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[modbus] Hub and helpers cleanup; tighten queue_pdu validation (#18847)

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This commit is contained in:
Bonne Eggleston
2026-08-28 13:16:41 -05:00
committed by GitHub
parent 8db07d0de5
commit 768ab5b672
9 changed files with 207 additions and 275 deletions
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tests/components/modbus/modbus_unknown_function_test.cpp
+23 -9
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@@ -54,7 +54,8 @@ class TestServerHub : public ModbusServerHub {
// The frame-length parsers have explicit cases for exactly these 13 codes; every other value - the
// assigned-but-unimplemented management codes, both user-defined ranges, and all unassigned codes -
// must classify as unknown length. The exception flag masks off first.
// must classify as unknown length. Exception replies are always the 2-byte spec shape, so every
// 0x80-set code is known length.
TEST(ModbusUnknownFunction, HelperMatchesParserCoverage) {
for (uint8_t fc : {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x0F, 0x10, 0x14, 0x15, 0x16, 0x17, 0x18}) {
EXPECT_FALSE(helpers::is_function_code_unknown_length(fc)) << "fc 0x" << std::hex << int(fc);
@@ -62,11 +63,13 @@ TEST(ModbusUnknownFunction, HelperMatchesParserCoverage) {
for (uint8_t fc : {0x07, 0x08, 0x0B, 0x0C, 0x11, 0x2A, 0x41, 0x48, 0x49, 0x64, 0x6E, 0x00, 0x7F}) {
EXPECT_TRUE(helpers::is_function_code_unknown_length(fc)) << "fc 0x" << std::hex << int(fc);
}
// Exception replies classify by their base code.
// Every exception-flagged code is known length (the 2-byte spec exception shape), whatever its base.
EXPECT_FALSE(helpers::is_function_code_unknown_length(0x83));
EXPECT_TRUE(helpers::is_function_code_unknown_length(0x87));
// Strictly wider than the user-defined ranges: every custom code is unknown-length, but not vice versa.
for (int fc = 0; fc <= 0xFF; fc++) {
EXPECT_FALSE(helpers::is_function_code_unknown_length(0x87));
EXPECT_FALSE(helpers::is_function_code_unknown_length(0xC9));
// Strictly wider than the user-defined ranges below 0x80: every non-exception custom code is
// unknown-length, but not vice versa.
for (int fc = 0; fc <= 0x7F; fc++) {
if (helpers::is_function_code_custom(fc))
EXPECT_TRUE(helpers::is_function_code_unknown_length(fc)) << "fc 0x" << std::hex << fc;
}
@@ -75,10 +78,10 @@ TEST(ModbusUnknownFunction, HelperMatchesParserCoverage) {
// Derived contract check: the helper must say "unknown" exactly when both length parsers fall
// through to default. With a zero-filled max-size PDU every explicit case returns at least 2
// (file records bottom out at 2, FIFO at 3) and only default returns MIN_PDU_SIZE, so comparing
// against MIN_PDU_SIZE detects a case added to either switch without updating the helper. The
// loop stops at 0x7F: above it the helper masks the exception flag off while client_pdu_length()
// switches on the unmasked byte and server_pdu_length() early-returns the exception length.
for (int fc = 0; fc <= 0x7F; fc++) {
// against MIN_PDU_SIZE detects a case added to either switch without updating the helper. Both
// parsers early-return the 2-byte exception shape above 0x7F, which the helper's own exception
// early-return mirrors, so the whole byte range is covered.
for (int fc = 0; fc <= 0xFF; fc++) {
const uint8_t pdu[MAX_PDU_SIZE] = {static_cast<uint8_t>(fc)}; // zero header fields
EXPECT_EQ(helpers::is_function_code_unknown_length(fc),
helpers::client_pdu_length(pdu, sizeof(pdu)) == MIN_PDU_SIZE)
@@ -89,6 +92,17 @@ TEST(ModbusUnknownFunction, HelperMatchesParserCoverage) {
}
}
// Broadcastable = writes plus unknown codes (possible vendor writes); everything known to expect a
// reply is not. Classifies the underlying code: the exception bit masks off first (0x85 as 0x05).
TEST(ModbusUnknownFunction, BroadcastableClassification) {
for (uint8_t fc : {0x05, 0x06, 0x0F, 0x10, 0x16, 0x49, 0x63, 0x6E, 0x85, 0xC9}) {
EXPECT_TRUE(helpers::is_function_code_broadcastable(fc)) << "fc 0x" << std::hex << int(fc);
}
for (uint8_t fc : {0x01, 0x02, 0x03, 0x04, 0x14, 0x15, 0x17, 0x18, 0x83, 0x97}) {
EXPECT_FALSE(helpers::is_function_code_broadcastable(fc)) << "fc 0x" << std::hex << int(fc);
}
}
// A response with a function code outside the user-defined ranges (0x49) has no length case in
// server_pdu_length(), so the parser must find the frame end by CRC scan - the same way it already
// handles user-defined codes. Frame: address + FC 0x49 + 3 data bytes + CRC = 7 bytes. Without the