From 41d1f45c99df8e6ad067eaeb5da9bd568e0f4e32 Mon Sep 17 00:00:00 2001
From: Kishan Sagathiya <kishansagathiya@gmail.com>
Date: Fri, 1 Apr 2022 20:46:17 +0530
Subject: [PATCH] implement Hash function for block announce handshake

---
 dot/network/block_announce.go     | 12 +++++++++---
 dot/network/gossip.go             |  4 +++-
 dot/network/notifications_test.go |  4 +++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/dot/network/block_announce.go b/dot/network/block_announce.go
index e7eafc5575..8c5771b67e 100644
--- a/dot/network/block_announce.go
+++ b/dot/network/block_announce.go
@@ -147,9 +147,15 @@ func (*BlockAnnounceHandshake) Type() byte {
 	return 0
 }
 
-// Hash ...
-func (*BlockAnnounceHandshake) Hash() (common.Hash, error) {
-	return common.Hash{}, nil
+// Hash returns blake2b hash of block announce handshake.
+func (hs *BlockAnnounceHandshake) Hash() (common.Hash, error) {
+	// scale encode each extrinsic
+	encMsg, err := hs.Encode()
+	if err != nil {
+		return common.Hash{}, fmt.Errorf("cannot encode handshake: %w", err)
+	}
+
+	return common.Blake2bHash(encMsg)
 }
 
 // IsHandshake returns true
diff --git a/dot/network/gossip.go b/dot/network/gossip.go
index ab0d862f50..d91f1c017e 100644
--- a/dot/network/gossip.go
+++ b/dot/network/gossip.go
@@ -40,7 +40,9 @@ func (g *gossip) hasSeen(msg NotificationsMessage) (bool, error) {
 	_, ok := g.seenMap[msgHash]
 	if !ok {
 		// set message to has been seen
-		g.seenMap[msgHash] = struct{}{}
+		if !msg.IsHandshake() {
+			g.seenMap[msgHash] = struct{}{}
+		}
 		return false, nil
 	}
 
diff --git a/dot/network/notifications_test.go b/dot/network/notifications_test.go
index 1d31a261d1..5670114262 100644
--- a/dot/network/notifications_test.go
+++ b/dot/network/notifications_test.go
@@ -189,7 +189,9 @@ func TestCreateNotificationsMessageHandler_BlockAnnounceHandshake(t *testing.T)
 		Roles:           4,
 		BestBlockNumber: 77,
 		BestBlockHash:   common.Hash{1},
-		GenesisHash:     common.Hash{2},
+		// we are using a different genesis here, thus this
+		// handshake would be validated to be incorrect.
+		GenesisHash: common.Hash{2},
 	}
 
 	err = handler(stream, testHandshake)