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 conversion, 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 necessary 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 discouraged; 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 converted, 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 written, 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 functions, 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 signifying 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)