NPF(3)                  NetBSD Library Functions Manual                 NPF(3)

NAME
     npf -- NPF packet filter library

LIBRARY
     library ``libnpf''

SYNOPSIS
     #include <npf.h>

     nl_config_t *
     npf_config_create(void);

     int
     npf_config_submit(nl_config_t *ncf, int fd);

     void
     npf_config_destroy(nl_config_t *ncf);

     int
     npf_config_flush(int fd);

     nl_rule_t *
     npf_rule_create(char *name, uint32_t attr, u_int if_idx);

     int
     npf_rule_setcode(nl_rule_t *rl, int type, const void *code, size_t sz);

     bool
     npf_rule_exists_p(nl_config_t *ncf, const char *name);

     int
     npf_rule_insert(nl_config_t *ncf, nl_rule_t *parent, nl_rule_t *rl,
         pri_t pri);

     int
     npf_rule_setproc(nl_config_t *ncf, nl_rule_t *rl, const char *name);

     void
     npf_rule_destroy(nl_rule_t *rl);

     nl_rproc_t *
     npf_rproc_create(char *name);

     bool
     npf_rproc_exists_p(nl_config_t *ncf, const char *name);

     int
     npf_rproc_insert(nl_config_t *ncf, nl_rproc_t *rp);

     nl_nat_t *
     npf_nat_create(int type, u_int flags, u_int if_idx, npf_addr_t *addr,
         int af, in_port_t port);

     int
     npf_nat_insert(nl_config_t *ncf, nl_nat_t *nt, pri_t pri);

     nl_table_t *
     npf_table_create(u_int id, int type);

     int
     npf_table_add_entry(nl_table_t *tl, in_addr_t addr, in_addr_t mask);

     bool
     npf_table_exists_p(nl_config_t *ncf, u_int tid);

     int
     npf_table_insert(nl_config_t *ncf, nl_table_t *tl);

     void
     npf_table_destroy(nl_table_t *tl);

     int
     npf_update_rule(int fd, const char *rname, nl_rule_t *rl);

     int
     npf_sessions_send(int fd, const char *fpath);

     int
     npf_sessions_recv(int fd, const char *fpath);

DESCRIPTION
     The npf library provides an interface to create an NPF configuration hav-
     ing rules, tables, procedures, or translation policies.  The configura-
     tion can be submitted to the kernel.

FUNCTIONS
   Configuration
     npf_config_create()
           Create a configuration.

     npf_config_submit(ncf, fd)
           Submit configuration ncf to the kernel.

     npf_config_destroy(ncf)
           Destroy the configuration ncf.

     npf_config_flush(fd)
           Flush the current configuration.

   Rule interface
     npf_rule_create(name, attr, if_idx)
           Create a rule with a given name, attribute and priorty.  Name can
           be NULL, in which case rule has no unique identifier.  Otherwise,
           rules shall not have duplicate names.  The following attributes,
           which can be ORed, are available:

           NPF_RULE_PASS
                   Decision of this rule is "pass".  If this attribute is not
                   specified, then packet "block" (drop) is the default.

           NPF_RULE_DEFAULT
                   This a default rule in the ruleset.  There can only be a
                   single rule having this attribute set in the ruleset.

           NPF_RULE_FINAL
                   Indicates that on rule match, further processing of the
                   ruleset should be stopped and this rule applied instantly.

           NPF_RULE_STATEFUL
                   Create a state (session) on match, track the connection and
                   therefore pass the backwards stream without inspection.

           NPF_RULE_RETRST
                   Return TCP RST packet in a case of packet block.

           NPF_RULE_RETICMP
                   Return ICMP destination unreachable in a case of packet
                   block.

           NPF_RULE_IN
                   Rule may match only if incoming packet.

           NPF_RULE_OUT
                   Rule may match only if outgoing packet.

           Interface is specified by if_idx, which is a numeral representation
           of an interface, given by if_nametoindex(3).  Zero indicates any
           interface.

     npf_rule_setcode(rl, type, code, sz)
           Assign compiled code for the rule specified by rl, used for filter
           criteria.  Pointer to the binary code is specified by code, and
           size of the memory area by sz.  Type of the code is specified by
           type.  Currently, only n-code is supported and NPF_CODE_NCODE
           should be passed.

     npf_rule_insert(ncf, parent, rl, pri)
           Insert the rule into the set of parent rule specified by parent.
           If value of parent is NULL, then insert into the main ruleset.

           Priority is the order of the rule in the ruleset.  Lower value
           means first to process, higher value - last to process.  If multi-
           ple rules have the same priority - order is unspecified.  A special
           constant NPF_PRI_NEXT may be passed to use the value of last used
           priority incremented by 1.

     npf_rule_setproc(ncf, rl, name)
           Set procedure for the specified rule.

     npf_rule_destroy(rl)
           Destroy the given rule.

   Rule procedure interface
     npf_rproc_create(name)
           Create a rule procedure with a given name.  Name must be unique for
           each procedure.

     npf_rproc_insert(ncf, rp)
           Insert rule procedure into the specified configuration.

   Translation interface
     npf_nat_create(type, flags, if_idx, addr, af, port)
           Create a NAT translation policy of a specified type.  There are two
           types:

           NPF_NATIN         Inbound NAT policy.

           NPF_NATOUT        Outbound NAT policy.

           A bi-directional NAT is obtained by combining two policies.  The
           following flags are supported:

           NPF_NAT_PORTS     Indicates to perform port translation.  Other-
                             wise, port translation is not performed and port
                             is ignored.

           NPF_NAT_PORTMAP   Effective only if NPF_NAT_PORTS flag is set.
                             Indicates to create a port map and select a ran-
                             dom port for translation.  Otherwise, port is
                             translated to the value specified by port is
                             used.

           Translation address is specified by addr, and its family by fa.
           Family must be either AF_INET for IPv4 or AF_INET6 for IPv6
           address.

     npf_nat_insert(ncf, nt, pri)
           Insert NAT policy, its rule, into the specified configuration.

   Table interface
     npf_table_create(index, type)
           Create NPF table of specified type.  The following types are sup-
           ported:

           NPF_TABLE_HASH   Indicates to use hash table for storage.

           NPF_TABLE_TREE   Indicates to use red-black tree for storage.  Ta-
                            ble is identified by index, which should be in the
                            range between 1 and NPF_MAX_TABLE_ID.

     npf_table_add_entry(tl, addr, mask)
           Add an entry of IPv4 address and mask, specified by addr and mask,
           to the table specified by tl.

     npf_table_exists_p(ncf, name)
           Determine whether table with ID tid exists in the configuration
           ncf.  Return true if exists, and false otherwise.

     npf_table_insert(ncf, tl)
           Insert table into set of configuration.  Routine performs a check
           for duplicate table ID.

     npf_table_destroy(tl)
           Destroy the specified table.

   Session interface
     npf_update_rule(fd, rname, rl)

     npf_sessions_send(fd, fpath)
           Read the file specified by fpath, and send sessions saved in it to
           the kernel.

     npf_sessions_recv(fd, fpath)
           Receive currently loaded session from the kernel, and save them to
           a file specified by fpath.

SEE ALSO
     npfctl(8), npf_ncode(9)

HISTORY
     The NPF library first appeared in NetBSD 6.0.

NetBSD 6.0                       July 1, 2012                       NetBSD 6.0

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