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Content-type: text/html
<HTML><HEAD><TITLE>Manpage of IPSEC_ATOSA</TITLE>
</HEAD><BODY>
<H1>IPSEC_ATOSA</H1>
Section: C Library Functions (3)<BR>Updated: 11 June 2001<BR><A HREF="#index">Index</A>
<A HREF="http://localhost/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB"> </A>
<H2>NAME</H2>
ipsec atosa, satoa - convert IPsec Security Association IDs to and from ASCII
<A NAME="lbAC"> </A>
<H2>SYNOPSIS</H2>
<B>#include <<A HREF="file:/usr/include/freeswan.h">freeswan.h</A>></B>
<P>
<B>const char *atosa(const char *src, size_t srclen,</B>
<BR>
<B>struct sa_id *sa);</B>
<BR>
<B>size_t satoa(struct sa_id sa, int format,</B>
<BR>
<B>char *dst, size_t dstlen);</B>
<P>
<B>struct sa_id {</B>
<BR>
<B>struct in_addr dst;</B>
<BR>
<B>ipsec_spi_t spi;</B>
<BR>
<B>int proto;</B>
<BR>
<B>};</B>
<A NAME="lbAD"> </A>
<H2>DESCRIPTION</H2>
These functions are obsolete; see
<I><A HREF="ipsec_ttosa.3.html">ipsec_ttosa</A></I>(3)
for their replacements.
<P>
<I>Atosa</I>
converts an ASCII Security Association (SA) specifier into an
<B>sa_id</B>
structure (containing
a destination-host address
in network byte order,
an SPI number in network byte order, and
a protocol code).
<I>Satoa</I>
does the reverse conversion, back to an ASCII SA specifier.
<P>
An SA is specified in ASCII with a mail-like syntax, e.g.
<B><A HREF="mailto:esp507@1.2.3.4">esp507@1.2.3.4</A></B>.
An SA specifier contains
a protocol prefix (currently
<B>ah</B>,
<B>esp</B>,
or
<B>tun</B>),
an unsigned integer SPI number,
and an IP address.
The SPI number can be decimal or hexadecimal
(with
<B>0x</B>
prefix), as accepted by
<I><A HREF="ipsec_atoul.3.html">ipsec_atoul</A></I>(3).
The IP address can be any form accepted by
<I><A HREF="ipsec_atoaddr.3.html">ipsec_atoaddr</A></I>(3),
e.g. dotted-decimal address or DNS name.
<P>
As a special case, the SA specifier
<B>%passthrough</B>
signifies the special SA used to indicate that packets should be
passed through unaltered.
(At present, this is a synonym for
<B><A HREF="mailto:tun0x0@0.0.0.0">tun0x0@0.0.0.0</A></B>,
but that is subject to change without notice.)
This form is known to both
<I>atosa</I>
and
<I>satoa</I>,
so the internal form of
<B>%passthrough</B>
is never visible.
<P>
The
<B><<A HREF="file:/usr/include/freeswan.h">freeswan.h</A>></B>
header file supplies the
<B>sa_id</B>
structure, as well as a data type
<B>ipsec_spi_t</B>
which is an unsigned 32-bit integer.
(There is no consistency between kernel and user on what such a type
is called, hence the header hides the differences.)
<P>
The protocol code uses the same numbers that IP does.
For user convenience, given the difficulty in acquiring the exact set of
protocol names used by the kernel,
<B><<A HREF="file:/usr/include/freeswan.h">freeswan.h</A>></B>
defines the names
<B>SA_ESP</B>,
<B>SA_AH</B>,
and
<B>SA_IPIP</B>
to have the same values as the kernel names
<B>IPPROTO_ESP</B>,
<B>IPPROTO_AH</B>,
and
<B>IPPROTO_IPIP</B>.
<P>
The
<I>srclen</I>
parameter of
<I>atosa</I>
specifies the length of the ASCII 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>dstlen</I>
parameter of
<I>satoa</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 a constant,
<B>SATOA_BUF</B>,
which is the size of a buffer just large enough for worst-case results.
<P>
The
<I>format</I>
parameter of
<I>satoa</I>
specifies what format is to be used for the conversion.
The value
<B>0</B>
(not the ASCII character
<B>'0'</B>,
but a zero value)
specifies a reasonable default
(currently
lowercase protocol prefix, lowercase hexadecimal SPI, dotted-decimal address).
The value
<B>d</B>
causes the SPI to be generated in decimal instead.
<P>
<I>Atosa</I>
returns
<B>NULL</B>
for success and
a pointer to a string-literal error message for failure;
see DIAGNOSTICS.
<I>Satoa</I>
returns
<B>0</B>
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.
<A NAME="lbAE"> </A>
<H2>SEE ALSO</H2>
<A HREF="ipsec_atoul.3.html">ipsec_atoul</A>(3), <A HREF="ipsec_atoaddr.3.html">ipsec_atoaddr</A>(3), <A HREF="inet.3.html">inet</A>(3)
<A NAME="lbAF"> </A>
<H2>DIAGNOSTICS</H2>
Fatal errors in
<I>atosa</I>
are:
empty input;
input too small to be a legal SA specifier;
no
<B>@</B>
in input;
unknown protocol prefix;
conversion error in
<I>atoul</I>
or
<I>atoaddr</I>.
<P>
Fatal errors in
<I>satoa</I>
are:
unknown format; unknown protocol code.
<A NAME="lbAG"> </A>
<H2>HISTORY</H2>
Written for the FreeS/WAN project by Henry Spencer.
<A NAME="lbAH"> </A>
<H2>BUGS</H2>
The
<B>tun</B>
protocol code is a FreeS/WANism which may eventually disappear.
<P>
The restriction of ASCII-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 ASCII-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 = atoaddr( /* ... */ );</B>
<B>if (error != NULL) {</B>
<B> /* something went wrong */</B>
</PRE>
</DL>
<P>
<HR>
<A NAME="index"> </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: 21:40:17 GMT, November 11, 2003
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