IPSEC_INITSUBNET(3)					     Library Functions Manual					       IPSEC_INITSUBNET(3)

NAME

       ipsec_initsubnet,  ipsec_addrtosubnet, ipsec_subnettypeof, ipsec_masktocount, ipsec_networkof, ipsec_maskof - initialize an ip_subnet, ini-
       tialize a singleton ip_subnet, get address type of an ip_subnet, convert subnet mask to bit count, get base address of  an  ip_subnet,  get
       subnet mask of an ip_subnet

SYNOPSIS

       #include <freeswan.h>

       const char *initsubnet(const ip_address *addr,
	   int maskbits, int clash, ip_subnet *dst);
       const char *addrtosubnet(const ip_address *addr,
	   ip_subnet *dst);

       int subnettypeof(const ip_subnet *src);
       int masktocount(const ip_address *src);
       void networkof(const ip_subnet *src, ip_address *dst);
       void maskof(const ip_subnet *src, ip_address *dst);

DESCRIPTION

       The  <freeswan.h>  library  uses an internal type ip_subnet to contain a description of an IP subnet (base address plus mask).  These func-
       tions provide basic tools for creating and examining this type.

       Initsubnet initializes a variable *dst of type ip_subnet from a base address and a count of mask bits.  The clash parameter specifies  what
       to do if the base address includes 1 bits outside the prefix specified by the mask (that is, in the ``host number'' part of the address):

	      '0'  zero out host-number bits

	      'x'  non-zero host-number bits are an error

       Initsubnet returns NULL for success and a pointer to a string-literal error message for failure; see DIAGNOSTICS.

       Addrtosubnet  initializes  an  ip_subnet  variable *dst to a ``singleton subnet'' containing the single address *addr.  It returns NULL for
       success and a pointer to a string-literal error message for failure.

       Subnettypeof returns the address type of a subnet, normally AF_INET or AF_INET6.  (The <freeswan.h> header file	arranges  to  include  the
       necessary headers for these names to be known.)

       Masktocount converts a subnet mask, expressed as an address, to a bit count suitable for use with initsubnet.  It returns -1 for error; see
       DIAGNOSTICS.

       Networkof fills in *dst with the base address of subnet src.

       Maskof fills in *dst with the subnet mask of subnet src, expressed as an address.

SEE ALSO

       inet(3), ipsec_ttosubnet(3), ipsec_rangetosubnet(3)

DIAGNOSTICS

       Fatal errors in initsubnet are: unknown address family; unknown clash value; impossible mask bit count; non-zero host-number bits and clash
       is  'x'.  Fatal errors in addrtosubnet are: unknown address family.  Fatal errors in masktocount are: unknown address family; mask bits not
       contiguous.

HISTORY

       Written for the FreeS/WAN project by Henry Spencer.

								   12 March 2002					       IPSEC_INITSUBNET(3)