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IPNAT(4)                                                 IPNAT(4)

       ipnat - Network Address Translation kernel interface

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

       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 *)

       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 strcture used with  the  NAT  interface  is  described

       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

       Recognised values for in_redir:


IPNAT(4)                                                 IPNAT(4)

       #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;

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


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