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man pages section 3: Basic Library Functions

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Updated: Thursday, June 13, 2019
 
 

getipsecalgbyname(3C)

Name

getipsecalgbyname, getipsecalgbynum, freeipsecalgent - query algorithm mapping entries

Synopsis

#include <netdb.h>

struct ipsecalgent *getipsecalgbyname
     (const char *alg_name, int protocol_num, int *errnop);
struct ipsecalgent *getipsecalgbynum(int alg_num,
     int protocol_num, int *errnop);
void freeipsecalgent(struct ipsecalgent *ptr);

Description

Use the getipsecalgbyname(), getipsecalgbynum(), freeipsecalgent() functions to obtain the IPsec algorithm mappings that are defined by ipsecalgs(8). The IPsec algorithms and associated protocol name spaces are defined by RFC 2407.

getipsecalgbyname() and getipsecalgbynum() return a structure that describes the algorithm entry found. This structure is described in the RETURN VALUES section below.

freeipsecalgent() must be used by the caller to free the structures returned by getipsecalgbyname() and getipsecalgbynum() when they are no longer needed.

Both getipsecalgbyname() and getipsecalgbynum() take as parameter the protocol identifier in which the algorithm is defined. See getipsecprotobyname(3C) and getipsecprotobynum(3C).

The following protocol numbers are pre-defined:

IPSEC_PROTO_ESP

Defines the encryption algorithms (transforms) that can be used by IPsec to provide data confidentiality.

IPSEC_PROTO_AH

Defines the authentication algorithms (transforms) that can be used by IPsec to provide authentication.

getipsecalgbyname() looks up the algorithm by its name, while getipsecalgbynum() looks up the algorithm by its assigned number.

Parameters

errnop

A pointer to an integer used to return an error status value on certain error conditions. See ERRORS.

Return Values

The getipsecalgbyname() and getipsecalgbynum() functions return a pointer to the structure ipsecalgent_t, defined in <netdb.h>. If the requested algorithm cannot be found, these functions return NULL.

The structure ipsecalgent_t is defined as follows:

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 */     
     int *a_mech_params;  /* mechanism specific parameters */
     int a_alg_flags;     /* algorithm flags */
} ipsecalgent_t;       

If a_key_increment is non-zero, a_key_sizes[0] contains the default key size for the algorithm. a_key_sizes[1] and a_key_sizes[2] specify the smallest and biggest key sizes support by the algorithm, and a_key_increment specifies the valid key size increments in that range.

If a_key_increment is zero, the array a_key_sizes 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 0. The first element of this array is used as the default key size for the algorithm.

a_name is an array of algorithm names, terminated by an element containing a NULL pointer. a_name[0] is the primary name for the algorithm.

a_proto_num is the protocol identifier of this algorithm. a_alg_num is the algorithm number. a_mech_name contains the mechanism name associated with the algorithm.

a_block_sizes 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 0.

a_block_sizes 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 0.

Errors

When the specified algorithm cannot be returned to the caller, getipsecalgbyname() and getipsecalgbynum() return a value of NULL and set the integer pointed to by the errnop parameter to one of the following values:

ENOMEM

Not enough memory

ENOENT

Specified algorithm not found

EINVAL

Specified protocol number not found

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Availability
system/library
MT-Level
MT-Safe
Interface Stability
Committed

See Also

getipsecprotobyname(3C), getipsecprotobynum(3C), attributes(7), cryptoadm(8), ipsecalgs(8)

Piper, D. RFC 2407, The Internet IP Security Domain of Interpretation for ISAKMP. Network Working Group. November, 1998.