Hi Vishnu, 2015-02-16 14:55 GMT+01:00 Vishnu Bhatt <vishnu.bh...@aricent.com>:
> Hi, > > > > I have a dissector code (atmii) and I am having problem in understanding > the following two lines of code: > > > > In proto_register_atmii() > > > > aal_dissector_table = register_dissector_table("atmii.aal2_payload", "AAL > payload type", FT_UINT8, BASE_DEC); > This create a dissector table (with a guint8 as identifier) that can be used by other dissectors so as to register themselves as the dissector to be called for a given payload type value, using something like: dissector_add_uint("atmii.aal2_payload", my_payload_type_value, my_dissector_handle); > > and then in dissect_atmii() > > > > if (!dissector_try_port(aal_dissector_table, payload_type, next_tvb, > pinfo, tree)) { > I guess this is a typo and you meant dissector_try_uint, right? proto_tree_add_item(atmii_tree,hf_atmii_aal2_payload, tvb, > ATM_HEADER_LENGTH, -1, FALSE); > > } > > > > > > What does these two lines of code do in general as I’ve seen them in other > protocols as well? > As indicated in proto.h: /* Look for a given value in a given uint dissector table and, if found, call the dissector with the arguments supplied, and return the number of bytes consumed, otherwise return 0. */ WS_DLL_PUBLIC int dissector_try_uint(dissector_table_t sub_dissectors, const guint32 uint_val, tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree); So with those 2 lines of code, your dissector tries to find a matching sub dissector for the payload using the payload type as parameter. If no matching dissector is found (reutnr value is 0), then it displays the payload as a byte field probably (hf_atmii_aal2_payload). Regards, Pascal.
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