dex: implement downloader for dex

We need governance state to verify block's signature (randomness),
but in ethereum fast sync mode, eth downloader only downloads the whole
state of pivot block, so we don't have governance state to verify the
downloaded block that is before pivot block if we don't processing
transaction.
To avoid running transactions, dex downloader also downloads the
governance state (merkle proof and storage) at snapshot height of each round,
so that we can verify blocks in fast sync mode.

1 files changed, 17 insertions, 8 deletions

diff --git a/dex/peer.go b/dex/peer.go
index 263dc5647..67aa50694 100644
--- a/dex/peer.go
+++ b/dex/peer.go
@@ -536,7 +536,7 @@ func (p *peer) AsyncSendPullVotes(pos coreTypes.Position) {
 }
 
 // SendBlockHeaders sends a batch of block headers to the remote peer.
-func (p *peer) SendBlockHeaders(headers []*types.Header) error {
+func (p *peer) SendBlockHeaders(headers []*types.HeaderWithGovState) error {
 	return p2p.Send(p.rw, BlockHeadersMsg, headers)
 }
 
@@ -563,25 +563,34 @@ func (p *peer) SendReceiptsRLP(receipts []rlp.RawValue) error {
 	return p2p.Send(p.rw, ReceiptsMsg, receipts)
 }
 
+func (p *peer) SendGovState(govState *types.GovState) error {
+	return p2p.Send(p.rw, GovStateMsg, govState)
+}
+
 // RequestOneHeader is a wrapper around the header query functions to fetch a
 // single header. It is used solely by the fetcher.
 func (p *peer) RequestOneHeader(hash common.Hash) error {
 	p.Log().Debug("Fetching single header", "hash", hash)
-	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: hash}, Amount: uint64(1), Skip: uint64(0), Reverse: false})
+	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: hash}, Amount: uint64(1), Skip: uint64(0), Reverse: false, WithGov: false})
 }
 
 // RequestHeadersByHash fetches a batch of blocks' headers corresponding to the
 // specified header query, based on the hash of an origin block.
-func (p *peer) RequestHeadersByHash(origin common.Hash, amount int, skip int, reverse bool) error {
-	p.Log().Debug("Fetching batch of headers", "count", amount, "fromhash", origin, "skip", skip, "reverse", reverse)
-	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse})
+func (p *peer) RequestHeadersByHash(origin common.Hash, amount int, skip int, reverse, withGov bool) error {
+	p.Log().Debug("Fetching batch of headers", "count", amount, "fromhash", origin, "skip", skip, "reverse", reverse, "withgov", withGov)
+	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Hash: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse, WithGov: withGov})
 }
 
 // RequestHeadersByNumber fetches a batch of blocks' headers corresponding to the
 // specified header query, based on the number of an origin block.
-func (p *peer) RequestHeadersByNumber(origin uint64, amount int, skip int, reverse bool) error {
-	p.Log().Debug("Fetching batch of headers", "count", amount, "fromnum", origin, "skip", skip, "reverse", reverse)
-	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse})
+func (p *peer) RequestHeadersByNumber(origin uint64, amount int, skip int, reverse, withGov bool) error {
+	p.Log().Debug("Fetching batch of headers", "count", amount, "fromnum", origin, "skip", skip, "reverse", reverse, "withgov", withGov)
+	return p2p.Send(p.rw, GetBlockHeadersMsg, &getBlockHeadersData{Origin: hashOrNumber{Number: origin}, Amount: uint64(amount), Skip: uint64(skip), Reverse: reverse, WithGov: withGov})
+}
+
+func (p *peer) RequestGovStateByHash(hash common.Hash) error {
+	p.Log().Debug("Fetching one gov state", "hash", hash)
+	return p2p.Send(p.rw, GetGovStateMsg, hash)
 }
 
 // RequestBodies fetches a batch of blocks' bodies corresponding to the hashes