Re: Siginificance of pinfo->fd->flags.visited

[Anders Broman <anders.broman () ericsson com>]

From: wireshark-dev-bounces () wireshark org [mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Vishnu Bhatt
Sent: den 10 januari 2014 10:54
To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] Siginificance of pinfo->fd->flags.visited

Thanks for the explanation.


  1.  << The result of a packet dissection is thrown away as soon as the packet has been read and presented, so if you 
'click' on a new packet the dissection has to be redone.>>

> "Thrown away" means it's not stored anywhere. Am I right? If yes, why is it thrown away?

As its not needed as the packet will be re dissected when the information is needed again. Saving the dissection result 
for every packet in a trace would require a lot of (RAM)memory.
(number of bytes times a factor > 10?)

> And also, few things are done only once using "flags.visited == FALSE", why then this variable is used, if the 
> previous results are not stored, then everything has to be redone.

Perhaps I expressed that poorly, if you need some result of the dissection you need to arrange to store it and protect 
that code with "flags.visited" to have it only executed once - the first time
When the packets are executed in order.


  1.  << Not sure what you are referring to here >>
> In packet-rlc.c in epan/dissectors, duplicity of RLC frames is checked, should that be done everytime?

No it should probably only be done once and the result saved.

Regards
Anders

________________________________
From: wireshark-dev-bounces () wireshark org<mailto:wireshark-dev-bounces () wireshark org> 
[mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Anders Broman
Sent: Friday, January 10, 2014 2:53 PM
To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] Siginificance of pinfo->fd->flags.visited



From: wireshark-dev-bounces () wireshark org<mailto:wireshark-dev-bounces () wireshark org> 
[mailto:wireshark-dev-bounces () wireshark org] On Behalf Of Vishnu Bhatt
Sent: den 10 januari 2014 08:59
To: wireshark-dev () wireshark org<mailto:wireshark-dev () wireshark org>
Subject: [Wireshark-dev] Siginificance of pinfo->fd->flags.visited

> Hello all,
>
> Can anyone please explain me the significance of pinfo->fd->flags.visited. I know that this variable is set to TRUE if 
> a packet has been visited once but if we click on the same packet then why all things are done again?

pinfo->fd->flags.visited is FALSE on the first pass when all packets are read in sequence then it's set to FALSE. The 
result of a packet dissection is thrown away as soon as the packet has been read and presented, so if you 'click' on a 
new packet the dissection has to be redone.

> Logically if a frame has been dissected once, it should not be checked again, so condition 
> "if(pinfo->fd->flags.visited == FALSE)" should always be checked before doing the dissection.
No true see above.

> Why the need of re-dissecting >the frame over and over again?

See above.

> My second doubt is that in RLC, if duplicity has already been checked then why to check it again? I mean should the 
> duplicity function be covered under "if(pinfo->fd->flags.visited == FALSE)"?


Not sure what you are referring to here...

Thanks
Vishnu Bhatt




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