NAME    [Toc]    [Back]

     inet_net_ntop, inet_net_pton - Internet network  number  manipulation routines

SYNOPSIS    [Toc]    [Back]

     #include <sys/socket.h>
     #include <netinet/in.h>
     #include <arpa/inet.h>

     char *
     inet_net_ntop(int  af, const void *src, int bits, char *dst,
size_t size);

     int
     inet_net_pton(int af, const char  *src,  void  *dst,  size_t
size);

DESCRIPTION    [Toc]    [Back]

     The  inet_net_ntop()  function  converts an Internet network
number from
     network format (usually a struct in_addr or some other binary form, in
     network  byte  order)  to CIDR presentation format (suitable
for external
     display purposes).  bits is the number of bits in  src  that
are the network
  number.   It returns NULL if a system error occurs (in
which case,
     errno will have been set), or it returns a  pointer  to  the
destination
     string.

     The  inet_net_pton() function converts a presentation format
Internet network
 number (that is, printable form as held in a  character
string) to
     network  format  (usually a struct in_addr or some other internal binary
     representation, in network byte order).  It returns the number of bits
     (either  computed  based  on  the  class,  or specified with
/CIDR), or -1 if a
     failure occurred (in which case errno will  have  been  set.
It will be set
     to ENOENT if the Internet network number was not valid).

     Caution:  The  dst  field  should  be  zeroed before calling
inet_net_pton() as
     the function will only fill the number of bytes necessary to
encode the
     network number in network byte order.

     The  only value for af currently supported is AF_INET.  size
is the size
     of the result buffer dst.

NETWORK NUMBERS (IP VERSION 4)    [Toc]    [Back]

     The external representation of Internet network numbers  may
be specified
     in one of the following forms:

           a
           a.b
           a.b.c
           a.b.c.d

     Any  of  the  above  four  forms may have ``/bits'' appended
where ``bits'' is
     in the range 0-32 and is used to explicitly specify the number of bits in
     the  network  address.   When ``/bits'' is not specified the
number of bits
     in the network address is calculated as the  larger  of  the
number of bits
     in  the class to which the address belongs and the number of
bits provided
     rounded up modulo 8.  Examples:

     10           an  8  bit  network  number  (class  A),  value
10.0.0.0.

     192           a  24  bit  network  number  (class  C), value
192.0.0.0.

     10.10        a 16 bit network number, value 10.10.0.0.

     10.1.2       a 24 bit network number, value 10.1.2.0.

     10.1.2.3     a 32 bit network number, value 10.1.2.3.

     10.1.2.3/24  a  24  bit  network  number  (explicit),  value
10.1.2.3.

     Note  that  when  the  number  of  bits  is  specified using
``/bits'' notation,
     the value of the address still includes all bits suplied  in
the external
     representation,  even  those bits which are the host part of
an internet
     address.  Also, unlike inet_pton(3) where the external  representation is
     assumed  to be an internet address, the external representation for
     inet_net_pton() is assumed to be a  network  address.   Thus
``10.1'' is assumed
 to be ``10.1.0.0'' not ``10.0.0.1''

     All  numbers  supplied as ``parts'' in a `.' notation may be
decimal, octal,
 or hexadecimal, as specified in the C language (i.e., a
leading 0x
     or  0X  implies  hexadecimal; otherwise, a leading 0 implies
octal; otherwise,
 the number is interpreted as decimal).

SEE ALSO    [Toc]    [Back]

     byteorder(3), inet(3), inet_pton(3), networks(5)

HISTORY    [Toc]    [Back]

     The inet_net_ntop and inet_net_pton functions first appeared
in BIND
     4.9.4.

OpenBSD      3.6                           June      18,     1997