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.

core/bloombits/matcher.go

@@ -18,6 +18,7 @@ package bloombits
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"math"
 	"sort"
@@ -60,6 +61,8 @@ type Retrieval struct {
 	Bit      uint
 	Sections []uint64
 	Bitsets  [][]byte
+	Error    error
+	Context  context.Context
 }
 
 // Matcher is a pipelined system of schedulers and logic matchers which perform
@@ -137,7 +140,7 @@ func (m *Matcher) addScheduler(idx uint) {
 // Start starts the matching process and returns a stream of bloom matches in
 // a given range of blocks. If there are no more matches in the range, the result
 // channel is closed.
-func (m *Matcher) Start(begin, end uint64, results chan uint64) (*MatcherSession, error) {
+func (m *Matcher) Start(ctx context.Context, begin, end uint64, results chan uint64) (*MatcherSession, error) {
 	// Make sure we're not creating concurrent sessions
 	if atomic.SwapUint32(&m.running, 1) == 1 {
 		return nil, errors.New("matcher already running")
@@ -149,6 +152,7 @@ func (m *Matcher) Start(begin, end uint64, results chan uint64) (*MatcherSession
 		matcher: m,
 		quit:    make(chan struct{}),
 		kill:    make(chan struct{}),
+		ctx:     ctx,
 	}
 	for _, scheduler := range m.schedulers {
 		scheduler.reset()
@@ -502,15 +506,28 @@ func (m *Matcher) distributor(dist chan *request, session *MatcherSession) {
 type MatcherSession struct {
 	matcher *Matcher
 
-	quit chan struct{} // Quit channel to request pipeline termination
-	kill chan struct{} // Term channel to signal non-graceful forced shutdown
-	pend sync.WaitGroup
+	quit     chan struct{} // Quit channel to request pipeline termination
+	kill     chan struct{} // Term channel to signal non-graceful forced shutdown
+	ctx      context.Context
+	err      error
+	stopping bool
+	lock     sync.Mutex
+	pend     sync.WaitGroup
 }
 
 // Close stops the matching process and waits for all subprocesses to terminate
 // before returning. The timeout may be used for graceful shutdown, allowing the
 // currently running retrievals to complete before this time.
-func (s *MatcherSession) Close(timeout time.Duration) {
+func (s *MatcherSession) Close() {
+	s.lock.Lock()
+	stopping := s.stopping
+	s.stopping = true
+	s.lock.Unlock()
+	// ensure that we only close the session once
+	if stopping {
+		return
+	}
+
 	// Bail out if the matcher is not running
 	select {
 	case <-s.quit:
@@ -519,10 +536,26 @@ func (s *MatcherSession) Close(timeout time.Duration) {
 	}
 	// Signal termination and wait for all goroutines to tear down
 	close(s.quit)
-	time.AfterFunc(timeout, func() { close(s.kill) })
+	time.AfterFunc(time.Second, func() { close(s.kill) })
 	s.pend.Wait()
 }
 
+// setError sets an error and stops the session
+func (s *MatcherSession) setError(err error) {
+	s.lock.Lock()
+	s.err = err
+	s.lock.Unlock()
+	s.Close()
+}
+
+// Error returns an error if one has happened during the session
+func (s *MatcherSession) Error() error {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	return s.err
+}
+
 // AllocateRetrieval assigns a bloom bit index to a client process that can either
 // immediately reuest and fetch the section contents assigned to this bit or wait
 // a little while for more sections to be requested.
@@ -618,9 +651,13 @@ func (s *MatcherSession) Multiplex(batch int, wait time.Duration, mux chan chan
 
 		case mux <- request:
 			// Retrieval accepted, something must arrive before we're aborting
-			request <- &Retrieval{Bit: bit, Sections: sections}
+			request <- &Retrieval{Bit: bit, Sections: sections, Context: s.ctx}
 
 			result := <-request
+			if result.Error != nil {
+				s.setError(result.Error)
+			}
+
 			s.DeliverSections(result.Bit, result.Sections, result.Bitsets)
 		}
 	}