Update finality depth check headtracker

.changeset/witty-onions-talk.md

@@ -0,0 +1,5 @@
+---
+"chainlink": minor
+---
+
+#internal Switched finality check in HeadTracker to use the underlying finality type

common/headtracker/head_tracker.go

@@ -250,8 +250,9 @@ func (ht *headTracker[HTH, S, ID, BLOCK_HASH]) handleNewHead(ctx context.Context
 		}
 	} else {
 		ht.log.Debugw("Got out of order head", "blockNum", head.BlockNumber(), "head", head.BlockHash(), "prevHead", prevHead.BlockNumber())
-		prevUnFinalizedHead := prevHead.BlockNumber() - int64(ht.config.FinalityDepth())
-		if head.BlockNumber() < prevUnFinalizedHead {
+		prevLatestFinalized := prevHead.LatestFinalizedHead()
+
+		if prevLatestFinalized != nil && prevLatestFinalized.IsValid() && head.BlockNumber() <= prevLatestFinalized.BlockNumber() {
 			promOldHead.WithLabelValues(ht.chainID.String()).Inc()
 			ht.log.Criticalf("Got very old block with number %d (highest seen was %d). This is a problem and either means a very deep re-org occurred, one of the RPC nodes has gotten far out of sync, or the chain went backwards in block numbers. This node may not function correctly without manual intervention.", head.BlockNumber(), prevHead.BlockNumber())
 			ht.SvcErrBuffer.Append(errors.New("got very old block"))

common/types/head.go

@@ -38,4 +38,7 @@ type Head[BLOCK_HASH Hashable] interface {
 	BlockDifficulty() *big.Int
 	// IsValid returns true if the head is valid.
 	IsValid() bool
+
+	// Returns the latest finalized based on finality tag or depth
+	LatestFinalizedHead() Head[BLOCK_HASH]
 }

core/chains/evm/types/models.go

@@ -168,11 +168,14 @@ func (h *Head) ChainHashes() []common.Hash {
 }
 
 func (h *Head) LatestFinalizedHead() commontypes.Head[common.Hash] {
-	for h != nil && !h.IsFinalized {
+	for h != nil {
+		if h.IsFinalized {
+			return h
+		}
 		h = h.Parent
 	}
 
-	return h
+	return nil
 }
 
 func (h *Head) ChainID() *big.Int {

core/internal/cltest/cltest.go

@@ -991,7 +991,7 @@ func AssertEthTxAttemptCountStays(t testing.TB, txStore txmgr.TestEvmTxStore, wa
 	return txaIds
 }
 
-// Head given the value convert it into an Head
+// Head given the value convert it into a Head
 func Head(val interface{}) *evmtypes.Head {
 	var h evmtypes.Head
 	time := uint64(0)