asn_get_objid_raw, asn_get_objid, asn_put_objid, asn_get_sequence,
asn_get_ipaddress_raw, asn_get_ipaddress, asn_put_ipaddress,
asn_get_uint32_raw, asn_put_uint32, asn_get_counter64_raw,
asn_put_counter64, asn_get_timeticks, asn_put_timeticks, asn_skip,
asn_slice_oid, asn_append_oid, asn_compare_oid, asn_is_suboid,
asn_oid2str_r, asn_oid2str -- ASN.1 library for SNMP
LIBRARY
Begemot SNMP library (libbsnmp, -lbsnmp)
SYNOPSIS
#include <bsnmp/asn1.h>
enum asn_err
asn_get_header(struct asn_buf *buf, u_char *type, asn_len_t *lenp);
enum asn_err
asn_put_header(struct asn_buf *buf, u_char type, asn_len_t len);
enum asn_err
asn_put_temp_header(struct asn_buf *buf, u_char type, u_char **ptr);
enum asn_err
asn_commit_header(struct asn_buf *buf, u_char *ptr);
enum asn_err
asn_get_integer_raw(struct asn_buf *buf, asn_len_t len, int32_t *res);
enum asn_err
asn_get_integer(struct asn_buf *buf, int32_t *res);
enum asn_err
asn_put_integer(struct asn_buf *buf, int32_t arg);
enum asn_err
asn_get_octetstring_raw(struct asn_buf *buf, asn_len_t len, u_char *out,
u_int *outsize);
enum asn_err
asn_get_octetstring(struct asn_buf *buf, u_char *out, u_int *outsize);
enum asn_err
asn_put_octetstring(struct asn_buf *buf, const u_char *str,
u_int strsize);
enum asn_err
asn_get_null_raw(struct asn_buf *buf, asn_len_t len);
enum asn_err
asn_get_null(struct asn_buf *buf);
enum asn_err
enum asn_err
asn_get_sequence(struct asn_buf *buf, asn_len_t *lenp);
enum asn_err
asn_get_ipaddress_raw(struct asn_buf *buf, asn_len_t len, u_char *ipa);
enum asn_err
asn_get_ipaddress(struct asn_buf *buf, u_char *ipa);
enum asn_err
asn_put_ipaddress(struct asn_buf *buf, const u_char *ipa);
enum asn_err
asn_get_uint32_raw(struct asn_buf *buf, asn_len_t len, u_int32_t *res);
enum asn_err
asn_put_uint32(struct asn_buf *buf, u_char type, u_int32_t val);
enum asn_err
asn_get_counter64_raw(struct asn_buf *buf, asn_len_t len,
u_int64_t *res);
enum asn_err
asn_put_counter64(struct asn_buf *buf, u_int64_t val);
enum asn_err
asn_get_timeticks(struct asn_buf *buf, u_int32_t *valp);
enum asn_err
asn_put_timeticks(struct asn_buf *buf, u_int32_t val);
enum asn_err
asn_skip(struct asn_buf *buf, asn_len_t len);
void
asn_slice_oid(struct asn_oid *dest, const struct asn_oid *src,
u_int from, u_int to);
void
asn_append_oid(struct asn_oid *to, const struct asn_oid *from);
int
asn_compare_oid(const struct asn_oid *oid1, const struct asn_oid *oid2);
int
asn_is_suboid(const struct asn_oid *oid1, const struct asn_oid *oid2);
char *
asn_oid2str_r(const struct asn_oid *oid, char *buf);
char *
struct asn_oid {
u_int len;
asn_subid_t subs[ASN_MAXOIDLEN];
};
This structure represents an OID with the restrictions defined in the
SNMP SMI. len holds the current length of the OID and subs holds the
elements of the OID.
struct asn_buf {
union {
u_char *ptr;
const u_char *cptr;
} asn_u;
size_t asn_len;
};
#define asn_cptr asn_u.cptr
#define asn_ptr asn_u.ptr
This structure is used to encode and decode ASN.1. It describes the out-
put buffer for encoding routines and the input buffer for decoding rou-
tines. For encoding asn_len holds the number of remaining free octets in
the buffer. The first free byte is pointed to by asn_ptr. For decoding
asn_len holds the number of remaining bytes to decode. The next byte to
decode is pointed to by asn_cptr.
Most of the functions return an error code enum asn_error:
enum asn_err {
/* conversion was ok */
ASN_ERR_OK = 0,
/* conversion failed and stopped */
ASN_ERR_FAILED = 1 | 0x1000,
/* length field bad, value skipped */
ASN_ERR_BADLEN = 2,
/* out of buffer, stopped */
ASN_ERR_EOBUF = 3 | 0x1000,
/* length ok, but value is out of range */
ASN_ERR_RANGE = 4,
/* not the expected tag, stopped */
ASN_ERR_TAG = 5 | 0x1000,
};
#define ASN_ERR_STOPPED(E) (((E) & 0x1000) != 0)
If ASN_ERR_STOPPED() returns true, the error was fatal and processing has
stopped at the point of error.
The function asn_get_header() reads the next header from the input octet
stream. It returns the tag in the variable pointed to by type (note that
only single byte tags are supported) and the decoded length field in the
value pointed to by lenp (this is restricted to a unsigned 32-bit value).
All errors in this function are fatal and stop processing.
The function asn_get_integer_raw() is used to decode a signed integer
value (32-bit). It assumes, that the header of the integer has been
decoded already. len is the length obtained from the ASN.1 header and
the integer will be returned in the value pointed to by res.
The function asn_get_integer() decodes a complete 32-bit signed integer
including the header. If the tag is wrong ASN_ERR_TAG is returned. The
function asn_put_integer() encodes a 32-bit signed integer.
The function asn_get_octetstring_raw() decodes the value field of an
ASN.1 octet string. The length obtained from the header must be fed into
the len argument and out must point to a buffer to receive the octet
string. On entry to the function outsize must point to the size of the
buffer. On exit outsize will point to the number of octets decoded (if
no error occurs this will be equal to len ). The function
asn_get_octetstring() decodes an octetstring including the header. out
must point to a buffer to receive the string, outsize must point to the
size of the buffer. On exit of the function outsize will point to the
number of octets decoded. The function asn_put_octetstring() encodes an
octetstring (including the header). str points to the string to encode
and strsize is the length of the string (the string may contain embedded
NULs).
The function asn_get_null_raw() decodes a null value. len is the length
obtained from the header and must be 0. The function asn_get_null()
decodes a null including the header and the function asn_put_null()
encodes a null.
The function asn_put_exception() is used to encode an SNMPv2 exception.
The exception type is type.
The function asn_get_objid_raw() is used to decode an OID value. len
must be the value length obtained from the header and oid will receive
the decoded OID. The function asn_get_objid() decodes a complete OID
(including the header) and the function asn_put_objid() encodes a com-
plete OID.
The function asn_get_sequence() decodes a sequence header. The length of
the sequence value will be stored in the value pointed to by lenp.
The function asn_get_ipaddress_raw() decodes an IP address value. len is
the length from the header and must be 4. ipa will receive the decoded
IP address and must point to a buffer of at least four bytes. The func-
tion asn_get_ipaddress() decodes a complete IP address (including the
header) and asn_put_ipaddress() encodes an IP address.
The function asn_get_uint32_raw() decodes an unsigned 32-bit integer
value. len is the length from the header and res will get the decoded
value. The function asn_put_uint32() encodes an unsigned 32-bit integer
value and inserts the tag given in type into the header.
subid to and generates a new OID in dest. If to is less or equal to from
the resulting OID will have a length of zero.
The function asn_append_oid() appends the OID from to the OID to given
that the resulting OID is not too long. If the maximum length is
exceeded the result is undefined.
The function asn_compare_oid() compares two oids and returns the values
-1, 0 or +1 when oid1 is lesser than, equal, or larger than oid2 resp.
The function asn_is_suboid() returns 1 if oid1 is equal to the leading
part of oid2. It returns 0 otherwise.
The function asn_oid2str_r() makes a printable string from oid. The
buffer pointed to by str must be large enough to hold the result. The
constant ASN_OIDSTRLEN is defined to be the length of the maximum string
generated by this function (including the trailing NUL). The function
asn_oid2str() makes a printable string from oid into a private buffer
that is overwritten by each call.
DIAGNOSTICS
When an error occurs in any of the function the function pointed to by
the global pointer
extern void (*asn_error)(const struct asn_buf *, const char *, ...);
is called with the current buffer (this may be NULL) and a printf(3)
style format string. There is a default error handler in the library
that prints a message starting with `ASN.1:' followed by the error mes-
sage and an optional dump of the buffer.
SEE ALSO
gensnmptree(1), bsnmpd(1), bsnmpagent(3), bsnmpclient(3), bsnmplib(3)
STANDARDS
This implementation conforms to the applicable IETF RFCs and ITU-T recom-
mendations.
AUTHORS
Hartmut Brandt <harti@freebsd.org> BSD October 4, 2005 BSD
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