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Merge pull request #11 from OpenCyphal-Garage/emrainey/issue7
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Turned on CRC16 and CRC32 Computation
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@emrainey
emrainey authored Jun 23, 2023
2 parents 1a9d0b1 + 5014876 commit ce45bf2
Showing 1 changed file with 101 additions and 3 deletions.
104 changes: 101 additions & 3 deletions cyphal_udp.lua
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Original file line number Diff line number Diff line change
@@ -1,5 +1,76 @@
-- Cyphal/UDP Wireshark Plugin which supports only the Cyphal/UDP Header

-- CRC32-C table lookup
local crc32c_table = {
0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b, 0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a, 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096, 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789,
0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859, 0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46,
0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829,
0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93,
0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc,
0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c, 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982,
0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d, 0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622,
0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f,
0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee, 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1,
0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e,
0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e, 0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351
}

--- CRC32-C (Castagnoli)
--- @see https://users.ece.cmu.edu/~koopman/networks/dsn02/dsn02_koopman.pdf
--- @see https://crc32c.machinezoo.com/
local function crc32c_calc(data)
local crc = 0xFFFFFFFF
local len = data:len()
for i = 1, len do
local index = bit.bxor(bit.band(crc, 0xFF), data:get_index(i - 1))
crc = bit.bxor(bit.rshift(crc, 8), crc32c_table[index + 1])
end
return bit.bnot(crc)
end

--- CRC16-CCITT FALSE function
-- @param str The ByteArray to hash.
-- @return The CRC hash.
local function crc16_ccitt(array)
local crc = 0xffff -- initial
local len = array:len()
local poly = 0x1021
local check = 0x8000
for i = 0, len - 1 do
local c = bit.lshift(array:get_index(i), 8)
crc = bit.band(bit.bxor(crc, c), 0xFFFF)
for j = 1, 8 do
local k = bit.band(crc, check)
crc = bit.band(bit.lshift(crc, 1), 0xFFFF)
if k ~= 0 then
crc = bit.bxor(crc, poly)
end
end
end
return crc
end

-- Protocol constants
local CYPHAL_UDP_PORT = 9382 -- The port number used by Cyphal/UDP
local CYPHAL_UDP_HEADER_SIZE = 24 -- The sizeof the Cyphal/UDP Header
Expand All @@ -24,8 +95,10 @@ frame_index = ProtoField.uint32("cyphal_udp.frame_index", "frame_index", base.DE
end_of_transfer = ProtoField.bool("cyphal_udp.end_of_transfer", "end_of_transfer", base.NONE)
user_data = ProtoField.uint16("cyphal_udp.user_data", "user_data", base.HEX)
crc16_ccitt_false = ProtoField.uint16("cyphal_udp.crc16_ccitt_false", "CRC16-CCITT-FALSE (BE)", base.HEX)
computed_crc16_ccitt_false = ProtoField.uint16("cyphal_udp.computed_crc16_ccitt_false", "CRC16-CCITT-FALSE [Computed]", base.HEX)
serialized_payload = ProtoField.bytes("cyphal_udp.serialized_payload", "serialized_payload", base.SPACE)
serialized_payload_size = ProtoField.uint32("cyphal_udp.serialized_payload_size", "serialized_payload_size", base.DEC)
computed_crc32 = ProtoField.uint32("cyphal_udp.computed_crc32", "CRC32-C [Computed]", base.HEX)
crc32 = ProtoField.uint32("cyphal_udp.crc32", "CRC32-C (LE)", base.HEX)

-- Protocol fields
Expand All @@ -45,12 +118,21 @@ cyphal_udp.fields = {
end_of_transfer,
user_data,
crc16_ccitt_false,
computed_crc16_ccitt_false,
serialized_payload,
serialized_payload_size,
computed_crc32,
crc32
-- Add more fields as needed
}

crc16_mismatch_expert = ProtoExpert.new("cyphal_udp.crc16_match", "crc16_match", expert.group.CHECKSUM, expert.severity.WARN)
crc32_mismatch_expert = ProtoExpert.new("cyphal_udp.crc32_match", "crc32_match", expert.group.CHECKSUM, expert.severity.WARN)

cyphal_udp.experts = {
crc16_mismatch_expert, crc32_mismatch_export
}

ipv4_source_address_field = Field.new("ip.src")
ipv4_destination_address_field = Field.new("ip.dst")

Expand Down Expand Up @@ -100,8 +182,15 @@ local function dissect_cyphal_udp(buffer, pinfo, tree)
header_tree:add_le(frame_index, fidx)
header_tree:add_le(end_of_transfer, eot)
header_tree:add_le(user_data, buffer(20, 2))
local header = buffer(0, CYPHAL_UDP_HEADER_SIZE-2):bytes()
local captured_crc16 = buffer(CYPHAL_UDP_HEADER_SIZE-2, 2)
header_tree:add(crc16_ccitt_false, captured_crc16)
local computed_crc16 = crc16_ccitt(header)
header_tree:add(computed_crc16_ccitt_false, computed_crc16)
-- process the number as BE
header_tree:add(crc16_ccitt_false, buffer(22, 2))
if not captured_crc16 == computed_crc16 then
header_tree:add_expert_info(PI_CHECKSUM, PI_WARN, "CRC16 Mismatch")
end
local len = buffer:len()
local crc_size = 0
if eot == 1 then
Expand All @@ -110,10 +199,19 @@ local function dissect_cyphal_udp(buffer, pinfo, tree)
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))
payload_tree:add_le(serialized_payload, buffer(CYPHAL_UDP_HEADER_SIZE, rem))
end
if eot == 1 then
footer_tree:add_le(crc32, buffer(len-crc_size, 4))
local captured_crc32 = buffer(len-crc_size, 4)
footer_tree:add_le(crc32, captured_crc32)
if fidx == 0 then -- We can only compute over 1 frame for now
local payload = buffer(CYPHAL_UDP_HEADER_SIZE, rem):bytes()
local crc32_local = crc32c_calc(payload)
footer_tree:add(computed_crc32, crc32_local)
if not crc32_local == captured_crc32 then
footer_tree:add_expert_info(PI_CHECKSUM, PI_WARN, "CRC32 Mismatch")
end
end
end
-- Add more field dissectors as needed
end
Expand Down

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