fix(abcip): CompactLogix native default connection size matches libplctag's Large Forward Open (found by T21 latency harness)

2026-10-07 19:34:30 -04:00
parent 2dc55ecb8f
commit c306c6f674
9 changed files with 101 additions and 22 deletions
@@ -41,7 +41,12 @@ public sealed record AbCipPlcFamilyProfile(

    public static readonly AbCipPlcFamilyProfile CompactLogix = new(
        LibplctagPlcAttribute: "compactlogix",
-        DefaultConnectionSize: 504, // 5069-L3x narrower buffer; safe baseline that never over-shoots
+        // Large Forward Open, matching libplctag: `plc=compactlogix` opens Large (0x5B, 4002) and the
+        // native transport must not pack into a third of the window (T21 latency harness: 504 cost ~3x
+        // the round trips per poll). A narrower 5069-L3x / pre-v20 target that refuses the Large open
+        // is covered by CipConnection's fallback — a regular open at min(size, 504) inside the same
+        // throttled attempt. An explicit ConnectionSize (driver options or per device) still wins.
+        DefaultConnectionSize: 4002,
        DefaultCipPath: "1,0",
        SupportsRequestPacking: true,
        SupportsConnectedMessaging: true,