570 lines
11 KiB
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570 lines
11 KiB
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<HTML><HEAD><TITLE>Manpage of IPSEC_TTOADDR</TITLE>
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</HEAD><BODY>
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<H1>IPSEC_TTOADDR</H1>
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Section: C Library Functions (3)<BR>Updated: 28 Sept 2001<BR><A HREF="#index">Index</A>
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<A HREF="http://localhost/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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ipsec ttoaddr, tnatoaddr, addrtot - convert Internet addresses to and from text
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<BR>
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ipsec ttosubnet, subnettot - convert subnet/mask text form to and from addresses
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:/usr/include/freeswan.h">freeswan.h</A>></B>
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<P>
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<B>const char *ttoaddr(const char *src, size_t srclen,</B>
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<BR>
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<B>int af, ip_address *addr);</B>
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<BR>
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<B>const char *tnatoaddr(const char *src, size_t srclen,</B>
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<BR>
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<B>int af, ip_address *addr);</B>
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<BR>
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<B>size_t addrtot(const ip_address *addr, int format,</B>
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<BR>
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<B>char *dst, size_t dstlen);</B>
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<P>
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<B>const char *ttosubnet(const char *src, size_t srclen,</B>
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<BR>
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<B>int af, ip_subnet *dst);</B>
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<BR>
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<B>size_t subnettot(const ip_subnet *sub, int format,</B>
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<BR>
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<B>char *dst, size_t dstlen);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<I>Ttoaddr</I>
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converts a text-string name or numeric address into a binary address
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(in network byte order).
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<I>Tnatoaddr</I>
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does the same conversion,
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but the only text forms it accepts are
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the ``official'' forms of
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numeric address (dotted-decimal for IPv4, colon-hex for IPv6).
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<I>Addrtot</I>
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does the reverse conversion, from binary address back to a text form.
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<I>Ttosubnet</I>
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and
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<I>subnettot</I>
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do likewise for the ``address/mask'' form used to write a
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specification of a subnet.
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<P>
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An IPv4 address is specified in text as a
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dotted-decimal address (e.g.
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<B>1.2.3.4</B>),
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an eight-digit network-order hexadecimal number with the usual C prefix (e.g.
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<B>0x01020304</B>,
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which is synonymous with
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<B>1.2.3.4</B>),
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an eight-digit host-order hexadecimal number with a
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<B>0h</B>
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prefix (e.g.
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<B>0h01020304</B>,
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which is synonymous with
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<B>1.2.3.4</B>
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on a big-endian host and
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<B>4.3.2.1</B>
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on a little-endian host),
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a DNS name to be looked up via
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<I><A HREF="gethostbyname.3.html">gethostbyname</A></I>(3),
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or an old-style network name to be looked up via
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<I><A HREF="getnetbyname.3.html">getnetbyname</A></I>(3).
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<P>
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A dotted-decimal address may be incomplete, in which case
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text-to-binary conversion implicitly appends
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as many instances of
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<B>.0</B>
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as necessary to bring it up to four components.
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The components of a dotted-decimal address are always taken as
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decimal, and leading zeros are ignored.
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For example,
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<B>10</B>
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is synonymous with
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<B>10.0.0.0</B>,
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and
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<B>128.009.000.032</B>
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is synonymous with
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<B>128.9.0.32</B>
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(the latter example is verbatim from RFC 1166).
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The result of applying
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<I>addrtot</I>
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to an IPv4 address is always complete and does not contain leading zeros.
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<P>
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Use of hexadecimal addresses is
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<B>strongly</B>
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<B>discouraged</B>;
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they are included only to save hassles when dealing with
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the handful of perverted programs which already print
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network addresses in hexadecimal.
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<P>
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An IPv6 address is specified in text with
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colon-hex notation (e.g.
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<B>0:56:78ab:22:33:44:55:66</B>),
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colon-hex with
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<B>::</B>
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abbreviating at most one subsequence of multiple zeros (e.g.
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<B>99:ab::54:068</B>,
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which is synonymous with
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<B>99:ab:0:0:0:0:54:68</B>),
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or a DNS name to be looked up via
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<I><A HREF="gethostbyname.3.html">gethostbyname</A></I>(3).
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The result of applying
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<I>addrtot</I>
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to an IPv6 address will use
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<B>::</B>
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abbreviation if possible,
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and will not contain leading zeros.
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<P>
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The letters in hexadecimal
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may be uppercase or lowercase or any mixture thereof.
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<P>
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DNS names may be complete (optionally terminated with a ``.'')
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or incomplete, and are looked up as specified by local system configuration
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(see
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<I><A HREF="resolver.5.html">resolver</A></I>(5)).
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The
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<I>h_addr</I>
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value returned by
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<I><A HREF="gethostbyname2.3.html">gethostbyname2</A></I>(3)
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is used,
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so with current DNS implementations,
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the result when the name corresponds to more than one address is
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difficult to predict.
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IPv4 name lookup resorts to
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<I><A HREF="getnetbyname.3.html">getnetbyname</A></I>(3)
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only if
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<I><A HREF="gethostbyname2.3.html">gethostbyname2</A></I>(3)
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fails.
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<P>
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A subnet specification is of the form <I>network</I><B>/</B><I>mask</I>.
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The
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<I>network</I>
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and
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<I>mask</I>
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can be any form acceptable to
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<I>ttoaddr</I>.
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In addition, and preferably, the
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<I>mask</I>
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can be a decimal integer (leading zeros ignored) giving a bit count,
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in which case
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it stands for a mask with that number of high bits on and all others off
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(e.g.,
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<B>24</B>
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in IPv4 means
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<B>255.255.255.0</B>).
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In any case, the mask must be contiguous
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(a sequence of high bits on and all remaining low bits off).
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As a special case, the subnet specification
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<B>%default</B>
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is a synonym for
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<B>0.0.0.0/0</B>
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or
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<B>::/0</B>
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in IPv4 or IPv6 respectively.
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<P>
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<I>Ttosubnet</I>
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ANDs the mask with the address before returning,
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so that any non-network bits in the address are turned off
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(e.g.,
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<B>10.1.2.3/24</B>
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is synonymous with
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<B>10.1.2.0/24</B>).
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<I>Subnettot</I>
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always generates the decimal-integer-bit-count
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form of the mask,
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with no leading zeros.
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<P>
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The
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<I>srclen</I>
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parameter of
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<I>ttoaddr</I>
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and
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<I>ttosubnet</I>
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specifies the length of the text string pointed to by
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<I>src</I>;
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it is an error for there to be anything else
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(e.g., a terminating NUL) within that length.
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As a convenience for cases where an entire NUL-terminated string is
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to be converted,
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a
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<I>srclen</I>
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value of
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<B>0</B>
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is taken to mean
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<B>strlen(src)</B>.
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<P>
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The
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<I>af</I>
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parameter of
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<I>ttoaddr</I>
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and
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<I>ttosubnet</I>
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specifies the address family of interest.
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It should be either
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<B>AF_INET</B>
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or
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<B>AF_INET6</B>.
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<P>
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The
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<I>dstlen</I>
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parameter of
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<I>addrtot</I>
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and
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<I>subnettot</I>
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specifies the size of the
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<I>dst</I>
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parameter;
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under no circumstances are more than
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<I>dstlen</I>
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bytes written to
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<I>dst</I>.
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A result which will not fit is truncated.
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<I>Dstlen</I>
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can be zero, in which case
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<I>dst</I>
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need not be valid and no result is written,
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but the return value is unaffected;
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in all other cases, the (possibly truncated) result is NUL-terminated.
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The
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<I>freeswan.h</I>
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header file defines constants,
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<B>ADDRTOT_BUF</B>
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and
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<B>SUBNETTOT_BUF</B>,
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which are the sizes of buffers just large enough for worst-case results.
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<P>
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The
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<I>format</I>
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parameter of
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<I>addrtot</I>
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and
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<I>subnettot</I>
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specifies what format is to be used for the conversion.
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The value
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<B>0</B>
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(not the character
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<B>'0'</B>,
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but a zero value)
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specifies a reasonable default,
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and is in fact the only format currently available in
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<I>subnettot</I>.
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<I>Addrtot</I>
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also accepts format values
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<B>'r'</B>
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(signifying a text form suitable for DNS reverse lookups,
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e.g.
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<B>4.3.2.1.IN-ADDR.ARPA.</B>
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for IPv4 and
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RFC 2874 format for IPv6),
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and
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<B>'R'</B>
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(signifying an alternate reverse-lookup form,
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an error for IPv4 and RFC 1886 format for IPv6).
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Reverse-lookup names always end with a ``.''.
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<P>
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The text-to-binary functions return NULL for success and
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a pointer to a string-literal error message for failure;
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see DIAGNOSTICS.
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The binary-to-text functions return
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<B>0</B>
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for a failure, and otherwise
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always return the size of buffer which would
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be needed to
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accommodate the full conversion result, including terminating NUL;
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it is the caller's responsibility to check this against the size of
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the provided buffer to determine whether truncation has occurred.
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<A NAME="lbAE"> </A>
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<H2>SEE ALSO</H2>
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<A HREF="inet.3.html">inet</A>(3)
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<A NAME="lbAF"> </A>
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<H2>DIAGNOSTICS</H2>
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Fatal errors in
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<I>ttoaddr</I>
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are:
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empty input;
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unknown address family;
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attempt to allocate temporary storage for a very long name failed;
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name lookup failed;
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syntax error in dotted-decimal or colon-hex form;
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dotted-decimal or colon-hex component too large.
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<P>
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Fatal errors in
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<I>ttosubnet</I>
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are:
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no
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<B>/</B>
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in
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<I>src</I>;
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<I>ttoaddr</I>
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error in conversion of
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<I>network</I>
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or
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<I>mask</I>;
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bit-count mask too big;
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mask non-contiguous.
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<P>
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Fatal errors in
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<I>addrtot</I>
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and
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<I>subnettot</I>
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are:
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unknown format.
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<A NAME="lbAG"> </A>
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<H2>HISTORY</H2>
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Written for the FreeS/WAN project by Henry Spencer.
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<A NAME="lbAH"> </A>
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<H2>BUGS</H2>
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The interpretation of incomplete dotted-decimal addresses
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(e.g.
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<B>10/24</B>
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means
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<B>10.0.0.0/24</B>)
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differs from that of some older conversion
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functions, e.g. those of
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<I><A HREF="inet.3.html">inet</A></I>(3).
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The behavior of the older functions has never been
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particularly consistent or particularly useful.
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<P>
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Ignoring leading zeros in dotted-decimal components and bit counts
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is arguably the most useful behavior in this application,
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but it might occasionally cause confusion with the historical use of leading
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zeros to denote octal numbers.
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<P>
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<I>Ttoaddr</I>
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does not support the mixed colon-hex-dotted-decimal
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convention used to embed an IPv4 address in an IPv6 address.
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<P>
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<I>Addrtot</I>
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always uses the
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<B>::</B>
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abbreviation (which can appear only once in an address) for the
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<I>first</I>
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sequence of multiple zeros in an IPv6 address.
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One can construct addresses (unlikely ones) in which this is suboptimal.
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<P>
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<I>Addrtot</I>
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<B>'r'</B>
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conversion of an IPv6 address uses lowercase hexadecimal,
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not the uppercase used in RFC 2874's examples.
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It takes careful reading of RFCs 2874, 2673, and 2234 to realize
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that lowercase is technically legitimate here,
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and there may be software which botches this
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and hence would have trouble with lowercase hex.
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<P>
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Possibly
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<I>subnettot</I>
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ought to recognize the
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<B>%default</B>
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case and generate that string as its output.
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Currently it doesn't.
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<P>
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It is barely possible that somebody, somewhere,
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might have a legitimate use for non-contiguous subnet masks.
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<P>
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<I><A HREF="Getnetbyname.3.html">Getnetbyname</A></I>(3)
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is a historical dreg.
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<P>
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<I>Tnatoaddr</I>
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probably should enforce completeness of dotted-decimal addresses.
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<P>
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The restriction of text-to-binary error reports to literal strings
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(so that callers don't need to worry about freeing them or copying them)
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does limit the precision of error reporting.
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<P>
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The text-to-binary error-reporting convention lends itself
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to slightly obscure code,
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because many readers will not think of NULL as signifying success.
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A good way to make it clearer is to write something like:
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<P>
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<DL COMPACT><DT><DD>
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<PRE>
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<B>const char *error;</B>
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<B>error = ttoaddr( /* ... */ );</B>
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<B>if (error != NULL) {</B>
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<B> /* something went wrong */</B>
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</PRE>
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</DL>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT><A HREF="#lbAB">NAME</A><DD>
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<DT><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT><A HREF="#lbAE">SEE ALSO</A><DD>
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<DT><A HREF="#lbAF">DIAGNOSTICS</A><DD>
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<DT><A HREF="#lbAG">HISTORY</A><DD>
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<DT><A HREF="#lbAH">BUGS</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="http://localhost/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 21:40:18 GMT, November 11, 2003
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</BODY>
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</HTML>
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