PF(4) OpenBSD Programmer's Manual PF(4)
NAME
pf - packet filter
SYNOPSIS
pseudo-device pf 1
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) interface. There are commands to enable and disable
the filter, load rulesets, add and remove individual rules or retrieve
state table entries and statistics. The most commonly used functions are
covered by pfctl(8).
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.
Fields of ioctl parameter structures that refer to packet data (like ad-
dresses and ports) are generally expected in network byte-order.
FILES
/dev/pf packet filtering device.
IOCTL INTERFACE
pf supports the following ioctl(2) commands:
DIOCSTART
Starts the packet filter.
DIOCSTOP
Stops the packet filter.
DIOCSTARTALTQ
Starts the ALTQ bandwidth control system.
DIOCSTOPALTQ
Stops the ALTQ bandwidth control system.
DIOCBEGINADDRS u_int32_t
Clears the buffer address pool and returns a ticket for subse-
quent DIOCADDADDR, DIOCADDRULE and DIOCCHANGERULE calls.
DIOCADDADDR struct pfioc_pooladdr
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;
};
Adds pool address addr to the buffer address pool to be used in
the following DIOCADDRULE or DIOCCHANGERULE call. All other mem-
bers of the structure are ignored.
DIOCBEGINRULES u_int32_t
Clears the inactive ruleset for the type of rule indicated by
rule.action and returns a ticket for subsequent DIOCADDRULE and
DIOCCOMMITRULES calls.
DIOCADDRULE struct pfioc_rule
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;
};
Adds rule at the end of the inactive ruleset. Requires ticket
obtained through preceding DIOCBEGINRULES call, and pool_ticket
obtained through DIOCBEGINADDRS call. DIOCADDADDR must also be
called if any pool addresses are required. The optional anchor
and ruleset names indicate the anchor and ruleset in which to ap-
pend the rule. nr and action are ignored.
DIOCCOMMITRULES u_int32_t
Switch inactive to active filter ruleset. Requires ticket.
DIOCBEGINALTQS u_int32_t
Clears the inactive list of queues and returns a ticket for sub-
sequent DIOCADDALTQ and DIOCCOMMITALTQS calls.
DIOCADDALTQ struct pfioc_altq
Adds
struct pfioc_altq {
u_int32_t ticket;
u_int32_t nr;
struct pf_altq altq;
};
DIOCCOMMITALTQS u_int32_t
Switch inactive to active list of queues. Requires ticket.
DIOCGETRULES struct pfioc_rule
Returns ticket for subsequent DIOCGETRULE calls and nr of rules
in the active ruleset.
DIOCGETRULE struct pfioc_rule
Returns rule number nr using ticket obtained through a preceding
DIOCGETRULES call.
DIOCGETADDRS struct pfioc_pooladdr
Returns ticket for subsequent DIOCGETADDR calls and nr of pool
addresses in the rule specified with r_action, r_num, anchor and
ruleset.
DIOCGETADDR struct pfioc_pooladdr
Returns pool address addr number nr from the rule specified with
r_action, r_num, anchor and ruleset using ticket obtained through
a preceding DIOCGETADDRS call.
DIOCGETALTQS struct pfioc_altq
Returns ticket for subsequent DIOCGETALTQ calls and nr of queues
in the active list.
DIOCGETALTQ struct pfioc_altq
Returns altq number nr using ticket obtained through a preceding
DIOCGETALTQS call.
DIOCGETQSTATS struct pfioc_qstats
Returns statistics on a queue.
struct pfioc_qstats {
u_int32_t ticket;
u_int32_t nr;
void *buf;
int nbytes;
u_int8_t scheduler;
};
A pointer to a buffer of statistics buf of length nbytes for the
queue specified by nr.
DIOCCLRSTATES
Clears the state table.
DIOCADDSTATE struct pfioc_state
Adds a state entry.
DIOCGETSTATE struct pfioc_state
struct pfioc_state {
u_int32_t nr;
struct pf_state state;
};
Extracts the entry with the specified number from the state
table.
DIOCKILLSTATES struct pfioc_state_kill
Removes matching entries from the state table. Returns the num-
ber of killed states in psk_af.
struct pfioc_state_kill {
int psk_af;
int psk_proto;
struct pf_rule_addr psk_src;
struct pf_rule_addr psk_dst;
};
DIOCSETSTATUSIF struct pfioc_if
struct pfioc_if {
char ifname[IFNAMSIZ];
};
Specifies the interface for which statistics are accumulated.
DIOCGETSTATUS struct pf_status
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;
};
Gets the internal packet filter statistics.
DIOCCLRSTATUS
Clears the internal packet filter statistics.
DIOCNATLOOK struct pfioc_natlook
Looks 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;
u_int8_t af;
u_int8_t proto;
u_int8_t direction;
};
DIOCSETDEBUG u_int32_t
Sets the debug level.
enum { PF_DEBUG_NONE=0, PF_DEBUG_URGENT=1, PF_DEBUG_MISC=2 };
DIOCGETSTATES struct pfioc_states
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
};
DIOCCHANGERULE struct pfioc_rule
Adds or removes the rule in the ruleset specified by rule.action.
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 };
The type of operation to be performed is indicated by action.
ticket must be set to the value obtained with PF_CHANGE_GET_TICK-
ET 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 and ruleset indicate which anchor and ruleset the opera-
tion applies to. nr indicates the rule number against which
PF_CHANGE_ADD_BEFORE, PF_CHANGE_ADD_AFTER or PF_CHANGE_REMOVE ac-
tions are applied.
DIOCCHANGEADDR struct pfioc_addr
Adds or removes a pool address addr from a rule specified with
r_action, r_num, anchor and ruleset.
DIOCSETTIMEOUT struct pfioc_tm
struct pfioc_tm {
int timeout;
int seconds;
};
DIOCGETTIMEOUT struct pfioc_tm
DIOCCLRRULECTRS
Clear per-rule statistics.
DIOCSETLIMIT struct pfioc_limit
Sets hard limits on the memory pools used by the packet filter.
struct pfioc_limit {
int index;
unsigned limit;
};
DIOCGETLIMIT struct pfioc_limit
DIOCRCLRTABLES struct pfioc_table
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_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
DIOCRADDTABLES 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.
struct pfr_table {
char pfrt_name[PF_TABLE_NAME_SIZE];
u_int32_t pfrt_flags;
};
DIOCRDELTABLES 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.
DIOCRGETTABLES 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 er-
ror.
DIOCRGETTSTATS struct pfioc_table
Like DIOCRGETTABLES, but returns 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;
long pfrts_tzero;
int pfrts_cnt;
int pfrts_refcnt;
};
#define pfrts_name pfrts_t.pfrt_name
#define pfrts_flags pfrts_t.pfrt_flags
DIOCRCLRTSTATS struct pfioc_table
Clears the statistics of one or more tables. On entry,
pfrio_buffer[pfrio_size] contains a table of pfr_table struc-
tures. On exit, pfrio_nzero contains the number of tables effec-
tively cleared.
DIOCRCLRADDRS 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.
DIOCRADDADDRS struct pfioc_table
Add one or more addresses to a table. On entry, pfrio_table con-
tains 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.
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
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 con-
tains the number of addresses effectively deleted.
DIOCRSETADDRS 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 mem-
bers. On entry, pfrio_table contains the table id and
pfrio_buffer[pfrio_size] contains the new list of pfr_addr struc-
tures. 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 DIOCRGETADDRS.
DIOCRGETADDRS 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 write-
able buffer for pfr_addr structures. On exit, pfrio_size con-
tains 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.
DIOCRGETASTATS struct pfioc_table
Like DIOCRGETADDRS, but returns 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];
long pfras_tzero;
};
DIOCRCLRASTATS 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.
DIOCRTSTADDRS 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 up-
dates the pfr_addr table by setting the pfra_fback member appro-
priately.
DIOCRSETTFLAGS struct pfioc_table
Change the const or persist flag of a table. On entry,
pfrio_buffer[pfrio_size] contains a table of pfr_table struc-
tures, 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 re-
moves the persist flag of an unreferenced table.
DIOCRINABEGIN 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.
DIOCRINACOMMIT 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 al-
tered by the commit operation.
DIOCRINADEFINE struct pfioc_table
Defines a table in the inactive set. On entry, pfrio_table con-
tains 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.
EXAMPLES
The following example demonstrates how to use the DIOCNATLOOK command to
find the internal host/port of a NATed connection.
#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 <stdio.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;
}
SEE ALSO
ioctl(2), bridge(4), pflog(4), pfsync(4), pfctl(8)
HISTORY
The pf packet filtering mechanism first appeared in OpenBSD 3.0.
OpenBSD 3.3 June 24, 2001 9