IPSEC_ATOADDR(3)					     Library Functions Manual						  IPSEC_ATOADDR(3)

NAME

       ipsec_atoaddr, ipsec_addrtoa, ipsec_atosubnet, ipsec_subnettoa - convert Internet addresses and Subnet masks to and from ASCII

SYNOPSIS

       #include <freeswan.h>

       const char *atoaddr(const char *src, size_t srclen,
	   struct in_addr *addr);
       size_t addrtoa(struct in_addr addr, int format,
	   char *dst, size_t dstlen);

       const char *atosubnet(const char *src, size_t srclen,
	   struct in_addr *addr, struct in_addr *mask);
       size_t subnettoa(struct in_addr addr, struct in_addr mask,
	   int format, char *dst, size_t dstlen);

DESCRIPTION

       These functions are obsolete; see ipsec_ttoaddr(3) for their replacements.

       Atoaddr	converts  an ASCII name or dotted-decimal address into a binary address (in network byte order).  Addrtoa does the reverse conver-
       sion, back to an ASCII dotted-decimal address.  Atosubnet and subnettoa do likewise for the ``address/mask'' ASCII form	used  to  write  a
       specification of a subnet.

       An  address  is	specified  in  ASCII as a dotted-decimal address (e.g.	1.2.3.4), an eight-digit network-order hexadecimal number with the
       usual C prefix (e.g.  0x01020304, which is synonymous with 1.2.3.4), an eight-digit host-order hexadecimal number with a  0h  prefix  (e.g.
       0h01020304,  which  is  synonymous  with  1.2.3.4 on a big-endian host and 4.3.2.1 on a little-endian host), a DNS name to be looked up via
       gethostbyname(3), or an old-style network name to be looked up via getnetbyname(3).

       A dotted-decimal address may be incomplete, in which case ASCII-to-binary conversion implicitly appends as many instances of .0	as  neces-
       sary  to  bring	it  up	to four components.  The components of a dotted-decimal address are always taken as decimal, and leading zeros are
       ignored.  For example, 10 is synonymous with 10.0.0.0, and 128.009.000.032 is synonymous with 128.9.0.32 (the latter  example  is  verbatim
       from RFC 1166).	The result of addrtoa is always complete and does not contain leading zeros.

       The  letters  in a hexadecimal address may be uppercase or lowercase or any mixture thereof.  Use of hexadecimal addresses is strongly dis-
       couraged; they are included only to save hassles when dealing with the handful of perverted programs which already print network  addresses
       in hexadecimal.

       DNS names may be complete (optionally terminated with a ``.'')  or incomplete, and are looked up as specified by local system configuration
       (see resolver(5)).  The h_addr value returned by gethostbyname(3) is used, so with current DNS implementations, the result  when  the  name
       corresponds to more than one address is difficult to predict.  Name lookup resorts to getnetbyname(3) only if gethostbyname(3) fails.

       A subnet specification is of the form network/mask.  The network and mask can be any form acceptable to atoaddr.  In addition, the mask can
       be a decimal integer (leading zeros ignored) giving a bit count, in which case it stands for a mask with that number of high  bits  on  and
       all  others off (e.g., 24 means 255.255.255.0).	In any case, the mask must be contiguous (a sequence of high bits on and all remaining low
       bits off).  As a special case, the subnet specification %default is a synonym for 0.0.0.0/0.

       Atosubnet ANDs the mask with the address before returning, so that any non-network bits in the address are turned off (e.g., 10.1.2.3/24 is
       synonymous  with  10.1.2.0/24).	Subnettoa generates the decimal-integer-bit-count form of the mask, with no leading zeros, unless the mask
       is non-contiguous.

       The srclen parameter of atoaddr and atosubnet specifies the length of the ASCII string pointed to by src; it is an error for  there  to	be
       anything else (e.g., a terminating NUL) within that length.  As a convenience for cases where an entire NUL-terminated string is to be con-
       verted, a srclen value of 0 is taken to mean strlen(src).

       The dstlen parameter of addrtoa and subnettoa specifies the size of the dst parameter; under no circumstances are more  than  dstlen  bytes
       written	to dst.  A result which will not fit is truncated.  Dstlen can be zero, in which case dst need not be valid and no result is writ-
       ten, but the return value is unaffected; in all other cases, the (possibly truncated) result is NUL-terminated.	The freeswan.h header file
       defines constants, ADDRTOA_BUF and SUBNETTOA_BUF, which are the sizes of buffers just large enough for worst-case results.

       The format parameter of addrtoa and subnettoa specifies what format is to be used for the conversion.  The value 0 (not the ASCII character
       '0', but a zero value) specifies a reasonable default, and is in fact the only format currently	available.   This  parameter  is  a  hedge
       against future needs.

       The  ASCII-to-binary  functions	return NULL for success and a pointer to a string-literal error message for failure; see DIAGNOSTICS.  The
       binary-to-ASCII functions return 0 for a failure, and otherwise always return the size of buffer which would be needed to  accommodate  the
       full  conversion result, including terminating NUL; it is the caller's responsibility to check this against the size of the provided buffer
       to determine whether truncation has occurred.

SEE ALSO

       inet(3)

DIAGNOSTICS

       Fatal errors in atoaddr are: empty input; attempt to allocate temporary storage for a very long name failed;  name  lookup  failed;  syntax
       error in dotted-decimal form; dotted-decimal component too large to fit in 8 bits.

       Fatal errors in atosubnet are: no / in src; atoaddr error in conversion of network or mask; bit-count mask too big; mask non-contiguous.

       Fatal errors in addrtoa and subnettoa are: unknown format.

HISTORY

       Written for the FreeS/WAN project by Henry Spencer.

BUGS

       The  interpretation of incomplete dotted-decimal addresses (e.g.  10/24 means 10.0.0.0/24) differs from that of some older conversion func-
       tions, e.g. those of inet(3).  The behavior of the older functions has never been particularly consistent or particularly useful.

       Ignoring leading zeros in dotted-decimal components and bit counts is arguably the most useful behavior in this application, but  it  might
       occasionally cause confusion with the historical use of leading zeros to denote octal numbers.

       It is barely possible that somebody, somewhere, might have a legitimate use for non-contiguous subnet masks.

       Getnetbyname(3) is a historical dreg.

       The  restriction  of  ASCII-to-binary  error  reports to literal strings (so that callers don't need to worry about freeing them or copying
       them) does limit the precision of error reporting.

       The ASCII-to-binary error-reporting convention lends itself to slightly obscure code, because many readers will not think of NULL as signi-
       fying success.  A good way to make it clearer is to write something like:

	      const char *error;

	      error = atoaddr( /* ... */ );
	      if (error != NULL) {
		      /* something went wrong */

								   11 June 2001 						  IPSEC_ATOADDR(3)