downloader: added missing blocks catchup functionality

When a parent is missing in the block list an attempt should be made to
fetch the missing parent and grandparents.

eth/downloader/queue.go

@@ -2,16 +2,20 @@ package downloader
 
 import (
 	"math"
+	"math/big"
 	"sync"
 	"time"
 
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	"gopkg.in/fatih/set.v0"
 )
 
 // queue represents hashes that are either need fetching or are being fetched
 type queue struct {
-	hashPool *set.Set
+	hashPool    *set.Set
+	fetchPool   *set.Set
+	blockHashes *set.Set
 
 	mu       sync.Mutex
 	fetching map[string]*chunk
@@ -20,8 +24,10 @@ type queue struct {
 
 func newqueue() *queue {
 	return &queue{
-		hashPool: set.New(),
-		fetching: make(map[string]*chunk),
+		hashPool:    set.New(),
+		fetchPool:   set.New(),
+		blockHashes: set.New(),
+		fetching:    make(map[string]*chunk),
 	}
 }
 
@@ -50,6 +56,8 @@ func (c *queue) get(p *peer, max int) *chunk {
 	})
 	// remove the fetchable hashes from hash pool
 	c.hashPool.Separate(hashes)
+	c.fetchPool.Merge(hashes)
+
 	// Create a new chunk for the seperated hashes. The time is being used
 	// to reset the chunk (timeout)
 	chunk := &chunk{hashes, time.Now()}
@@ -60,6 +68,22 @@ func (c *queue) get(p *peer, max int) *chunk {
 	return chunk
 }
 
+func (c *queue) has(hash common.Hash) bool {
+	return c.hashPool.Has(hash) || c.fetchPool.Has(hash)
+}
+
+func (c *queue) addBlock(id string, block *types.Block, td *big.Int) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	// when adding a block make sure it doesn't already exist
+	if !c.blockHashes.Has(block.Hash()) {
+		c.hashPool.Remove(block.Hash())
+		c.blocks = append(c.blocks, block)
+	}
+}
+
+// deliver delivers a chunk to the queue that was requested of the peer
 func (c *queue) deliver(id string, blocks []*types.Block) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -70,15 +94,19 @@ func (c *queue) deliver(id string, blocks []*types.Block) {
 		delete(c.fetching, id)
 
 		// seperate the blocks and the hashes
-		chunk.seperate(blocks)
+		blockHashes := chunk.fetchedHashes(blocks)
+		// merge block hashes
+		c.blockHashes.Merge(blockHashes)
 		// Add the blocks
 		c.blocks = append(c.blocks, blocks...)
 
 		// Add back whatever couldn't be delivered
 		c.hashPool.Merge(chunk.hashes)
+		c.fetchPool.Separate(chunk.hashes)
 	}
 }
 
+// puts puts sets of hashes on to the queue for fetching
 func (c *queue) put(hashes *set.Set) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
@@ -91,8 +119,12 @@ type chunk struct {
 	itime  time.Time
 }
 
-func (ch *chunk) seperate(blocks []*types.Block) {
+func (ch *chunk) fetchedHashes(blocks []*types.Block) *set.Set {
+	fhashes := set.New()
 	for _, block := range blocks {
-		ch.hashes.Remove(block.Hash())
+		fhashes.Add(block.Hash())
 	}
+	ch.hashes.Separate(fhashes)
+
+	return fhashes
 }