Packet Filter pseudo-device
Packet filtering takes place in io-pkt. A pseudo-device, /dev/pf, lets user processes control the behavior of the packet filter through an ioctl() interface. There are commands to enable and disable the filter, load rule sets, add and remove individual rules or state table entries, and retrieve statistics. The most commonly used functions are covered by pfctl.
In QNX Neutrino 6.5.0 and later, ioctl() handles embedded pointers, so you don't have to use ioctl_socket() instead.
Manipulations such as loading a rule set that involve more than a single ioctl() call require a ticket, which prevents the occurrence of multiple concurrent manipulations.
Fields of ioctl() parameter structures that refer to packet data (such as addresses and ports) are generally expected in network-byte order.
Rules and address tables are contained in anchors. When servicing an ioctl() request, if the anchor field of the argument structure is empty, io-pkt uses the default anchor (i.e., the main rule set) in operations. Anchors are specified by name and may be nested, with components separated by slashes, similar to the way that filesystem hierarchies are laid out. The final component of the anchor path is the anchor under which operations will be performed.
ioctl() interface
The pf pseudo-device supports the following ioctl() commands, available through <net/pfvar.h>:
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;
};
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;
};
This call requires a ticket obtained through a preceding DIOCXBEGIN call and a pool_ticket obtained through a DIOCBEGINADDRS call. You must also call DIOCADDADDR if any pool addresses are required.
The optional anchor name indicates the anchor in which to append the rule. The nr and action members. are ignored.
struct pfioc_altq {
u_int32_t action;
u_int32_t ticket;
u_int32_t nr;
struct pf_altq altq;
};
(QNX Neutrino 7.0 or later) If action is set to PF_GET_CLR_CNTR, the per-rule statistics for the requested rule are cleared.
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.
struct pfioc_ruleset {
u_int32_t nr;
char path[MAXPATHLEN];
char name[PF_ANCHOR_NAME_SIZE];
};
Nested anchors, since they aren't directly attached to the given anchor, aren't included. This ioctl() command returns EINVAL if the given anchor doesn't exist.
struct pfioc_state {
u_int32_t nr;
struct pf_state state;
};
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];
};
struct pfioc_if {
char ifname[IFNAMSIZ];
};
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_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];
};
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;
};
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 are gathered into pf_states, and ps_len is set to the size they take in memory (i.e., sizeof(struct pf_state) * nr). If ps_len is nonzero, as many states that can fit into ps_len as possible are gathered, and ps_len is updated to the size those rules take in memory.
You must set ticket to the value obtained with PF_CHANGE_GET_TICKET for all actions except PF_CHANGE_GET_TICKET. You must set pool_ticket to the value obtained with the DIOCBEGINADDRS call for all actions except PF_CHANGE_REMOVE and PF_CHANGE_GET_TICKET. The anchor indicates which anchor the operation applies to. The nr member indicates the rule number against which to apply PF_CHANGE_ADD_BEFORE, PF_CHANGE_ADD_AFTER, or PF_CHANGE_REMOVE actions.
struct pfioc_tm {
int timeout;
int seconds;
};
The old value is placed into seconds. For the possible values of timeout, see the PFTM_* values in <net/pfvar.h>.
struct pfioc_limit {
int index;
unsigned limit;
};
enum { PF_LIMIT_STATES, PF_LIMIT_SRC_NODES,
PF_LIMIT_FRAGS };
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
struct pfr_table {
char pfrt_anchor[MAXPATHLEN];
char pfrt_name[PF_TABLE_NAME_SIZE];
u_int32_t pfrt_flags;
u_int8_t pfrt_fback;
};
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
The pfr_addr structure is defined as follows:
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
On entry, pfrio_table contains the table ID, and pfrio_buffer[pfrio_size] contains the new list of pfr_addr structures. Additionally, if pfrio_size2 is nonzero, pfrio_buffer[pfrio_size..pfrio_size2] must be a writeable buffer, into which io-pkt 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 io-pkt. If pfrio_size2 was set on entry, pfrio_size2 points to the size of the buffer used, exactly as for DIOCRGETADDRS.
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;
};
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;
};
For each rule set, a ticket is returned for subsequent “add rule” ioctl() commands, as well as for the DIOCXCOMMIT and DIOCXROLLBACK calls.
Rule set types, identified by rs_num, include the following:
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;
};
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 patch level. 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 PF_OSFP_* definition in <net/pfvar.h>. 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.
This ioctl() command doesn't use the fp_getnum member.
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
};
You must call ioctl() once with psn_len set to 0. If ioctl() returns without error, psn_len is set to the size of the buffer required to hold all the pf_src_node structures held in the table. You should then allocate a buffer of this size and place a pointer to this buffer in psn_buf. You must then call ioctl() again to fill this buffer with the actual source node data. After that call, psn_len is set to the length of the buffer actually used.
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 it isn't empty, you can use pfiio_name to restrict the search to a specific interface or driver. The pfiio_buffer[pfiio_size] member 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 io-pkt manager replaces this value with the real number of entries it wants to return.
You should set pfiio_esize to sizeof(struct pfi_if). You should set pfiio_flags to PFI_FLAG_GROUP, PFI_FLAG_INSTANCE, or both, to tell io-pkt to return a group of interfaces (drivers, such as fxp), real interface instances (e.g., 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 */
The filtering process is the same as for DIOCIGETIFACES.
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 <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;
}
The following functionality is missing from pf in this version of NetBSD: