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lua dissector - data from subtree doesn't displayed

asked 2019-01-10 09:44:24 +0000

BMWE gravatar image

Hello,

I've generated some lua dissector as shown below. However, on Wireshark, I see that Status value is 0xF1000000 but Element1 value is 0 instead of 1.

Where I'm wrong and how to fix it?

f.structureName_elementName1 = ProtoField.uint32("c.structureName.elementName", "Element1", base.dec,FAIL_OK, 0x8000000)
f.Status = ProtoField.new("Status","c.Status",ftypes.BYTES)

...
local Status_subtree=subtree:add_le(f.Status, buffer(100,4))
Status_subtree:add_le(f.structureName_elementName, buffer(100,4))
...
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answered 2019-01-10 14:57:01 +0000

cmaynard gravatar image

I'm assuming that the least significant bit of the 4 bytes of the status field in little-endian byte order is the Element1 field?

If that's the case, try changing the mask to isolate the least significant bit instead of the most significant bit, e.g.:

f.structureName_elementName1 = ProtoField.uint32("c.structureName.elementName", "Element1", base.dec, FAIL_OK, 0x0000001)
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This is Motorola format - big-endian.

When I used it (by mistake) with little endian, I the value was assigned, but to wrong element

BMWE gravatar imageBMWE ( 2019-01-10 19:52:09 +0000 )edit

OK, so presumably you meant to write the following and once you changed it the problem was solved?

Status_subtree:add(f.structureName_elementName, buffer(100,4))
cmaynard gravatar imagecmaynard ( 2019-01-10 22:14:38 +0000 )edit

Thank you! Issue solved.

BMWE gravatar imageBMWE ( 2019-01-13 06:21:52 +0000 )edit

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Asked: 2019-01-10 09:44:24 +0000

Seen: 39 times

Last updated: Jan 10