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IPSEC_ATOASR

Section: C Library Functions (3)
Updated: 13 Oct 1998
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NAME

ipsec atoasr - convert ASCII to Internet address, subnet, or range
ipsec rangetoa - convert Internet address range to ASCII

SYNOPSIS

#include <freeswan.h>

const char *atoasr(const char *src, size_t srclen,
char *type, struct in_addr *addrs);
size_t rangetoa(struct in_addr *addrs, int format,
char *dst, size_t dstlen);

DESCRIPTION

Atoasr converts an ASCII address, subnet, or address range into a suitable combination of binary addresses (in network byte order). Rangetoa converts an address range back into ASCII, using dotted-decimal form for the addresses (the other reverse conversions are handled by ipsec_addrtoa(3) and ipsec_subnettoa(3)).

A single address can be any form acceptable to ipsec_atoaddr(3): dotted decimal, DNS name, or hexadecimal number. A subnet specification uses the form network/mask interpreted by ipsec_atosubnet(3).

An address range is two ipsec_atoaddr(3) addresses separated by a ... 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 . to suppress completion attempts. The begin address of a range must be less than or equal to the end address.

The srclen parameter of atoasr 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 type parameter of atoasr must point to a char variable used to record which form was found. The addrs parameter must point to a two-element array of struct in_addr which receives the results. The values stored into *type, and the corresponding values in the array, are:

*typeaddrs[0]addrs[1]

address'a'address-

subnet 's'networkmask

range 'r'beginend

The dstlen parameter of rangetoa 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 a constant, RANGETOA_BUF, which is the size of a buffer just large enough for worst-case results.

The format parameter of rangetoa 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.

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

DIAGNOSTICS

Fatal errors in atoasr are: empty input; error in ipsec_atoaddr(3) or ipsec_atosubnet(3) during conversion; begin address of range exceeds end address.

Fatal errors in rangetoa are: unknown format.

HISTORY

Written for the FreeS/WAN project by Henry Spencer.

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.

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:

const char *error;

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

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