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$FreeBSD: head/contrib/pf/man/pf.4 128403 2004-04-18 13:59:12Z mlaier $
.Dd June 24, 2001 .Dt PF 4 .Os .Sh NAME .Nm pf .Nd packet filter .Sh SYNOPSIS .Cd "options PFIL_HOOKS" .Cd "device pf" .Sh DESCRIPTION Packet filtering takes place in the kernel. A pseudo-device,
a /dev/pf , allows userland processes to control the behavior of the packet filter through an .Xr ioctl 2 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 .Xr pfctl 8 .
p Manipulations like loading a ruleset that involve more than a single ioctl call require a so-called ticket, which prevents the occurrence of multiple concurrent manipulations.
p Fields of ioctl parameter structures that refer to packet data (like addresses and ports) are generally expected in network byte-order. .Sh FILES l -tag -width /dev/pf -compact t Pa /dev/pf packet filtering device. .El .Sh IOCTL INTERFACE pf supports the following .Xr ioctl 2 commands: l -tag -width xxxxxx t Dv DIOCSTART Starts the packet filter. t Dv DIOCSTOP Stops the packet filter. t Dv DIOCSTARTALTQ Starts the ALTQ bandwidth control system. t Dv DIOCSTOPALTQ Stops the ALTQ bandwidth control system. t Dv DIOCBEGINADDRS Fa "u_int32_t" Clears the buffer address pool and returns a ticket for subsequent DIOCADDADDR, DIOCADDRULE and DIOCCHANGERULE calls. t Dv DIOCADDADDR Fa "struct pfioc_pooladdr" d -literal 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[PF_ANCHOR_NAME_SIZE]; char ruleset[PF_RULESET_NAME_SIZE]; struct pf_pooladdr addr; }; .Ed
p Adds pool address .Va addr to the buffer address pool to be used in the following DIOCADDRULE or DIOCCHANGERULE call. All other members of the structure are ignored. t Dv DIOCBEGINRULES Fa "u_int32_t" Clears the inactive ruleset for the type of rule indicated by .Va rule.action and returns a ticket for subsequent DIOCADDRULE and DIOCCOMMITRULES calls. t Dv DIOCADDRULE Fa "struct pfioc_rule" d -literal struct pfioc_rule { u_int32_t action; u_int32_t ticket; u_int32_t pool_ticket; u_int32_t nr; char anchor[PF_ANCHOR_NAME_SIZE]; char ruleset[PF_RULESET_NAME_SIZE]; struct pf_rule rule; }; .Ed
p Adds .Va rule at the end of the inactive ruleset. Requires .Va ticket obtained through preceding DIOCBEGINRULES call, and .Va pool_ticket obtained through DIOCBEGINADDRS call. DIOCADDADDR must also be called if any pool addresses are required. The optional .Va anchor and .Va ruleset names indicate the anchor and ruleset in which to append the rule. .Va nr and .Va action are ignored. t Dv DIOCCOMMITRULES Fa "u_int32_t" Switch inactive to active filter ruleset. Requires .Va ticket . t Dv DIOCBEGINALTQS Fa "u_int32_t" Clears the inactive list of queues and returns a ticket for subsequent DIOCADDALTQ and DIOCCOMMITALTQS calls. t Dv DIOCADDALTQ Fa "struct pfioc_altq" Adds d -literal struct pfioc_altq { u_int32_t ticket; u_int32_t nr; struct pf_altq altq; }; .Ed t Dv DIOCCOMMITALTQS Fa "u_int32_t" Switch inactive to active list of queues. Requires .Va ticket . t Dv DIOCGETRULES Fa "struct pfioc_rule" Returns .Va ticket for subsequent DIOCGETRULE calls and .Va nr of rules in the active ruleset. t Dv DIOCGETRULE Fa "struct pfioc_rule" Returns .Va rule number .Va nr using .Va ticket obtained through a preceding DIOCGETRULES call. t Dv DIOCGETADDRS Fa "struct pfioc_pooladdr" Returns .Va ticket for subsequent DIOCGETADDR calls and .Va nr of pool addresses in the rule specified with .Va r_action , .Va r_num , .Va anchor and .Va ruleset . t Dv DIOCGETADDR Fa "struct pfioc_pooladdr" Returns pool address .Va addr number .Va nr from the rule specified with .Va r_action , .Va r_num , .Va anchor and .Va ruleset using .Va ticket obtained through a preceding DIOCGETADDRS call. t Dv DIOCGETALTQS Fa "struct pfioc_altq" Returns .Va ticket for subsequent DIOCGETALTQ calls and .Va nr of queues in the active list. t Dv DIOCGETALTQ Fa "struct pfioc_altq" Returns .Va altq number .Va nr using .Va ticket obtained through a preceding DIOCGETALTQS call. t Dv DIOCGETQSTATS Fa "struct pfioc_qstats" Returns statistics on a queue. d -literal struct pfioc_qstats { u_int32_t ticket; u_int32_t nr; void *buf; int nbytes; u_int8_t scheduler; }; .Ed
p A pointer to a buffer of statistics .Va buf of length .Va nbytes for the queue specified by .Va nr . t Dv DIOCCLRSTATES Clears the state table. t Dv DIOCADDSTATE Fa "struct pfioc_state" Adds a state entry. t Dv DIOCGETSTATE Fa "struct pfioc_state" d -literal struct pfioc_state { u_int32_t nr; struct pf_state state; }; .Ed
p Extracts the entry with the specified number from the state table. t Dv DIOCKILLSTATES Fa "struct pfioc_state_kill" Removes matching entries from the state table. Returns the number of killed states in psk_af. d -literal struct pfioc_state_kill { int psk_af; int psk_proto; struct pf_rule_addr psk_src; struct pf_rule_addr psk_dst; }; .Ed t Dv DIOCSETSTATUSIF Fa "struct pfioc_if" d -literal struct pfioc_if { char ifname[IFNAMSIZ]; }; .Ed
p Specifies the interface for which statistics are accumulated. t Dv DIOCGETSTATUS Fa "struct pf_status" d -literal struct pf_status { u_int64_t counters[PFRES_MAX]; u_int64_t fcounters[FCNT_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 since; u_int32_t debug; }; .Ed
p Gets the internal packet filter statistics. t Dv DIOCCLRSTATUS Clears the internal packet filter statistics. t Dv DIOCNATLOOK Fa "struct pfioc_natlook" Looks up a state table entry by source and destination addresses and ports. d -literal 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; u_int8_t af; u_int8_t proto; u_int8_t direction; }; .Ed t Dv DIOCSETDEBUG Fa "u_int32_t" Sets the debug level. d -literal enum { PF_DEBUG_NONE=0, PF_DEBUG_URGENT=1, PF_DEBUG_MISC=2 }; .Ed t Dv DIOCGETSTATES Fa "struct pfioc_states" d -literal struct pfioc_states { int ps_len; union { caddr_t psu_buf; struct pf_state *psu_states; } ps_u; #define ps_buf ps_u.psu_buf #define ps_states ps_u.psu_states }; .Ed t Dv DIOCCHANGERULE Fa "struct pfioc_rule" Adds or removes the .Va rule in the ruleset specified by .Va rule.action . d -literal enum { PF_CHANGE_ADD_HEAD=1, PF_CHANGE_ADD_TAIL=2, PF_CHANGE_ADD_BEFORE=3, PF_CHANGE_ADD_AFTER=4, PF_CHANGE_REMOVE=5, PF_CHANGE_GET_TICKET=6 }; .Ed
p The type of operation to be performed is indicated by .Va action .
p .Va ticket must be set to the value obtained with PF_CHANGE_GET_TICKET for all actions except PF_CHANGE_GET_TICKET. .Va 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.
p .Va anchor and .Va ruleset indicate which anchor and ruleset the operation applies to. .Va nr indicates the rule number against which PF_CHANGE_ADD_BEFORE, PF_CHANGE_ADD_AFTER or PF_CHANGE_REMOVE actions are applied. t Dv DIOCCHANGEADDR Fa "struct pfioc_pooladdr" Adds or removes a pool address .Va addr from a rule specified with .Va r_action , .Va r_num , .Va anchor and .Va ruleset . t Dv DIOCSETTIMEOUT Fa "struct pfioc_tm" d -literal struct pfioc_tm { int timeout; int seconds; }; .Ed t Dv DIOCGETTIMEOUT Fa "struct pfioc_tm" t Dv DIOCCLRRULECTRS Clear per-rule statistics. t Dv DIOCSETLIMIT Fa "struct pfioc_limit" Sets hard limits on the memory pools used by the packet filter. d -literal struct pfioc_limit { int index; unsigned limit; }; .Ed t Dv DIOCGETLIMIT Fa "struct pfioc_limit" t Dv DIOCRCLRTABLES Fa "struct pfioc_table" Clear all tables. All the IOCTLs that manipulate radix tables use the same structure described below. For .Dv DIOCRCLRTABLES, pfrio_ndel contains on exit the number of tables deleted. d -literal 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; int 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 .Ed t Dv DIOCRADDTABLES Fa "struct pfioc_table" Creates one or more tables. On entry, pfrio_buffer[pfrio_size] contains a table of pfr_table structures. On exit, pfrio_nadd contains the number of tables effectively created. d -literal struct pfr_table { char pfrt_anchor[PF_ANCHOR_NAME_SIZE]; char pfrt_ruleset[PF_RULESET_NAME_SIZE]; char pfrt_name[PF_TABLE_NAME_SIZE]; u_int32_t pfrt_flags; u_int8_t pfrt_fback; }; .Ed t Dv DIOCRDELTABLES Fa "struct pfioc_table" Deletes one or more tables. On entry, pfrio_buffer[pfrio_size] contains a table of pfr_table structures. On exit, pfrio_nadd contains the number of tables effectively deleted. t Dv DIOCRGETTABLES Fa "struct pfioc_table" 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. t Dv DIOCRGETTSTATS Fa "struct pfioc_table" Like .Dv DIOCRGETTABLES , but returns an array of pfr_tstats structures. d -literal 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; long 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 .Ed t Dv DIOCRCLRTSTATS Fa "struct pfioc_table" Clears the statistics of one or more tables. On entry, pfrio_buffer[pfrio_size] contains a table of pfr_table structures. On exit, pfrio_nzero contains the number of tables effectively cleared. t Dv DIOCRCLRADDRS Fa "struct pfioc_table" 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. t Dv DIOCRADDADDRS Fa "struct pfioc_table" Add one or more addresses to a table. On entry, pfrio_table contains the table id and pfrio_buffer[pfrio_size] contains the list of pfr_addr structures to add. On exit, pfrio_nadd contains the number of addresses effectively added. d -literal 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 .Ed t Dv DIOCRDELADDRS Fa "struct pfioc_table" Delete one or more addresses from a table. On entry, pfrio_table contains the table id and pfrio_buffer[pfrio_size] contains the list of pfr_addr structures to delete. On exit, pfrio_ndel contains the number of addresses effectively deleted. t Dv DIOCRSETADDRS Fa "struct pfioc_table" 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[pfrio_size] contains the new list of pfr_addr structures. In addition to that, if size2 is nonzero, 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 .Dv DIOCRGETADDRS . t Dv DIOCRGETADDRS Fa "struct pfioc_table" 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 return the required buffer size, without returning an error. t Dv DIOCRGETASTATS Fa "struct pfioc_table" Like .Dv DIOCRGETADDRS , but returns an array of pfr_astats structures. d -literal 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]; long pfras_tzero; }; .Ed t Dv DIOCRCLRASTATS Fa "struct pfioc_table" Clears the statistics of one or more addresses. On entry, pfrio_table contains the table id and pfrio_buffer[pfrio_size] contains a table of pfr_addr structures to clear. On exit, pfrio_nzero contains the number of addresses effectively cleared. t Dv DIOCRTSTADDRS Fa "struct pfioc_table" Test if the given addresses match a table. On entry, pfrio_table contains the table id and pfrio_buffer[pfrio_size] contains a table of pfr_addr structures to test. On exit, the kernel updates the pfr_addr table by setting the pfra_fback member appropriately. t Dv DIOCRSETTFLAGS Fa "struct pfioc_table" Change the .Va const or .Va persist flag of a table. On entry, pfrio_buffer[pfrio_size] contains a table of pfr_table structures, and pfrio_setflag contains the flags to add, while pfrio_clrflag contains 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 .Va persist flag of an unreferenced table. t Dv DIOCRINABEGIN Fa "struct pfioc_table" Starts a transaction with the inactive set of tables. Cleans up any leftover from a previously aborted transaction, and returns a new ticket. On exit, pfrio_ndel contains the number of leftover table deleted, and pfrio_ticket contains a valid ticket to use for the following two IOCTLs. t Dv DIOCRINACOMMIT Fa "struct pfioc_table" Commit the inactive set of tables into the active set. While copying the addresses, do a best effort to keep statistics for addresses present before and after the commit. On entry, io->pfrio_ticket takes a valid ticket. On exit, io->pfrio_nadd and io->pfrio_nchange contain the number of tables added and altered by the commit operation. t Dv DIOCRINADEFINE Fa "struct pfioc_table" Defines a table in the inactive set. On entry, pfrio_table contains the table id and pfrio_buffer[pfrio_size] contains the list 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. t Dv DIOCFPFLUSH Flush the passive OS fingerprint table. t Dv DIOCFPADD Fa "struct pf_osfp_ioctl" d -literal 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; u_int16_t fp_mss; u_int16_t fp_wsize; u_int16_t fp_psize; u_int8_t fp_ttl; u_int8_t fp_wscale; u_int8_t fp_flags; int fp_getnum; }; .Ed
p Add a passive OS fingerprint to the table. Set .Va fp_os.fp_os to the packed fingerprint, .Va fp_os.fp_class_nm to the name of the class (Linux, Windows, etc), .Va fp_os.fp_version_nm to the name of the version (NT, 95, 98), and .Va fp_os.fp_subtype_nm to the name of the subtype or patchlevel. The members .Va fp_mss , .Va fp_wsize , .Va fp_psize , .Va fp_ttl , and .Va fp_wscale are set to the TCP MSS, the TCP window size, the IP length and the IP TTL of the TCP SYN packet respectively. The .Va fp_flags member is filled according to the net/pfvar.h include file PF_OSFP_* defines. The .Va fp_getnum is not used with this ioctl.
p The structure's slack space must be zeroed for correct operation; memset the whole structure to zero before filling and sending to the kernel. t Dv DIOCFPGET Fa "struct pf_osfp_ioctl" d -literal 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; u_int16_t fp_mss; u_int16_t fp_wsize; u_int16_t fp_psize; u_int8_t fp_ttl; u_int8_t fp_wscale; u_int8_t fp_flags; int fp_getnum; }; .Ed
p Get the passive OS fingerprint number .Va 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 .Va fp_getnum number until the ioctl returns EBUSY. .El .Sh EXAMPLES The following example demonstrates how to use the DIOCNATLOOK command to find the internal host/port of a NATed connection. d -literal #include <sys/types.h> #include <sys/socket.h> #include <sys/ioctl.h> #include <sys/fcntl.h> #include <net/if.h> #include <netinet/in.h> #include <net/pfvar.h> #include <err.h> #include <stdio.h> #include <stdlib.h> 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 <gwy addr> <gwy port> <ext addr> <ext port>\\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; } .Ed .Sh SEE ALSO .Xr ioctl 2 , .Xr bridge 4 , .Xr pflog 4 , .Xr pfsync 4 , .Xr pfctl 8 .Sh HISTORY The .Nm packet filtering mechanism first appeared in .Ox 3.0 .