cmd/devp2p/internal/ethtest/snap.go

@@ -407,7 +407,9 @@ func (s *Suite) TestSnapTrieNodes(t *utesting.T) {
 				{[]byte{1}, []byte{0}},
 			},
 			nBytes: 5000,
-			expHashes: []common.Hash{},
+			expHashes: []common.Hash{
+				common.HexToHash("0x1ee1bb2fbac4d46eab331f3e8551e18a0805d084ed54647883aa552809ca968d"),
+			},
 		},
 		{
 			// The leaf is only a couple of levels down, so the continued trie traversal causes lookup failures.
@@ -437,7 +439,35 @@ func (s *Suite) TestSnapTrieNodes(t *utesting.T) {
 				common.HexToHash("0xbcefee69b37cca1f5bf3a48aebe08b35f2ea1864fa958bb0723d909a0e0d28d8"),
 			},
 		},
-	} {
+		{
+			/*
+				A test against this account, requesting trie nodes for the storage trie
+				{
+				  "balance": "0",
+				  "nonce": 1,
+				  "root": "0xbe3d75a1729be157e79c3b77f00206db4d54e3ea14375a015451c88ec067c790",
+				  "codeHash": "0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470",
+				  "storage": {
+				    "0x405787fa12a823e0f2b7631cc41b3ba8828b3321ca811111fa75cd3aa3bb5ace": "02",
+				    "0xb10e2d527612073b26eecdfd717e6a320cf44b4afac2b0732d9fcbe2b7fa0cf6": "01",
+				    "0xc2575a0e9e593c00f959f8c92f12db2869c3395a3b0502d05e2516446f71f85b": "03"
+				  },
+				  "key": "0xf493f79c43bd747129a226ad42529885a4b108aba6046b2d12071695a6627844"
+				}
+			*/
+			root: s.chain.RootAt(999),
+			paths: []snap.TrieNodePathSet{
+				{
+					common.FromHex("0xf493f79c43bd747129a226ad42529885a4b108aba6046b2d12071695a6627844"),
+					[]byte{0},
+				},
+			},
+			nBytes: 5000,
+			expHashes: []common.Hash{
+				common.HexToHash("0xbe3d75a1729be157e79c3b77f00206db4d54e3ea14375a015451c88ec067c790"),
+			},
+		},
+	}[7:] {
 		tc := tc
 		if err := s.snapGetTrieNodes(t, &tc); err != nil {
 			t.Errorf("test %d \n #hashes %x\n root: %#x\n bytes: %d\nfailed: %v", i, len(tc.expHashes), tc.root, tc.nBytes, err)

eth/protocols/snap/handler.go

@@ -493,14 +493,8 @@ func ServiceGetTrieNodesQuery(chain *core.BlockChain, req *GetTrieNodesPacket, s
 		// We don't have the requested state available, bail out
 		return nil, nil
 	}
+	// The 'snap' might be nil, in which case we cannot serve storage slots.
 	snap := chain.Snapshots().Snapshot(req.Root)
-	if snap == nil {
-		// We don't have the requested state snapshotted yet, bail out.
-		// In reality we could still serve using the account and storage
-		// tries only, but let's protect the node a bit while it's doing
-		// snapshot generation.
-		return nil, nil
-	}
 	// Retrieve trie nodes until the packet size limit is reached
 	var (
 		nodes [][]byte
@@ -524,13 +518,26 @@ func ServiceGetTrieNodesQuery(chain *core.BlockChain, req *GetTrieNodesPacket, s
 			bytes += uint64(len(blob))
 
 		default:
+			var stRoot common.Hash
 			// Storage slots requested, open the storage trie and retrieve from there
+			if snap == nil {
+				// We don't have the requested state snapshotted yet (or it is stale),
+				// but can look up the account via the trie instead.
+				account, err := accTrie.TryGetAccountWithPreHashedKey(pathset[0])
+				loads += 8 // We don't know the exact cost of lookup, this is an estimate
+				if err != nil || account == nil {
+					break
+				}
+				stRoot = account.Root
+			} else {
 				account, err := snap.Account(common.BytesToHash(pathset[0]))
 				loads++ // always account database reads, even for failures
 				if err != nil || account == nil {
 					break
 				}
-			id := trie.StorageTrieID(req.Root, common.BytesToHash(pathset[0]), common.BytesToHash(account.Root))
+				stRoot = common.BytesToHash(account.Root)
+			}
+			id := trie.StorageTrieID(req.Root, common.BytesToHash(pathset[0]), stRoot)
 			stTrie, err := trie.NewStateTrie(id, triedb)
 			loads++ // always account database reads, even for failures
 			if err != nil {