bl -tag -width xxxx 1154.It Ar on Aq Ar interface 1155Specifies the interface the queue operates on. 1156If not given, it operates on all matching interfaces. 1157.It Ar bandwidth Aq Ar bw 1158Specifies the maximum bitrate to be processed by the queue. 1159This value must not exceed the value of the parent 1160.Ar queue 1161and can be specified as an absolute value or a percentage of the parent 1162queue's bandwidth. 1163If not specified, defaults to 100% of the parent queue's bandwidth. 1164The 1165.Ar priq 1166scheduler does not support bandwidth specification. 1167.It Ar priority Aq Ar level 1168Between queues a priority level can be set. 1169For 1170.Ar cbq 1171and 1172.Ar hfsc , 1173the range is 0 to 7 and for 1174.Ar priq , 1175the range is 0 to 15. 1176The default for all is 1. 1177.Ar Priq 1178queues with a higher priority are always served first. 1179.Ar Cbq 1180and 1181.Ar Hfsc 1182queues with a higher priority are preferred in the case of overload. 1183.It Ar qlimit Aq Ar limit 1184The maximum number of packets held in the queue. 1185The default is 50. 1186.El 1187.Pp 1188The 1189.Ar scheduler 1190can get additional parameters with 1191.Xo Aq Ar scheduler 1192.Pf ( Aq Ar parameters ) . 1193.Xc 1194Parameters are as follows: 1195.Bl -tag -width Fl 1196.It Ar default 1197Packets not matched by another queue are assigned to this one. 1198Exactly one default queue is required. 1199.It Ar red 1200Enable RED (Random Early Detection) on this queue. 1201RED drops packets with a probability proportional to the average 1202queue length. 1203.It Ar rio 1204Enables RIO on this queue. 1205RIO is RED with IN/OUT, thus running 1206RED two times more than RIO would achieve the same effect. 1207RIO is currently not supported in the GENERIC kernel. 1208.It Ar ecn 1209Enables ECN (Explicit Congestion Notification) on this queue. 1210ECN implies RED. 1211.El 1212.Pp 1213The 1214.Ar cbq 1215.Ar scheduler 1216supports an additional option: 1217.Bl -tag -width Fl 1218.It Ar borrow 1219The queue can borrow bandwidth from the parent. 1220.El 1221.Pp 1222The 1223.Ar hfsc 1224.Ar scheduler 1225supports some additional options: 1226.Bl -tag -width Fl 1227.It Ar realtime Aq Ar sc 1228The minimum required bandwidth for the queue. 1229.It Ar upperlimit Aq Ar sc 1230The maximum allowed bandwidth for the queue. 1231.It Ar linkshare Aq Ar sc 1232The bandwidth share of a backlogged queue. 1233.El 1234.Pp 1235.Aq Ar sc 1236is an acronym for 1237.Ar service curve . 1238.Pp 1239The format for service curve specifications is 1240.Ar ( m1 , d , m2 ) . 1241.Ar m2 1242controls the bandwidth assigned to the queue. 1243.Ar m1 1244and 1245.Ar d 1246are optional and can be used to control the initial bandwidth assignment. 1247For the first 1248.Ar d 1249milliseconds the queue gets the bandwidth given as 1250.Ar m1 , 1251afterwards the value given in 1252.Ar m2 . 1253.Pp 1254Furthermore, with 1255.Ar cbq 1256and 1257.Ar hfsc , 1258child queues can be specified as in an 1259.Ar altq 1260declaration, thus building a tree of queues using a part of 1261their parent's bandwidth. 1262.Pp 1263Packets can be assigned to queues based on filter rules by using the 1264.Ar queue 1265keyword. 1266Normally only one 1267.Ar queue 1268is specified; when a second one is specified it will instead be used for 1269packets which have a 1270.Em TOS 1271of 1272.Em lowdelay 1273and for TCP ACKs with no data payload. 1274.Pp 1275To continue the previous example, the examples below would specify the 1276four referenced 1277queues, plus a few child queues. 1278Interactive 1279.Xr ssh 1 1280sessions get priority over bulk transfers like 1281.Xr scp 1 1282and 1283.Xr sftp 1 . 1284The queues may then be referenced by filtering rules (see 1285.Sx PACKET FILTERING 1286below). 1287.Bd -literal 1288queue std bandwidth 10% cbq(default) 1289queue http bandwidth 60% priority 2 cbq(borrow red) \e 1290 { employees, developers } 1291queue developers bandwidth 75% cbq(borrow) 1292queue employees bandwidth 15% 1293queue mail bandwidth 10% priority 0 cbq(borrow ecn) 1294queue ssh bandwidth 20% cbq(borrow) { ssh_interactive, ssh_bulk } 1295queue ssh_interactive bandwidth 50% priority 7 cbq(borrow) 1296queue ssh_bulk bandwidth 50% priority 0 cbq(borrow) 1297 1298block return out on dc0 inet all queue std 1299pass out on dc0 inet proto tcp from $developerhosts to any port 80 \e 1300 queue developers 1301pass out on dc0 inet proto tcp from $employeehosts to any port 80 \e 1302 queue employees 1303pass out on dc0 inet proto tcp from any to any port 22 \e 1304 queue(ssh_bulk, ssh_interactive) 1305pass out on dc0 inet proto tcp from any to any port 25 \e 1306 queue mail 1307.Ed 1308.Sh QUEUEING with dummynet 1309Queueing can also be done with 1310.Xr dummynet 4 . 1311Queues and pipes can be created with 1312.Xr dnctl 8 . 1313.Pp 1314Packets can be assigned to queues and pipes using 1315.Ar dnqueue 1316and 1317.Ar dnpipe 1318respectively. 1319.Pp 1320Both 1321.Ar dnqueue 1322and 1323.Ar dnpipe 1324take either a single pipe or queue number or two numbers as arguments. 1325The first pipe or queue number will be used to shape the traffic in the rule 1326direction, the second will be used to shape the traffic in the reverse 1327direction. 1328If the rule does not specify a direction the first packet to create state will 1329be shaped according to the first number, and the response traffic according to 1330the second. 1331.Pp 1332If the 1333.Xr dummynet 4 1334module is not loaded any traffic sent into a queue or pipe will be dropped. 1335.Sh TRANSLATION 1336Translation rules modify either the source or destination address of the 1337packets associated with a stateful connection. 1338A stateful connection is automatically created to track packets matching 1339such a rule as long as they are not blocked by the filtering section of 1340.Nm pf.conf . 1341The translation engine modifies the specified address and/or port in the 1342packet, recalculates IP, TCP and UDP checksums as necessary, and passes 1343it to the packet filter for evaluation. 1344.Pp 1345Since translation occurs before filtering the filter 1346engine will see packets as they look after any 1347addresses and ports have been translated. 1348Filter rules will therefore have to filter based on the translated 1349address and port number. 1350Packets that match a translation rule are only automatically passed if 1351the 1352.Ar pass 1353modifier is given, otherwise they are 1354still subject to 1355.Ar block 1356and 1357.Ar pass 1358rules. 1359.Pp 1360The state entry created permits 1361.Xr pf 4 1362to keep track of the original address for traffic associated with that state 1363and correctly direct return traffic for that connection. 1364.Pp 1365Various types of translation are possible with pf: 1366.Bl -tag -width xxxx 1367.It Ar binat 1368A 1369.Ar binat 1370rule specifies a bidirectional mapping between an external IP netblock 1371and an internal IP netblock. 1372.It Ar nat 1373A 1374.Ar nat 1375rule specifies that IP addresses are to be changed as the packet 1376traverses the given interface. 1377This technique allows one or more IP addresses 1378on the translating host to support network traffic for a larger range of 1379machines on an "inside" network. 1380Although in theory any IP address can be used on the inside, it is strongly 1381recommended that one of the address ranges defined by RFC 1918 be used. 1382These netblocks are: 1383.Bd -literal 138410.0.0.0 - 10.255.255.255 (all of net 10, i.e., 10/8) 1385172.16.0.0 - 172.31.255.255 (i.e., 172.16/12) 1386192.168.0.0 - 192.168.255.255 (i.e., 192.168/16) 1387.Ed 1388.It Pa rdr 1389The packet is redirected to another destination and possibly a 1390different port. 1391.Ar rdr 1392rules can optionally specify port ranges instead of single ports. 1393rdr ... port 2000:2999 -\*(Gt ... port 4000 1394redirects ports 2000 to 2999 (inclusive) to port 4000. 1395rdr ... port 2000:2999 -\*(Gt ... port 4000:* 1396redirects port 2000 to 4000, 2001 to 4001, ..., 2999 to 4999. 1397.El 1398.Pp 1399In addition to modifying the address, some translation rules may modify 1400source or destination ports for 1401.Xr tcp 4 1402or 1403.Xr udp 4 1404connections; implicitly in the case of 1405.Ar nat 1406rules and explicitly in the case of 1407.Ar rdr 1408rules. 1409Port numbers are never translated with a 1410.Ar binat 1411rule. 1412.Pp 1413Evaluation order of the translation rules is dependent on the type 1414of the translation rules and of the direction of a packet. 1415.Ar binat 1416rules are always evaluated first. 1417Then either the 1418.Ar rdr 1419rules are evaluated on an inbound packet or the 1420.Ar nat 1421rules on an outbound packet. 1422Rules of the same type are evaluated in the same order in which they 1423appear in the ruleset. 1424The first matching rule decides what action is taken. 1425.Pp 1426The 1427.Ar no 1428option prefixed to a translation rule causes packets to remain untranslated, 1429much in the same way as 1430.Ar drop quick 1431works in the packet filter (see below). 1432If no rule matches the packet it is passed to the filter engine unmodified. 1433.Pp 1434Translation rules apply only to packets that pass through 1435the specified interface, and if no interface is specified, 1436translation is applied to packets on all interfaces. 1437For instance, redirecting port 80 on an external interface to an internal 1438web server will only work for connections originating from the outside. 1439Connections to the address of the external interface from local hosts will 1440not be redirected, since such packets do not actually pass through the 1441external interface. 1442Redirections cannot reflect packets back through the interface they arrive 1443on, they can only be redirected to hosts connected to different interfaces 1444or to the firewall itself. 1445.Pp 1446Note that redirecting external incoming connections to the loopback 1447address, as in 1448.Bd -literal -offset indent 1449rdr on ne3 inet proto tcp to port smtp -\*(Gt 127.0.0.1 port spamd 1450.Ed 1451.Pp 1452will effectively allow an external host to connect to daemons 1453bound solely to the loopback address, circumventing the traditional 1454blocking of such connections on a real interface. 1455Unless this effect is desired, any of the local non-loopback addresses 1456should be used as redirection target instead, which allows external 1457connections only to daemons bound to this address or not bound to 1458any address. 1459.Pp 1460See 1461.Sx TRANSLATION EXAMPLES 1462below. 1463.Sh PACKET FILTERING 1464.Xr pf 4 1465has the ability to 1466.Ar block 1467, 1468.Ar pass 1469and 1470.Ar match 1471packets based on attributes of their layer 3 (see 1472.Xr ip 4 1473and 1474.Xr ip6 4 ) 1475and layer 4 (see 1476.Xr icmp 4 , 1477.Xr icmp6 4 , 1478.Xr tcp 4 , 1479.Xr sctp 4 , 1480.Xr udp 4 ) 1481headers. 1482In addition, packets may also be 1483assigned to queues for the purpose of bandwidth control. 1484.Pp 1485For each packet processed by the packet filter, the filter rules are 1486evaluated in sequential order, from first to last. 1487For 1488.Ar block 1489and 1490.Ar pass 1491, the last matching rule decides what action is taken. 1492For 1493.Ar match 1494, rules are evaluated every time they match; the pass/block state of a packet 1495remains unchanged. 1496If no rule matches the packet, the default action is to pass 1497the packet. 1498.Pp 1499The following actions can be used in the filter: 1500.Bl -tag -width xxxx 1501.It Ar block 1502The packet is blocked. 1503There are a number of ways in which a 1504.Ar block 1505rule can behave when blocking a packet. 1506The default behaviour is to 1507.Ar drop 1508packets silently, however this can be overridden or made 1509explicit either globally, by setting the 1510.Ar block-policy 1511option, or on a per-rule basis with one of the following options: 1512.Pp 1513.Bl -tag -width xxxx -compact 1514.It Ar drop 1515The packet is silently dropped. 1516.It Ar return-rst 1517This applies only to 1518.Xr tcp 4 1519packets, and issues a TCP RST which closes the 1520connection. 1521.It Ar return-icmp 1522.It Ar return-icmp6 1523This causes ICMP messages to be returned for packets which match the rule. 1524By default this is an ICMP UNREACHABLE message, however this 1525can be overridden by specifying a message as a code or number. 1526.It Ar return 1527This causes a TCP RST to be returned for 1528.Xr tcp 4 1529packets, an SCTP ABORT for SCTP 1530and an ICMP UNREACHABLE for UDP and other packets. 1531.El 1532.Pp 1533Options returning ICMP packets currently have no effect if 1534.Xr pf 4 1535operates on a 1536.Xr if_bridge 4 , 1537as the code to support this feature has not yet been implemented. 1538.Pp 1539The simplest mechanism to block everything by default and only pass 1540packets that match explicit rules is specify a first filter rule of: 1541.Bd -literal -offset indent 1542block all 1543.Ed 1544.It Ar match 1545The packet is matched. 1546This mechanism is used to provide fine grained filtering without altering the 1547block/pass state of a packet. 1548.Ar match 1549rules differ from 1550.Ar block 1551and 1552.Ar pass 1553rules in that parameters are set for every rule a packet matches, not only 1554on the last matching rule. 1555For the following parameters, this means that the parameter effectively becomes 1556"sticky" until explicitly overridden: 1557.Ar queue , 1558.Ar dnpipe , 1559.Ar dnqueue , 1560.Ar rtable , 1561.Ar scrub 1562. 1563.It Ar pass 1564The packet is passed; 1565state is created unless the 1566.Ar no state 1567option is specified. 1568.El 1569.Pp 1570By default 1571.Xr pf 4 1572filters packets statefully; the first time a packet matches a 1573.Ar pass 1574rule, a state entry is created; for subsequent packets the filter checks 1575whether the packet matches any state. 1576If it does, the packet is passed without evaluation of any rules. 1577After the connection is closed or times out, the state entry is automatically 1578removed. 1579.Pp 1580This has several advantages. 1581For TCP connections, comparing a packet to a state involves checking 1582its sequence numbers, as well as TCP timestamps if a 1583.Ar scrub reassemble tcp 1584rule applies to the connection. 1585If these values are outside the narrow windows of expected 1586values, the packet is dropped. 1587This prevents spoofing attacks, such as when an attacker sends packets with 1588a fake source address/port but does not know the connection's sequence 1589numbers. 1590Similarly, 1591.Xr pf 4 1592knows how to match ICMP replies to states. 1593For example, 1594.Bd -literal -offset indent 1595pass out inet proto icmp all icmp-type echoreq 1596.Ed 1597.Pp 1598allows echo requests (such as those created by 1599.Xr ping 8 ) 1600out statefully, and matches incoming echo replies correctly to states. 1601.Pp 1602Also, looking up states is usually faster than evaluating rules. 1603If there are 50 rules, all of them are evaluated sequentially in O(n). 1604Even with 50000 states, only 16 comparisons are needed to match a 1605state, since states are stored in a binary search tree that allows 1606searches in O(log2 n). 1607.Pp 1608Furthermore, correct handling of ICMP error messages is critical to 1609many protocols, particularly TCP. 1610.Xr pf 4 1611matches ICMP error messages to the correct connection, checks them against 1612connection parameters, and passes them if appropriate. 1613For example if an ICMP source quench message referring to a stateful TCP 1614connection arrives, it will be matched to the state and get passed. 1615.Pp 1616Finally, state tracking is required for 1617.Ar nat , binat No and Ar rdr 1618rules, in order to track address and port translations and reverse the 1619translation on returning packets. 1620.Pp 1621.Xr pf 4 1622will also create state for other protocols which are effectively stateless by 1623nature. 1624UDP packets are matched to states using only host addresses and ports, 1625and other protocols are matched to states using only the host addresses. 1626.Pp 1627If stateless filtering of individual packets is desired, 1628the 1629.Ar no state 1630keyword can be used to specify that state will not be created 1631if this is the last matching rule. 1632A number of parameters can also be set to affect how 1633.Xr pf 4 1634handles state tracking. 1635See 1636.Sx STATEFUL TRACKING OPTIONS 1637below for further details. 1638.Sh PARAMETERS 1639The rule parameters specify the packets to which a rule applies. 1640A packet always comes in on, or goes out through, one interface. 1641Most parameters are optional. 1642If a parameter is specified, the rule only applies to packets with 1643matching attributes. 1644Certain parameters can be expressed as lists, in which case 1645.Xr pfctl 8 1646generates all needed rule combinations. 1647.Bl -tag -width xxxx 1648.It Ar in No or Ar out 1649This rule applies to incoming or outgoing packets. 1650If neither 1651.Ar in 1652nor 1653.Ar out 1654are specified, the rule will match packets in both directions. 1655.It Ar log 1656In addition to the action specified, a log message is generated. 1657Only the packet that establishes the state is logged, 1658unless the 1659.Ar no state 1660option is specified. 1661The logged packets are sent to a 1662.Xr pflog 4 1663interface, by default 1664.Ar pflog0 . 1665This interface is monitored by the 1666.Xr pflogd 8 1667logging daemon, which dumps the logged packets to the file 1668.Pa /var/log/pflog 1669in 1670.Xr pcap 3 1671binary format. 1672.It Ar log (all) 1673Used to force logging of all packets for a connection. 1674This is not necessary when 1675.Ar no state 1676is explicitly specified. 1677As with 1678.Ar log , 1679packets are logged to 1680.Xr pflog 4 . 1681.It Ar log (user) 1682Logs the 1683.Ux 1684user ID of the user that owns the socket and the PID of the process that 1685has the socket open where the packet is sourced from or destined to 1686(depending on which socket is local). 1687This is in addition to the normal information logged. 1688.Pp 1689Only the first packet 1690logged via 1691.Ar log (all, user) 1692will have the user credentials logged when using stateful matching. 1693.It Ar log (to Aq Ar interface ) 1694Send logs to the specified 1695.Xr pflog 4 1696interface instead of 1697.Ar pflog0 . 1698.It Ar quick 1699If a packet matches a rule which has the 1700.Ar quick 1701option set, this rule 1702is considered the last matching rule, and evaluation of subsequent rules 1703is skipped. 1704.It Ar on Aq Ar interface 1705This rule applies only to packets coming in on, or going out through, this 1706particular interface or interface group. 1707For more information on interface groups, 1708see the 1709.Ic group 1710keyword in 1711.Xr ifconfig 8 . 1712.It Aq Ar af 1713This rule applies only to packets of this address family. 1714Supported values are 1715.Ar inet 1716and 1717.Ar inet6 . 1718.It Ar proto Aq Ar protocol 1719This rule applies only to packets of this protocol. 1720Common protocols are 1721.Xr icmp 4 , 1722.Xr icmp6 4 , 1723.Xr tcp 4 , 1724.Xr sctp 4 , 1725and 1726.Xr udp 4 . 1727For a list of all the protocol name to number mappings used by 1728.Xr pfctl 8 , 1729see the file 1730.Pa /etc/protocols . 1731.It Xo 1732.Ar from Aq Ar source 1733.Ar port Aq Ar source 1734.Ar os Aq Ar source 1735.Ar to Aq Ar dest 1736.Ar port Aq Ar dest 1737.Xc 1738This rule applies only to packets with the specified source and destination 1739addresses and ports. 1740.Pp 1741Addresses can be specified in CIDR notation (matching netblocks), as 1742symbolic host names, interface names or interface group names, or as any 1743of the following keywords: 1744.Pp 1745.Bl -tag -width xxxxxxxxxxxxxx -compact 1746.It Ar any 1747Any address. 1748.It Ar no-route 1749Any address which is not currently routable. 1750.It Ar urpf-failed 1751Any source address that fails a unicast reverse path forwarding (URPF) 1752check, i.e. packets coming in on an interface other than that which holds 1753the route back to the packet's source address. 1754.It Aq Ar table 1755Any address that matches the given table. 1756.El 1757.Pp 1758Ranges of addresses are specified by using the 1759.Sq - 1760operator. 1761For instance: 1762.Dq 10.1.1.10 - 10.1.1.12 1763means all addresses from 10.1.1.10 to 10.1.1.12, 1764hence addresses 10.1.1.10, 10.1.1.11, and 10.1.1.12. 1765.Pp 1766Interface names and interface group names can have modifiers appended: 1767.Pp 1768.Bl -tag -width xxxxxxxxxxxx -compact 1769.It Ar :network 1770Translates to the network(s) attached to the interface. 1771.It Ar :broadcast 1772Translates to the interface's broadcast address(es). 1773.It Ar :peer 1774Translates to the point-to-point interface's peer address(es). 1775.It Ar :0 1776Do not include interface aliases. 1777.El 1778.Pp 1779Host names may also have the 1780.Ar :0 1781option appended to restrict the name resolution to the first of each 1782v4 and non-link-local v6 address found. 1783.Pp 1784Host name resolution and interface to address translation are done at 1785ruleset load-time. 1786When the address of an interface (or host name) changes (under DHCP or PPP, 1787for instance), the ruleset must be reloaded for the change to be reflected 1788in the kernel. 1789Surrounding the interface name (and optional modifiers) in parentheses 1790changes this behaviour. 1791When the interface name is surrounded by parentheses, the rule is 1792automatically updated whenever the interface changes its address. 1793The ruleset does not need to be reloaded. 1794This is especially useful with 1795.Ar nat . 1796.Pp 1797Ports can be specified either by number or by name. 1798For example, port 80 can be specified as 1799.Em www . 1800For a list of all port name to number mappings used by 1801.Xr pfctl 8 , 1802see the file 1803.Pa /etc/services . 1804.Pp 1805Ports and ranges of ports are specified by using these operators: 1806.Bd -literal -offset indent 1807= (equal) 1808!= (unequal) 1809\*(Lt (less than) 1810\*(Le (less than or equal) 1811\*(Gt (greater than) 1812\*(Ge (greater than or equal) 1813: (range including boundaries) 1814\*(Gt\*(Lt (range excluding boundaries) 1815\*(Lt\*(Gt (except range) 1816.Ed 1817.Pp 1818.Sq \*(Gt\*(Lt , 1819.Sq \*(Lt\*(Gt 1820and 1821.Sq \&: 1822are binary operators (they take two arguments). 1823For instance: 1824.Bl -tag -width Fl 1825.It Ar port 2000:2004 1826means 1827.Sq all ports \*(Ge 2000 and \*(Le 2004 , 1828hence ports 2000, 2001, 2002, 2003 and 2004. 1829.It Ar port 2000 \*(Gt\*(Lt 2004 1830means 1831.Sq all ports \*(Gt 2000 and \*(Lt 2004 , 1832hence ports 2001, 2002 and 2003. 1833.It Ar port 2000 \*(Lt\*(Gt 2004 1834means 1835.Sq all ports \*(Lt 2000 or \*(Gt 2004 , 1836hence ports 1-1999 and 2005-65535. 1837.El 1838.Pp 1839The operating system of the source host can be specified in the case of TCP 1840rules with the 1841.Ar OS 1842modifier. 1843See the 1844.Sx OPERATING SYSTEM FINGERPRINTING 1845section for more information. 1846.Pp 1847The host, port and OS specifications are optional, as in the following examples: 1848.Bd -literal -offset indent 1849pass in all 1850pass in from any to any 1851pass in proto tcp from any port \*(Le 1024 to any 1852pass in proto tcp from any to any port 25 1853pass in proto tcp from 10.0.0.0/8 port \*(Gt 1024 \e 1854 to ! 10.1.2.3 port != ssh 1855pass in proto tcp from any os "OpenBSD" 1856.Ed 1857.It Ar all 1858This is equivalent to "from any to any". 1859.It Ar group Aq Ar group 1860Similar to 1861.Ar user , 1862this rule only applies to packets of sockets owned by the specified group. 1863.It Ar user Aq Ar user 1864This rule only applies to packets of sockets owned by the specified user. 1865For outgoing connections initiated from the firewall, this is the user 1866that opened the connection. 1867For incoming connections to the firewall itself, this is the user that 1868listens on the destination port. 1869For forwarded connections, where the firewall is not a connection endpoint, 1870the user and group are 1871.Em unknown . 1872.Pp 1873All packets, both outgoing and incoming, of one connection are associated 1874with the same user and group. 1875Only TCP and UDP packets can be associated with users; for other protocols 1876these parameters are ignored. 1877.Pp 1878User and group refer to the effective (as opposed to the real) IDs, in 1879case the socket is created by a setuid/setgid process. 1880User and group IDs are stored when a socket is created; 1881when a process creates a listening socket as root (for instance, by 1882binding to a privileged port) and subsequently changes to another 1883user ID (to drop privileges), the credentials will remain root. 1884.Pp 1885User and group IDs can be specified as either numbers or names. 1886The syntax is similar to the one for ports. 1887The value 1888.Em unknown 1889matches packets of forwarded connections. 1890.Em unknown 1891can only be used with the operators 1892.Cm = 1893and 1894.Cm != . 1895Other constructs like 1896.Cm user \*(Ge unknown 1897are invalid. 1898Forwarded packets with unknown user and group ID match only rules 1899that explicitly compare against 1900.Em unknown 1901with the operators 1902.Cm = 1903or 1904.Cm != . 1905For instance 1906.Cm user \*(Ge 0 1907does not match forwarded packets. 1908The following example allows only selected users to open outgoing 1909connections: 1910.Bd -literal -offset indent 1911block out proto { tcp, udp } all 1912pass out proto { tcp, udp } all user { \*(Lt 1000, dhartmei } 1913.Ed 1914.It Xo Ar flags Aq Ar a 1915.Pf / Ns Aq Ar b 1916.No \*(Ba / Ns Aq Ar b 1917.No \*(Ba any 1918.Xc 1919This rule only applies to TCP packets that have the flags 1920.Aq Ar a 1921set out of set 1922.Aq Ar b . 1923Flags not specified in 1924.Aq Ar b 1925are ignored. 1926For stateful connections, the default is 1927.Ar flags S/SA . 1928To indicate that flags should not be checked at all, specify 1929.Ar flags any . 1930The flags are: (F)IN, (S)YN, (R)ST, (P)USH, (A)CK, (U)RG, (E)CE, and C(W)R. 1931.Bl -tag -width Fl 1932.It Ar flags S/S 1933Flag SYN is set. 1934The other flags are ignored. 1935.It Ar flags S/SA 1936This is the default setting for stateful connections. 1937Out of SYN and ACK, exactly SYN may be set. 1938SYN, SYN+PSH and SYN+RST match, but SYN+ACK, ACK and ACK+RST do not. 1939This is more restrictive than the previous example. 1940.It Ar flags /SFRA 1941If the first set is not specified, it defaults to none. 1942All of SYN, FIN, RST and ACK must be unset. 1943.El 1944.Pp 1945Because 1946.Ar flags S/SA 1947is applied by default (unless 1948.Ar no state 1949is specified), only the initial SYN packet of a TCP handshake will create 1950a state for a TCP connection. 1951It is possible to be less restrictive, and allow state creation from 1952intermediate 1953.Pq non-SYN 1954packets, by specifying 1955.Ar flags any . 1956This will cause 1957.Xr pf 4 1958to synchronize to existing connections, for instance 1959if one flushes the state table. 1960However, states created from such intermediate packets may be missing 1961connection details such as the TCP window scaling factor. 1962States which modify the packet flow, such as those affected by 1963.Ar nat , binat No or Ar rdr 1964rules, 1965.Ar modulate No or Ar synproxy state 1966options, or scrubbed with 1967.Ar reassemble tcp 1968will also not be recoverable from intermediate packets. 1969Such connections will stall and time out. 1970.It Xo Ar icmp-type Aq Ar type 1971.Ar code Aq Ar code 1972.Xc 1973.It Xo Ar icmp6-type Aq Ar type 1974.Ar code Aq Ar code 1975.Xc 1976This rule only applies to ICMP or ICMPv6 packets with the specified type 1977and code. 1978Text names for ICMP types and codes are listed in 1979.Xr icmp 4 1980and 1981.Xr icmp6 4 . 1982This parameter is only valid for rules that cover protocols ICMP or 1983ICMP6. 1984The protocol and the ICMP type indicator 1985.Po 1986.Ar icmp-type 1987or 1988.Ar icmp6-type 1989.Pc 1990must match. 1991.It Xo Ar tos Aq Ar string 1992.No \*(Ba Aq Ar number 1993.Xc 1994This rule applies to packets with the specified 1995.Em TOS 1996bits set. 1997.Em TOS 1998may be 1999given as one of 2000.Ar critical , 2001.Ar inetcontrol , 2002.Ar lowdelay , 2003.Ar netcontrol , 2004.Ar throughput , 2005.Ar reliability , 2006or one of the DiffServ Code Points: 2007.Ar ef , 2008.Ar va , 2009.Ar af11 No ... Ar af43 , 2010.Ar cs0 No ... Ar cs7 ; 2011or as either hex or decimal. 2012.Pp 2013For example, the following rules are identical: 2014.Bd -literal -offset indent 2015pass all tos lowdelay 2016pass all tos 0x10 2017pass all tos 16 2018.Ed 2019.It Ar allow-opts 2020By default, IPv4 packets with IP options or IPv6 packets with routing 2021extension headers are blocked. 2022When 2023.Ar allow-opts 2024is specified for a 2025.Ar pass 2026rule, packets that pass the filter based on that rule (last matching) 2027do so even if they contain IP options or routing extension headers. 2028For packets that match state, the rule that initially created the 2029state is used. 2030The implicit 2031.Ar pass 2032rule that is used when a packet does not match any rules does not 2033allow IP options. 2034.It Ar label Aq Ar string 2035Adds a label (name) to the rule, which can be used to identify the rule. 2036For instance, 2037pfctl -s labels 2038shows per-rule statistics for rules that have labels. 2039.Pp 2040The following macros can be used in labels: 2041.Pp 2042.Bl -tag -width $srcaddr -compact -offset indent 2043.It Ar $if 2044The interface. 2045.It Ar $srcaddr 2046The source IP address. 2047.It Ar $dstaddr 2048The destination IP address. 2049.It Ar $srcport 2050The source port specification. 2051.It Ar $dstport 2052The destination port specification. 2053.It Ar $proto 2054The protocol name. 2055.It Ar $nr 2056The rule number. 2057.El 2058.Pp 2059For example: 2060.Bd -literal -offset indent 2061ips = \&"{ 1.2.3.4, 1.2.3.5 }\&" 2062pass in proto tcp from any to $ips \e 2063 port \*(Gt 1023 label \&"$dstaddr:$dstport\&" 2064.Ed 2065.Pp 2066expands to 2067.Bd -literal -offset indent 2068pass in inet proto tcp from any to 1.2.3.4 \e 2069 port \*(Gt 1023 label \&"1.2.3.4:\*(Gt1023\&" 2070pass in inet proto tcp from any to 1.2.3.5 \e 2071 port \*(Gt 1023 label \&"1.2.3.5:\*(Gt1023\&" 2072.Ed 2073.Pp 2074The macro expansion for the 2075.Ar label 2076directive occurs only at configuration file parse time, not during runtime. 2077.It Ar ridentifier Aq Ar number 2078Add an identifier (number) to the rule, which can be used to correlate the rule 2079to pflog entries, even after ruleset updates. 2080.It Xo Ar queue Aq Ar queue 2081.No \*(Ba ( Aq Ar queue , 2082.Aq Ar queue ) 2083.Xc 2084Packets matching this rule will be assigned to the specified queue. 2085If two queues are given, packets which have a 2086.Em TOS 2087of 2088.Em lowdelay 2089and TCP ACKs with no data payload will be assigned to the second one. 2090See 2091.Sx QUEUEING 2092for setup details. 2093.Pp 2094For example: 2095.Bd -literal -offset indent 2096pass in proto tcp to port 25 queue mail 2097pass in proto tcp to port 22 queue(ssh_bulk, ssh_prio) 2098.Ed 2099.It Cm set prio Ar priority | Pq Ar priority , priority 2100Packets matching this rule will be assigned a specific queueing priority. 2101Priorities are assigned as integers 0 through 7. 2102If the packet is transmitted on a 2103.Xr vlan 4 2104interface, the queueing priority will be written as the priority 2105code point in the 802.1Q VLAN header. 2106If two priorities are given, packets which have a TOS of 2107.Cm lowdelay 2108and TCP ACKs with no data payload will be assigned to the second one. 2109.Pp 2110For example: 2111.Bd -literal -offset indent 2112pass in proto tcp to port 25 set prio 2 2113pass in proto tcp to port 22 set prio (2, 5) 2114.Ed 2115.It Ar tag Aq Ar string 2116Packets matching this rule will be tagged with the 2117specified string. 2118The tag acts as an internal marker that can be used to 2119identify these packets later on. 2120This can be used, for example, to provide trust between 2121interfaces and to determine if packets have been 2122processed by translation rules. 2123Tags are 2124.Qq sticky , 2125meaning that the packet will be tagged even if the rule 2126is not the last matching rule. 2127Further matching rules can replace the tag with a 2128new one but will not remove a previously applied tag. 2129A packet is only ever assigned one tag at a time. 2130Packet tagging can be done during 2131.Ar nat , 2132.Ar rdr , 2133.Ar binat 2134or 2135.Ar ether 2136rules in addition to filter rules. 2137Tags take the same macros as labels (see above). 2138.It Ar tagged Aq Ar string 2139Used with filter, translation or scrub rules 2140to specify that packets must already 2141be tagged with the given tag in order to match the rule. 2142Inverse tag matching can also be done 2143by specifying the 2144.Cm !\& 2145operator before the 2146.Ar tagged 2147keyword. 2148.It Ar rtable Aq Ar number 2149Used to select an alternate routing table for the routing lookup. 2150Only effective before the route lookup happened, i.e. when filtering inbound. 2151.It Xo Ar divert-to Aq Ar host 2152.Ar port Aq Ar port 2153.Xc 2154Used to 2155.Xr divert 4 2156packets to the given divert 2157.Ar port . 2158Historically 2159.Ox pf has another meaning for this, and 2160.Fx pf uses 2161this syntax to support 2162.Xr divert 4 instead. Hence, 2163.Ar host 2164has no meaning and can be set to anything like 127.0.0.1. 2165If a packet is re-injected and does not change direction then it will not be 2166re-diverted. 2167.It Ar divert-reply 2168It has no meaning in 2169.Fx pf . 2170.It Ar probability Aq Ar number 2171A probability attribute can be attached to a rule, with a value set between 21720 and 1, bounds not included. 2173In that case, the rule will be honoured using the given probability value 2174only. 2175For example, the following rule will drop 20% of incoming ICMP packets: 2176.Bd -literal -offset indent 2177block in proto icmp probability 20% 2178.Ed 2179.It Ar prio Aq Ar number 2180Only match packets which have the given queueing priority assigned. 2181.El 2182.Sh ROUTING 2183If a packet matches a rule with a route option set, the packet filter will 2184route the packet according to the type of route option. 2185When such a rule creates state, the route option is also applied to all 2186packets matching the same connection. 2187.Bl -tag -width xxxx 2188.It Ar route-to 2189The 2190.Ar route-to 2191option routes the packet to the specified interface with an optional address 2192for the next hop. 2193When a 2194.Ar route-to 2195rule creates state, only packets that pass in the same direction as the 2196filter rule specifies will be routed in this way. 2197Packets passing in the opposite direction (replies) are not affected 2198and are routed normally. 2199.It Ar reply-to 2200The 2201.Ar reply-to 2202option is similar to 2203.Ar route-to , 2204but routes packets that pass in the opposite direction (replies) to the 2205specified interface. 2206Opposite direction is only defined in the context of a state entry, and 2207.Ar reply-to 2208is useful only in rules that create state. 2209It can be used on systems with multiple external connections to 2210route all outgoing packets of a connection through the interface 2211the incoming connection arrived through (symmetric routing enforcement). 2212.It Ar dup-to 2213The 2214.Ar dup-to 2215option creates a duplicate of the packet and routes it like 2216.Ar route-to . 2217The original packet gets routed as it normally would. 2218.El 2219.Sh POOL OPTIONS 2220For 2221.Ar nat 2222and 2223.Ar rdr 2224rules, (as well as for the 2225.Ar route-to , 2226.Ar reply-to 2227and 2228.Ar dup-to 2229rule options) for which there is a single redirection address which has a 2230subnet mask smaller than 32 for IPv4 or 128 for IPv6 (more than one IP 2231address), a variety of different methods for assigning this address can be 2232used: 2233.Bl -tag -width xxxx 2234.It Ar bitmask 2235The 2236.Ar bitmask 2237option applies the network portion of the redirection address to the address 2238to be modified (source with 2239.Ar nat , 2240destination with 2241.Ar rdr ) . 2242.It Ar random 2243The 2244.Ar random 2245option selects an address at random within the defined block of addresses. 2246.It Ar source-hash 2247The 2248.Ar source-hash 2249option uses a hash of the source address to determine the redirection address, 2250ensuring that the redirection address is always the same for a given source. 2251An optional key can be specified after this keyword either in hex or as a 2252string; by default 2253.Xr pfctl 8 2254randomly generates a key for source-hash every time the 2255ruleset is reloaded. 2256.It Ar round-robin 2257The 2258.Ar round-robin 2259option loops through the redirection address(es). 2260.Pp 2261When more than one redirection address is specified, 2262.Ar round-robin 2263is the only permitted pool type. 2264.It Ar static-port 2265With 2266.Ar nat 2267rules, the 2268.Ar static-port 2269option prevents 2270.Xr pf 4 2271from modifying the source port on TCP and UDP packets. 2272.It Xo Ar map-e-portset Aq Ar psid-offset 2273.No / Aq Ar psid-len 2274.No / Aq Ar psid 2275.Xc 2276With 2277.Ar nat 2278rules, the 2279.Ar map-e-portset 2280option enables the source port translation of MAP-E (RFC 7597) Customer Edge. 2281In order to make the host act as a MAP-E Customer Edge, setting up a tunneling 2282interface and pass rules for encapsulated packets are required in addition 2283to the map-e-portset nat rule. 2284.Pp 2285For example: 2286.Bd -literal -offset indent 2287nat on $gif_mape_if from $int_if:network to any \e 2288 -> $ipv4_mape_src map-e-portset 6/8/0x34 2289.Ed 2290.Pp 2291sets PSID offset 6, PSID length 8, PSID 0x34. 2292.El 2293.Pp 2294Additionally, the 2295.Ar sticky-address 2296option can be specified to help ensure that multiple connections from the 2297same source are mapped to the same redirection address. 2298This option can be used with the 2299.Ar random 2300and 2301.Ar round-robin 2302pool options. 2303Note that by default these associations are destroyed as soon as there are 2304no longer states which refer to them; in order to make the mappings last 2305beyond the lifetime of the states, increase the global options with 2306.Ar set timeout src.track . 2307See 2308.Sx STATEFUL TRACKING OPTIONS 2309for more ways to control the source tracking. 2310.Sh STATE MODULATION 2311Much of the security derived from TCP is attributable to how well the 2312initial sequence numbers (ISNs) are chosen. 2313Some popular stack implementations choose 2314.Em very 2315poor ISNs and thus are normally susceptible to ISN prediction exploits. 2316By applying a 2317.Ar modulate state 2318rule to a TCP connection, 2319.Xr pf 4 2320will create a high quality random sequence number for each connection 2321endpoint. 2322.Pp 2323The 2324.Ar modulate state 2325directive implicitly keeps state on the rule and is 2326only applicable to TCP connections. 2327.Pp 2328For instance: 2329.Bd -literal -offset indent 2330block all 2331pass out proto tcp from any to any modulate state 2332pass in proto tcp from any to any port 25 flags S/SFRA modulate state 2333.Ed 2334.Pp 2335Note that modulated connections will not recover when the state table 2336is lost (firewall reboot, flushing the state table, etc...). 2337.Xr pf 4 2338will not be able to infer a connection again after the state table flushes 2339the connection's modulator. 2340When the state is lost, the connection may be left dangling until the 2341respective endpoints time out the connection. 2342It is possible on a fast local network for the endpoints to start an ACK 2343storm while trying to resynchronize after the loss of the modulator. 2344The default 2345.Ar flags 2346settings (or a more strict equivalent) should be used on 2347.Ar modulate state 2348rules to prevent ACK storms. 2349.Pp 2350Note that alternative methods are available 2351to prevent loss of the state table 2352and allow for firewall failover. 2353See 2354.Xr carp 4 2355and 2356.Xr pfsync 4 2357for further information. 2358.Sh SYN PROXY 2359By default, 2360.Xr pf 4 2361passes packets that are part of a 2362.Xr tcp 4 2363handshake between the endpoints. 2364The 2365.Ar synproxy state 2366option can be used to cause 2367.Xr pf 4 2368itself to complete the handshake with the active endpoint, perform a handshake 2369with the passive endpoint, and then forward packets between the endpoints. 2370.Pp 2371No packets are sent to the passive endpoint before the active endpoint has 2372completed the handshake, hence so-called SYN floods with spoofed source 2373addresses will not reach the passive endpoint, as the sender can't complete the 2374handshake. 2375.Pp 2376The proxy is transparent to both endpoints, they each see a single 2377connection from/to the other endpoint. 2378.Xr pf 4 2379chooses random initial sequence numbers for both handshakes. 2380Once the handshakes are completed, the sequence number modulators 2381(see previous section) are used to translate further packets of the 2382connection. 2383.Ar synproxy state 2384includes 2385.Ar modulate state . 2386.Pp 2387Rules with 2388.Ar synproxy 2389will not work if 2390.Xr pf 4 2391operates on a 2392.Xr bridge 4 . 2393.Pp 2394Example: 2395.Bd -literal -offset indent 2396pass in proto tcp from any to any port www synproxy state 2397.Ed 2398.Sh STATEFUL TRACKING OPTIONS 2399A number of options related to stateful tracking can be applied on a 2400per-rule basis. 2401.Ar keep state , 2402.Ar modulate state 2403and 2404.Ar synproxy state 2405support these options, and 2406.Ar keep state 2407must be specified explicitly to apply options to a rule. 2408.Pp 2409.Bl -tag -width xxxx -compact 2410.It Ar max Aq Ar number 2411Limits the number of concurrent states the rule may create. 2412When this limit is reached, further packets that would create 2413state will not match this rule until existing states time out. 2414.It Ar no-sync 2415Prevent state changes for states created by this rule from appearing on the 2416.Xr pfsync 4 2417interface. 2418.It Xo Aq Ar timeout 2419.Aq Ar seconds 2420.Xc 2421Changes the timeout values used for states created by this rule. 2422For a list of all valid timeout names, see 2423.Sx OPTIONS 2424above. 2425.It Ar sloppy 2426Uses a sloppy TCP connection tracker that does not check sequence 2427numbers at all, which makes insertion and ICMP teardown attacks way 2428easier. 2429This is intended to be used in situations where one does not see all 2430packets of a connection, e.g. in asymmetric routing situations. 2431Cannot be used with modulate or synproxy state. 2432.El 2433.Pp 2434Multiple options can be specified, separated by commas: 2435.Bd -literal -offset indent 2436pass in proto tcp from any to any \e 2437 port www keep state \e 2438 (max 100, source-track rule, max-src-nodes 75, \e 2439 max-src-states 3, tcp.established 60, tcp.closing 5) 2440.Ed 2441.Pp 2442When the 2443.Ar source-track 2444keyword is specified, the number of states per source IP is tracked. 2445.Pp 2446.Bl -tag -width xxxx -compact 2447.It Ar source-track rule 2448The maximum number of states created by this rule is limited by the rule's 2449.Ar max-src-nodes 2450and 2451.Ar max-src-states 2452options. 2453Only state entries created by this particular rule count toward the rule's 2454limits. 2455.It Ar source-track global 2456The number of states created by all rules that use this option is limited. 2457Each rule can specify different 2458.Ar max-src-nodes 2459and 2460.Ar max-src-states 2461options, however state entries created by any participating rule count towards 2462each individual rule's limits. 2463.El 2464.Pp 2465The following limits can be set: 2466.Pp 2467.Bl -tag -width xxxx -compact 2468.It Ar max-src-nodes Aq Ar number 2469Limits the maximum number of source addresses which can simultaneously 2470have state table entries. 2471.It Ar max-src-states Aq Ar number 2472Limits the maximum number of simultaneous state entries that a single 2473source address can create with this rule. 2474.El 2475.Pp 2476For stateful TCP connections, limits on established connections (connections 2477which have completed the TCP 3-way handshake) can also be enforced 2478per source IP. 2479.Pp 2480.Bl -tag -width xxxx -compact 2481.It Ar max-src-conn Aq Ar number 2482Limits the maximum number of simultaneous TCP connections which have 2483completed the 3-way handshake that a single host can make. 2484.It Xo Ar max-src-conn-rate Aq Ar number 2485.No / Aq Ar seconds 2486.Xc 2487Limit the rate of new connections over a time interval. 2488The connection rate is an approximation calculated as a moving average. 2489.El 2490.Pp 2491Because the 3-way handshake ensures that the source address is not being 2492spoofed, more aggressive action can be taken based on these limits. 2493With the 2494.Ar overload Aq Ar table 2495state option, source IP addresses which hit either of the limits on 2496established connections will be added to the named table. 2497This table can be used in the ruleset to block further activity from 2498the offending host, redirect it to a tarpit process, or restrict its 2499bandwidth. 2500.Pp 2501The optional 2502.Ar flush 2503keyword kills all states created by the matching rule which originate 2504from the host which exceeds these limits. 2505The 2506.Ar global 2507modifier to the flush command kills all states originating from the 2508offending host, regardless of which rule created the state. 2509.Pp 2510For example, the following rules will protect the webserver against 2511hosts making more than 100 connections in 10 seconds. 2512Any host which connects faster than this rate will have its address added 2513to the 2514.Aq bad_hosts 2515table and have all states originating from it flushed. 2516Any new packets arriving from this host will be dropped unconditionally 2517by the block rule. 2518.Bd -literal -offset indent 2519block quick from \*(Ltbad_hosts\*(Gt 2520pass in on $ext_if proto tcp to $webserver port www keep state \e 2521 (max-src-conn-rate 100/10, overload \*(Ltbad_hosts\*(Gt flush global) 2522.Ed 2523.Sh OPERATING SYSTEM FINGERPRINTING 2524Passive OS Fingerprinting is a mechanism to inspect nuances of a TCP 2525connection's initial SYN packet and guess at the host's operating system. 2526Unfortunately these nuances are easily spoofed by an attacker so the 2527fingerprint is not useful in making security decisions. 2528But the fingerprint is typically accurate enough to make policy decisions 2529upon. 2530.Pp 2531The fingerprints may be specified by operating system class, by 2532version, or by subtype/patchlevel. 2533The class of an operating system is typically the vendor or genre 2534and would be 2535.Ox 2536for the 2537.Xr pf 4 2538firewall itself. 2539The version of the oldest available 2540.Ox 2541release on the main FTP site 2542would be 2.6 and the fingerprint would be written 2543.Pp 2544.Dl \&"OpenBSD 2.6\&" 2545.Pp 2546The subtype of an operating system is typically used to describe the 2547patchlevel if that patch led to changes in the TCP stack behavior. 2548In the case of 2549.Ox , 2550the only subtype is for a fingerprint that was 2551normalized by the 2552.Ar no-df 2553scrub option and would be specified as 2554.Pp 2555.Dl \&"OpenBSD 3.3 no-df\&" 2556.Pp 2557Fingerprints for most popular operating systems are provided by 2558.Xr pf.os 5 . 2559Once 2560.Xr pf 4 2561is running, a complete list of known operating system fingerprints may 2562be listed by running: 2563.Pp 2564.Dl # pfctl -so 2565.Pp 2566Filter rules can enforce policy at any level of operating system specification 2567assuming a fingerprint is present. 2568Policy could limit traffic to approved operating systems or even ban traffic 2569from hosts that aren't at the latest service pack. 2570.Pp 2571The 2572.Ar unknown 2573class can also be used as the fingerprint which will match packets for 2574which no operating system fingerprint is known. 2575.Pp 2576Examples: 2577.Bd -literal -offset indent 2578pass out proto tcp from any os OpenBSD 2579block out proto tcp from any os Doors 2580block out proto tcp from any os "Doors PT" 2581block out proto tcp from any os "Doors PT SP3" 2582block out from any os "unknown" 2583pass on lo0 proto tcp from any os "OpenBSD 3.3 lo0" 2584.Ed 2585.Pp 2586Operating system fingerprinting is limited only to the TCP SYN packet. 2587This means that it will not work on other protocols and will not match 2588a currently established connection. 2589.Pp 2590Caveat: operating system fingerprints are occasionally wrong. 2591There are three problems: an attacker can trivially craft his packets to 2592appear as any operating system he chooses; 2593an operating system patch could change the stack behavior and no fingerprints 2594will match it until the database is updated; 2595and multiple operating systems may have the same fingerprint. 2596.Sh BLOCKING SPOOFED TRAFFIC 2597"Spoofing" is the faking of IP addresses, typically for malicious 2598purposes. 2599The 2600.Ar antispoof 2601directive expands to a set of filter rules which will block all 2602traffic with a source IP from the network(s) directly connected 2603to the specified interface(s) from entering the system through 2604any other interface. 2605.Pp 2606For example, the line 2607.Bd -literal -offset indent 2608antispoof for lo0 2609.Ed 2610.Pp 2611expands to 2612.Bd -literal -offset indent 2613block drop in on ! lo0 inet from 127.0.0.1/8 to any 2614block drop in on ! lo0 inet6 from ::1 to any 2615.Ed 2616.Pp 2617For non-loopback interfaces, there are additional rules to block incoming 2618packets with a source IP address identical to the interface's IP(s). 2619For example, assuming the interface wi0 had an IP address of 10.0.0.1 and a 2620netmask of 255.255.255.0, 2621the line 2622.Bd -literal -offset indent 2623antispoof for wi0 inet 2624.Ed 2625.Pp 2626expands to 2627.Bd -literal -offset indent 2628block drop in on ! wi0 inet from 10.0.0.0/24 to any 2629block drop in inet from 10.0.0.1 to any 2630.Ed 2631.Pp 2632Caveat: Rules created by the 2633.Ar antispoof 2634directive interfere with packets sent over loopback interfaces 2635to local addresses. 2636One should pass these explicitly. 2637.Sh FRAGMENT HANDLING 2638The size of IP datagrams (packets) can be significantly larger than the 2639maximum transmission unit (MTU) of the network. 2640In cases when it is necessary or more efficient to send such large packets, 2641the large packet will be fragmented into many smaller packets that will each 2642fit onto the wire. 2643Unfortunately for a firewalling device, only the first logical fragment will 2644contain the necessary header information for the subprotocol that allows 2645.Xr pf 4 2646to filter on things such as TCP ports or to perform NAT. 2647.Pp 2648Besides the use of 2649.Ar set reassemble 2650option or 2651.Ar scrub 2652rules as described in 2653.Sx TRAFFIC NORMALIZATION 2654above, there are three options for handling fragments in the packet filter. 2655.Pp 2656One alternative is to filter individual fragments with filter rules. 2657If no 2658.Ar scrub 2659rule applies to a fragment or 2660.Ar set reassemble 2661is set to 2662.Cm no 2663, it is passed to the filter. 2664Filter rules with matching IP header parameters decide whether the 2665fragment is passed or blocked, in the same way as complete packets 2666are filtered. 2667Without reassembly, fragments can only be filtered based on IP header 2668fields (source/destination address, protocol), since subprotocol header 2669fields are not available (TCP/UDP port numbers, ICMP code/type). 2670The 2671.Ar fragment 2672option can be used to restrict filter rules to apply only to 2673fragments, but not complete packets. 2674Filter rules without the 2675.Ar fragment 2676option still apply to fragments, if they only specify IP header fields. 2677For instance, the rule 2678.Bd -literal -offset indent 2679pass in proto tcp from any to any port 80 2680.Ed 2681.Pp 2682never applies to a fragment, even if the fragment is part of a TCP 2683packet with destination port 80, because without reassembly this information 2684is not available for each fragment. 2685This also means that fragments cannot create new or match existing 2686state table entries, which makes stateful filtering and address 2687translation (NAT, redirection) for fragments impossible. 2688.Pp 2689It's also possible to reassemble only certain fragments by specifying 2690source or destination addresses or protocols as parameters in 2691.Ar scrub 2692rules. 2693.Pp 2694In most cases, the benefits of reassembly outweigh the additional 2695memory cost, and it's recommended to use 2696.Ar set reassemble 2697option or 2698.Ar scrub 2699rules with the 2700.Ar fragment reassemble 2701modifier to reassemble 2702all fragments. 2703.Pp 2704The memory allocated for fragment caching can be limited using 2705.Xr pfctl 8 . 2706Once this limit is reached, fragments that would have to be cached 2707are dropped until other entries time out. 2708The timeout value can also be adjusted. 2709.Pp 2710When forwarding reassembled IPv6 packets, pf refragments them with 2711the original maximum fragment size. 2712This allows the sender to determine the optimal fragment size by 2713path MTU discovery. 2714.Sh ANCHORS 2715Besides the main ruleset, 2716.Xr pfctl 8 2717can load rulesets into 2718.Ar anchor 2719attachment points. 2720An 2721.Ar anchor 2722is a container that can hold rules, address tables, and other anchors. 2723.Pp 2724An 2725.Ar anchor 2726has a name which specifies the path where 2727.Xr pfctl 8 2728can be used to access the anchor to perform operations on it, such as 2729attaching child anchors to it or loading rules into it. 2730Anchors may be nested, with components separated by 2731.Sq / 2732characters, similar to how file system hierarchies are laid out. 2733The main ruleset is actually the default anchor, so filter and 2734translation rules, for example, may also be contained in any anchor. 2735.Pp 2736An anchor can reference another 2737.Ar anchor 2738attachment point 2739using the following kinds 2740of rules: 2741.Bl -tag -width xxxx 2742.It Ar nat-anchor Aq Ar name 2743Evaluates the 2744.Ar nat 2745rules in the specified 2746.Ar anchor . 2747.It Ar rdr-anchor Aq Ar name 2748Evaluates the 2749.Ar rdr 2750rules in the specified 2751.Ar anchor . 2752.It Ar binat-anchor Aq Ar name 2753Evaluates the 2754.Ar binat 2755rules in the specified 2756.Ar anchor . 2757.It Ar anchor Aq Ar name 2758Evaluates the filter rules in the specified 2759.Ar anchor . 2760.It Xo Ar load anchor 2761.Aq Ar name 2762.Ar from Aq Ar file 2763.Xc 2764Loads the rules from the specified file into the 2765anchor 2766.Ar name . 2767.El 2768.Pp 2769When evaluation of the main ruleset reaches an 2770.Ar anchor 2771rule, 2772.Xr pf 4 2773will proceed to evaluate all rules specified in that anchor. 2774.Pp 2775Matching filter and translation rules marked with the 2776.Ar quick 2777option are final and abort the evaluation of the rules in other 2778anchors and the main ruleset. 2779If the 2780.Ar anchor 2781itself is marked with the 2782.Ar quick 2783option, 2784ruleset evaluation will terminate when the anchor is exited if the packet is 2785matched by any rule within the anchor. 2786.Pp 2787.Ar anchor 2788rules are evaluated relative to the anchor in which they are contained. 2789For example, all 2790.Ar anchor 2791rules specified in the main ruleset will reference anchor 2792attachment points underneath the main ruleset, and 2793.Ar anchor 2794rules specified in a file loaded from a 2795.Ar load anchor 2796rule will be attached under that anchor point. 2797.Pp 2798Rules may be contained in 2799.Ar anchor 2800attachment points which do not contain any rules when the main ruleset 2801is loaded, and later such anchors can be manipulated through 2802.Xr pfctl 8 2803without reloading the main ruleset or other anchors. 2804For example, 2805.Bd -literal -offset indent 2806ext_if = \&"kue0\&" 2807block on $ext_if all 2808anchor spam 2809pass out on $ext_if all 2810pass in on $ext_if proto tcp from any \e 2811 to $ext_if port smtp 2812.Ed 2813.Pp 2814blocks all packets on the external interface by default, then evaluates 2815all rules in the 2816.Ar anchor 2817named "spam", and finally passes all outgoing connections and 2818incoming connections to port 25. 2819.Bd -literal -offset indent 2820# echo \&"block in quick from 1.2.3.4 to any\&" \&| \e 2821 pfctl -a spam -f - 2822.Ed 2823.Pp 2824This loads a single rule into the 2825.Ar anchor , 2826which blocks all packets from a specific address. 2827.Pp 2828The anchor can also be populated by adding a 2829.Ar load anchor 2830rule after the 2831.Ar anchor 2832rule: 2833.Bd -literal -offset indent 2834anchor spam 2835load anchor spam from "/etc/pf-spam.conf" 2836.Ed 2837.Pp 2838When 2839.Xr pfctl 8 2840loads 2841.Nm pf.conf , 2842it will also load all the rules from the file 2843.Pa /etc/pf-spam.conf 2844into the anchor. 2845.Pp 2846Optionally, 2847.Ar anchor 2848rules can specify packet filtering parameters using the same syntax as 2849filter rules. 2850When parameters are used, the 2851.Ar anchor 2852rule is only evaluated for matching packets. 2853This allows conditional evaluation of anchors, like: 2854.Bd -literal -offset indent 2855block on $ext_if all 2856anchor spam proto tcp from any to any port smtp 2857pass out on $ext_if all 2858pass in on $ext_if proto tcp from any to $ext_if port smtp 2859.Ed 2860.Pp 2861The rules inside 2862.Ar anchor 2863spam are only evaluated for 2864.Ar tcp 2865packets with destination port 25. 2866Hence, 2867.Bd -literal -offset indent 2868# echo \&"block in quick from 1.2.3.4 to any" \&| \e 2869 pfctl -a spam -f - 2870.Ed 2871.Pp 2872will only block connections from 1.2.3.4 to port 25. 2873.Pp 2874Anchors may end with the asterisk 2875.Pq Sq * 2876character, which signifies that all anchors attached at that point 2877should be evaluated in the alphabetical ordering of their anchor name. 2878For example, 2879.Bd -literal -offset indent 2880anchor "spam/*" 2881.Ed 2882.Pp 2883will evaluate each rule in each anchor attached to the 2884.Li spam 2885anchor. 2886Note that it will only evaluate anchors that are directly attached to the 2887.Li spam 2888anchor, and will not descend to evaluate anchors recursively. 2889.Pp 2890Since anchors are evaluated relative to the anchor in which they are 2891contained, there is a mechanism for accessing the parent and ancestor 2892anchors of a given anchor. 2893Similar to file system path name resolution, if the sequence 2894.Dq .. 2895appears as an anchor path component, the parent anchor of the current 2896anchor in the path evaluation at that point will become the new current 2897anchor. 2898As an example, consider the following: 2899.Bd -literal -offset indent 2900# echo ' anchor "spam/allowed" ' | pfctl -f - 2901# echo -e ' anchor "../banned" \en pass' | \e 2902 pfctl -a spam/allowed -f - 2903.Ed 2904.Pp 2905Evaluation of the main ruleset will lead into the 2906.Li spam/allowed 2907anchor, which will evaluate the rules in the 2908.Li spam/banned 2909anchor, if any, before finally evaluating the 2910.Ar pass 2911rule. 2912.Pp 2913Filter rule 2914.Ar anchors 2915can also be loaded inline in the ruleset within a brace ('{' '}') delimited 2916block. 2917Brace delimited blocks may contain rules or other brace-delimited blocks. 2918When anchors are loaded this way the anchor name becomes optional. 2919.Bd -literal -offset indent 2920anchor "external" on $ext_if { 2921 block 2922 anchor out { 2923 pass proto tcp from any to port { 25, 80, 443 } 2924 } 2925 pass in proto tcp to any port 22 2926} 2927.Ed 2928.Pp 2929Since the parser specification for anchor names is a string, any 2930reference to an anchor name containing 2931.Sq / 2932characters will require double quote 2933.Pq Sq \&" 2934characters around the anchor name. 2935.Sh SCTP CONSIDERATIONS 2936.Xr pf 4 2937supports 2938.Xr sctp 4 2939connections. 2940It can match ports, track state and NAT SCTP traffic. 2941However, it will not alter port numbers during nat or rdr translations. 2942Doing so would break SCTP multihoming. 2943.Sh TRANSLATION EXAMPLES 2944This example maps incoming requests on port 80 to port 8080, on 2945which a daemon is running (because, for example, it is not run as root, 2946and therefore lacks permission to bind to port 80). 2947.Bd -literal 2948# use a macro for the interface name, so it can be changed easily 2949ext_if = \&"ne3\&" 2950 2951# map daemon on 8080 to appear to be on 80 2952rdr on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 port 8080 2953.Ed 2954.Pp 2955If the 2956.Ar pass 2957modifier is given, packets matching the translation rule are passed without 2958inspecting the filter rules: 2959.Bd -literal 2960rdr pass on $ext_if proto tcp from any to any port 80 -\*(Gt 127.0.0.1 \e 2961 port 8080 2962.Ed 2963.Pp 2964In the example below, vlan12 is configured as 192.168.168.1; 2965the machine translates all packets coming from 192.168.168.0/24 to 204.92.77.111 2966when they are going out any interface except vlan12. 2967This has the net effect of making traffic from the 192.168.168.0/24 2968network appear as though it is the Internet routable address 2969204.92.77.111 to nodes behind any interface on the router except 2970for the nodes on vlan12. 2971(Thus, 192.168.168.1 can talk to the 192.168.168.0/24 nodes.) 2972.Bd -literal 2973nat on ! vlan12 from 192.168.168.0/24 to any -\*(Gt 204.92.77.111 2974.Ed 2975.Pp 2976In the example below, the machine sits between a fake internal 144.19.74.* 2977network, and a routable external IP of 204.92.77.100. 2978The 2979.Ar no nat 2980rule excludes protocol AH from being translated. 2981.Bd -literal 2982# NO NAT 2983no nat on $ext_if proto ah from 144.19.74.0/24 to any 2984nat on $ext_if from 144.19.74.0/24 to any -\*(Gt 204.92.77.100 2985.Ed 2986.Pp 2987In the example below, packets bound for one specific server, as well as those 2988generated by the sysadmins are not proxied; all other connections are. 2989.Bd -literal 2990# NO RDR 2991no rdr on $int_if proto { tcp, udp } from any to $server port 80 2992no rdr on $int_if proto { tcp, udp } from $sysadmins to any port 80 2993rdr on $int_if proto { tcp, udp } from any to any port 80 -\*(Gt 127.0.0.1 \e 2994 port 80 2995.Ed 2996.Pp 2997This longer example uses both a NAT and a redirection. 2998The external interface has the address 157.161.48.183. 2999On localhost, we are running 3000.Xr ftp-proxy 8 , 3001waiting for FTP sessions to be redirected to it. 3002The three mandatory anchors for 3003.Xr ftp-proxy 8 3004are omitted from this example; see the 3005.Xr ftp-proxy 8 3006manpage. 3007.Bd -literal 3008# NAT 3009# Translate outgoing packets' source addresses (any protocol). 3010# In this case, any address but the gateway's external address is mapped. 3011nat on $ext_if inet from ! ($ext_if) to any -\*(Gt ($ext_if) 3012 3013# NAT PROXYING 3014# Map outgoing packets' source port to an assigned proxy port instead of 3015# an arbitrary port. 3016# In this case, proxy outgoing isakmp with port 500 on the gateway. 3017nat on $ext_if inet proto udp from any port = isakmp to any -\*(Gt ($ext_if) \e 3018 port 500 3019 3020# BINAT 3021# Translate outgoing packets' source address (any protocol). 3022# Translate incoming packets' destination address to an internal machine 3023# (bidirectional). 3024binat on $ext_if from 10.1.2.150 to any -\*(Gt $ext_if 3025 3026# Translate packets arriving on $peer_if addressed to 172.22.16.0/20 3027# to the corresponding address in 172.21.16.0/20 (bidirectional). 3028binat on $peer_if from 172.21.16.0/20 to any -> 172.22.16.0/20 3029 3030# RDR 3031# Translate incoming packets' destination addresses. 3032# As an example, redirect a TCP and UDP port to an internal machine. 3033rdr on $ext_if inet proto tcp from any to ($ext_if) port 8080 \e 3034 -\*(Gt 10.1.2.151 port 22 3035rdr on $ext_if inet proto udp from any to ($ext_if) port 8080 \e 3036 -\*(Gt 10.1.2.151 port 53 3037 3038# RDR 3039# Translate outgoing ftp control connections to send them to localhost 3040# for proxying with ftp-proxy(8) running on port 8021. 3041rdr on $int_if proto tcp from any to any port 21 -\*(Gt 127.0.0.1 port 8021 3042.Ed 3043.Pp 3044In this example, a NAT gateway is set up to translate internal addresses 3045using a pool of public addresses (192.0.2.16/28) and to redirect 3046incoming web server connections to a group of web servers on the internal 3047network. 3048.Bd -literal 3049# NAT LOAD BALANCE 3050# Translate outgoing packets' source addresses using an address pool. 3051# A given source address is always translated to the same pool address by 3052# using the source-hash keyword. 3053nat on $ext_if inet from any to any -\*(Gt 192.0.2.16/28 source-hash 3054 3055# RDR ROUND ROBIN 3056# Translate incoming web server connections to a group of web servers on 3057# the internal network. 3058rdr on $ext_if proto tcp from any to any port 80 \e 3059 -\*(Gt { 10.1.2.155, 10.1.2.160, 10.1.2.161 } round-robin 3060.Ed 3061.Sh FILTER EXAMPLES 3062.Bd -literal 3063# The external interface is kue0 3064# (157.161.48.183, the only routable address) 3065# and the private network is 10.0.0.0/8, for which we are doing NAT. 3066 3067# Reassemble incoming traffic 3068set reassemble yes 3069 3070# use a macro for the interface name, so it can be changed easily 3071ext_if = \&"kue0\&" 3072 3073# block and log everything by default 3074block return log on $ext_if all 3075 3076# block anything coming from source we have no back routes for 3077block in from no-route to any 3078 3079# block packets whose ingress interface does not match the one in 3080# the route back to their source address 3081block in from urpf-failed to any 3082 3083# block and log outgoing packets that do not have our address as source, 3084# they are either spoofed or something is misconfigured (NAT disabled, 3085# for instance), we want to be nice and do not send out garbage. 3086block out log quick on $ext_if from ! 157.161.48.183 to any 3087 3088# silently drop broadcasts (cable modem noise) 3089block in quick on $ext_if from any to 255.255.255.255 3090 3091# block and log incoming packets from reserved address space and invalid 3092# addresses, they are either spoofed or misconfigured, we cannot reply to 3093# them anyway (hence, no return-rst). 3094block in log quick on $ext_if from { 10.0.0.0/8, 172.16.0.0/12, \e 3095 192.168.0.0/16, 255.255.255.255/32 } to any 3096 3097# ICMP 3098 3099# pass out/in certain ICMP queries and keep state (ping) 3100# state matching is done on host addresses and ICMP id (not type/code), 3101# so replies (like 0/0 for 8/0) will match queries 3102# ICMP error messages (which always refer to a TCP/UDP packet) are 3103# handled by the TCP/UDP states 3104pass on $ext_if inet proto icmp all icmp-type 8 code 0 3105 3106# UDP 3107 3108# pass out all UDP connections and keep state 3109pass out on $ext_if proto udp all 3110 3111# pass in certain UDP connections and keep state (DNS) 3112pass in on $ext_if proto udp from any to any port domain 3113 3114# TCP 3115 3116# pass out all TCP connections and modulate state 3117pass out on $ext_if proto tcp all modulate state 3118 3119# pass in certain TCP connections and keep state (SSH, SMTP, DNS, IDENT) 3120pass in on $ext_if proto tcp from any to any port { ssh, smtp, domain, \e 3121 auth } 3122 3123# Do not allow Windows 9x SMTP connections since they are typically 3124# a viral worm. Alternately we could limit these OSes to 1 connection each. 3125block in on $ext_if proto tcp from any os {"Windows 95", "Windows 98"} \e 3126 to any port smtp 3127 3128# IPv6 3129# pass in/out all IPv6 traffic: note that we have to enable this in two 3130# different ways, on both our physical interface and our tunnel 3131pass quick on gif0 inet6 3132pass quick on $ext_if proto ipv6 3133 3134# Packet Tagging 3135 3136# three interfaces: $int_if, $ext_if, and $wifi_if (wireless). NAT is 3137# being done on $ext_if for all outgoing packets. tag packets in on 3138# $int_if and pass those tagged packets out on $ext_if. all other 3139# outgoing packets (i.e., packets from the wireless network) are only 3140# permitted to access port 80. 3141 3142pass in on $int_if from any to any tag INTNET 3143pass in on $wifi_if from any to any 3144 3145block out on $ext_if from any to any 3146pass out quick on $ext_if tagged INTNET 3147pass out on $ext_if proto tcp from any to any port 80 3148 3149# tag incoming packets as they are redirected to spamd(8). use the tag 3150# to pass those packets through the packet filter. 3151 3152rdr on $ext_if inet proto tcp from \*(Ltspammers\*(Gt to port smtp \e 3153 tag SPAMD -\*(Gt 127.0.0.1 port spamd 3154 3155block in on $ext_if 3156pass in on $ext_if inet proto tcp tagged SPAMD 3157.Ed 3158.Sh GRAMMAR 3159Syntax for 3160.Nm 3161in BNF: 3162.Bd -literal 3163line = ( option | ether-rule | pf-rule | nat-rule | binat-rule | 3164 rdr-rule | antispoof-rule | altq-rule | queue-rule | 3165 trans-anchors | anchor-rule | anchor-close | load-anchor | 3166 table-rule | include ) 3167 3168option = "set" ( [ "timeout" ( timeout | "{" timeout-list "}" ) ] | 3169 [ "ruleset-optimization" [ "none" | "basic" | "profile" ]] | 3170 [ "optimization" [ "default" | "normal" | 3171 "high-latency" | "satellite" | 3172 "aggressive" | "conservative" ] ] 3173 [ "limit" ( limit-item | "{" limit-list "}" ) ] | 3174 [ "loginterface" ( interface-name | "none" ) ] | 3175 [ "block-policy" ( "drop" | "return" ) ] | 3176 [ "state-policy" ( "if-bound" | "floating" ) ] 3177 [ "state-defaults" state-opts ] 3178 [ "require-order" ( "yes" | "no" ) ] 3179 [ "fingerprints" filename ] | 3180 [ "skip on" ifspec ] | 3181 [ "debug" ( "none" | "urgent" | "misc" | "loud" ) ] 3182 [ "keepcounters" ] ) 3183 3184ether-rule = "ether" etheraction [ ( "in" | "out" ) ] 3185 [ "quick" ] [ "on" ifspec ] [ "bridge-to" interface-name ] 3186 [ etherprotospec ] etherhosts [ "l3" hosts ] 3187 [ etherfilteropt-list ] 3188 3189pf-rule = action [ ( "in" | "out" ) ] 3190 [ "log" [ "(" logopts ")"] ] [ "quick" ] 3191 [ "on" ifspec ] [ route ] [ af ] [ protospec ] 3192 hosts [ filteropt-list ] 3193 3194logopts = logopt [ "," logopts ] 3195logopt = "all" | "user" | "to" interface-name 3196 3197etherfilteropt-list = etherfilteropt-list etherfilteropt | etherfilteropt 3198etherfilteropt = "tag" string | "tagged" string | "queue" ( string ) | 3199 "ridentifier" number | "label" string 3200 3201filteropt-list = filteropt-list filteropt | filteropt 3202filteropt = user | group | flags | icmp-type | icmp6-type | "tos" tos | 3203 ( "no" | "keep" | "modulate" | "synproxy" ) "state" 3204 [ "(" state-opts ")" ] | 3205 "fragment" | "no-df" | "min-ttl" number | "set-tos" tos | 3206 "max-mss" number | "random-id" | "reassemble tcp" | 3207 fragmentation | "allow-opts" | 3208 "label" string | "tag" string | [ ! ] "tagged" string | 3209 "set prio" ( number | "(" number [ [ "," ] number ] ")" ) | 3210 "queue" ( string | "(" string [ [ "," ] string ] ")" ) | 3211 "rtable" number | "probability" number"%" | "prio" number | 3212 "dnpipe" ( number | "(" number "," number ")" ) | 3213 "dnqueue" ( number | "(" number "," number ")" ) | 3214 "ridentifier" number 3215 3216nat-rule = [ "no" ] "nat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3217 [ "on" ifspec ] [ af ] 3218 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3219 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 3220 [ portspec ] [ pooltype ] [ "static-port" ] 3221 [ "map-e-portset" number "/" number "/" number ] ] 3222 3223binat-rule = [ "no" ] "binat" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3224 [ "on" interface-name ] [ af ] 3225 [ "proto" ( proto-name | proto-number ) ] 3226 "from" address [ "/" mask-bits ] "to" ipspec 3227 [ "tag" string ] [ "tagged" string ] 3228 [ "-\*(Gt" address [ "/" mask-bits ] ] 3229 3230rdr-rule = [ "no" ] "rdr" [ "pass" [ "log" [ "(" logopts ")" ] ] ] 3231 [ "on" ifspec ] [ af ] 3232 [ protospec ] hosts [ "tag" string ] [ "tagged" string ] 3233 [ "-\*(Gt" ( redirhost | "{" redirhost-list "}" ) 3234 [ portspec ] [ pooltype ] ] 3235 3236antispoof-rule = "antispoof" [ "log" ] [ "quick" ] 3237 "for" ifspec [ af ] [ "label" string ] 3238 [ "ridentifier" number ] 3239 3240table-rule = "table" "\*(Lt" string "\*(Gt" [ tableopts-list ] 3241tableopts-list = tableopts-list tableopts | tableopts 3242tableopts = "persist" | "const" | "counters" | "file" string | 3243 "{" [ tableaddr-list ] "}" 3244tableaddr-list = tableaddr-list [ "," ] tableaddr-spec | tableaddr-spec 3245tableaddr-spec = [ "!" ] tableaddr [ "/" mask-bits ] 3246tableaddr = hostname | ifspec | "self" | 3247 ipv4-dotted-quad | ipv6-coloned-hex 3248 3249altq-rule = "altq on" interface-name queueopts-list 3250 "queue" subqueue 3251queue-rule = "queue" string [ "on" interface-name ] queueopts-list 3252 subqueue 3253 3254anchor-rule = "anchor" [ string ] [ ( "in" | "out" ) ] [ "on" ifspec ] 3255 [ af ] [ protospec ] [ hosts ] [ filteropt-list ] [ "{" ] 3256 3257anchor-close = "}" 3258 3259trans-anchors = ( "nat-anchor" | "rdr-anchor" | "binat-anchor" ) string 3260 [ "on" ifspec ] [ af ] [ "proto" ] [ protospec ] [ hosts ] 3261 3262load-anchor = "load anchor" string "from" filename 3263 3264queueopts-list = queueopts-list queueopts | queueopts 3265queueopts = [ "bandwidth" bandwidth-spec ] | 3266 [ "qlimit" number ] | [ "tbrsize" number ] | 3267 [ "priority" number ] | [ schedulers ] 3268schedulers = ( cbq-def | priq-def | hfsc-def ) 3269bandwidth-spec = "number" ( "b" | "Kb" | "Mb" | "Gb" | "%" ) 3270 3271etheraction = "pass" | "block" 3272action = "pass" | "match" | "block" [ return ] | [ "no" ] "scrub" 3273return = "drop" | "return" | "return-rst" [ "( ttl" number ")" ] | 3274 "return-icmp" [ "(" icmpcode [ [ "," ] icmp6code ] ")" ] | 3275 "return-icmp6" [ "(" icmp6code ")" ] 3276icmpcode = ( icmp-code-name | icmp-code-number ) 3277icmp6code = ( icmp6-code-name | icmp6-code-number ) 3278 3279ifspec = ( [ "!" ] ( interface-name | interface-group ) ) | 3280 "{" interface-list "}" 3281interface-list = [ "!" ] ( interface-name | interface-group ) 3282 [ [ "," ] interface-list ] 3283route = ( "route-to" | "reply-to" | "dup-to" ) 3284 ( routehost | "{" routehost-list "}" ) 3285 [ pooltype ] 3286af = "inet" | "inet6" 3287 3288etherprotospec = "proto" ( proto-number | "{" etherproto-list "}" ) 3289etherproto-list = proto-number [ [ "," ] etherproto-list ] 3290protospec = "proto" ( proto-name | proto-number | 3291 "{" proto-list "}" ) 3292proto-list = ( proto-name | proto-number ) [ [ "," ] proto-list ] 3293 3294etherhosts = "from" macaddress "to" macaddress 3295macaddress = mac | mac "/" masklen | mac "&" mask 3296 3297hosts = "all" | 3298 "from" ( "any" | "no-route" | "urpf-failed" | "self" | host | 3299 "{" host-list "}" ) [ port ] [ os ] 3300 "to" ( "any" | "no-route" | "self" | host | 3301 "{" host-list "}" ) [ port ] 3302 3303ipspec = "any" | host | "{" host-list "}" 3304host = [ "!" ] ( address [ "/" mask-bits ] | "\*(Lt" string "\*(Gt" ) 3305redirhost = address [ "/" mask-bits ] 3306routehost = "(" interface-name [ address [ "/" mask-bits ] ] ")" 3307address = ( interface-name | interface-group | 3308 "(" ( interface-name | interface-group ) ")" | 3309 hostname | ipv4-dotted-quad | ipv6-coloned-hex ) 3310host-list = host [ [ "," ] host-list ] 3311redirhost-list = redirhost [ [ "," ] redirhost-list ] 3312routehost-list = routehost [ [ "," ] routehost-list ] 3313 3314port = "port" ( unary-op | binary-op | "{" op-list "}" ) 3315portspec = "port" ( number | name ) [ ":" ( "*" | number | name ) ] 3316os = "os" ( os-name | "{" os-list "}" ) 3317user = "user" ( unary-op | binary-op | "{" op-list "}" ) 3318group = "group" ( unary-op | binary-op | "{" op-list "}" ) 3319 3320unary-op = [ "=" | "!=" | "\*(Lt" | "\*(Le" | "\*(Gt" | "\*(Ge" ] 3321 ( name | number ) 3322binary-op = number ( "\*(Lt\*(Gt" | "\*(Gt\*(Lt" | ":" ) number 3323op-list = ( unary-op | binary-op ) [ [ "," ] op-list ] 3324 3325os-name = operating-system-name 3326os-list = os-name [ [ "," ] os-list ] 3327 3328flags = "flags" ( [ flag-set ] "/" flag-set | "any" ) 3329flag-set = [ "F" ] [ "S" ] [ "R" ] [ "P" ] [ "A" ] [ "U" ] [ "E" ] 3330 [ "W" ] 3331 3332icmp-type = "icmp-type" ( icmp-type-code | "{" icmp-list "}" ) 3333icmp6-type = "icmp6-type" ( icmp-type-code | "{" icmp-list "}" ) 3334icmp-type-code = ( icmp-type-name | icmp-type-number ) 3335 [ "code" ( icmp-code-name | icmp-code-number ) ] 3336icmp-list = icmp-type-code [ [ "," ] icmp-list ] 3337 3338tos = ( "lowdelay" | "throughput" | "reliability" | 3339 [ "0x" ] number ) 3340 3341state-opts = state-opt [ [ "," ] state-opts ] 3342state-opt = ( "max" number | "no-sync" | timeout | "sloppy" | 3343 "source-track" [ ( "rule" | "global" ) ] | 3344 "max-src-nodes" number | "max-src-states" number | 3345 "max-src-conn" number | 3346 "max-src-conn-rate" number "/" number | 3347 "overload" "\*(Lt" string "\*(Gt" [ "flush" ] | 3348 "if-bound" | "floating" ) 3349 3350fragmentation = [ "fragment reassemble" ] 3351 3352timeout-list = timeout [ [ "," ] timeout-list ] 3353timeout = ( "tcp.first" | "tcp.opening" | "tcp.established" | 3354 "tcp.closing" | "tcp.finwait" | "tcp.closed" | 3355 "sctp.first" | "sctp.opening" | "sctp.established" | 3356 "sctp.closing" | "sctp.closed" | 3357 "udp.first" | "udp.single" | "udp.multiple" | 3358 "icmp.first" | "icmp.error" | 3359 "other.first" | "other.single" | "other.multiple" | 3360 "frag" | "interval" | "src.track" | 3361 "adaptive.start" | "adaptive.end" ) number 3362 3363limit-list = limit-item [ [ "," ] limit-list ] 3364limit-item = ( "states" | "frags" | "src-nodes" ) number 3365 3366pooltype = ( "bitmask" | "random" | 3367 "source-hash" [ ( hex-key | string-key ) ] | 3368 "round-robin" ) [ sticky-address ] 3369 3370subqueue = string | "{" queue-list "}" 3371queue-list = string [ [ "," ] string ] 3372cbq-def = "cbq" [ "(" cbq-opt [ [ "," ] cbq-opt ] ")" ] 3373priq-def = "priq" [ "(" priq-opt [ [ "," ] priq-opt ] ")" ] 3374hfsc-def = "hfsc" [ "(" hfsc-opt [ [ "," ] hfsc-opt ] ")" ] 3375cbq-opt = ( "default" | "borrow" | "red" | "ecn" | "rio" ) 3376priq-opt = ( "default" | "red" | "ecn" | "rio" ) 3377hfsc-opt = ( "default" | "red" | "ecn" | "rio" | 3378 linkshare-sc | realtime-sc | upperlimit-sc ) 3379linkshare-sc = "linkshare" sc-spec 3380realtime-sc = "realtime" sc-spec 3381upperlimit-sc = "upperlimit" sc-spec 3382sc-spec = ( bandwidth-spec | 3383 "(" bandwidth-spec number bandwidth-spec ")" ) 3384include = "include" filename 3385.Ed 3386.Sh FILES 3387.Bl -tag -width "/etc/protocols" -compact 3388.It Pa /etc/hosts 3389Host name database. 3390.It Pa /etc/pf.conf 3391Default location of the ruleset file. 3392The file has to be created manually as it is not installed with a 3393standard installation. 3394.It Pa /etc/pf.os 3395Default location of OS fingerprints. 3396.It Pa /etc/protocols 3397Protocol name database. 3398.It Pa /etc/services 3399Service name database. 3400.El 3401.Sh SEE ALSO 3402.Xr altq 4 , 3403.Xr carp 4 , 3404.Xr icmp 4 , 3405.Xr icmp6 4 , 3406.Xr ip 4 , 3407.Xr ip6 4 , 3408.Xr pf 4 , 3409.Xr pfsync 4 , 3410.Xr tcp 4 , 3411.Xr sctp 4 , 3412.Xr udp 4 , 3413.Xr hosts 5 , 3414.Xr pf.os 5 , 3415.Xr protocols 5 , 3416.Xr services 5 , 3417.Xr ftp-proxy 8 , 3418.Xr pfctl 8 , 3419.Xr pflogd 8 3420.Sh HISTORY 3421The 3422.Nm 3423file format first appeared in 3424.Ox 3.0 . 3425