op-node: Skip conf depth check if L1 head is empty

The L1 Head block in the conf depth is pulled from the L1 State object.
The L1 State is never initialized at startup but instead from the new head
channel. This means that prior to the first new head, any code which calls
BlockByNumber would always fail if the conf depth was not zero.

op-node/rollup/driver/conf_depth.go

@@ -6,6 +6,7 @@ import (
 	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/rollup/derive"
 	"github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/common"
 )
 
 // confDepth is an util that wraps the L1 input fetcher used in the pipeline,
@@ -30,7 +31,9 @@ func (c *confDepth) L1BlockRefByNumber(ctx context.Context, num uint64) (eth.L1B
 	// TODO: performance optimization: buffer the l1Unsafe, invalidate any reorged previous buffer content,
 	// and instantly return the origin by number from the buffer if we can.
 
-	if num == 0 || c.depth == 0 || num+c.depth <= c.l1Head().Number {
+	// Don't apply the conf depth is l1Head is empty (as it is during the startup case before the l1State is initialized).
+	l1Head := c.l1Head()
+	if num == 0 || c.depth == 0 || num+c.depth <= l1Head.Number || l1Head.Hash == (common.Hash{}) {
 		return c.L1Fetcher.L1BlockRefByNumber(ctx, num)
 	}
 	return eth.L1BlockRef{}, ethereum.NotFound

op-node/rollup/driver/conf_depth_test.go

@@ -9,11 +9,15 @@ import (
 	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum-optimism/optimism/op-node/testutils"
 	"github.com/ethereum/go-ethereum"
+	"github.com/ethereum/go-ethereum/common"
 )
 
+var exHash = common.Hash{0xff}
+
 type confTest struct {
 	name  string
 	head  uint64
+	hash  common.Hash // hash of head block
 	req   uint64
 	depth uint64
 	pass  bool
@@ -21,7 +25,7 @@ type confTest struct {
 
 func (ct *confTest) Run(t *testing.T) {
 	l1Fetcher := &testutils.MockL1Source{}
-	l1Head := eth.L1BlockRef{Number: ct.head}
+	l1Head := eth.L1BlockRef{Number: ct.head, Hash: ct.hash}
 	l1HeadGetter := func() eth.L1BlockRef { return l1Head }
 
 	cd := NewConfDepth(ct.depth, l1HeadGetter, l1Fetcher)
@@ -43,18 +47,19 @@ func TestConfDepth(t *testing.T) {
 	// note: we're not testing overflows.
 	// If a request is large enough to overflow the conf depth check, it's not returning anything anyway.
 	testCases := []confTest{
-		{name: "zero conf future", head: 4, req: 5, depth: 0, pass: true},
-		{name: "zero conf present", head: 4, req: 4, depth: 0, pass: true},
-		{name: "zero conf past", head: 4, req: 4, depth: 0, pass: true},
-		{name: "one conf future", head: 4, req: 5, depth: 1, pass: false},
-		{name: "one conf present", head: 4, req: 4, depth: 1, pass: false},
-		{name: "one conf past", head: 4, req: 3, depth: 1, pass: true},
-		{name: "two conf future", head: 4, req: 5, depth: 2, pass: false},
-		{name: "two conf present", head: 4, req: 4, depth: 2, pass: false},
-		{name: "two conf not like 1", head: 4, req: 3, depth: 2, pass: false},
-		{name: "two conf pass", head: 4, req: 2, depth: 2, pass: true},
-		{name: "easy pass", head: 100, req: 20, depth: 5, pass: true},
-		{name: "genesis case", head: 0, req: 0, depth: 4, pass: true},
+		{name: "zero conf future", head: 4, hash: exHash, req: 5, depth: 0, pass: true},
+		{name: "zero conf present", head: 4, hash: exHash, req: 4, depth: 0, pass: true},
+		{name: "zero conf past", head: 4, hash: exHash, req: 4, depth: 0, pass: true},
+		{name: "one conf future", head: 4, hash: exHash, req: 5, depth: 1, pass: false},
+		{name: "one conf present", head: 4, hash: exHash, req: 4, depth: 1, pass: false},
+		{name: "one conf past", head: 4, hash: exHash, req: 3, depth: 1, pass: true},
+		{name: "two conf future", head: 4, hash: exHash, req: 5, depth: 2, pass: false},
+		{name: "two conf present", head: 4, hash: exHash, req: 4, depth: 2, pass: false},
+		{name: "two conf not like 1", head: 4, hash: exHash, req: 3, depth: 2, pass: false},
+		{name: "two conf pass", head: 4, hash: exHash, req: 2, depth: 2, pass: true},
+		{name: "easy pass", head: 100, hash: exHash, req: 20, depth: 5, pass: true},
+		{name: "genesis case", head: 0, hash: exHash, req: 0, depth: 4, pass: true},
+		{name: "no L1 state", req: 10, depth: 4, pass: true},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, tc.Run)