This commit is contained in:
Martin Willi
@@ -0,0 +1,377 @@
|
||||
.TH IPSEC_TTOADDR 3 "28 Sept 2001"
|
||||
.\" RCSID $Id: ttoaddr.3,v 1.1 2004/03/15 20:35:26 as Exp $
|
||||
.SH NAME
|
||||
ipsec ttoaddr, tnatoaddr, addrtot \- convert Internet addresses to and from text
|
||||
.br
|
||||
ipsec ttosubnet, subnettot \- convert subnet/mask text form to and from addresses
|
||||
.SH SYNOPSIS
|
||||
.B "#include <freeswan.h>
|
||||
.sp
|
||||
.B "const char *ttoaddr(const char *src, size_t srclen,"
|
||||
.ti +1c
|
||||
.B "int af, ip_address *addr);"
|
||||
.br
|
||||
.B "const char *tnatoaddr(const char *src, size_t srclen,"
|
||||
.ti +1c
|
||||
.B "int af, ip_address *addr);"
|
||||
.br
|
||||
.B "size_t addrtot(const ip_address *addr, int format,"
|
||||
.ti +1c
|
||||
.B "char *dst, size_t dstlen);"
|
||||
.sp
|
||||
.B "const char *ttosubnet(const char *src, size_t srclen,"
|
||||
.ti +1c
|
||||
.B "int af, ip_subnet *dst);"
|
||||
.br
|
||||
.B "size_t subnettot(const ip_subnet *sub, int format,"
|
||||
.ti +1c
|
||||
.B "char *dst, size_t dstlen);"
|
||||
.SH DESCRIPTION
|
||||
.I Ttoaddr
|
||||
converts a text-string name or numeric address into a binary address
|
||||
(in network byte order).
|
||||
.I Tnatoaddr
|
||||
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
|
||||
does the reverse conversion, from binary address back to a text form.
|
||||
.I Ttosubnet
|
||||
and
|
||||
.I subnettot
|
||||
do likewise for the ``address/mask'' form used to write a
|
||||
specification of a subnet.
|
||||
.PP
|
||||
An IPv4 address is specified in text as a
|
||||
dotted-decimal address (e.g.
|
||||
.BR 1.2.3.4 ),
|
||||
an eight-digit network-order hexadecimal number with the usual C prefix (e.g.
|
||||
.BR 0x01020304 ,
|
||||
which is synonymous with
|
||||
.BR 1.2.3.4 ),
|
||||
an eight-digit host-order hexadecimal number with a
|
||||
.B 0h
|
||||
prefix (e.g.
|
||||
.BR 0h01020304 ,
|
||||
which is synonymous with
|
||||
.B 1.2.3.4
|
||||
on a big-endian host and
|
||||
.B 4.3.2.1
|
||||
on a little-endian host),
|
||||
a DNS name to be looked up via
|
||||
.IR gethostbyname (3),
|
||||
or an old-style network name to be looked up via
|
||||
.IR getnetbyname (3).
|
||||
.PP
|
||||
A dotted-decimal address may be incomplete, in which case
|
||||
text-to-binary conversion implicitly appends
|
||||
as many instances of
|
||||
.B .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,
|
||||
.B 10
|
||||
is synonymous with
|
||||
.BR 10.0.0.0 ,
|
||||
and
|
||||
.B 128.009.000.032
|
||||
is synonymous with
|
||||
.BR 128.9.0.32
|
||||
(the latter example is verbatim from RFC 1166).
|
||||
The result of applying
|
||||
.I addrtot
|
||||
to an IPv4 address is always complete and does not contain leading zeros.
|
||||
.PP
|
||||
Use of hexadecimal addresses is
|
||||
.B strongly
|
||||
.BR discouraged ;
|
||||
they are included only to save hassles when dealing with
|
||||
the handful of perverted programs which already print
|
||||
network addresses in hexadecimal.
|
||||
.PP
|
||||
An IPv6 address is specified in text with
|
||||
colon-hex notation (e.g.
|
||||
.BR 0:56:78ab:22:33:44:55:66 ),
|
||||
colon-hex with
|
||||
.B ::
|
||||
abbreviating at most one subsequence of multiple zeros (e.g.
|
||||
.BR 99:ab::54:068 ,
|
||||
which is synonymous with
|
||||
.BR 99:ab:0:0:0:0:54:68 ),
|
||||
or a DNS name to be looked up via
|
||||
.IR gethostbyname (3).
|
||||
The result of applying
|
||||
.I addrtot
|
||||
to an IPv6 address will use
|
||||
.B ::
|
||||
abbreviation if possible,
|
||||
and will not contain leading zeros.
|
||||
.PP
|
||||
The letters in hexadecimal
|
||||
may be uppercase or lowercase or any mixture thereof.
|
||||
.PP
|
||||
DNS names may be complete (optionally terminated with a ``.'')
|
||||
or incomplete, and are looked up as specified by local system configuration
|
||||
(see
|
||||
.IR resolver (5)).
|
||||
The
|
||||
.I h_addr
|
||||
value returned by
|
||||
.IR gethostbyname2 (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
|
||||
.IR getnetbyname (3)
|
||||
only if
|
||||
.IR gethostbyname2 (3)
|
||||
fails.
|
||||
.PP
|
||||
A subnet specification is of the form \fInetwork\fB/\fImask\fR.
|
||||
The
|
||||
.I network
|
||||
and
|
||||
.I mask
|
||||
can be any form acceptable to
|
||||
.IR ttoaddr .
|
||||
In addition, and preferably, the
|
||||
.I 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.,
|
||||
.B 24
|
||||
in IPv4 means
|
||||
.BR 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
|
||||
.B %default
|
||||
is a synonym for
|
||||
.B 0.0.0.0/0
|
||||
or
|
||||
.B ::/0
|
||||
in IPv4 or IPv6 respectively.
|
||||
.PP
|
||||
.I Ttosubnet
|
||||
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
|
||||
is synonymous with
|
||||
.BR 10.1.2.0/24 ).
|
||||
.I Subnettot
|
||||
always generates the decimal-integer-bit-count
|
||||
form of the mask,
|
||||
with no leading zeros.
|
||||
.PP
|
||||
The
|
||||
.I srclen
|
||||
parameter of
|
||||
.I ttoaddr
|
||||
and
|
||||
.I ttosubnet
|
||||
specifies the length of the text 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 af
|
||||
parameter of
|
||||
.I ttoaddr
|
||||
and
|
||||
.I ttosubnet
|
||||
specifies the address family of interest.
|
||||
It should be either
|
||||
.B AF_INET
|
||||
or
|
||||
.BR AF_INET6 .
|
||||
.PP
|
||||
The
|
||||
.I dstlen
|
||||
parameter of
|
||||
.I addrtot
|
||||
and
|
||||
.I subnettot
|
||||
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 constants,
|
||||
.B ADDRTOT_BUF
|
||||
and
|
||||
.BR SUBNETTOT_BUF ,
|
||||
which are the sizes of buffers just large enough for worst-case results.
|
||||
.PP
|
||||
The
|
||||
.I format
|
||||
parameter of
|
||||
.I addrtot
|
||||
and
|
||||
.I subnettot
|
||||
specifies what format is to be used for the conversion.
|
||||
The value
|
||||
.B 0
|
||||
(not the character
|
||||
.BR '0' ,
|
||||
but a zero value)
|
||||
specifies a reasonable default,
|
||||
and is in fact the only format currently available in
|
||||
.IR subnettot .
|
||||
.I Addrtot
|
||||
also accepts format values
|
||||
.B 'r'
|
||||
(signifying a text form suitable for DNS reverse lookups,
|
||||
e.g.
|
||||
.B 4.3.2.1.IN-ADDR.ARPA.
|
||||
for IPv4 and
|
||||
RFC 2874 format for IPv6),
|
||||
and
|
||||
.B 'R'
|
||||
(signifying an alternate reverse-lookup form,
|
||||
an error for IPv4 and RFC 1886 format for IPv6).
|
||||
Reverse-lookup names always end with a ``.''.
|
||||
.PP
|
||||
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
|
||||
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.
|
||||
.SH SEE ALSO
|
||||
inet(3)
|
||||
.SH DIAGNOSTICS
|
||||
Fatal errors in
|
||||
.I ttoaddr
|
||||
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.
|
||||
.PP
|
||||
Fatal errors in
|
||||
.I ttosubnet
|
||||
are:
|
||||
no
|
||||
.B /
|
||||
in
|
||||
.IR src ;
|
||||
.I ttoaddr
|
||||
error in conversion of
|
||||
.I network
|
||||
or
|
||||
.IR mask ;
|
||||
bit-count mask too big;
|
||||
mask non-contiguous.
|
||||
.PP
|
||||
Fatal errors in
|
||||
.I addrtot
|
||||
and
|
||||
.I subnettot
|
||||
are:
|
||||
unknown format.
|
||||
.SH HISTORY
|
||||
Written for the FreeS/WAN project by Henry Spencer.
|
||||
.SH BUGS
|
||||
The interpretation of incomplete dotted-decimal addresses
|
||||
(e.g.
|
||||
.B 10/24
|
||||
means
|
||||
.BR 10.0.0.0/24 )
|
||||
differs from that of some older conversion
|
||||
functions, e.g. those of
|
||||
.IR inet (3).
|
||||
The behavior of the older functions has never been
|
||||
particularly consistent or particularly useful.
|
||||
.PP
|
||||
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.
|
||||
.PP
|
||||
.I Ttoaddr
|
||||
does not support the mixed colon-hex-dotted-decimal
|
||||
convention used to embed an IPv4 address in an IPv6 address.
|
||||
.PP
|
||||
.I Addrtot
|
||||
always uses the
|
||||
.B ::
|
||||
abbreviation (which can appear only once in an address) for the
|
||||
.I first
|
||||
sequence of multiple zeros in an IPv6 address.
|
||||
One can construct addresses (unlikely ones) in which this is suboptimal.
|
||||
.PP
|
||||
.I Addrtot
|
||||
.B 'r'
|
||||
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.
|
||||
.PP
|
||||
Possibly
|
||||
.I subnettot
|
||||
ought to recognize the
|
||||
.B %default
|
||||
case and generate that string as its output.
|
||||
Currently it doesn't.
|
||||
.PP
|
||||
It is barely possible that somebody, somewhere,
|
||||
might have a legitimate use for non-contiguous subnet masks.
|
||||
.PP
|
||||
.IR Getnetbyname (3)
|
||||
is a historical dreg.
|
||||
.PP
|
||||
.I Tnatoaddr
|
||||
probably should enforce completeness of dotted-decimal addresses.
|
||||
.PP
|
||||
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.
|
||||
.PP
|
||||
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:
|
||||
.PP
|
||||
.RS
|
||||
.nf
|
||||
.B "const char *error;"
|
||||
.sp
|
||||
.B "error = ttoaddr( /* ... */ );"
|
||||
.B "if (error != NULL) {"
|
||||
.B " /* something went wrong */"
|
||||
.fi
|
||||
.RE
|
||||
Reference in New Issue
Block a user