Ethereal-dev: RE: [Ethereal-dev] Truncated frames, SCSI & decoding question

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From: Biot Olivier <Olivier.Biot@xxxxxxxxxxx>
Date: Wed, 22 Oct 2003 10:23:07 +0200
See attached patch: defines frame.truncated (FT_BOOLEAN) only if frame is
truncated.

Please review and commit.

Regards,

Olivier

| -----Original Message-----
| From: Dinesh G Dutt
| 
| Hi all,
| 
| I have a problem related to decoding for which I have a solution. I'd
| appreciate it if you could give me feedback on the proposal 
| and suggest better
| alternatives, if possible.
| 
| The basic problem has to do with marking a frame as a 
| "Malformed Frame". It is
| possible with the MDS family of switches & analyzer adapters 
| to truncate frames
| delivered to Ethereal to prevent fewer frame drops and for other
| reasons. Separately, in SCSI, an initiator may allocate fewer 
| bytes than
| required to return a response. For example, a normal INQUIRY 
| response is about
| 48 bytes long, but there are lots of cases where hosts 
| allocate as few as 4
| bytes. In each of these cases, the frame is smaller than 
| normal. Marking such
| frames as "Malformed" seems to cause confusion and affects 
| viewing experience
| according to the feedback that I've received. 
| 
| It would be slow and bad for readability to check for every 
| field if there are
| sufficient bytes present. What I was thinking was to instead 
| add a field to the
| packet_info structure called "truncated". If this bit is set, 
| instead of
| marking a frame as malformed when an exception is thrown, we 
| should mark the
| frame as "truncated". 
| 
| Any suggestions would be much appreciated. I'll make the 
| relevant changes and
| hope to check it in before the upcoming release, if the 
| changes are simple
| enough. 
| 
| Thanks,
| 
| Dinesh
| -- 
| I am not young enough to know everything. - Oscar Wilde
| 
| 
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| 

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