ipnat(4)

IPNAT(4)         DEVICES AND NETWORK INTERFACES          IPNAT(4)

NAME

     ipnat - Network Address Translation kernel interface

SYNOPSIS

     #include <netinet/ip_compat.h>
     #include <netinet/ip_fil.h>
     #include <netinet/ip_proxy.h>
     #include <netinet/ip_nat.h>

IOCTLS

     To add and delete rules to the NAT list, two 'basic'  ioctls
     are provided for use.  The ioctl's are called as:

          ioctl(fd, SIOCADNAT, struct ipnat **)
          ioctl(fd, SIOCRMNAT, struct ipnat **)
          ioctl(fd, SIOCGNATS, struct natstat **)
          ioctl(fd, SIOCGNATL, struct natlookup **)

     Unlike ipf(4), there is only a single list supported by  the
     kernel NAT interface.  An inactive list which can be swapped
     to is not currently supported.

     These ioctl's are implemented as being  routing  ioctls  and
     thus  the  same rules for the various routing ioctls and the
     file descriptor are employed, mainly being that the fd  must
     be  that  of  the  device  associated with the module (i.e.,
     /dev/ipl).

     The structure used  with  the  NAT  interface  is  described
     below:

     typedef struct  ipnat   {
             struct  ipnat   *in_next;
             void    *in_ifp;
             u_short in_flags;
             u_short in_pnext;
             u_short in_port[2];
             struct  in_addr in_in[2];
             struct  in_addr in_out[2];
             struct  in_addr in_nextip;
             int     in_space;
             int     in_redir; /* 0 if it's a mapping, 1 if it's a hard redir */
             char    in_ifname[IFNAMSIZ];
     } ipnat_t;

     #define in_pmin         in_port[0]      /* Also holds static redir port */
     #define in_pmax         in_port[1]
     #define in_nip          in_nextip.s_addr
     #define in_inip         in_in[0].s_addr
     #define in_inmsk        in_in[1].s_addr
     #define in_outip        in_out[0].s_addr
     #define in_outmsk       in_out[1].s_addr

                          Last change:                          1

IPNAT(4)         DEVICES AND NETWORK INTERFACES          IPNAT(4)

     Recognised values for in_redir:

     #define NAT_MAP         0
     #define NAT_REDIRECT    1

     NAT statistics Statistics on the number of  packets  mapped,
     going  in  and out are kept, the number of times a new entry
     is added and deleted (through expiration) to the  NAT  table
     and the current usage level of the NAT table.

     Pointers to the NAT table inside the kernel, as well  as  to
     the  top  of  the  internal  NAT  lists constructed with the
     SIOCADNAT ioctls.  The table itself is a hash table of  size
     NAT_SIZE (default size is 367).

     To retrieve the statistics,  the  SIOCGNATS  ioctl  must  be
     used, with the appropriate structure passed by reference, as
     follows:
          ioctl(fd, SIOCGNATS, struct natstat *)

     typedef struct  natstat {
             u_long  ns_mapped[2];
             u_long  ns_added;
             u_long  ns_expire;
             u_long  ns_inuse;
             nat_t   ***ns_table;
             ipnat_t *ns_list;
     } natstat_t;

BUGS

     It would be nice if there were more flexibility when  adding
     and deleting filter rules.

FILES

     /dev/ipnat

SEE ALSO

     ipf(4), ipnat(5), ipf(8), ipnat(8), ipfstat(8)

                          Last change:                          2