bridge: correctly calculate 2/3+ majority

Adds test vectors.

ghstack-source-id: 1f7e0d783fdcb8b0d27b621f464efd0d1cc06deb
Pull Request resolved: https://github.com/certusone/wormhole/pull/58

bridge/cmd/guardiand/processor.go

@@ -5,7 +5,6 @@ import (
 	"crypto/ecdsa"
 	"encoding/hex"
 	"fmt"
-	"math"
 	"strings"
 	"time"
 
@@ -218,7 +217,7 @@ func vaaConsensusProcessor(lockC chan *common.ChainLock, setC chan *common.Guard
 					}
 
 					// 2/3+ majority required for VAA to be valid - wait until we have quorum to submit VAA.
-					quorum := int(math.Ceil((float64(len(gs.Keys)) / 3) * 2))
+					quorum := CalculateQuorum(len(gs.Keys))
 
 					logger.Info("aggregation state for VAA",
 						zap.String("digest", hash),
@@ -303,7 +302,7 @@ func checkDevModeGuardianSetUpdate(ctx context.Context, vaaC chan *vaa.VAA, gs *
 			defer cancel()
 			tx, err := devnet.SubmitVAA(timeout, *ethRPC, v)
 			if err != nil {
-				return fmt.Errorf("failed to submit devnet guardian set change: %v")
+				return fmt.Errorf("failed to submit devnet guardian set change: %v", err)
 			}
 
 			logger.Info("devnet guardian set change submitted to Ethereum", zap.Any("tx", tx), zap.Any("vaa", v))

bridge/cmd/guardiand/quorum.go

@@ -0,0 +1,9 @@
+package main
+
+// CalculateQuorum returns the minimum number of have that needs to sign a VAA for a given guardian set.
+//
+// The canonical source is the calculation in the contracts (solana/bridge/src/processor.rs and
+// ethereum/contracts/Wormhole.sol), and this needs to match the implementation in the contracts.
+func CalculateQuorum(numGuardians int) int {
+	return ((numGuardians*10/3)*2)/10 + 1
+}

bridge/cmd/guardiand/quorum_test.go

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestCalculateQuorum(t *testing.T) {
+	tests := []struct {
+		have int
+		want int
+	}{
+		{have: 1, want: 1},
+		{have: 2, want: 2},
+		{have: 3, want: 3},
+		{have: 4, want: 3},
+		{have: 5, want: 4},
+		{have: 6, want: 5},
+		{have: 7, want: 5},
+		{have: 8, want: 6},
+		{have: 9, want: 7},
+		{have: 10, want: 7},
+		{have: 11, want: 8},
+		{have: 12, want: 9},
+		{have: 20, want: 14},
+		{have: 25, want: 17},
+		{have: 100, want: 67},
+	}
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("%d have", tt.have), func(t *testing.T) {
+			if got := CalculateQuorum(tt.have); got != tt.want {
+				t.Errorf("CalculateQuorum(%d) = %v, want %v", tt.have, got, tt.want)
+			}
+		})
+	}
+}