Wireshark-dev: Re: [Wireshark-dev] asn2wrs problem when value needed from tagged type
From: "Kukosa, Tomas" <[email protected]>
Date: Mon, 30 Apr 2007 12:44:42 +0200
Hi Anders,

you can try to use:

#.FN_BODY OrigTransactionID/_untag VAL_PTR = parameter_tvb
...

which should modify type inside tag.

BTW When you would like to introduce ASN.1 context for BER too, please
do not create new one bur use common one for all ASN.1 encodings.

Regards,
  Tomas


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Anders Broman
Sent: Monday, April 30, 2007 12:36 PM
To: [email protected]
Subject: [Wireshark-dev] asn2wrs problem when value needed from tagged
type

Hi,
There is a problem with the tagged type if a value needs to be returned
from
it.

As the following example from TCAP:

#.FN_BODY OrigTransactionID VAL_PTR = parameter_tvb
tvbuff_t *parameter_tvb;
guint8 len, i;
proto_item *tid_item;
proto_tree *subtree;
tid_item = proto_tree_add_text(tree, tvb, offset, -1, "Source
Transaction
ID");
subtree = proto_item_add_subtree(tid_item, ett_otid);

%(DEFAULT_BODY)s

The generated code will be:
static int
dissect_tcap_OCTET_STRING_SIZE_1_4(gboolean implicit_tag _U_, tvbuff_t
*tvb
_U_, int offset _U_, packet_info *pinfo _U_, proto_tree *tree _U_, int
hf_index _U_) {
  offset = dissect_ber_octet_string(implicit_tag, pinfo, tree, tvb,
offset,
hf_index,
                                       NULL);

  return offset;
}



static int
dissect_tcap_OrigTransactionID(gboolean implicit_tag _U_, tvbuff_t *tvb
_U_,
int offset _U_, packet_info *pinfo _U_, proto_tree *tree _U_, int
hf_index
_U_) {
#line 159 "tcap.cnf"
tvbuff_t *parameter_tvb;
guint8 len, i;
proto_item *tid_item;
proto_tree *subtree;
tid_item = proto_tree_add_text(tree, tvb, offset, -1, "Source
Transaction
ID");
subtree = proto_item_add_subtree(tid_item, ett_otid);

  offset = dissect_ber_tagged_type(implicit_tag, pinfo, tree, tvb,
offset,
                                      hf_index, BER_CLASS_APP, 8, TRUE,
dissect_tcap_OCTET_STRING_SIZE_1_4);

I think this can be solved by using
typedef struct _asn1_ber_ctx_t {
  proto_item *created_item;
  void *value_ptr;
  void *private_data;
} asn1_ber_ctx_t;

In packet-ber.c similar to packet-per.c if the code above could be
changed
to something like the code
Below only for the tagged type as a start as there is a lot of changes
needed otherwise.
Regards
Anders

static int
dissect_tcap_OCTET_STRING_SIZE_1_4(gboolean implicit_tag _U_, tvbuff_t
*tvb
_U_, int offset _U_, asn1_ber_ctx_t *actx, packet_info *pinfo _U_,
proto_tree *tree _U_, int hf_index _U_) {
  offset = dissect_ber_octet_string(implicit_tag, pinfo, tree, tvb,
offset,
hf_index,
                                       actx->value_ptr);

  return offset;
}



static int
dissect_tcap_OrigTransactionID(gboolean implicit_tag _U_, tvbuff_t *tvb
_U_,
int offset _U_, packet_info *pinfo _U_, proto_tree *tree _U_, int
hf_index
_U_) {
#line 159 "tcap.cnf"
tvbuff_t *parameter_tvb;
guint8 len, i;
proto_item *tid_item;
proto_tree *subtree;
tid_item = proto_tree_add_text(tree, tvb, offset, -1, "Source
Transaction
ID");
subtree = proto_item_add_subtree(tid_item, ett_otid);

  offset = dissect_ber_tagged_type(implicit_tag, pinfo, tree, tvb,
offset,
actx
                                      hf_index, BER_CLASS_APP, 8, TRUE,
dissect_tcap_OCTET_STRING_SIZE_1_4);

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