[svn-upgrade] Integrating new upstream version, strongswan (4.1.1)

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+.TH IPSEC_ATOSA 3 "11 June 2001"
+.\" RCSID $Id: atosa.3,v 1.1 2004/03/15 20:35:26 as Exp $
+.SH NAME
+ipsec atosa, satoa \- convert IPsec Security Association IDs to and from ASCII
+.SH SYNOPSIS
+.B "#include <freeswan.h>
+.sp
+.B "const char *atosa(const char *src, size_t srclen,"
+.ti +1c
+.B "struct sa_id *sa);
+.br
+.B "size_t satoa(struct sa_id sa, int format,"
+.ti +1c
+.B "char *dst, size_t dstlen);"
+.sp
+.B "struct sa_id {"
+.ti +1c
+.B "struct in_addr dst;"
+.ti +1c
+.B "ipsec_spi_t spi;"
+.ti +1c
+.B "int proto;"
+.br
+.B "};"
+.SH DESCRIPTION
+These functions are obsolete; see
+.IR ipsec_ttosa (3)
+for their replacements.
+.PP
+.I Atosa
+converts an ASCII Security Association (SA) specifier into an
+.B sa_id
+structure (containing
+a destination-host address
+in network byte order,
+an SPI number in network byte order, and
+a protocol code).
+.I Satoa
+does the reverse conversion, back to an ASCII SA specifier.
+.PP
+An SA is specified in ASCII with a mail-like syntax, e.g.
+.BR esp507@1.2.3.4 .
+An SA specifier contains
+a protocol prefix (currently
+.BR ah ,
+.BR esp ,
+or
+.BR tun ),
+an unsigned integer SPI number,
+and an IP address.
+The SPI number can be decimal or hexadecimal
+(with
+.B 0x
+prefix), as accepted by
+.IR ipsec_atoul (3).
+The IP address can be any form accepted by
+.IR ipsec_atoaddr (3),
+e.g. dotted-decimal address or DNS name.
+.PP
+As a special case, the SA specifier
+.B %passthrough
+signifies the special SA used to indicate that packets should be
+passed through unaltered.
+(At present, this is a synonym for
+.BR tun0x0@0.0.0.0 ,
+but that is subject to change without notice.)
+This form is known to both
+.I atosa
+and
+.IR satoa ,
+so the internal form of
+.B %passthrough
+is never visible.
+.PP
+The
+.B <freeswan.h>
+header file supplies the
+.B sa_id
+structure, as well as a data type
+.B ipsec_spi_t
+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.)
+.PP
+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 <freeswan.h>
+defines the names
+.BR SA_ESP ,
+.BR SA_AH ,
+and
+.B SA_IPIP
+to have the same values as the kernel names
+.BR IPPROTO_ESP ,
+.BR IPPROTO_AH ,
+and
+.BR IPPROTO_IPIP .
+.PP
+The
+.I srclen
+parameter of
+.I atosa
+specifies the length of the ASCII 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 dstlen
+parameter of
+.I satoa
+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 a constant,
+.BR SATOA_BUF ,
+which is the size of a buffer just large enough for worst-case results.
+.PP
+The
+.I format
+parameter of
+.I satoa
+specifies what format is to be used for the conversion.
+The value
+.B 0
+(not the ASCII character
+.BR '0' ,
+but a zero value)
+specifies a reasonable default
+(currently
+lowercase protocol prefix, lowercase hexadecimal SPI, dotted-decimal address).
+The value
+.B d
+causes the SPI to be generated in decimal instead.
+.PP
+.I Atosa
+returns
+.B NULL
+for success and
+a pointer to a string-literal error message for failure;
+see DIAGNOSTICS.
+.I Satoa
+returns
+.B 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.
+.SH SEE ALSO
+ipsec_atoul(3), ipsec_atoaddr(3), inet(3)
+.SH DIAGNOSTICS
+Fatal errors in
+.I atosa
+are:
+empty input;
+input too small to be a legal SA specifier;
+no
+.B @
+in input;
+unknown protocol prefix;
+conversion error in
+.I atoul
+or
+.IR atoaddr .
+.PP
+Fatal errors in
+.I satoa
+are:
+unknown format; unknown protocol code.
+.SH HISTORY
+Written for the FreeS/WAN project by Henry Spencer.
+.SH BUGS
+The
+.B tun
+protocol code is a FreeS/WANism which may eventually disappear.
+.PP
+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.
+.PP
+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:
+.PP
+.RS
+.nf
+.B "const char *error;"
+.sp
+.B "error = atoaddr( /* ... */ );"
+.B "if (error != NULL) {"
+.B "        /* something went wrong */"
+.fi
+.RE