_asn1_ctx_t Struct Reference

Central context object threaded through all ASN.1 dissection calls. More...

#include <asn1.h>

Public Attributes
uint32_t	signature
asn1_enc_e	encoding
bool	aligned
packet_info *	pinfo
proto_item *	created_item
struct _asn1_stack_frame_t *	stack
void *	value_ptr
void *	private_data
struct {
int   hf_index
bool   data_value_descr_present
bool   direct_ref_present
bool   indirect_ref_present
tvbuff_t *   data_value_descriptor
const char *   direct_reference
int32_t   indirect_reference
int   encoding
tvbuff_t *   single_asn1_type
tvbuff_t *   octet_aligned
tvbuff_t *   arbitrary
union {
struct {
unsigned(*   ber_callback )(bool imp_tag, tvbuff_t *tvb,              unsigned offset, struct             _asn1_ctx_t *actx, proto_tree             *tree, int hf_index)
	BER callback to dissect the contained EXTERNAL value. More...
}   ber
struct {
unsigned(*   type_cb )(tvbuff_t *tvb, uint32_t             offset, struct _asn1_ctx_t             *actx, proto_tree *tree, int             hf_index)
	PER callback to dissect the contained EXTERNAL value. More...
}   per
}   u
}	external
	Decoding state for ASN.1 EXTERNAL type values.
struct {
proto_tree *   tree
proto_tree *   top_tree
void *   tree_ctx
}	subtree
	Protocol subtree pointers for building nested dissection trees.
struct {
int   hf_index
bool   data_value_descr_present
tvbuff_t *   data_value_descriptor
int   identification
int32_t   presentation_context_id
const char *   abstract_syntax
const char *   transfer_syntax
tvbuff_t *   data_value
union {
struct {
int(*   ber_callback )(bool imp_tag, tvbuff_t *tvb,              int offset, struct             _asn1_ctx_t *actx, proto_tree             *tree, int hf_index)
	BER callback to dissect the contained EMBEDDED PDV value. More...
}   ber
struct {
int(*   type_cb )(tvbuff_t *tvb, int offset,              struct _asn1_ctx_t *actx,              proto_tree *tree, int             hf_index)
	PER callback to dissect the contained EMBEDDED PDV value. More...
}   per
}   u
}	embedded_pdv
	Decoding state for ASN.1 EMBEDDED PDV type values.
struct _rose_ctx_t *	rose_ctx

Detailed Description

Central context object threaded through all ASN.1 dissection calls.

Carries encoding parameters, packet metadata, the type-resolution stack, and per-PDU working state for EXTERNAL and EMBEDDED PDV types.

Member Data Documentation

abstract_syntax

const char* _asn1_ctx_t::abstract_syntax

Abstract syntax OID string (when identification == 0 or 1), or NULL.

aligned

bool _asn1_ctx_t::aligned

True if PER encoding is byte-aligned (relevant when encoding == ASN1_ENC_PER).

arbitrary

tvbuff_t* _asn1_ctx_t::arbitrary

Buffer for arbitrary (bit-string) encoding, or NULL.

[struct] [1/2]

struct { ... } _asn1_ctx_t::ber

BER-specific dissection callback.

[struct] [2/2]

struct { ... } _asn1_ctx_t::ber

BER-specific dissection callback.

ber_callback [1/2]

int(* _asn1_ctx_t::ber_callback) (bool imp_tag, tvbuff_t *tvb, int offset, struct _asn1_ctx_t *actx, proto_tree *tree, int hf_index)

BER callback to dissect the contained EMBEDDED PDV value.

Parameters

imp_tag	True if the tag is implicitly encoded.
tvb	Buffer containing the value.
offset	Byte offset into tvb.
actx	The enclosing ASN.1 context.
tree	Protocol tree to populate.
hf_index	Field index for the value item.

Returns

Number of bytes consumed.

ber_callback [2/2]

unsigned(* _asn1_ctx_t::ber_callback) (bool imp_tag, tvbuff_t *tvb, unsigned offset, struct _asn1_ctx_t *actx, proto_tree *tree, int hf_index)

BER callback to dissect the contained EXTERNAL value.

Parameters

imp_tag	True if the tag is implicitly encoded.
tvb	Buffer containing the value.
offset	Byte offset into tvb.
actx	The enclosing ASN.1 context.
tree	Protocol tree to populate.
hf_index	Field index for the value item.

Returns

Number of bytes consumed.

created_item

proto_item* _asn1_ctx_t::created_item

The most recently created protocol tree item, available for post-hoc annotation.

data_value

tvbuff_t* _asn1_ctx_t::data_value

Buffer containing the embedded PDV data value.

data_value_descr_present

bool _asn1_ctx_t::data_value_descr_present

True if the data-value-descriptor field is present.

data_value_descriptor

tvbuff_t* _asn1_ctx_t::data_value_descriptor

Buffer containing the data-value-descriptor string, or NULL.

direct_ref_present

bool _asn1_ctx_t::direct_ref_present

True if the direct-reference OID is present.

direct_reference

const char* _asn1_ctx_t::direct_reference

Direct-reference OID string, or NULL.

[struct]

struct { ... } _asn1_ctx_t::embedded_pdv

Decoding state for ASN.1 EMBEDDED PDV type values.

State for the currently decoded EMBEDDED PDV type instance.

encoding [1/2]

asn1_enc_e _asn1_ctx_t::encoding

Transfer syntax in use for this PDU.

encoding [2/2]

int _asn1_ctx_t::encoding

Encoding of the contained value: 0 = single-ASN1-type, 1 = octet-aligned, 2 = arbitrary.

[struct]

struct { ... } _asn1_ctx_t::external

Decoding state for ASN.1 EXTERNAL type values.

State for the currently decoded EXTERNAL type instance.

hf_index

int _asn1_ctx_t::hf_index

Protocol-tree field index for the EXTERNAL value.

Protocol-tree field index for the EMBEDDED PDV value.

identification

int _asn1_ctx_t::identification

Identification choice in use: 0 = syntaxes, 1 = syntax, 2 = presentation-context-id, 3 = context-negotiation, 4 = transfer-syntax, 5 = fixed.

indirect_ref_present

bool _asn1_ctx_t::indirect_ref_present

True if the indirect-reference integer is present.

indirect_reference

int32_t _asn1_ctx_t::indirect_reference

Indirect-reference presentation-context ID.

octet_aligned

tvbuff_t* _asn1_ctx_t::octet_aligned

Buffer for octet-aligned encoding, or NULL.

[struct] [1/2]

struct { ... } _asn1_ctx_t::per

PER-specific dissection callback.

[struct] [2/2]

struct { ... } _asn1_ctx_t::per

PER-specific dissection callback.

pinfo

packet_info* _asn1_ctx_t::pinfo

Wireshark packet metadata for the current frame.

presentation_context_id

int32_t _asn1_ctx_t::presentation_context_id

Presentation context ID (when identification == 2 or 3).

private_data

void* _asn1_ctx_t::private_data

Opaque pointer reserved for per-dissector private state.

rose_ctx

struct _rose_ctx_t* _asn1_ctx_t::rose_ctx

Optional ROSE (Remote Operations Service Element) context, or NULL.

signature

uint32_t _asn1_ctx_t::signature

Must equal ASN1_CTX_SIGNATURE; guards against stale pointers.

single_asn1_type

tvbuff_t* _asn1_ctx_t::single_asn1_type

Buffer for single-ASN1-type encoding, or NULL.

stack

struct _asn1_stack_frame_t* _asn1_ctx_t::stack

Top of the parameterized type resolution stack.

top_tree

proto_tree* _asn1_ctx_t::top_tree

Root protocol tree for the current PDU.

transfer_syntax

const char* _asn1_ctx_t::transfer_syntax

Transfer syntax OID string (when identification == 0, 4), or NULL.

tree

proto_tree* _asn1_ctx_t::tree

Current working subtree for item insertion.

tree_ctx

void* _asn1_ctx_t::tree_ctx

Opaque per-tree context pointer.

type_cb [1/2]

int(* _asn1_ctx_t::type_cb) (tvbuff_t *tvb, int offset, struct _asn1_ctx_t *actx, proto_tree *tree, int hf_index)

PER callback to dissect the contained EMBEDDED PDV value.

Parameters

tvb	Buffer containing the value.
offset	Bit offset into tvb.
actx	The enclosing ASN.1 context.
tree	Protocol tree to populate.
hf_index	Field index for the value item.

Returns

Number of bits consumed.

type_cb [2/2]

unsigned(* _asn1_ctx_t::type_cb) (tvbuff_t *tvb, uint32_t offset, struct _asn1_ctx_t *actx, proto_tree *tree, int hf_index)

PER callback to dissect the contained EXTERNAL value.

Parameters

tvb	Buffer containing the value.
offset	Bit offset into tvb.
actx	The enclosing ASN.1 context.
tree	Protocol tree to populate.
hf_index	Field index for the value item.

Returns

Number of bits consumed.

[union] [1/2]

union { ... } _asn1_ctx_t::u

Encoding-specific dissection callback.

[union] [2/2]

union { ... } _asn1_ctx_t::u

Encoding-specific dissection callback.

value_ptr

void* _asn1_ctx_t::value_ptr

Generic pointer to the most recently decoded value; type depends on context.

---

The documentation for this struct was generated from the following file:

• /builds/wireshark/wireshark/epan/asn1.h