les, light: LES/2 protocol version (#14970)

This PR implements the new LES protocol version extensions:

* new and more efficient Merkle proofs reply format (when replying to
  a multiple Merkle proofs request, we just send a single set of trie
  nodes containing all necessary nodes)
* BBT (BloomBitsTrie) works similarly to the existing CHT and contains
  the bloombits search data to speed up log searches
* GetTxStatusMsg returns the inclusion position or the
  pending/queued/unknown state of a transaction referenced by hash
* an optional signature of new block data (number/hash/td) can be
  included in AnnounceMsg to provide an option for "very light
  clients" (mobile/embedded devices) to skip expensive Ethash check
  and accept multiple signatures of somewhat trusted servers (still a
  lot better than trusting a single server completely and retrieving
  everything through RPC). The new client mode is not implemented in
  this PR, just the protocol extension.

1 files changed, 50 insertions, 19 deletions

diff --git a/core/chain_indexer.go b/core/chain_indexer.go
index f4c207dcc..837c908ab 100644
--- a/core/chain_indexer.go
+++ b/core/chain_indexer.go
@@ -36,13 +36,14 @@ import (
 type ChainIndexerBackend interface {
 	// Reset initiates the processing of a new chain segment, potentially terminating
 	// any partially completed operations (in case of a reorg).
-	Reset(section uint64)
+	Reset(section uint64, lastSectionHead common.Hash) error
 
 	// Process crunches through the next header in the chain segment. The caller
 	// will ensure a sequential order of headers.
 	Process(header *types.Header)
 
-	// Commit finalizes the section metadata and stores it into the database.
+	// Commit finalizes the section metadata and stores it into the database. This
+	// interface will usually be a batch writer.
 	Commit() error
 }
 
@@ -100,11 +101,34 @@ func NewChainIndexer(chainDb, indexDb ethdb.Database, backend ChainIndexerBacken
 	return c
 }
 
+// AddKnownSectionHead marks a new section head as known/processed if it is newer
+// than the already known best section head
+func (c *ChainIndexer) AddKnownSectionHead(section uint64, shead common.Hash) {
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	if section < c.storedSections {
+		return
+	}
+	c.setSectionHead(section, shead)
+	c.setValidSections(section + 1)
+}
+
+// IndexerChain interface is used for connecting the indexer to a blockchain
+type IndexerChain interface {
+	CurrentHeader() *types.Header
+	SubscribeChainEvent(ch chan<- ChainEvent) event.Subscription
+}
+
 // Start creates a goroutine to feed chain head events into the indexer for
 // cascading background processing. Children do not need to be started, they
 // are notified about new events by their parents.
-func (c *ChainIndexer) Start(currentHeader *types.Header, chainEventer func(ch chan<- ChainEvent) event.Subscription) {
-	go c.eventLoop(currentHeader, chainEventer)
+func (c *ChainIndexer) Start(chain IndexerChain) {
+	ch := make(chan ChainEvent, 10)
+	sub := chain.SubscribeChainEvent(ch)
+	currentHeader := chain.CurrentHeader()
+
+	go c.eventLoop(currentHeader, ch, sub)
 }
 
 // Close tears down all goroutines belonging to the indexer and returns any error
@@ -125,12 +149,14 @@ func (c *ChainIndexer) Close() error {
 			errs = append(errs, err)
 		}
 	}
+
 	// Close all children
 	for _, child := range c.children {
 		if err := child.Close(); err != nil {
 			errs = append(errs, err)
 		}
 	}
+
 	// Return any failures
 	switch {
 	case len(errs) == 0:
@@ -147,12 +173,10 @@ func (c *ChainIndexer) Close() error {
 // eventLoop is a secondary - optional - event loop of the indexer which is only
 // started for the outermost indexer to push chain head events into a processing
 // queue.
-func (c *ChainIndexer) eventLoop(currentHeader *types.Header, chainEventer func(ch chan<- ChainEvent) event.Subscription) {
+func (c *ChainIndexer) eventLoop(currentHeader *types.Header, ch chan ChainEvent, sub event.Subscription) {
 	// Mark the chain indexer as active, requiring an additional teardown
 	atomic.StoreUint32(&c.active, 1)
 
-	events := make(chan ChainEvent, 10)
-	sub := chainEventer(events)
 	defer sub.Unsubscribe()
 
 	// Fire the initial new head event to start any outstanding processing
@@ -169,7 +193,7 @@ func (c *ChainIndexer) eventLoop(currentHeader *types.Header, chainEventer func(
 			errc <- nil
 			return
 
-		case ev, ok := <-events:
+		case ev, ok := <-ch:
 			// Received a new event, ensure it's not nil (closing) and update
 			if !ok {
 				errc := <-c.quit
@@ -178,7 +202,9 @@ func (c *ChainIndexer) eventLoop(currentHeader *types.Header, chainEventer func(
 			}
 			header := ev.Block.Header()
 			if header.ParentHash != prevHash {
-				c.newHead(FindCommonAncestor(c.chainDb, prevHeader, header).Number.Uint64(), true)
+				if h := FindCommonAncestor(c.chainDb, prevHeader, header); h != nil {
+					c.newHead(h.Number.Uint64(), true)
+				}
 			}
 			c.newHead(header.Number.Uint64(), false)
 
@@ -233,9 +259,10 @@ func (c *ChainIndexer) newHead(head uint64, reorg bool) {
 // down into the processing backend.
 func (c *ChainIndexer) updateLoop() {
 	var (
-		updating bool
-		updated  time.Time
+		updated   time.Time
+		updateMsg bool
 	)
+
 	for {
 		select {
 		case errc := <-c.quit:
@@ -250,7 +277,7 @@ func (c *ChainIndexer) updateLoop() {
 				// Periodically print an upgrade log message to the user
 				if time.Since(updated) > 8*time.Second {
 					if c.knownSections > c.storedSections+1 {
-						updating = true
+						updateMsg = true
 						c.log.Info("Upgrading chain index", "percentage", c.storedSections*100/c.knownSections)
 					}
 					updated = time.Now()
@@ -259,7 +286,7 @@ func (c *ChainIndexer) updateLoop() {
 				section := c.storedSections
 				var oldHead common.Hash
 				if section > 0 {
-					oldHead = c.sectionHead(section - 1)
+					oldHead = c.SectionHead(section - 1)
 				}
 				// Process the newly defined section in the background
 				c.lock.Unlock()
@@ -270,11 +297,11 @@ func (c *ChainIndexer) updateLoop() {
 				c.lock.Lock()
 
 				// If processing succeeded and no reorgs occcurred, mark the section completed
-				if err == nil && oldHead == c.sectionHead(section-1) {
+				if err == nil && oldHead == c.SectionHead(section-1) {
 					c.setSectionHead(section, newHead)
 					c.setValidSections(section + 1)
-					if c.storedSections == c.knownSections && updating {
-						updating = false
+					if c.storedSections == c.knownSections && updateMsg {
+						updateMsg = false
 						c.log.Info("Finished upgrading chain index")
 					}
 
@@ -311,7 +338,11 @@ func (c *ChainIndexer) processSection(section uint64, lastHead common.Hash) (com
 	c.log.Trace("Processing new chain section", "section", section)
 
 	// Reset and partial processing
-	c.backend.Reset(section)
+
+	if err := c.backend.Reset(section, lastHead); err != nil {
+		c.setValidSections(0)
+		return common.Hash{}, err
+	}
 
 	for number := section * c.sectionSize; number < (section+1)*c.sectionSize; number++ {
 		hash := GetCanonicalHash(c.chainDb, number)
@@ -341,7 +372,7 @@ func (c *ChainIndexer) Sections() (uint64, uint64, common.Hash) {
 	c.lock.Lock()
 	defer c.lock.Unlock()
 
-	return c.storedSections, c.storedSections*c.sectionSize - 1, c.sectionHead(c.storedSections - 1)
+	return c.storedSections, c.storedSections*c.sectionSize - 1, c.SectionHead(c.storedSections - 1)
 }
 
 // AddChildIndexer adds a child ChainIndexer that can use the output of this one
@@ -383,7 +414,7 @@ func (c *ChainIndexer) setValidSections(sections uint64) {
 
 // sectionHead retrieves the last block hash of a processed section from the
 // index database.
-func (c *ChainIndexer) sectionHead(section uint64) common.Hash {
+func (c *ChainIndexer) SectionHead(section uint64) common.Hash {
 	var data [8]byte
 	binary.BigEndian.PutUint64(data[:], section)