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I started to make a lua port of the PTP/IP dissector split into the PTP/IP part and an dependent an PTP part. The idea is the PTP/IP dissector parses the IP specific structure parts (length, packet type) and then passes these to an PTP packet dissector.

However, in the PTP dissector I can not declare the 'imported' fields of the PTP/IP dissector:

top level

local length_field ="ptp.length")
local packet_type_field ="ptp.pktType")   
local header_offset_field ="ptp.headerOffset") -- protocol specific offset from the PTP/IP or PTP dissector

results in an error message bad argument #1 to 'new' (Field new: a field with this name must exist).

When I move it to function ptp_proto.dissector(tvb,pinfo,tree) the error message is (Field new: A Field extractor must be defined before Taps or Dissectors are called)

asked 08 Mar '16, 04:43

Thomas%20E's gravatar image

Thomas E
accept rate: 0%

Maybe this is due to the order which Wireshark finds & executes your .lua files. Try creating a new script that initializes your dissectors in correct order.

Renaming your files in alphabetical order could also work .. if sorting order of read .lua files is the issue.

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answered 27 Apr '16, 14:56

kim's gravatar image

accept rate: 50%

It worked. The 'parent' dissector needs to load before the child dissectors. An implementation is at

(30 May '16, 07:49) Thomas E
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question asked: 08 Mar '16, 04:43

question was seen: 1,393 times

last updated: 30 May '16, 07:49

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