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IPSEC_ATOADDR(3)           Library Functions Manual           IPSEC_ATOADDR(3)



NAME
       ipsec atoaddr, addrtoa - convert Internet addresses to and from ASCII
       ipsec atosubnet, subnettoa - convert subnet/mask ASCII form to and from
       addresses

SYNOPSIS
       #include <&lt;freeswan.h>&gt;

       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  replace-
       ments.

       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 specifica-
       tion 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  geth-
       ostbyname(3),  or an old-style network name to be looked up via getnet-
       byname(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 discour-
       aged;  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  configura-
       tion  (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 any-
       thing  else  (e.g., a terminating NUL) within that length.  As a conve-
       nience 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  writ-
       ten  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 trun-
       cated) result is NUL-terminated.  The freeswan.h  header  file  defines
       constants,  ADDRTOA_BUF  and SUBNETTOA_BUF, which are the sizes of buf-
       fers 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 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)