fix(ablegacy): refuse native status-bit and PLC-5 writes before creating the runtime (#593)
A first-touch native write to a T/C/R status-bit sub-element (T4:0.DN) created and initialised the tag's runtime before the runtime's write refusal could fire; the init is one READ, so against a device lacking the file (the ab_server fixture has no T/C/R) it surfaced as BadCommunicationError + Degraded health instead of BadNotSupported. The bit-RMW path was not involved: AbLegacyAddress rejects sub-element + /N, so a status bit's BitIndex is always null. NativeAbLegacyTagRuntime.WriteRefusal is now the single predicate (status bit by address whatever the authored type; any PLC-5 write), asked by the driver via IAbLegacyTagFactory.WriteRefusal (default null, so libplctag is unchanged) before EnsureTagRuntimeAsync and ahead of the bit-RMW branch. Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
This commit is contained in:
Joseph Doherty
+11
@@ -81,6 +81,13 @@ public sealed class AbLegacyUnsupportedPathTests(AbLegacyServerFixture sim)
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}
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/// <summary>A native status-bit sub-element write is refused locally on the families that carry T/C/R files.</summary>
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/// <remarks>
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/// ⚠️ <b>The fixture has NO T/C/R files</b> (the SLC500 ab_server serves N7/F8/B3/L19 only), and that is what
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/// makes this test discriminating: the write is FIRST-TOUCH (nothing reads the status-bit tag beforehand),
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/// so a driver that created and initialised the tag's runtime before refusing would issue an init READ of a
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/// missing file and report <c>BadCommunicationError</c> + Degraded health — exactly how this test first
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/// failed (#593 follow-up). It passes only if the driver refuses before any wire request for the tag.
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/// </remarks>
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/// <param name="address">The status-bit address.</param>
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[AbLegacyTheory]
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[InlineData("T4:0.DN")]
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@@ -103,5 +110,9 @@ public sealed class AbLegacyUnsupportedPathTests(AbLegacyServerFixture sim)
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results.Single().StatusCode.ShouldBe(AbLegacyStatusMapper.BadNotSupported);
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drv.GetHealth().State.ShouldBe(DriverState.Healthy);
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// The refusal left the connection usable.
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(await drv.ReadAsync(["Scratch"], TestContext.Current.CancellationToken)).Single().StatusCode
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.ShouldBe(AbLegacyStatusMapper.Good);
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}
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}
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+173
@@ -0,0 +1,173 @@
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using Shouldly;
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using Xunit;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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using ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.PlcFamilies;
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using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport;
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using ZB.MOM.WW.OtOpcUa.Driver.Ab.Transport.Tests.Fakes;
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namespace ZB.MOM.WW.OtOpcUa.Driver.AbLegacy.Tests;
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/// <summary>
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/// Gitea #593 follow-up: a native write the runtime would refuse (a T/C/R status-bit sub-element such as
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/// <c>T4:0.DN</c>, or any PLC-5 write) is refused by the DRIVER before a runtime is created — so the
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/// refusal holds on a FIRST-TOUCH write too, with zero PCCC requests on the wire.
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/// </summary>
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/// <remarks>
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/// Before the fix the write path created and initialised the tag's runtime first, and a native init is one
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/// READ. Against a device whose T/C/R file is missing — the <c>ab_server</c> fixture has none — that read
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/// failed, so the write surfaced as <c>BadCommunicationError</c>, evicted the handle and degraded health
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/// (the comms-loss watchdog's input) instead of the documented <c>BadNotSupported</c>. These tests run the
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/// PRODUCTION <see cref="NativeAbLegacyTagFactory"/> over a real socket to a <see cref="FakeEipServer"/>
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/// that, like <c>ab_server</c>, only has an N7 file, and count the PCCC requests it receives.
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/// </remarks>
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[Trait("Category", "Unit")]
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public sealed class NativeAbLegacyRefusedWriteTests
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{
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private static readonly byte[] FixedId = [0x07, 0x3D, 0xF3, 0x45, 0x43, 0x50, 0x21];
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/// <summary>A PCCC-only fake: N7 exists (reads answer one zero word, writes succeed); every other file answers
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/// "file does not exist" (STS F0 / EXT 06 → NotFound), as a device without that file would.</summary>
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private sealed class N7OnlyServer : IAsyncDisposable
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{
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private int _pccc;
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public FakeEipServer Server { get; } = new() { ZeroReplyContext = true };
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/// <summary>Execute PCCC requests received (reads AND writes).</summary>
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public int PcccRequests => Volatile.Read(ref _pccc);
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public N7OnlyServer()
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{
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Server.Handler = req =>
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{
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if (FakeEipServer.Command(req) != Ab.Transport.Eip.EncapCommand.SendRRData) return null;
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var cip = FakeEipServer.RequestCip(req);
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Interlocked.Increment(ref _pccc);
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// cip: 4B 02 20 67 24 01 | id(7) | cmd 0F, sts, tns(2), fnc, byteCount, file#, fileType, element, sub
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var fileNumber = cip[19];
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byte[] head = [0xCB, 0x00, 0x00, 0x00, .. FixedId, 0x4F];
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return fileNumber == 7
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? FakeEipServer.RRReply(req, [.. head, 0x00, cip[15], cip[16], .. cip[17] == 0xA2 ? new byte[] { 0, 0 } : []])
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: FakeEipServer.RRReply(req, [.. head, 0xF0, cip[15], cip[16], 0x06]); // EXT 06: file does not exist
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};
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}
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public ValueTask DisposeAsync() => Server.DisposeAsync();
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}
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// These tests call the driver's WriteAsync/ReadAsync directly to pin its OWN status mapping; resilience
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// wrapping (CapabilityInvoker) is out of scope and would retry/mask the very status under test.
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#pragma warning disable OTOPCUA0001
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private static async Task<AbLegacyDriver> DriverAsync(
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N7OnlyServer s, AbLegacyPlcFamily family, params AbLegacyTagDefinition[] tags)
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{
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var host = $"ab://127.0.0.1:{s.Server.Port}/1,0";
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var driver = new AbLegacyDriver(new AbLegacyDriverOptions
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{
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Devices = [new AbLegacyDeviceOptions(host, family)],
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RawTags = AbLegacyRawTags.Entries(tags.Select(t => t with { DeviceHostAddress = host }).ToArray()),
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Timeout = TimeSpan.FromSeconds(5),
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Probe = new AbLegacyProbeOptions { Enabled = false },
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}, "drv-refused-write", new NativeAbLegacyTagFactory(new DeviceSessionPool()));
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await driver.InitializeAsync("{}", TestContext.Current.CancellationToken);
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return driver;
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}
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private static AbLegacyTagDefinition Tag(string name, string address, AbLegacyDataType type, bool writable = false) =>
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new(name, "", address, type, Writable: writable);
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/// <summary>
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/// A first-touch status-bit write is BadNotSupported with nothing on the wire and health unchanged, even
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/// though the device has no such file. The positive control (an N7 read on the same driver afterwards) is
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/// what proves the fake counts requests — and that the refusal left the connection usable.
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/// </summary>
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[Theory]
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[InlineData("T4:0.DN", AbLegacyDataType.Bit)]
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[InlineData("C5:0.CU", AbLegacyDataType.Bit)]
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[InlineData("R6:0.EN", AbLegacyDataType.Bit)]
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[InlineData("T4:0.TT", AbLegacyDataType.Int)] // the refusal follows the ADDRESS, not the authored type
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[InlineData("C5:0.DN", AbLegacyDataType.TimerElement)]
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public async Task A_first_touch_status_bit_write_is_BadNotSupported_with_nothing_on_the_wire(
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string address, AbLegacyDataType type)
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{
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var ct = TestContext.Current.CancellationToken;
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await using var s = new N7OnlyServer();
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var driver = await DriverAsync(s, AbLegacyPlcFamily.Slc500,
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Tag("Scratch", "N7:5", AbLegacyDataType.Int),
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Tag("Bit", address, type, writable: true));
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var health = driver.GetHealth();
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var results = await driver.WriteAsync([new WriteRequest("Bit", true)], ct);
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results.Single().StatusCode.ShouldBe(AbLegacyStatusMapper.BadNotSupported);
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s.PcccRequests.ShouldBe(0);
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driver.GetHealth().ShouldBe(health);
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// Positive control: the same driver does reach this server, and the refusal did not poison anything.
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(await driver.ReadAsync(["Scratch"], ct)).Single().StatusCode.ShouldBe(AbLegacyStatusMapper.Good);
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s.PcccRequests.ShouldBeGreaterThan(0); // init read + read
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driver.GetHealth().State.ShouldBe(DriverState.Healthy);
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await driver.ShutdownAsync(ct);
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s.Server.HandlerErrors.ShouldBeEmpty();
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}
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/// <summary>A PLC-5 write (including a bit-within-word RMW, which would otherwise READ the parent word
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/// first) is refused with nothing on the wire.</summary>
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[Theory]
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[InlineData("N7:5", AbLegacyDataType.Int, (short)7)]
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[InlineData("N7:5/3", AbLegacyDataType.Bit, true)]
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public async Task A_first_touch_PLC5_write_is_BadNotSupported_with_nothing_on_the_wire(
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string address, AbLegacyDataType type, object value)
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{
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var ct = TestContext.Current.CancellationToken;
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await using var s = new N7OnlyServer();
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var driver = await DriverAsync(s, AbLegacyPlcFamily.Plc5, Tag("W", address, type, writable: true));
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var health = driver.GetHealth();
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(await driver.WriteAsync([new WriteRequest("W", value)], ct)).Single().StatusCode
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.ShouldBe(AbLegacyStatusMapper.BadNotSupported);
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s.PcccRequests.ShouldBe(0);
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driver.GetHealth().ShouldBe(health);
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await driver.ShutdownAsync(ct);
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}
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/// <summary>Positive control for the refusal's scope: an ordinary SLC write still reaches the wire, so the
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/// pre-check is not swallowing every write (the T/C/R word sub-element case is
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/// <c>NativeAbLegacyTagRuntimeTests.A_word_sub_element_write_through_the_driver_sends_a_typed_write</c>).</summary>
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[Fact]
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public async Task An_SLC_word_write_still_reaches_the_wire()
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{
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var ct = TestContext.Current.CancellationToken;
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await using var s = new N7OnlyServer();
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var driver = await DriverAsync(s, AbLegacyPlcFamily.Slc500, Tag("W", "N7:5", AbLegacyDataType.Int, writable: true));
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(await driver.WriteAsync([new WriteRequest("W", (short)7)], ct)).Single().StatusCode
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.ShouldBe(AbLegacyStatusMapper.Good);
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s.PcccRequests.ShouldBeGreaterThanOrEqualTo(1);
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await driver.ShutdownAsync(ct);
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}
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#pragma warning restore OTOPCUA0001
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[Theory]
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[InlineData("slc500", "T4:0.DN", true)]
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[InlineData("slc500", "C5:0.UA", true)]
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[InlineData("micrologix", "R6:0.FD", true)]
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[InlineData("slc500", "T4:0.PRE", false)]
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[InlineData("slc500", "T4:0.ACC", false)]
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[InlineData("slc500", "R6:0.POS", false)]
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[InlineData("slc500", "N7:0/3", false)]
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[InlineData("slc500", "B3:0/0", false)]
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[InlineData("slc500", "N7:0", false)]
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[InlineData("plc5", "N7:0", true)]
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[InlineData("plc5", "T4:0.PRE", true)]
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[InlineData("slc500", "T4:0.NOPE", false)] // unknown sub-element: refused by the runtime's own address check
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[InlineData("slc500", "garbage", false)]
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public void The_write_refusal_predicate_covers_status_bits_and_PLC5_only(string plc, string tag, bool refused)
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{
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var p = new AbLegacyTagCreateParams("h", 44818, "1,0", plc, tag, TimeSpan.FromSeconds(1));
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(NativeAbLegacyTagRuntime.WriteRefusal(p) is not null).ShouldBe(refused);
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(new NativeAbLegacyTagFactory().WriteRefusal(p) is not null).ShouldBe(refused);
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}
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}
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