atoasr.3

This a good VPN source

.TH IPSEC_ATOASR 3 "11 June 2001"
.\" RCSID $Id: atoasr.3,v 1.10 2004/04/09 18:00:38 mcr Exp $
.SH NAME
ipsec atoasr \- convert ASCII to Internet address, subnet, or range
.br
ipsec rangetoa \- convert Internet address range to ASCII
.SH SYNOPSIS
.B "#include <freeswan.h>
.sp
.B "const char *atoasr(const char *src, size_t srclen,"
.ti +1c
.B "char *type, struct in_addr *addrs);"
.br
.B "size_t rangetoa(struct in_addr *addrs, int format,
.ti +1c
.B "char *dst, size_t dstlen);"
.SH DESCRIPTION
These functions are obsolete;
there is no current equivalent,
because so far they have not proved useful.
.PP
.I Atoasr
converts an ASCII address, subnet, or address range
into a suitable combination of binary addresses
(in network byte order).
.I Rangetoa
converts an address range back into ASCII,
using dotted-decimal form for the addresses
(the other reverse conversions are handled by
.IR ipsec_addrtoa (3)
and
.IR ipsec_subnettoa (3)).
.PP
A single address can be any form acceptable to
.IR ipsec_atoaddr (3):
dotted decimal, DNS name, or hexadecimal number.
A subnet
specification uses the form \fInetwork\fB/\fImask\fR
interpreted by
.IR ipsec_atosubnet (3).
.PP
An address range is two
.IR ipsec_atoaddr (3)
addresses separated by a
.B ...
delimiter.
If there are four dots rather than three, the first is taken as
part of the begin address,
e.g. for a complete DNS name which ends with
.B .
to suppress completion attempts.
The begin address of a range must be
less than or equal to the end address.
.PP
The
.I srclen
parameter of
.I atoasr
specifies the length of the ASCII string pointed to by
.IR 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
.I srclen
value of
.B 0
is taken to mean
.BR strlen(src) .
.PP
The
.I type
parameter of
.I atoasr
must point to a
.B char
variable used to record which form was found.
The
.I addrs
parameter must point to a two-element array of
.B "struct in_addr"
which receives the results.
The values stored into
.BR *type ,
and the corresponding values in the array, are:
.PP
.ta 3c +2c +3c
	*type	addrs[0]	addrs[1]
.sp 0.8
address	\&\fB'a'\fR	address	-
.br
subnet	\&\fB's'\fR	network	mask
.br
range	\&\fB'r'\fR	begin	end
.PP
The
.I dstlen
parameter of
.I rangetoa
specifies the size of the
.I dst
parameter;
under no circumstances are more than
.I dstlen
bytes written to
.IR dst .
A result which will not fit is truncated.
.I Dstlen
can be zero, in which case
.I 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
.I freeswan.h
header file defines a constant,
.BR RANGETOA_BUF ,
which is the size of a buffer just large enough for worst-case results.
.PP
The
.I format
parameter of
.I rangetoa
specifies what format is to be used for the conversion.
The value
.B 0
(not the ASCII character
.BR '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.
.PP
.I Atoasr
returns NULL for success and
a pointer to a string-literal error message for failure;
see DIAGNOSTICS.
.I Rangetoa
returns
.B 0
for a failure, and otherwise
always returns 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.
.SH SEE ALSO
ipsec_atoaddr(3), ipsec_atosubnet(3)
.SH DIAGNOSTICS
Fatal errors in
.I atoasr
are:
empty input;
error in
.IR ipsec_atoaddr (3)
or
.IR ipsec_atosubnet (3)
during conversion;
begin address of range exceeds end address.
.PP
Fatal errors in
.I rangetoa
are:
unknown format.
.SH HISTORY
Written for the FreeS/WAN project by Henry Spencer.
.SH BUGS
The restriction of 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.
.PP
The 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:
.PP
.RS
.nf
.B "const char *error;"
.sp
.B "error = atoasr( /* ... */ );"
.B "if (error != NULL) {"
.B "        /* something went wrong */"
.fi
.RE