PF(4) BSD Programmer's Manual PF(4)NAMEpf - packet filter
SYNOPSIS
pseudo-device pfDESCRIPTION
Packet filtering takes place in the kernel. A pseudo-device, /dev/pf, al-
lows 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 state table
entries, and retrieve 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.
IOCTL INTERFACEpf supports the following ioctl(2) 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)).
DIOCSTOPALTQ
Stop the ALTQ bandwidth control system.
DIOCBEGINADDRS 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;
};
Clear the buffer address pool and get a ticket for subsequent
DIOCADDADDR, DIOCADDRULE, and DIOCCHANGERULE calls.
DIOCADDADDR struct pfioc_pooladdr
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
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;
};
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 op-
tional anchor and ruleset names indicate the anchor and ruleset
in which to append the rule. nr and action are ignored.
DIOCADDALTQ struct pfioc_altq
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
Get a ticket for subsequent DIOCGETRULE calls and the number nr
of rules in the active ruleset.
DIOCGETRULE struct pfioc_rule
Get a rule by its number nr using the ticket obtained through a
preceding DIOCGETRULES call.
DIOCGETADDRS struct pfioc_pooladdr
Get a ticket for subsequent DIOCGETADDR calls and the number nr
of pool addresses in the rule specified with r_action, r_num,
anchor, and ruleset.
DIOCGETADDR struct pfioc_pooladdr
Get the pool address addr by its number nr from the rule speci-
fied with r_action, r_num, anchor, and ruleset using the ticket
obtained through a preceding DIOCGETADDRS call.
DIOCGETALTQS struct pfioc_altq
Get a ticket for subsequent DIOCGETALTQ calls and the number nr
of queues in the active list.
DIOCGETALTQ struct pfioc_altq
Get the queueing discipline altq by its number nr using a ticket
obtained through a preceding DIOCGETALTQS call.
DIOCGETQSTATS struct pfioc_qstats
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.
DIOCADDSTATE struct pfioc_state
Add a state entry.
struct pfioc_state {
u_int32_t nr;
struct pf_state state;
};
DIOCGETSTATE struct pfioc_state
Extract the entry with the specified number nr from the state
table.
DIOCKILLSTATES struct pfioc_state_kill
Remove matching entries from the state table. This call returns
the number of killed states in psk_af.
struct pfioc_state_kill {
sa_family_t psk_af;
int psk_proto;
struct pf_rule_addr psk_src;
struct pf_rule_addr psk_dst;
char psk_ifname[IFNAMSIZ];
};
DIOCCLRSTATES struct pfioc_state_kill
Clear all states. It works like DIOCKILLSTATES, but ignores the
psk_af, psk_proto, psk_src, and psk_dst fields of the
pfioc_state_kill structure.
DIOCSETSTATUSIF struct pfioc_if
Specify the interface for which statistics are accumulated.
struct pfioc_if {
char ifname[IFNAMSIZ];
};
DIOCGETSTATUS struct pf_status
Get the internal packet filter statistics.
struct pf_status {
u_int64_t counters[PFRES_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_int64_t stateid;
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];
};
DIOCCLRSTATUS
Clear the internal packet filter statistics.
DIOCNATLOOK struct pfioc_natlook
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
Set the debug level.
enum { PF_DEBUG_NONE, PF_DEBUG_URGENT, PF_DEBUG_MISC,
PF_DEBUG_NOISY };
DIOCGETSTATES struct pfioc_states
Get state table entries.
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
};
If ps_len is zero, all states will be gathered into pf_states and
ps_len will be set to the size they take in memory (i.e.,
sizeof(struct pf_state) * nr). If ps_len is non-zero, as many
states that can fit into ps_len as possible will be gathered, and
ps_len will be updated to the size those rules take in memory.
DIOCCHANGERULE struct pfioc_rule
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 and ruleset indicate to which anchor and ruleset 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
Add or remove the pool address addr from the rule specified by
r_action, r_num, anchor, and ruleset.
DIOCSETTIMEOUT struct pfioc_tm
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
Get the state timeout of timeout. The value will be placed into
the seconds field.
DIOCCLRRULECTRS
Clear per-rule statistics.
DIOCSETLIMIT struct pfioc_limit
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 };
DIOCGETLIMIT struct pfioc_limit
Get the hard limit for the memory pool indicated by index.
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_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
Create 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_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;
};
DIOCRDELTABLES struct pfioc_table
Delete 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
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;
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
DIOCRCLRTSTATS struct pfioc_table
Clear 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 members.
On entry, pfrio_table contains the table ID and
pfrio_buffer[pfrio_size] contains the new list of pfr_addr struc-
tures. 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
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 contains
the number of addresses written into the buffer. If the buffer
was too small, the kernel does not store anything but just re-
turns the required buffer size, without returning an error.
DIOCRGETASTATS struct pfioc_table
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];
long pfras_tzero;
};
DIOCRCLRASTATS struct pfioc_table
Clear 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 updates
the pfr_addr table by setting the pfra_fback member appropriate-
ly.
DIOCRSETTFLAGS struct pfioc_table
Change the PFR_TFLAG_CONST or PFR_TFLAG_PERSIST flags 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 re-
moves the PFR_TFLAG_PERSIST flag of an unreferenced table.
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.
DIOCXBEGIN struct pfioc_trans
#define PF_RULESET_ALTQ (PF_RULESET_MAX)
#define PF_RULESET_TABLE (PF_RULESET_MAX+1)
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[PF_ANCHOR_NAME_SIZE];
char ruleset[PF_RULESET_NAME_SIZE];
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.
DIOCXCOMMIT struct pfioc_trans
Atomically switch a vector of inactive rulesets to the active ru-
lesets. 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. Returns EBUSY if a concurrent pro-
cess is trying to update some of the same rulesets concurrently.
DIOCXROLLBACK struct pfioc_trans
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.
DIOCOSFPFLUSH
Flush the passive OS fingerprint table.
DIOCOSFPADD struct pf_osfp_ioctl
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 op-
tions, and the TCP window scaling constant of the TCP SYN packet,
respectively.
The fp_flags member is filled according to the <net/pfvar.h> in-
clude 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) the whole structure to zero before filling and sending
to the kernel.
DIOCOSFPGET struct pf_osfp_ioctl
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
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 allocat-
ed, 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
Get the list of interfaces and interface drivers 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;
};
#define PFI_FLAG_GROUP 0x0001 /* gets groups of interfaces */
#define PFI_FLAG_INSTANCE 0x0002 /* gets single interfaces */
#define PFI_FLAG_ALLMASK 0x0003
If not empty, pfiio_name can be used to restrict the search to a
specific interface or driver. pfiio_buffer[pfiio_size] is the
user-supplied buffer for returning the data. On entry, pfiio_size
represents the number of pfi_if 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_if). pfiio_flags should be set to
PFI_FLAG_GROUP, PFI_FLAG_INSTANCE, or both, to tell the kernel to
return a group of interfaces (drivers, like "fxp"), real inter-
face instances (like "fxp1") or both. The data is returned in the
pfi_if structure described below:
struct pfi_if {
char pfif_name[IFNAMSIZ];
u_int64_t pfif_packets[2][2][2];
u_int64_t pfif_bytes[2][2][2];
u_int64_t pfif_addcnt;
u_int64_t pfif_delcnt;
long pfif_tzero;
int pfif_states;
int pfif_rules;
int pfif_flags;
};
#define PFI_IFLAG_GROUP 0x0001 /* group of interfaces */
#define PFI_IFLAG_INSTANCE 0x0002 /* single instance */
#define PFI_IFLAG_CLONABLE 0x0010 /* clonable group */
#define PFI_IFLAG_DYNAMIC 0x0020 /* dynamic group */
#define PFI_IFLAG_ATTACHED 0x0040 /* interface attached */
DIOCICLRISTATS struct pfioc_iface
Clear the statistics counters of one or more interfaces.
pfiio_name and pfiio_flags can be used to select which interfaces
need to be cleared. The filtering process is the same as for
DIOCIGETIFACES. pfiio_nzero will be set by the kernel to the
number of interfaces and drivers that have been cleared.
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 <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;
}
SEE ALSOioctl(2), bridge(4), pflog(4), pfsync(4), pfctl(8), altq(9)HISTORY
The pf packet filtering mechanism first appeared in OpenBSD 3.0.
MirOS BSD #10-current June 24, 2001 10
