consensus: customized getWork endpoint

consensus/ethash/api.go

@@ -31,13 +31,16 @@ type API struct {
 	ethash *Ethash // Make sure the mode of ethash is normal.
 }
 
-// GetWork returns a work package for external miner.
+// getWork returns a work package for external miner.
+//
+// User can specify a customized extra to replace the extra field
+// in the block header when the given string is not empty.
 //
 // The work package consists of 3 strings:
 //   result[0] - 32 bytes hex encoded current block header pow-hash
 //   result[1] - 32 bytes hex encoded seed hash used for DAG
 //   result[2] - 32 bytes hex encoded boundary condition ("target"), 2^256/difficulty
-func (api *API) GetWork() ([3]string, error) {
+func (api *API) getWork(extra string) ([3]string, error) {
 	if api.ethash.config.PowMode != ModeNormal && api.ethash.config.PowMode != ModeTest {
 		return [3]string{}, errors.New("not supported")
 	}
@@ -48,7 +51,7 @@ func (api *API) GetWork() ([3]string, error) {
 	)
 
 	select {
-	case api.ethash.fetchWorkCh <- &sealWork{errc: errc, res: workCh}:
+	case api.ethash.fetchWorkCh <- &sealWork{extra: extra, errc: errc, res: workCh}:
 	case <-api.ethash.exitCh:
 		return [3]string{}, errEthashStopped
 	}
@@ -61,6 +64,18 @@ func (api *API) GetWork() ([3]string, error) {
 	}
 }
 
+// GetWork returns a default work package for external miner.
+//
+// Note this function is a legacy for backward compatibility.
+func (api *API) GetWork() ([3]string, error) {
+	return api.getWork("")
+}
+
+// GetCustomizedWork returns a customized work package for external miner.
+func (api *API) GetCustomizedWork(extra string) ([3]string, error) {
+	return api.getWork(extra)
+}
+
 // SubmitWork can be used by external miner to submit their POW solution.
 // It returns an indication if the work was accepted.
 // Note either an invalid solution, a stale work a non-existent work will return false.

consensus/ethash/ethash.go

@@ -431,8 +431,9 @@ type hashrate struct {
 
 // sealWork wraps a seal work package for remote sealer.
 type sealWork struct {
-	errc chan error
+	extra string // The specified string used to fill the block extra field
-	res  chan [3]string
+	errc  chan error
+	res   chan [3]string
 }
 
 // Ethash is a consensus engine based on proof-of-work implementing the ethash

consensus/ethash/ethash_test.go

@@ -117,6 +117,7 @@ func TestRemoteSealer(t *testing.T) {
 	if res := api.SubmitWork(types.BlockNonce{}, sealhash, common.Hash{}); res {
 		t.Error("expect to return false when submit a fake solution")
 	}
+
 	// Push new block with same block number to replace the original one.
 	header = &types.Header{Number: big.NewInt(1), Difficulty: big.NewInt(1000)}
 	block = types.NewBlockWithHeader(header)
@@ -128,6 +129,31 @@ func TestRemoteSealer(t *testing.T) {
 	}
 }
 
+func TestCustomizedWork(t *testing.T) {
+	ethash := NewTester(nil, true)
+	defer ethash.Close()
+
+	api := &API{ethash}
+	header := &types.Header{Number: big.NewInt(1), Difficulty: big.NewInt(100)}
+	block := types.NewBlockWithHeader(header)
+
+	// Push new work.
+	results := make(chan *types.Block, 1)
+	ethash.Seal(nil, block, results, nil)
+
+	// Get customized mining work.
+	expect := &types.Header{Number: big.NewInt(1), Difficulty: big.NewInt(100), Extra: []byte("extra")}
+	expectSealhash := ethash.SealHash(expect)
+	if work, err := api.GetCustomizedWork("extra"); err != nil || work[0] != expectSealhash.Hex() {
+		t.Errorf("expect to return a customized work, have %s, want %s", work[0], expectSealhash.Hex())
+	}
+
+	// Submit fake solution for customized work
+	if !api.SubmitWork(types.BlockNonce{}, expectSealhash, common.Hash{}) {
+		t.Error("submit solution for customized work failed")
+	}
+}
+
 func TestHashRate(t *testing.T) {
 	var (
 		hashrate = []hexutil.Uint64{100, 200, 300}

consensus/ethash/sealer.go

@@ -245,6 +245,24 @@ func (ethash *Ethash) remote(notify []string, noverify bool) {
 		currentBlock = block
 		works[hash] = block
 	}
+	// customizeWork creates a work package for external miner
+	// with customized extra data.
+	customizeWork := func(extra string) [3]string {
+		newHeader := currentBlock.Header()
+		newHeader.Extra = []byte(extra)
+		newBlock := types.NewBlockWithHeader(newHeader)
+
+		// Recalculate mining work
+		var work [3]string
+		hash := ethash.SealHash(newHeader)
+		work[0] = hash.Hex()
+		work[1] = currentWork[1]
+		work[2] = currentWork[2]
+
+		// Trace the seal work fetched by remote sealer.
+		works[hash] = newBlock
+		return work
+	}
 	// submitWork verifies the submitted pow solution, returning
 	// whether the solution was accepted or not (not can be both a bad pow as well as
 	// any other error, like no pending work or stale mining result).
@@ -313,11 +331,16 @@ func (ethash *Ethash) remote(notify []string, noverify bool) {
 			notifyWork()
 
 		case work := <-ethash.fetchWorkCh:
-			// Return current mining work to remote miner.
 			if currentBlock == nil {
+				// Return error message if there is no available mining work yet.
 				work.errc <- errNoMiningWork
-			} else {
+			} else if work.extra == "" {
+				// Return the default current mining work if no extra customized data
+				// specified.
 				work.res <- currentWork
+			} else {
+				// Return the customized mining work.
+				work.res <- customizeWork(work.extra)
 			}
 
 		case result := <-ethash.submitWorkCh: