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Hi! Wireshark and Lua newbie here. I am trying to use a post dissector to dissect Bluetooth LE GATT data. The data has already been decode by the built in dissector as btatt.value and I figured I could further dissect btatt.value.

However, the code below doesn't work. I keep getting this error message:

calling 'add' on bad self (string expected, got userdata)

-- Source code below:

` ble_gatt_value = Field.new("btatt.value")

trivial_proto = Proto("trivial","Trivial Postdissector")

gattval_field = ProtoField.bytes("trivial.gatt_value","GATT Value", base.DASH)

trivial_proto.fields = {gattval_field}

function trivial_proto.dissector(buffer,pinfo,tree)

local src_gatt_val = ble_gatt_value()

if src_gatt_val then 
    --print(src_gatt_val)
    local subtree = tree:add(trivial_proto, src_gatt_val, "Trivial Protocol Data")
    subtree:add(gattval_field,src_gatt_val)

end

end

register_postdissector(trivial_proto) `

What am I doing wrong? I have seen several examples but they all used the function argument buffer(x,y) with tree:add()

Thanks in advance.

Hi! Wireshark and Lua newbie here. I am trying to use a post dissector to dissect Bluetooth LE GATT data. The data has already been decode by the built in dissector as btatt.value and I figured I could further dissect btatt.value.

However, the code below doesn't work. I keep getting this error message:

calling 'add' on bad self (string expected, got userdata)
userdata)

ble_gatt_value = Field.new("btatt.value")
 
Field.new("btatt.value")

trivial_proto = Proto("trivial","Trivial Postdissector")
 
Postdissector")

gattval_field = ProtoField.bytes("trivial.gatt_value","GATT Value", base.DASH)
 
base.DASH)

trivial_proto.fields = {gattval_field}
 
{gattval_field}

function trivial_proto.dissector(buffer,pinfo,tree)
 
trivial_proto.dissector(buffer,pinfo,tree)

    local src_gatt_val = ble_gatt_value()

 if src_gatt_val then 
     --print(src_gatt_val)
     local subtree = tree:add(trivial_proto, src_gatt_val, "Trivial Protocol Data")
     subtree:add(gattval_field,src_gatt_val)

 end
end

register_postdissector(trivial_proto)
 
end
 
register_postdissector(trivial_proto)
` 
What am I doing wrong? I have seen several examples but they all used the function argument buffer(x,y) buffer(x,y) with tree:add()
 
Thanks in advance.