[thirdparty/strongswan.git] / doc / manpage.d / ipsec_subnettot.3.html

Content-type: text/html

<HTML><HEAD><TITLE>Manpage of IPSEC_TTOADDR</TITLE>
</HEAD><BODY>
<H1>IPSEC_TTOADDR</H1>
Section: C Library Functions (3)<BR>Updated: 28 Sept 2001<BR><A HREF="#index">Index</A>
<A HREF="http://localhost/cgi-bin/man/man2html">Return to Main Contents</A><HR>


<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>

ipsec ttoaddr, tnatoaddr, addrtot - convert Internet addresses to and from text
<BR>

ipsec ttosubnet, subnettot - convert subnet/mask text form to and from addresses
<A NAME="lbAC">&nbsp;</A>
<H2>SYNOPSIS</H2>

<B>#include &lt;<A HREF="file:/usr/include/freeswan.h">freeswan.h</A>&gt;</B>

<P>
<B>const char *ttoaddr(const char *src, size_t srclen,</B>

<BR>
&nbsp;
<B>int af, ip_address *addr);</B>

<BR>

<B>const char *tnatoaddr(const char *src, size_t srclen,</B>

<BR>
&nbsp;
<B>int af, ip_address *addr);</B>

<BR>

<B>size_t addrtot(const ip_address *addr, int format,</B>

<BR>
&nbsp;
<B>char *dst, size_t dstlen);</B>

<P>
<B>const char *ttosubnet(const char *src, size_t srclen,</B>

<BR>
&nbsp;
<B>int af, ip_subnet *dst);</B>

<BR>

<B>size_t subnettot(const ip_subnet *sub, int format,</B>

<BR>
&nbsp;
<B>char *dst, size_t dstlen);</B>

<A NAME="lbAD">&nbsp;</A>
<H2>DESCRIPTION</H2>

<I>Ttoaddr</I>

converts a text-string name or numeric address into a binary address
(in network byte order).
<I>Tnatoaddr</I>

does the same conversion,
but the only text forms it accepts are
the ``official'' forms of
numeric address (dotted-decimal for IPv4, colon-hex for IPv6).
<I>Addrtot</I>

does the reverse conversion, from binary address back to a text form.
<I>Ttosubnet</I>

and
<I>subnettot</I>

do likewise for the ``address/mask'' form used to write a
specification of a subnet.
<P>

An IPv4 address is specified in text as a
dotted-decimal address (e.g.
<B>1.2.3.4</B>),

an eight-digit network-order hexadecimal number with the usual C prefix (e.g.
<B>0x01020304</B>,

which is synonymous with
<B>1.2.3.4</B>),

an eight-digit host-order hexadecimal number with a
<B>0h</B>

prefix (e.g.
<B>0h01020304</B>,

which is synonymous with
<B>1.2.3.4</B>

on a big-endian host and
<B>4.3.2.1</B>

on a little-endian host),
a DNS name to be looked up via
<I><A HREF="gethostbyname.3.html">gethostbyname</A></I>(3),

or an old-style network name to be looked up via
<I><A HREF="getnetbyname.3.html">getnetbyname</A></I>(3).

<P>

A dotted-decimal address may be incomplete, in which case
text-to-binary conversion implicitly appends
as many instances of
<B>.0</B>

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,
<B>10</B>

is synonymous with
<B>10.0.0.0</B>,

and
<B>128.009.000.032</B>

is synonymous with
<B>128.9.0.32</B>

(the latter example is verbatim from RFC 1166).
The result of applying
<I>addrtot</I>

to an IPv4 address is always complete and does not contain leading zeros.
<P>

Use of hexadecimal addresses is
<B>strongly</B>

<B>discouraged</B>;

they are included only to save hassles when dealing with
the handful of perverted programs which already print 
network addresses in hexadecimal.
<P>

An IPv6 address is specified in text with
colon-hex notation (e.g.
<B>0:56:78ab:22:33:44:55:66</B>),

colon-hex with
<B>::</B>

abbreviating at most one subsequence of multiple zeros (e.g.
<B>99:ab::54:068</B>,

which is synonymous with
<B>99:ab:0:0:0:0:54:68</B>),

or a DNS name to be looked up via
<I><A HREF="gethostbyname.3.html">gethostbyname</A></I>(3).

The result of applying
<I>addrtot</I>

to an IPv6 address will use
<B>::</B>

abbreviation if possible,
and will not contain leading zeros.
<P>

The letters in hexadecimal
may be uppercase or lowercase or any mixture thereof.
<P>

DNS names may be complete (optionally terminated with a ``.'')
or incomplete, and are looked up as specified by local system configuration
(see
<I><A HREF="resolver.5.html">resolver</A></I>(5)).

The
<I>h_addr</I>

value returned by
<I><A HREF="gethostbyname2.3.html">gethostbyname2</A></I>(3)

is used,
so with current DNS implementations,
the result when the name corresponds to more than one address is
difficult to predict.
IPv4 name lookup resorts to
<I><A HREF="getnetbyname.3.html">getnetbyname</A></I>(3)

only if
<I><A HREF="gethostbyname2.3.html">gethostbyname2</A></I>(3)

fails.
<P>

A subnet specification is of the form <I>network</I><B>/</B><I>mask</I>.
The
<I>network</I>

and
<I>mask</I>

can be any form acceptable to
<I>ttoaddr</I>.

In addition, and preferably, the
<I>mask</I>

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.,
<B>24</B>

in IPv4 means
<B>255.255.255.0</B>).

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
<B>%default</B>

is a synonym for
<B>0.0.0.0/0</B>

or
<B>::/0</B>

in IPv4 or IPv6 respectively.
<P>

<I>Ttosubnet</I>

ANDs the mask with the address before returning,
so that any non-network bits in the address are turned off
(e.g.,
<B>10.1.2.3/24</B>

is synonymous with
<B>10.1.2.0/24</B>).

<I>Subnettot</I>

always generates the decimal-integer-bit-count
form of the mask,
with no leading zeros.
<P>

The
<I>srclen</I>

parameter of
<I>ttoaddr</I>

and
<I>ttosubnet</I>

specifies the length of the text string pointed to by
<I>src</I>;

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</I>

value of
<B>0</B>

is taken to mean
<B>strlen(src)</B>.

<P>

The
<I>af</I>

parameter of
<I>ttoaddr</I>

and
<I>ttosubnet</I>

specifies the address family of interest.
It should be either
<B>AF_INET</B>

or
<B>AF_INET6</B>.

<P>

The
<I>dstlen</I>

parameter of
<I>addrtot</I>

and
<I>subnettot</I>

specifies the size of the
<I>dst</I>

parameter;
under no circumstances are more than
<I>dstlen</I>

bytes written to
<I>dst</I>.

A result which will not fit is truncated.
<I>Dstlen</I>

can be zero, in which case
<I>dst</I>

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</I>

header file defines constants,
<B>ADDRTOT_BUF</B>

and
<B>SUBNETTOT_BUF</B>,

which are the sizes of buffers just large enough for worst-case results.
<P>

The
<I>format</I>

parameter of
<I>addrtot</I>

and
<I>subnettot</I>

specifies what format is to be used for the conversion.
The value
<B>0</B>

(not the character
<B>'0'</B>,

but a zero value)
specifies a reasonable default,
and is in fact the only format currently available in
<I>subnettot</I>.

<I>Addrtot</I>

also accepts format values
<B>'r'</B>

(signifying a text form suitable for DNS reverse lookups,
e.g.
<B>4.3.2.1.IN-ADDR.ARPA.</B>

for IPv4 and
RFC 2874 format for IPv6),
and
<B>'R'</B>

(signifying an alternate reverse-lookup form,
an error for IPv4 and RFC 1886 format for IPv6).
Reverse-lookup names always end with a ``.''.
<P>

The text-to-binary functions return NULL for success and
a pointer to a string-literal error message for failure;
see DIAGNOSTICS.
The binary-to-text functions return
<B>0</B>

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.
<A NAME="lbAE">&nbsp;</A>
<H2>SEE ALSO</H2>

<A HREF="inet.3.html">inet</A>(3)
<A NAME="lbAF">&nbsp;</A>
<H2>DIAGNOSTICS</H2>

Fatal errors in
<I>ttoaddr</I>

are:
empty input;
unknown address family;
attempt to allocate temporary storage for a very long name failed;
name lookup failed;
syntax error in dotted-decimal or colon-hex form;
dotted-decimal or colon-hex component too large.
<P>

Fatal errors in
<I>ttosubnet</I>

are:
no
<B>/</B>

in
<I>src</I>;

<I>ttoaddr</I>

error in conversion of
<I>network</I>

or
<I>mask</I>;

bit-count mask too big;
mask non-contiguous.
<P>

Fatal errors in
<I>addrtot</I>

and
<I>subnettot</I>

are:
unknown format.
<A NAME="lbAG">&nbsp;</A>
<H2>HISTORY</H2>

Written for the FreeS/WAN project by Henry Spencer.
<A NAME="lbAH">&nbsp;</A>
<H2>BUGS</H2>

The interpretation of incomplete dotted-decimal addresses
(e.g.
<B>10/24</B>

means
<B>10.0.0.0/24</B>)

differs from that of some older conversion
functions, e.g. those of
<I><A HREF="inet.3.html">inet</A></I>(3).

The behavior of the older functions has never been
particularly consistent or particularly useful.
<P>

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.
<P>

<I>Ttoaddr</I>

does not support the mixed colon-hex-dotted-decimal
convention used to embed an IPv4 address in an IPv6 address.
<P>

<I>Addrtot</I>

always uses the
<B>::</B>

abbreviation (which can appear only once in an address) for the
<I>first</I>

sequence of multiple zeros in an IPv6 address.
One can construct addresses (unlikely ones) in which this is suboptimal.
<P>

<I>Addrtot</I>

<B>'r'</B>

conversion of an IPv6 address uses lowercase hexadecimal,
not the uppercase used in RFC 2874's examples.
It takes careful reading of RFCs 2874, 2673, and 2234 to realize
that lowercase is technically legitimate here,
and there may be software which botches this
and hence would have trouble with lowercase hex.
<P>

Possibly
<I>subnettot</I>

ought to recognize the
<B>%default</B>

case and generate that string as its output.
Currently it doesn't.
<P>

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

<I><A HREF="Getnetbyname.3.html">Getnetbyname</A></I>(3)

is a historical dreg.
<P>

<I>Tnatoaddr</I>

probably should enforce completeness of dotted-decimal addresses.
<P>

The restriction of text-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.
<P>

The text-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:
<P>

<DL COMPACT><DT><DD>
<PRE>
<B>const char *error;</B>

<B>error = ttoaddr( /* ... */ );</B>
<B>if (error != NULL) {</B>
<B>        /* something went wrong */</B>
</PRE>

</DL>

<P>

<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT><A HREF="#lbAB">NAME</A><DD>
<DT><A HREF="#lbAC">SYNOPSIS</A><DD>
<DT><A HREF="#lbAD">DESCRIPTION</A><DD>
<DT><A HREF="#lbAE">SEE ALSO</A><DD>
<DT><A HREF="#lbAF">DIAGNOSTICS</A><DD>
<DT><A HREF="#lbAG">HISTORY</A><DD>
<DT><A HREF="#lbAH">BUGS</A><DD>
</DL>
<HR>
This document was created by
<A HREF="http://localhost/cgi-bin/man/man2html">man2html</A>,
using the manual pages.<BR>
Time: 21:40:18 GMT, November 11, 2003
</BODY>
</HTML>
Commit	Line	Data
997358a6 MW	1	Content-type: text/html
	2
	3	<HTML><HEAD><TITLE>Manpage of IPSEC_TTOADDR</TITLE>
	4	</HEAD><BODY>
	5	<H1>IPSEC_TTOADDR</H1>
	6	Section: C Library Functions (3)<BR>Updated: 28 Sept 2001<BR><A HREF="#index">Index</A>
	7	<A HREF="http://localhost/cgi-bin/man/man2html">Return to Main Contents</A><HR>
	8
	9
	10	<A NAME="lbAB"> </A>
	11	<H2>NAME</H2>
	12
	13	ipsec ttoaddr, tnatoaddr, addrtot - convert Internet addresses to and from text
	14	<BR>
	15
	16	ipsec ttosubnet, subnettot - convert subnet/mask text form to and from addresses
	17	<A NAME="lbAC"> </A>
	18	<H2>SYNOPSIS</H2>
	19
	20	<B>#include <<A HREF="file:/usr/include/freeswan.h">freeswan.h</A>></B>
	21
	22	<P>
	23	<B>const char ttoaddr(const char src, size_t srclen,</B>
	24
	25	<BR>
	26
	27	<B>int af, ip_address *addr);</B>
	28
	29	<BR>
	30
	31	<B>const char tnatoaddr(const char src, size_t srclen,</B>
	32
	33	<BR>
	34
	35	<B>int af, ip_address *addr);</B>
	36
	37	<BR>
	38
	39	<B>size_t addrtot(const ip_address *addr, int format,</B>
	40
	41	<BR>
	42
	43	<B>char *dst, size_t dstlen);</B>
	44
	45	<P>
	46	<B>const char ttosubnet(const char src, size_t srclen,</B>
	47
	48	<BR>
	49
	50	<B>int af, ip_subnet *dst);</B>
	51
	52	<BR>
	53
	54	<B>size_t subnettot(const ip_subnet *sub, int format,</B>
	55
	56	<BR>
	57
	58	<B>char *dst, size_t dstlen);</B>
	59
	60	<A NAME="lbAD"> </A>
	61	<H2>DESCRIPTION</H2>
	62
	63	<I>Ttoaddr</I>
	64
65	converts a text-string name or numeric address into a binary address
66	(in network byte order).
67	<I>Tnatoaddr</I>
68
69	does the same conversion,
70	but the only text forms it accepts are
71	the ``official'' forms of
72	numeric address (dotted-decimal for IPv4, colon-hex for IPv6).
73	<I>Addrtot</I>
74
75	does the reverse conversion, from binary address back to a text form.
76	<I>Ttosubnet</I>
77
78	and
79	<I>subnettot</I>
80
81	do likewise for the ``address/mask'' form used to write a
82	specification of a subnet.
83	<P>
84
85	An IPv4 address is specified in text as a
86	dotted-decimal address (e.g.
87	<B>1.2.3.4</B>),
88
89	an eight-digit network-order hexadecimal number with the usual C prefix (e.g.
90	<B>0x01020304</B>,
91
92	which is synonymous with
93	<B>1.2.3.4</B>),
94
95	an eight-digit host-order hexadecimal number with a
96	<B>0h</B>
97
98	prefix (e.g.
99	<B>0h01020304</B>,
100
101	which is synonymous with
102	<B>1.2.3.4</B>
103
104	on a big-endian host and
105	<B>4.3.2.1</B>
106
107	on a little-endian host),
108	a DNS name to be looked up via
109	<I><A HREF="gethostbyname.3.html">gethostbyname</A></I>(3),
110
111	or an old-style network name to be looked up via
112	<I><A HREF="getnetbyname.3.html">getnetbyname</A></I>(3).
113
114	<P>
115
116	A dotted-decimal address may be incomplete, in which case
117	text-to-binary conversion implicitly appends
118	as many instances of
119	<B>.0</B>
120
121	as necessary to bring it up to four components.
122	The components of a dotted-decimal address are always taken as
123	decimal, and leading zeros are ignored.
124	For example,
125	<B>10</B>
126
127	is synonymous with
128	<B>10.0.0.0</B>,
129
130	and
131	<B>128.009.000.032</B>
132
133	is synonymous with
134	<B>128.9.0.32</B>
135
136	(the latter example is verbatim from RFC 1166).
137	The result of applying
138	<I>addrtot</I>
139
140	to an IPv4 address is always complete and does not contain leading zeros.
141	<P>
142
143	Use of hexadecimal addresses is
144	<B>strongly</B>
145
146	<B>discouraged</B>;
147
148	they are included only to save hassles when dealing with
149	the handful of perverted programs which already print
150	network addresses in hexadecimal.
151	<P>
152
153	An IPv6 address is specified in text with
154	colon-hex notation (e.g.
155	<B>0:56:78ab:22:33:44:55:66</B>),
156
157	colon-hex with
158	<B>::</B>
159
160	abbreviating at most one subsequence of multiple zeros (e.g.
161	<B>99:ab::54:068</B>,
162
163	which is synonymous with
164	<B>99:ab:0:0:0:0:54:68</B>),
165
166	or a DNS name to be looked up via
167	<I><A HREF="gethostbyname.3.html">gethostbyname</A></I>(3).
168
169	The result of applying
170	<I>addrtot</I>
171
172	to an IPv6 address will use
173	<B>::</B>
174
175	abbreviation if possible,
176	and will not contain leading zeros.
177	<P>
178
179	The letters in hexadecimal
180	may be uppercase or lowercase or any mixture thereof.
181	<P>
182
183	DNS names may be complete (optionally terminated with a ``.'')
184	or incomplete, and are looked up as specified by local system configuration
185	(see
186	<I><A HREF="resolver.5.html">resolver</A></I>(5)).
187
188	The
189	<I>h_addr</I>
190
191	value returned by
192	<I><A HREF="gethostbyname2.3.html">gethostbyname2</A></I>(3)
193
194	is used,
195	so with current DNS implementations,
196	the result when the name corresponds to more than one address is
197	difficult to predict.
198	IPv4 name lookup resorts to
199	<I><A HREF="getnetbyname.3.html">getnetbyname</A></I>(3)
200
201	only if
202	<I><A HREF="gethostbyname2.3.html">gethostbyname2</A></I>(3)
203
204	fails.
205	<P>
206
207	A subnet specification is of the form <I>network</I><B>/</B><I>mask</I>.
208	The
209	<I>network</I>
210
211	and
212	<I>mask</I>
213
214	can be any form acceptable to
215	<I>ttoaddr</I>.
216
217	In addition, and preferably, the
218	<I>mask</I>
219
220	can be a decimal integer (leading zeros ignored) giving a bit count,
221	in which case
222	it stands for a mask with that number of high bits on and all others off
223	(e.g.,
224	<B>24</B>
225
226	in IPv4 means
227	<B>255.255.255.0</B>).
228
229	In any case, the mask must be contiguous
230	(a sequence of high bits on and all remaining low bits off).
231	As a special case, the subnet specification
232	<B>%default</B>
233
234	is a synonym for
235	<B>0.0.0.0/0</B>
236
237	or
238	<B>::/0</B>
239
240	in IPv4 or IPv6 respectively.
241	<P>
242
243	<I>Ttosubnet</I>
244
245	ANDs the mask with the address before returning,
246	so that any non-network bits in the address are turned off
247	(e.g.,
248	<B>10.1.2.3/24</B>
249
250	is synonymous with
251	<B>10.1.2.0/24</B>).
252
253	<I>Subnettot</I>
254
255	always generates the decimal-integer-bit-count
256	form of the mask,
257	with no leading zeros.
258	<P>
259
260	The
261	<I>srclen</I>
262
263	parameter of
264	<I>ttoaddr</I>
265
266	and
267	<I>ttosubnet</I>
268
269	specifies the length of the text string pointed to by
270	<I>src</I>;
271
272	it is an error for there to be anything else
273	(e.g., a terminating NUL) within that length.
274	As a convenience for cases where an entire NUL-terminated string is
275	to be converted,
276	a
277	<I>srclen</I>
278
279	value of
280	<B>0</B>
281
282	is taken to mean
283	<B>strlen(src)</B>.
284
285	<P>
286
287	The
288	<I>af</I>
289
290	parameter of
291	<I>ttoaddr</I>
292
293	and
294	<I>ttosubnet</I>
295
296	specifies the address family of interest.
297	It should be either
298	<B>AF_INET</B>
299
300	or
301	<B>AF_INET6</B>.
302
303	<P>
304
305	The
306	<I>dstlen</I>
307
308	parameter of
309	<I>addrtot</I>
310
311	and
312	<I>subnettot</I>
313
314	specifies the size of the
315	<I>dst</I>
316
317	parameter;
318	under no circumstances are more than
319	<I>dstlen</I>
320
321	bytes written to
322	<I>dst</I>.
323
324	A result which will not fit is truncated.
325	<I>Dstlen</I>
326
327	can be zero, in which case
328	<I>dst</I>
329
330	need not be valid and no result is written,
331	but the return value is unaffected;
332	in all other cases, the (possibly truncated) result is NUL-terminated.
333	The
334	<I>freeswan.h</I>
335
336	header file defines constants,
337	<B>ADDRTOT_BUF</B>
338
339	and
340	<B>SUBNETTOT_BUF</B>,
341
342	which are the sizes of buffers just large enough for worst-case results.
343	<P>
344
345	The
346	<I>format</I>
347
348	parameter of
349	<I>addrtot</I>
350
351	and
352	<I>subnettot</I>
353
354	specifies what format is to be used for the conversion.
355	The value
356	<B>0</B>
357
358	(not the character
359	<B>'0'</B>,
360
361	but a zero value)
362	specifies a reasonable default,
363	and is in fact the only format currently available in
364	<I>subnettot</I>.
365
366	<I>Addrtot</I>
367
368	also accepts format values
369	<B>'r'</B>
370
371	(signifying a text form suitable for DNS reverse lookups,
372	e.g.
373	<B>4.3.2.1.IN-ADDR.ARPA.</B>
374
375	for IPv4 and
376	RFC 2874 format for IPv6),
377	and
378	<B>'R'</B>
379
380	(signifying an alternate reverse-lookup form,
381	an error for IPv4 and RFC 1886 format for IPv6).
382	Reverse-lookup names always end with a ``.''.
383	<P>
384
385	The text-to-binary functions return NULL for success and
386	a pointer to a string-literal error message for failure;
387	see DIAGNOSTICS.
388	The binary-to-text functions return
389	<B>0</B>
390
391	for a failure, and otherwise
392	always return the size of buffer which would
393	be needed to
394	accommodate the full conversion result, including terminating NUL;
395	it is the caller's responsibility to check this against the size of
396	the provided buffer to determine whether truncation has occurred.
397	<A NAME="lbAE"> </A>
398	<H2>SEE ALSO</H2>
399
400	<A HREF="inet.3.html">inet</A>(3)
401	<A NAME="lbAF"> </A>
402	<H2>DIAGNOSTICS</H2>
403
404	Fatal errors in
405	<I>ttoaddr</I>
406
407	are:
408	empty input;
409	unknown address family;
410	attempt to allocate temporary storage for a very long name failed;
411	name lookup failed;
412	syntax error in dotted-decimal or colon-hex form;
413	dotted-decimal or colon-hex component too large.
414	<P>
415
416	Fatal errors in
417	<I>ttosubnet</I>
418
419	are:
420	no
421	<B>/</B>
422
423	in
424	<I>src</I>;
425
426	<I>ttoaddr</I>
427
428	error in conversion of
429	<I>network</I>
430
431	or
432	<I>mask</I>;
433
434	bit-count mask too big;
435	mask non-contiguous.
436	<P>
437
438	Fatal errors in
439	<I>addrtot</I>
440
441	and
442	<I>subnettot</I>
443
444	are:
445	unknown format.
446	<A NAME="lbAG"> </A>
447	<H2>HISTORY</H2>
448
449	Written for the FreeS/WAN project by Henry Spencer.
450	<A NAME="lbAH"> </A>
451	<H2>BUGS</H2>
452
453	The interpretation of incomplete dotted-decimal addresses
454	(e.g.
455	<B>10/24</B>
456
457	means
458	<B>10.0.0.0/24</B>)
459
460	differs from that of some older conversion
461	functions, e.g. those of
462	<I><A HREF="inet.3.html">inet</A></I>(3).
463
464	The behavior of the older functions has never been
465	particularly consistent or particularly useful.
466	<P>
467
468	Ignoring leading zeros in dotted-decimal components and bit counts
469	is arguably the most useful behavior in this application,
470	but it might occasionally cause confusion with the historical use of leading
471	zeros to denote octal numbers.
472	<P>
473
474	<I>Ttoaddr</I>
475
476	does not support the mixed colon-hex-dotted-decimal
477	convention used to embed an IPv4 address in an IPv6 address.
478	<P>
479
480	<I>Addrtot</I>
481
482	always uses the
483	<B>::</B>
484
485	abbreviation (which can appear only once in an address) for the
486	<I>first</I>
487
488	sequence of multiple zeros in an IPv6 address.
489	One can construct addresses (unlikely ones) in which this is suboptimal.
490	<P>
491
492	<I>Addrtot</I>
493
494	<B>'r'</B>
495
496	conversion of an IPv6 address uses lowercase hexadecimal,
497	not the uppercase used in RFC 2874's examples.
498	It takes careful reading of RFCs 2874, 2673, and 2234 to realize
499	that lowercase is technically legitimate here,
500	and there may be software which botches this
501	and hence would have trouble with lowercase hex.
502	<P>
503
504	Possibly
505	<I>subnettot</I>
506
507	ought to recognize the
508	<B>%default</B>
509
510	case and generate that string as its output.
511	Currently it doesn't.
512	<P>
513
514	It is barely possible that somebody, somewhere,
515	might have a legitimate use for non-contiguous subnet masks.
516	<P>
517
518	<I><A HREF="Getnetbyname.3.html">Getnetbyname</A></I>(3)
519
520	is a historical dreg.
521	<P>
522
523	<I>Tnatoaddr</I>
524
525	probably should enforce completeness of dotted-decimal addresses.
526	<P>
527
528	The restriction of text-to-binary error reports to literal strings
529	(so that callers don't need to worry about freeing them or copying them)
530	does limit the precision of error reporting.
531	<P>
532
533	The text-to-binary error-reporting convention lends itself
534	to slightly obscure code,
535	because many readers will not think of NULL as signifying success.
536	A good way to make it clearer is to write something like:
537	<P>
538
539	<DL COMPACT><DT><DD>
540	<PRE>
541	<B>const char *error;</B>
542
543	<B>error = ttoaddr( /* ... */ );</B>
544	<B>if (error != NULL) {</B>
545	<B> /* something went wrong */</B>
546	</PRE>
547
548	</DL>
549
550	<P>
551
552	<HR>
553	<A NAME="index"> </A><H2>Index</H2>
554	<DL>
555	<DT><A HREF="#lbAB">NAME</A><DD>
556	<DT><A HREF="#lbAC">SYNOPSIS</A><DD>
557	<DT><A HREF="#lbAD">DESCRIPTION</A><DD>
558	<DT><A HREF="#lbAE">SEE ALSO</A><DD>
559	<DT><A HREF="#lbAF">DIAGNOSTICS</A><DD>
560	<DT><A HREF="#lbAG">HISTORY</A><DD>
561	<DT><A HREF="#lbAH">BUGS</A><DD>
562	</DL>
563	<HR>
564	This document was created by
565	<A HREF="http://localhost/cgi-bin/man/man2html">man2html</A>,
566	using the manual pages.<BR>
567	Time: 21:40:18 GMT, November 11, 2003
568	</BODY>
569	</HTML>