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Only show CRC32 when EOT is set. #10

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Jun 11, 2023
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Only show CRC32 when EOT is set. #10

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12 changes: 9 additions & 3 deletions cyphal_udp.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -93,22 +93,28 @@ local function dissect_cyphal_udp(buffer, pinfo, tree)
header_tree:add_le(service_not_message, snm)
header_tree:add_le(data_specifier, buffer(6, 2))
header_tree:add_le(transfer_id, buffer(8, 8))
-- process the number as BE
header_tree:add_le(frame_index_eot, buffer(16, 4))
local fi = buffer(16, 4):le_uint()
local fidx = bit.band(fi, 0x7FFFFFFF)
local eot = bit.rshift(bit.band(fi, 0x80000000), 31)
header_tree:add_le(frame_index, fidx)
header_tree:add_le(end_of_transfer, eot)
header_tree:add_le(user_data, buffer(20, 2))
-- process the number as BE
header_tree:add(crc16_ccitt_false, buffer(22, 2))
local len = buffer:len()
local rem = len - CYPHAL_UDP_HEADER_SIZE - 4 -- the remaining bytes minus CRC32C
local crc_size = 0
if eot == 1 then
crc_size = 4
end
local rem = len - CYPHAL_UDP_HEADER_SIZE - crc_size -- the remaining bytes minus CRC32C (if EOT)
if rem > 0 then
payload_tree:add_le(serialized_payload_size, rem)
payload_tree:add_le(serialized_payload, buffer(24, rem))
end
footer_tree:add_le(crc32, buffer(len-4, 4))
if eot == 1 then
footer_tree:add_le(crc32, buffer(len-crc_size, 4))
end
-- Add more field dissectors as needed
end

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