Re: function of dissector_try_uint()

[Pascal Quantin <pascal.quantin () gmail com>]

2015-02-17 8:48 GMT+01:00 Vishnu Bhatt <vishnu.bhatt () aricent com>:

>  Thanks for the reply. Can you please tell me what is the function of p_get_proto_data()
> in Wireshark. Specifically, in case of FP frame, what is the role of this
> function?
>
>
>
>     p_fp_info = (fp_info *)p_get_proto_data(wmem_file_scope(), pinfo,
> proto_fp, 0);

Hi Vishnu,

you can find a detailed description of those functions in
doc/README.dissector file, chapter 2.5:

2.5 Per-packet information.

Information can be stored for each data packet that is processed by the
dissector.  The information is added with the p_add_proto_data function and
retrieved with the p_get_proto_data function.  The data pointers passed into
the p_add_proto_data are not managed by the proto_data routines, however the
data pointer memory scope must match that of the scope parameter.
The two most common use cases for p_add_proto_data/p_get_proto_data are for
persistent data about the packet for the lifetime of the capture (file
scope)
and to exchange data between dissectors across a single packet (packet
scope).
It is also used to provide packet data for Decode As dialog (packet scope).

void
p_add_proto_data(wmem_allocator_t *scope, packet_info *pinfo, int proto,
guint32 key, void *proto_data)
void *
p_get_proto_data(wmem_allocator_t *scope, packet_info *pinfo, int proto,
guint32 key)

Where:
    scope      - Lifetime of the data to be stored, typically
wmem_file_scope()
                 or pinfo->pool (packet scope).  Must match scope of data
                 allocated.
    pinfo      - The packet info pointer.
    proto      - Protocol id returned by the proto_register_protocol call
                 during initialization
    key        - key associated with 'proto_data'
    proto_data - pointer to the dissector data.

For FP protocol, this is used to store data later used by sub dissectors
like RLC or RRC.


> Thanks
>
> Vishnu Bhatt
>
>
>
> *From:* wireshark-dev-bounces () wireshark org [mailto:
> wireshark-dev-bounces () wireshark org] *On Behalf Of *Anders Broman
> *Sent:* Monday, February 16, 2015 7:37 PM
>
> *To:* Developer support list for Wireshark
> *Subject:* Re: [Wireshark-dev] function of dissector_try_uint()
>
>
>
>
>
>
>
> *From:* wireshark-dev-bounces () wireshark org [
> mailto:wireshark-dev-bounces () wireshark org
> <wireshark-dev-bounces () wireshark org>] *On Behalf Of *Anders Broman
> *Sent:* den 16 februari 2015 15:05
> *To:* Developer support list for Wireshark
> *Subject:* Re: [Wireshark-dev] function of dissector_try_uint()
>
>
>
>
>
>
>
> *From:* wireshark-dev-bounces () wireshark org
> [mailto:wireshark-dev-bounces () wireshark org] *On Behalf Of *Vishnu Bhatt
> *Sent:* den 16 februari 2015 14:55
> *To:* Developer support list for Wireshark
> *Subject:* [Wireshark-dev] function of dissector_try_uint()
>
>
>
> > 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);
>
>
>
> Registers a dissector table with the name  atmii.aal2_payload in which it
> will be possible to register a callback for an UINT8 value. Compare with
> the UDP table where a dissector can
>
> Register to be called for a message with UDP port number. SIP registers
> for port 5060 for instance.
>
>
>
> and then in dissect_atmii()
>
>
>
> if (!dissector_try_port(aal_dissector_table, payload_type, next_tvb,
> pinfo, tree)) {
>
> proto_tree_add_item(atmii_tree,hf_atmii_aal2_payload, tvb,
> ATM_HEADER_LENGTH, -1, FALSE);
>
> }
>
>
>
> The atmii.aal2_payload  table will be searched for a match on payload
> type if a match is found the callback will be executed handing next_tvb to
> the called function.
>
> If no match is found(no dissector registered for the payload type FALSE
> will be returned.
>
>
>
> > What does these two lines of code do in general as I’ve seen them in
> other protocols as well?
>
>
>
> Oh, and you can see who has registered in the table in the Internal menu
> in the main menu bar and with what value.
>
>
>
> Thanks
>
> Vishnu
>
> "DISCLAIMER: This message is proprietary to Aricent and is intended solely
> for the use of the individual to whom it is addressed. It may contain
> privileged or confidential information and should not be circulated or used
> for any purpose other than for what it is intended. If you have received
> this message in error, please notify the originator immediately. If you are
> not the intended recipient, you are notified that you are strictly
> prohibited from using, copying, altering, or disclosing the contents of
> this message. Aricent accepts no responsibility for loss or damage arising
> from the use of the information transmitted by this email including damage
> from virus."
>  "DISCLAIMER: This message is proprietary to Aricent and is intended
> solely for the use of the individual to whom it is addressed. It may
> contain privileged or confidential information and should not be circulated
> or used for any purpose other than for what it is intended. If you have
> received this message in error, please notify the originator immediately.
> If you are not the intended recipient, you are notified that you are
> strictly prohibited from using, copying, altering, or disclosing the
> contents of this message. Aricent accepts no responsibility for loss or
> damage arising from the use of the information transmitted by this email
> including damage from virus."
>
> ___________________________________________________________________________
> Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
> Archives:    http://www.wireshark.org/lists/wireshark-dev
> Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
>              mailto:wireshark-dev-request () wireshark org
> ?subject=unsubscribe
___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    http://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
             mailto:wireshark-dev-request () wireshark org?subject=unsubscribe