--- name: "pf" section: "4" platform: "freebsd" package: "base" version: "16.0-CURRENT-20261027-61c70dc16a79" release: "FreeBSD 16.0-CURRENT (2026-10-27)" platforms: ["linux", "freebsd", "openbsd"] url: "https://new.carta.tech/pf" --- # pf(4) packet filter ## NAME **pf** – packet filter ## SYNOPSIS **device pf** **options PF\_DEFAULT\_TO\_DROP** In [rc.conf(5)](/rc.conf/5.md): **pf\_enable="YES"** In [loader.conf(5)](/loader.conf/5.md): **net.pf.states\_hashsize** **net.pf.source\_nodes\_hashsize** **net.pf.rule\_tag\_hashsize** **net.pf.udpendpoint\_hashsize** **net.pf.default\_to\_drop** In [sysctl.conf(5)](/sysctl.conf/5.md): **net.pf.request\_maxcount** **net.pf.filter\_local** ## DESCRIPTION Packet filtering takes place in the kernel. A pseudo-device, */dev/pf*, allows userland processes to control the behavior of the packet filter through an [ioctl(2)](/ioctl/2.md) interface. There are commands to enable and disable the filter, load rulesets, add and remove individual rules or state table entries, and retrieve statistics. The most commonly used functions are covered by [pfctl(8)](/pfctl/8.md). Manipulations like loading a ruleset that involve more than a single [ioctl(2)](/ioctl/2.md) call require a so-called *ticket*, which prevents the occurrence of multiple concurrent manipulations. Fields of [ioctl(2)](/ioctl/2.md) parameter structures that refer to packet data (like addresses and ports) are generally expected in network byte-order. Rules and address tables are contained in so-called *anchors*. When servicing an [ioctl(2)](/ioctl/2.md) request, if the anchor field of the argument structure is empty, the kernel will use the default anchor (i.e., the main ruleset) in operations. Anchors are specified by name and may be nested, with components separated by ‘/’ characters, similar to how file system hierarchies are laid out. The final component of the anchor path is the anchor under which operations will be performed. ## SYSCTL VARIABLES The following variables can be entered at the [loader(8)](/loader/8.md) prompt, set in [loader.conf(5)](/loader.conf/5.md), [sysctl.conf(5)](/sysctl.conf/5.md), or changed at runtime with [sysctl(8)](/sysctl/8.md): - *net.pf.filter\_local* This tells **pf** to also filter on the loopback output hook. This is typically used to allow redirect rules to adjust the source address. - *net.pf.request\_maxcount* The maximum number of items in a single ioctl call. ## LOADER TUNABLES The following tunables can be entered at the [loader(8)](/loader/8.md) prompt, or set in [loader.conf(5)](/loader.conf/5.md): - *net.pf.states\_hashsize* Size of hash table that stores states. Should be power of 2. Default value is 131072. - *net.pf.source\_nodes\_hashsize* Size of hash table that stores source nodes. Should be power of 2. Default value is 32768. - *net.pf.rule\_tag\_hashsize* Size of the hash table that stores tags. - *net.pf.udpendpoint\_hashsize* Size of hash table that store UDP endpoint mappings. Should be power of 2. Default value is 32768. - *net.pf.default\_to\_drop* This value overrides **options PF\_DEFAULT\_TO\_DROP** from kernel configuration file. - *net.pf.filter\_local* This tells **pf** to also filter on the loopback output hook. This is typically used to allow redirect rules to adjust the source address. - *net.pf.request\_maxcount* The maximum number of items in a single ioctl call. Read only [sysctl(8)](/sysctl/8.md) variables with matching names are provided to obtain current values at runtime. ## KERNEL OPTIONS The following options in the kernel configuration file are related to **pf** operation: - PF\_DEFAULT\_TO\_DROP Change default policy to drop by default ## IOCTL INTERFACE **pf** supports the following [ioctl(2)](/ioctl/2.md) commands, available through ⟨*net/pfvar.h*⟩: - DIOCSTART Start the packet filter. - DIOCSTOP Stop the packet filter. - DIOCSTARTALTQ Start the ALTQ bandwidth control system (see [altq(9)](/altq/9.md)). - DIOCSTOPALTQ Stop the ALTQ bandwidth control system. - DIOCBEGINADDRS *struct pfioc\_pooladdr \*pp* ``` struct pfioc_pooladdr { u_int32_t action; u_int32_t ticket; u_int32_t nr; u_int32_t r_num; u_int8_t r_action; u_int8_t r_last; u_int8_t af; char anchor[MAXPATHLEN]; struct pf_pooladdr addr; }; ``` Clear the buffer address pool and get a *ticket* for subsequent DIOCADDADDR, DIOCADDRULE, and DIOCCHANGERULE calls. - DIOCADDADDR *struct pfioc\_pooladdr \*pp* Add the pool address *addr* to the buffer address pool to be used in the following DIOCADDRULE or DIOCCHANGERULE call. All other members of the structure are ignored. - DIOCADDRULE *struct pfioc\_rule \*pr* ``` struct pfioc_rule { u_int32_t action; u_int32_t ticket; u_int32_t pool_ticket; u_int32_t nr; char anchor[MAXPATHLEN]; char anchor_call[MAXPATHLEN]; struct pf_rule rule; }; ``` Add *rule* at the end of the inactive ruleset. This call requires a *ticket* obtained through a preceding DIOCXBEGIN call and a *pool\_ticket* obtained through a DIOCBEGINADDRS call. DIOCADDADDR must also be called if any pool addresses are required. The optional *anchor* name indicates the anchor in which to append the rule. *nr* and *action* are ignored. - DIOCADDALTQ *struct pfioc\_altq \*pa* Add an ALTQ discipline or queue. ``` struct pfioc_altq { u_int32_t action; u_int32_t ticket; u_int32_t nr; struct pf_altq altq; }; ``` - DIOCGETRULES *struct pfioc\_rule \*pr* Get a *ticket* for subsequent DIOCGETRULE calls and the number *nr* of rules in the active ruleset. - DIOCGETRULE *struct pfioc\_rule \*pr* Get a *rule* by its number *nr* using the *ticket* obtained through a preceding DIOCGETRULES call. If *action* is set to PF\_GET\_CLR\_CNTR, the per-rule statistics on the requested rule are cleared. - DIOCGETADDRS *struct pfioc\_pooladdr \*pp* Get a *ticket* for subsequent DIOCGETADDR calls and the number *nr* of pool addresses in the rule specified with *r\_action*, *r\_num*, and *anchor*. - DIOCGETADDR *struct pfioc\_pooladdr \*pp* Get the pool address *addr* by its number *nr* from the rule specified with *r\_action*, *r\_num*, and *anchor* using the *ticket* obtained through a preceding DIOCGETADDRS call. - DIOCGETALTQS *struct pfioc\_altq \*pa* Get a *ticket* for subsequent DIOCGETALTQ calls and the number *nr* of queues in the active list. - DIOCGETALTQ *struct pfioc\_altq \*pa* Get the queueing discipline *altq* by its number *nr* using the *ticket* obtained through a preceding DIOCGETALTQS call. - DIOCGETQSTATS *struct pfioc\_qstats \*pq* Get the statistics on a queue. ``` struct pfioc_qstats { u_int32_t ticket; u_int32_t nr; void *buf; int nbytes; u_int8_t scheduler; }; ``` This call fills in a pointer to the buffer of statistics *buf*, of length *nbytes*, for the queue specified by *nr*. - DIOCGETRULESETS *struct pfioc\_ruleset \*pr* ``` struct pfioc_ruleset { u_int32_t nr; char path[MAXPATHLEN]; char name[PF_ANCHOR_NAME_SIZE]; }; ``` Get the number *nr* of rulesets (i.e., anchors) directly attached to the anchor named by *path* for use in subsequent DIOCGETRULESET calls. Nested anchors, since they are not directly attached to the given anchor, will not be included. This ioctl returns ENOENT if the parent anchor given at *path* does not exist. - DIOCGETRULESET *struct pfioc\_ruleset \*pr* Get a ruleset (i.e., an anchor) *name* by its number *nr* from the given anchor *path*, the maximum number of which can be obtained from a preceding DIOCGETRULESETS call. This ioctl returns ENOENT if the parent anchor given by *path* does not exist or EBUSY if the index passed in by *nr* is greater than the number of anchors. - DIOCADDSTATE *struct pfioc\_state \*ps* Add a state entry. ``` struct pfioc_state { struct pfsync_state state; }; ``` - DIOCGETSTATENV *struct pfioc\_nv \*nv* Extract the entry identified by the *id* and *creatorid* fields of the *state* nvlist from the state table. - DIOCKILLSTATESNV *struct pfioc\_nv nv* Remove matching entries from the state table. This ioctl returns the number of killed states in *killed*. ``` nvlist pf_state_cmp { number id; number creatorid; number direction; }; nvlist pf_kill { nvlist pf_state_cmp cmp; number af; number proto; nvlist pf_rule_addr src; nvlist pf_rule_addr dst; string ifname[IFNAMSIZ]; string label[PF_RULE_LABEL_SIZE]; }; ``` - DIOCCLRSTATESNV *struct pfioc\_nv nv* Clear all states. It works like DIOCKILLSTATESNV, but ignores the *af*, *proto*, *src*, and *dst* fields of the *pf\_kill* nvlist. - DIOCSETSTATUSIF *struct pfioc\_if \*pi* Specify the interface for which statistics are accumulated. ``` struct pfioc_if { char ifname[IFNAMSIZ]; }; ``` - DIOCGETSTATUS *struct pf\_status \*s* Get the internal packet filter statistics. ``` struct pf_status { u_int64_t counters[PFRES_MAX]; u_int64_t lcounters[LCNT_MAX]; u_int64_t fcounters[FCNT_MAX]; u_int64_t scounters[SCNT_MAX]; u_int64_t pcounters[2][2][3]; u_int64_t bcounters[2][2]; u_int32_t running; u_int32_t states; u_int32_t src_nodes; u_int32_t since; u_int32_t debug; u_int32_t hostid; char ifname[IFNAMSIZ]; u_int8_t pf_chksum[MD5_DIGEST_LENGTH]; }; ``` - DIOCCLRSTATUS Clear the internal packet filter statistics. - DIOCNATLOOK *struct pfioc\_natlook \*pnl* Look up a state table entry by source and destination addresses and ports. ``` struct pfioc_natlook { struct pf_addr saddr; struct pf_addr daddr; struct pf_addr rsaddr; struct pf_addr rdaddr; u_int16_t sport; u_int16_t dport; u_int16_t rsport; u_int16_t rdport; sa_family_t af; u_int8_t proto; u_int8_t direction; }; ``` - DIOCSETDEBUG *u\_int32\_t \*level* Set the debug level. ``` enum { PF_DEBUG_NONE, PF_DEBUG_URGENT, PF_DEBUG_MISC, PF_DEBUG_NOISY }; ``` - DIOCGETSTATESV2 *struct pfioc\_states\_v2 \*ps* Get state table entries. ``` struct pfioc_states_v2 { int ps_len; uint64_t ps_req_version; union { void *ps_buf; struct pf_state_export *ps_states; }; }; struct pf_state_export { uint64_t version; uint64_t id; char ifname[IFNAMSIZ]; char orig_ifname[IFNAMSIZ]; struct pf_state_key_export key[2]; struct pf_state_peer_export src; struct pf_state_peer_export dst; struct pf_addr rt_addr; uint32_t rule; uint32_t anchor; uint32_t nat_rule; uint32_t creation; uint32_t expire; uint32_t spare0; uint64_t packets[2]; uint64_t bytes[2]; uint32_t creatorid; uint32_t spare1; sa_family_t af; uint8_t proto; uint8_t direction; uint8_t log; uint8_t state_flags_compat; uint8_t timeout; uint8_t sync_flags; uint8_t updates; uint16_t state_flags; uint16_t qid; uint16_t pqid; uint16_t dnpipe; uint16_t dnrpipe; int32_t rtableid; uint8_t min_ttl; uint8_t set_tos; uint16_t max_mss; uint8_t set_prio[2]; uint8_t rt; char rt_ifname[IFNAMSIZ]; uint8_t spare[72]; }; ``` - DIOCCHANGERULE *struct pfioc\_rule \*pcr* Add or remove the *rule* in the ruleset specified by *rule.action*. The type of operation to be performed is indicated by *action*, which can be any of the following: ``` enum { PF_CHANGE_NONE, PF_CHANGE_ADD_HEAD, PF_CHANGE_ADD_TAIL, PF_CHANGE_ADD_BEFORE, PF_CHANGE_ADD_AFTER, PF_CHANGE_REMOVE, PF_CHANGE_GET_TICKET }; ``` *ticket* must be set to the value obtained with PF\_CHANGE\_GET\_TICKET for all actions except PF\_CHANGE\_GET\_TICKET. *pool\_ticket* must be set to the value obtained with the DIOCBEGINADDRS call for all actions except PF\_CHANGE\_REMOVE and PF\_CHANGE\_GET\_TICKET. *anchor* indicates to which anchor the operation applies. *nr* indicates the rule number against which PF\_CHANGE\_ADD\_BEFORE, PF\_CHANGE\_ADD\_AFTER, or PF\_CHANGE\_REMOVE actions are applied. - DIOCCHANGEADDR *struct pfioc\_pooladdr \*pca* Add or remove the pool address *addr* from the rule specified by *r\_action*, *r\_num*, and *anchor*. - DIOCSETTIMEOUT *struct pfioc\_tm \*pt* ``` struct pfioc_tm { int timeout; int seconds; }; ``` Set the state timeout of *timeout* to *seconds*. The old value will be placed into *seconds*. For possible values of *timeout*, consult the PFTM\_\* values in ⟨*net/pfvar.h*⟩. - DIOCGETTIMEOUT *struct pfioc\_tm \*pt* Get the state timeout of *timeout*. The value will be placed into the *seconds* field. - DIOCCLRRULECTRS Clear per-rule statistics. - DIOCSETLIMIT *struct pfioc\_limit \*pl* Set the hard limits on the memory pools used by the packet filter. ``` struct pfioc_limit { int index; unsigned limit; }; enum { PF_LIMIT_STATES, PF_LIMIT_SRC_NODES, PF_LIMIT_FRAGS, PF_LIMIT_TABLE_ENTRIES, PF_LIMIT_MAX }; ``` - DIOCGETLIMIT *struct pfioc\_limit \*pl* Get the hard *limit* for the memory pool indicated by *index*. - DIOCRCLRTABLES *struct pfioc\_table \*io* Clear all tables. All the ioctls that manipulate radix tables use the same structure described below. For DIOCRCLRTABLES, *pfrio\_ndel* contains on exit the number of tables deleted. ``` struct pfioc_table { struct pfr_table pfrio_table; void *pfrio_buffer; int pfrio_esize; int pfrio_size; int pfrio_size2; int pfrio_nadd; int pfrio_ndel; int pfrio_nchange; int pfrio_flags; u_int32_t pfrio_ticket; }; #define pfrio_exists pfrio_nadd #define pfrio_nzero pfrio_nadd #define pfrio_nmatch pfrio_nadd #define pfrio_naddr pfrio_size2 #define pfrio_setflag pfrio_size2 #define pfrio_clrflag pfrio_nadd ``` - DIOCRADDTABLES *struct pfioc\_table \*io* Create one or more tables. On entry, *pfrio\_buffer* must point to an array of *struct* *pfr\_table* containing at least *pfrio\_size* elements. *pfrio\_esize* must be the size of *struct* *pfr\_table*. On exit, *pfrio\_nadd* contains the number of tables effectively created. ``` struct pfr_table { char pfrt_anchor[MAXPATHLEN]; char pfrt_name[PF_TABLE_NAME_SIZE]; u_int32_t pfrt_flags; u_int8_t pfrt_fback; }; ``` - DIOCRDELTABLES *struct pfioc\_table \*io* Delete one or more tables. On entry, *pfrio\_buffer* must point to an array of *struct* *pfr\_table* containing at least *pfrio\_size* elements. *pfrio\_esize* must be the size of *struct* *pfr\_table*. On exit, *pfrio\_ndel* contains the number of tables effectively deleted. - DIOCRGETTABLES *struct pfioc\_table \*io* Get the list of all tables. On entry, *pfrio\_buffer\[pfrio\_size\]* contains a valid writeable buffer for *pfr\_table* structures. On exit, *pfrio\_size* contains the number of tables written into the buffer. If the buffer is too small, the kernel does not store anything but just returns the required buffer size, without error. - DIOCRGETTSTATS *struct pfioc\_table \*io* This call is like DIOCRGETTABLES but is used to get an array of *pfr\_tstats* structures. ``` struct pfr_tstats { struct pfr_table pfrts_t; u_int64_t pfrts_packets [PFR_DIR_MAX][PFR_OP_TABLE_MAX]; u_int64_t pfrts_bytes [PFR_DIR_MAX][PFR_OP_TABLE_MAX]; u_int64_t pfrts_match; u_int64_t pfrts_nomatch; time_t pfrts_tzero; int pfrts_cnt; int pfrts_refcnt[PFR_REFCNT_MAX]; }; #define pfrts_name pfrts_t.pfrt_name #define pfrts_flags pfrts_t.pfrt_flags ``` - DIOCRCLRTSTATS *struct pfioc\_table \*io* Clear the statistics of one or more tables. On entry, *pfrio\_buffer* must point to an array of *struct* *pfr\_table* containing at least *pfrio\_size* elements. *pfrio\_esize* must be the size of *struct* *pfr\_table*. On exit, *pfrio\_nzero* contains the number of tables effectively cleared. - DIOCRCLRADDRS *struct pfioc\_table \*io* Clear all addresses in a table. On entry, *pfrio\_table* contains the table to clear. On exit, *pfrio\_ndel* contains the number of addresses removed. - DIOCRADDADDRS *struct pfioc\_table \*io* Add one or more addresses to a table. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer* must point to an array of *struct* *pfr\_addr* containing at least *pfrio\_size* elements to add to the table. *pfrio\_esize* must be the size of *struct* *pfr\_addr*. On exit, *pfrio\_nadd* contains the number of addresses effectively added. ``` struct pfr_addr { union { struct in_addr _pfra_ip4addr; struct in6_addr _pfra_ip6addr; } pfra_u; u_int8_t pfra_af; u_int8_t pfra_net; u_int8_t pfra_not; u_int8_t pfra_fback; }; #define pfra_ip4addr pfra_u._pfra_ip4addr #define pfra_ip6addr pfra_u._pfra_ip6addr ``` - DIOCRDELADDRS *struct pfioc\_table \*io* Delete one or more addresses from a table. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer* must point to an array of *struct* *pfr\_addr* containing at least *pfrio\_size* elements to delete from the table. *pfrio\_esize* must be the size of *struct* *pfr\_addr*. On exit, *pfrio\_ndel* contains the number of addresses effectively deleted. - DIOCRSETADDRS *struct pfioc\_table \*io* Replace the content of a table by a new address list. This is the most complicated command, which uses all the structure members. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer* must point to an array of *struct* *pfr\_addr* containing at least *pfrio\_size* elements which become the new contents of the table. *pfrio\_esize* must be the size of *struct* *pfr\_addr*. Additionally, if *pfrio\_size2* is non-zero, *pfrio\_buffer\[pfrio\_size..pfrio\_size2\]* must be a writeable buffer, into which the kernel can copy the addresses that have been deleted during the replace operation. On exit, *pfrio\_ndel*, *pfrio\_nadd*, and *pfrio\_nchange* contain the number of addresses deleted, added, and changed by the kernel. If *pfrio\_size2* was set on entry, *pfrio\_size2* will point to the size of the buffer used, exactly like DIOCRGETADDRS. - DIOCRGETADDRS *struct pfioc\_table \*io* Get all the addresses of a table. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer\[pfrio\_size\]* contains a valid writeable buffer for *pfr\_addr* structures. On exit, *pfrio\_size* contains the number of addresses written into the buffer. If the buffer was too small, the kernel does not store anything but just returns the required buffer size, without returning an error. - DIOCRGETASTATS *struct pfioc\_table \*io* This call is like DIOCRGETADDRS but is used to get an array of *pfr\_astats* structures. ``` struct pfr_astats { struct pfr_addr pfras_a; u_int64_t pfras_packets [PFR_DIR_MAX][PFR_OP_ADDR_MAX]; u_int64_t pfras_bytes [PFR_DIR_MAX][PFR_OP_ADDR_MAX]; time_t pfras_tzero; }; ``` - DIOCRCLRASTATS *struct pfioc\_table \*io* Clear the statistics of one or more addresses. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer* must point to an array of *struct* *pfr\_addr* containing at least *pfrio\_size* elements to be cleared from the table. *pfrio\_esize* must be the size of *struct* *pfr\_addr*. On exit, *pfrio\_nzero* contains the number of addresses effectively cleared. - DIOCRTSTADDRS *struct pfioc\_table \*io* Test if the given addresses match a table. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer* must point to an array of *struct* *pfr\_addr* containing at least *pfrio\_size* elements, each of which will be tested for a match in the table. *pfrio\_esize* must be the size of *struct* *pfr\_addr*. On exit, the kernel updates the *pfr\_addr* array by setting the *pfra\_fback* member appropriately. - DIOCRSETTFLAGS *struct pfioc\_table \*io* Change the PFR\_TFLAG\_CONST or PFR\_TFLAG\_PERSIST flags of a table. On entry, *pfrio\_buffer* must point to an array of *struct* *pfr\_table* containing at least *pfrio\_size* elements. *pfrio\_esize* must be the size of *struct* *pfr\_table*. *pfrio\_setflag* must contain the flags to add, while *pfrio\_clrflag* must contain the flags to remove. On exit, *pfrio\_nchange* and *pfrio\_ndel* contain the number of tables altered or deleted by the kernel. Yes, tables can be deleted if one removes the PFR\_TFLAG\_PERSIST flag of an unreferenced table. - DIOCRINADEFINE *struct pfioc\_table \*io* Defines a table in the inactive set. On entry, *pfrio\_table* contains the table ID and *pfrio\_buffer\[pfrio\_size\]* contains an array of *pfr\_addr* structures to put in the table. A valid ticket must also be supplied to *pfrio\_ticket*. On exit, *pfrio\_nadd* contains 0 if the table was already defined in the inactive list or 1 if a new table has been created. *pfrio\_naddr* contains the number of addresses effectively put in the table. - DIOCXBEGIN *struct pfioc\_trans \*io* ``` struct pfioc_trans { int size; /* number of elements */ int esize; /* size of each element in bytes */ struct pfioc_trans_e { int rs_num; char anchor[MAXPATHLEN]; u_int32_t ticket; } *array; }; ``` Clear all the inactive rulesets specified in the *pfioc\_trans\_e* array. For each ruleset, a ticket is returned for subsequent "add rule" ioctls, as well as for the DIOCXCOMMIT and DIOCXROLLBACK calls. Ruleset types, identified by *rs\_num*, include the following: - PF\_RULESET\_SCRUB Scrub (packet normalization) rules. - PF\_RULESET\_FILTER Filter rules. - PF\_RULESET\_NAT NAT (Network Address Translation) rules. - PF\_RULESET\_BINAT Bidirectional NAT rules. - PF\_RULESET\_RDR Redirect rules. - PF\_RULESET\_ALTQ ALTQ disciplines. - PF\_RULESET\_TABLE Address tables. - DIOCXCOMMIT *struct pfioc\_trans \*io* Atomically switch a vector of inactive rulesets to the active rulesets. This call is implemented as a standard two-phase commit, which will either fail for all rulesets or completely succeed. All tickets need to be valid. This ioctl returns EBUSY if another process is concurrently updating some of the same rulesets. - DIOCXROLLBACK *struct pfioc\_trans \*io* Clean up the kernel by undoing all changes that have taken place on the inactive rulesets since the last DIOCXBEGIN. DIOCXROLLBACK will silently ignore rulesets for which the ticket is invalid. - DIOCSETHOSTID *u\_int32\_t \*hostid* Set the host ID, which is used by [pfsync(4)](/pfsync/4.md) to identify which host created state table entries. - DIOCOSFPFLUSH Flush the passive OS fingerprint table. - DIOCOSFPADD *struct pf\_osfp\_ioctl \*io* ``` struct pf_osfp_ioctl { struct pf_osfp_entry { SLIST_ENTRY(pf_osfp_entry) fp_entry; pf_osfp_t fp_os; char fp_class_nm[PF_OSFP_LEN]; char fp_version_nm[PF_OSFP_LEN]; char fp_subtype_nm[PF_OSFP_LEN]; } fp_os; pf_tcpopts_t fp_tcpopts; u_int16_t fp_wsize; u_int16_t fp_psize; u_int16_t fp_mss; u_int16_t fp_flags; u_int8_t fp_optcnt; u_int8_t fp_wscale; u_int8_t fp_ttl; int fp_getnum; }; ``` Add a passive OS fingerprint to the table. Set *fp\_os.fp\_os* to the packed fingerprint, *fp\_os.fp\_class\_nm* to the name of the class (Linux, Windows, etc), *fp\_os.fp\_version\_nm* to the name of the version (NT, 95, 98), and *fp\_os.fp\_subtype\_nm* to the name of the subtype or patchlevel. The members *fp\_mss*, *fp\_wsize*, *fp\_psize*, *fp\_ttl*, *fp\_optcnt*, and *fp\_wscale* are set to the TCP MSS, the TCP window size, the IP length, the IP TTL, the number of TCP options, and the TCP window scaling constant of the TCP SYN packet, respectively. The *fp\_flags* member is filled according to the ⟨*net/pfvar.h*⟩ include file PF\_OSFP\_\* defines. The *fp\_tcpopts* member contains packed TCP options. Each option uses PF\_OSFP\_TCPOPT\_BITS bits in the packed value. Options include any of PF\_OSFP\_TCPOPT\_NOP, PF\_OSFP\_TCPOPT\_SACK, PF\_OSFP\_TCPOPT\_WSCALE, PF\_OSFP\_TCPOPT\_MSS, or PF\_OSFP\_TCPOPT\_TS. The *fp\_getnum* member is not used with this ioctl. The structure's slack space must be zeroed for correct operation; [memset(3)](/memset/3.md) the whole structure to zero before filling and sending to the kernel. - DIOCOSFPGET *struct pf\_osfp\_ioctl \*io* Get the passive OS fingerprint number *fp\_getnum* from the kernel's fingerprint list. The rest of the structure members will come back filled. Get the whole list by repeatedly incrementing the *fp\_getnum* number until the ioctl returns EBUSY. - DIOCGETSRCNODES *struct pfioc\_src\_nodes \*psn* ``` struct pfioc_src_nodes { int psn_len; union { caddr_t psu_buf; struct pf_src_node *psu_src_nodes; } psn_u; #define psn_buf psn_u.psu_buf #define psn_src_nodes psn_u.psu_src_nodes }; ``` Get the list of source nodes kept by sticky addresses and source tracking. The ioctl must be called once with *psn\_len* set to 0. If the ioctl returns without error, *psn\_len* will be set to the size of the buffer required to hold all the *pf\_src\_node* structures held in the table. A buffer of this size should then be allocated, and a pointer to this buffer placed in *psn\_buf*. The ioctl must then be called again to fill this buffer with the actual source node data. After that call, *psn\_len* will be set to the length of the buffer actually used. - DIOCCLRSRCNODES Clear the tree of source tracking nodes. - DIOCIGETIFACES *struct pfioc\_iface \*io* Get the list of interfaces and interface groups known to **pf**. All the ioctls that manipulate interfaces use the same structure described below: ``` struct pfioc_iface { char pfiio_name[IFNAMSIZ]; void *pfiio_buffer; int pfiio_esize; int pfiio_size; int pfiio_nzero; int pfiio_flags; }; ``` If not empty, *pfiio\_name* can be used to restrict the search to a specific interface or group. *pfiio\_buffer\[pfiio\_size\]* is the user-supplied buffer for returning the data. On entry, *pfiio\_size* contains the number of *pfi\_kif* entries that can fit into the buffer. The kernel will replace this value by the real number of entries it wants to return. *pfiio\_esize* should be set to sizeof(struct pfi\_kif). The data is returned in the *pfi\_kif* structure described below: ``` struct pfi_kif { char pfik_name[IFNAMSIZ]; union { RB_ENTRY(pfi_kif) pfik_tree; LIST_ENTRY(pfi_kif) pfik_list; }; u_int64_t pfik_packets[2][2][2]; u_int64_t pfik_bytes[2][2][2]; u_int32_t pfik_tzero; u_int pfik_flags; struct ifnet *pfik_ifp; struct ifg_group *pfik_group; u_int pfik_rulerefs; TAILQ_HEAD(, pfi_dynaddr) pfik_dynaddrs; }; ``` - DIOCSETIFFLAG *struct pfioc\_iface \*io* Set the user settable flags (described above) of the **pf** internal interface description. The filtering process is the same as for DIOCIGETIFACES. ``` #define PFI_IFLAG_SKIP 0x0100 /* skip filtering on interface */ ``` - DIOCCLRIFFLAG *struct pfioc\_iface \*io* Works as DIOCSETIFFLAG above but clears the flags. - DIOCKILLSRCNODES *struct pfioc\_iface \*io* Explicitly remove source tracking nodes. ## FILES - */dev/pf* packet filtering device. ## EXAMPLES The following example demonstrates how to use the DIOCNATLOOK command to find the internal host/port of a NATed connection: ``` #include #include #include #include #include #include #include #include #include #include u_int32_t read_address(const char *s) { int a, b, c, d; sscanf(s, "%i.%i.%i.%i", &a, &b, &c, &d); return htonl(a << 24 | b << 16 | c << 8 | d); } void print_address(u_int32_t a) { a = ntohl(a); printf("%d.%d.%d.%d", a >> 24 & 255, a >> 16 & 255, a >> 8 & 255, a & 255); } int main(int argc, char *argv[]) { struct pfioc_natlook nl; int dev; if (argc != 5) { printf("%s \n", argv[0]); return 1; } dev = open("/dev/pf", O_RDWR); if (dev == -1) err(1, "open(\"/dev/pf\") failed"); memset(&nl, 0, sizeof(struct pfioc_natlook)); nl.saddr.v4.s_addr = read_address(argv[1]); nl.sport = htons(atoi(argv[2])); nl.daddr.v4.s_addr = read_address(argv[3]); nl.dport = htons(atoi(argv[4])); nl.af = AF_INET; nl.proto = IPPROTO_TCP; nl.direction = PF_IN; if (ioctl(dev, DIOCNATLOOK, &nl)) err(1, "DIOCNATLOOK"); printf("internal host "); print_address(nl.rsaddr.v4.s_addr); printf(":%u\n", ntohs(nl.rsport)); return 0; } ``` ## SEE ALSO [ioctl(2)](/ioctl/2.md), [altq(4)](/altq/4.md), [if\_bridge(4)](/if_bridge/4.md), [pflog(4)](/pflog/4.md), [pfsync(4)](/pfsync/4.md), [pfctl(8)](/pfctl/8.md), [altq(9)](/altq/9.md) ## HISTORY The **pf** packet filtering mechanism first appeared in OpenBSD 3.0 and then FreeBSD 5.2. This implementation is derived from OpenBSD 4.5. A number of individual features, improvements, bug fixes and security fixes have been ported from later versions of OpenBSD. It has been heavily modified to be capable of running in multithreaded FreeBSD kernel and scale its performance on multiple CPUs.