'\" te
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.TH GETIPSECALGBYNAME 3NSL "February 21, 2023"
.SH NAME
getipsecalgbyname, getipsecalgbynum, freeipsecalgent \- query algorithm mapping
entries
.SH SYNOPSIS
.nf
\fBcc\fR \fB-flag \&.\|.\|.\fR  \fIfile\fR \&.\|.\|.\fB-l\fRnsl [\fB -library \&.\|.\|. \fR]
#include <netdb.h>



\fBstruct ipsecalgent *\fR\fBgetipsecalgbyname\fR
     (\fBconst char *\fR\fIalg_name\fR, \fBint\fR \fIprotocol_num\fR, \fBint *\fR\fIerrnop\fR
.fi

.LP
.nf
\fBstruct ipsecalgent *\fR\fBgetipsecalgbynum\fR(\fBint\fR \fIalg_num\fR, \fBint\fR \fIprotocol_num\fR,
     \fBint *\fR\fIerrnop\fR
.fi

.LP
.nf
\fBvoid\fR \fBfreeipsecalgent\fR(\fBstruct ipsecalgent *\fR\fIptr\fR
.fi

.SH DESCRIPTION
Use the \fBgetipsecalgbyname()\fR, \fBgetipsecalgbynum()\fR,
\fBfreeipsecalgent()\fR functions to obtain the IPsec algorithm mappings  that
are defined by \fBipsecalgs\fR(8). The IPsec algorithms and associated
protocol name spaces are defined by \fIRFC 2407\fR.
.sp
.LP
\fBgetipsecalgbyname()\fR and \fBgetipsecalgbynum()\fR return a structure that
describes the algorithm entry found. This structure is described in the
\fBRETURN VALUES\fR section below.
.sp
.LP
\fBfreeipsecalgent()\fR must be used by the caller to free the structures
returned by \fBgetipsecalgbyname()\fR and \fBgetipsecalgbynum()\fR when they
are no longer needed.
.sp
.LP
Both \fBgetipsecalgbyname()\fR and \fBgetipsecalgbynum()\fR take as parameter
the protocol identifier in which the algorithm is defined. See
\fBgetipsecprotobyname\fR(3NSL) and \fBgetipsecprotobyname\fR(3NSL).
.sp
.LP
The following protocol numbers are pre-defined:
.sp
.ne 2
.na
\fB\fBIPSEC_PROTO_ESP\fR\fR
.ad
.RS 19n
Defines the encryption algorithms (transforms) that can be used by IPsec to
provide data confidentiality.
.RE

.sp
.ne 2
.na
\fB\fBIPSEC_PROTO_AH\fR\fR
.ad
.RS 19n
Defines the authentication algorithms (transforms) that can be used by IPsec to
provide authentication.
.RE

.sp
.LP
\fBgetipsecalgbyname()\fR looks up the algorithm by its name, while
\fBgetipsecalgbynum()\fR looks up the algorithm by its assigned number.
.SH PARAMETERS
.ne 2
.na
\fB\fIerrnop\fR\fR
.ad
.RS 10n
A  pointer to an integer used to return an error status value on certain error
conditions. See \fBERRORS\fR.
.RE

.SH RETURN VALUES
The \fBgetipsecalgbyname()\fR and \fBgetipsecalgbynum()\fR functions return a
pointer to the structure \fBipsecalgent_t\fR, defined in <\fBnetdb.h\fR>.   If
the requested algorithm cannot be found, these functions return \fINULL\fR.
.sp
.LP
The structure \fBipsecalgent_t\fR is defined as follows:
.sp
.in +2
.nf
typedef struct ipsecalgent {
     char **a_names;      /* algorithm names */
     int a_proto_num;     /* protocol number */
     int a_alg_num;       /* algorithm number */
     char *a_mech_name;   /* mechanism name */
     int *a_block_sizes;  /* supported block sizes */
     int *a_key_sizes;    /* supported key sizes */
     int a_key_increment; /* key size increment */
} ipsecalgent_t;
.fi
.in -2

.sp
.LP
If \fBa_key_increment\fR is non-zero, \fBa_key_sizes[0]\fR contains the default
key size for the algorithm. \fBa_key_sizes[1]\fR and \fBa_key_sizes[2]\fR
specify the smallest and biggest key sizes support by the algorithm, and
\fBa_key_increment\fR specifies the valid key size increments in that range.
.sp
.LP
If \fBa_key_increment\fR is zero, the array \fBa_key_sizes\fR  contains the set
of key sizes, in bits, supported by the  algorithm. The last key length in the
array is followed by an element of value \fB0\fR. The first element of this
array is used as the default key size for the algorithm.
.sp
.LP
\fBa_name\fR is an array of algorithm names, terminated by an element
containing a \fINULL\fR pointer. \fBa_name[0]\fR is the  primary name for the
algorithm.
.sp
.LP
\fBa_proto_num\fR is the protocol identifier of this algorithm. \fBa_alg_num\fR
is the algorithm number. \fBa_mech_name\fR contains the mechanism name
associated with the algorithm.
.sp
.LP
\fBa_block_sizes\fR is an array containing the supported block lengths or MAC
lengths, in bytes, supported by the algorithm.  The last valid value in the
array is followed by an element containing the value \fB0\fR.
.SH ERRORS
When the specified algorithm cannot be returned to the caller,
\fBgetipsecalgbynam()\fR and \fBgetipsecalgbynum()\fR return a value of
\fINULL\fR and set the integer pointed to by the \fIerrnop\fR parameter to one
of the following values:
.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Not enough memory
.RE

.sp
.ne 2
.na
\fB\fBENOENT\fR\fR
.ad
.RS 10n
Specified algorithm not found
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
Specified protocol number not found
.RE

.SH ATTRIBUTES
See \fBattributes\fR(7)  for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
MT Level	MT Safe
_
Interface Stability	Evolving
.TE

.SH SEE ALSO
.BR getipsecprotobyname (3NSL),
.BR attributes (7),
.BR cryptoadm (8),
.BR ipsecalgs (8)
.sp
.LP
Piper, D. \fIRFC 2407, The Internet IP Security Domain of Interpretation for
ISAKMP\fR. Network Working Group. November, 1998.