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viewing USB packet, display a signed int?

asked 2019-02-27 15:25:31 +0000

Hello All, Thanks for such a wonderful tool! I am a beginner with Wireshark. Last night I was chasing down an issue which actually was not an issue. I was debugging my USB enumeration and kept seeing my logical minimum values displayed as positive when in fact it is a signed integer and needs to be interpreted that way. Is it possible to change the way Wireshark displays these values so it reports the correct signed value? Thanks!

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answered 2019-02-27 16:30:48 +0000

grahamb gravatar image

Sure, the place to raise a bug is the Wireshark Bugzilla, attaching a capture that shows the issue.

Please check that you have tested with the latest version of Wireshark (2.6.6, or the 3.0 rc) and have checked Bugzilla for an existing report of the issue before creating a new one.

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So are you saying this is a potential bug in the software? I just assumed there may be a way to tell Wireshark to interpret the value as signed and not unsigned. I did a quick scan of the bugzilla list but didnt find anything relevant. I will create a bug report if that is what needs to happen but didn't want to create an unnecessary bug report if this isn't truly a bug.

meraviglioso gravatar imagemeraviglioso ( 2019-02-27 20:00:46 +0000 )edit

What make you believe that the value should be a signed integer? Do you have a specification document that shows that it should be regarded as such?

grahamb gravatar imagegrahamb ( 2019-03-08 19:12:27 +0000 )edit

If you refer to the USB HID Usage Tables, (found here: https://www.usb.org/document-library/...) you will see many times negative values referenced. One of the main areas is the logical minimum value that you would set. I was not trying to say that raw USB should read this as signed. I was simply querying whether you could assign a filter to show the value as a signed. I am no expert in this field. I did not report a bug as I don't know that there is a bug.

meraviglioso gravatar imagemeraviglioso ( 2019-03-13 04:03:06 +0000 )edit

A "filter" is used to limit the capture or display of packets, so that won't help here.

Although custom columns are supported, they don't allow any mathematics operations on the column contents, so that isn't possible.

Can you provide a public link to a capture along with details of the field(s) that appear to be incorrectly displayed?

grahamb gravatar imagegrahamb ( 2019-03-13 13:28:01 +0000 )edit

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Asked: 2019-02-27 15:25:31 +0000

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Last updated: Feb 27