handle duration overflow

types/proposal.go

@@ -99,6 +99,12 @@ func (p *Proposal) IsTimely(recvTime time.Time, sp SynchronyParams, round int32)
 	roundModifier := time.Duration(math.Exp2(float64(round / 10)))
 	msgDelay := sp.MessageDelay * roundModifier
 
+	if msgDelay <= 0 {
+		// In the case that messaeg delay overflows after applying the round modifier, use the maximum
+		// duration instead.
+		msgDelay = time.Nanosecond * math.MaxInt64
+	}
+
 	// lhs is `proposedBlockTime - Precision` in the first inequality
 	lhs := p.Timestamp.Add(-sp.Precision)
 	// rhs is `proposedBlockTime + MsgDelay + Precision` in the second inequality

types/proposal_test.go

@@ -266,6 +266,17 @@ func TestIsTimely(t *testing.T) {
 			expectTimely: true,
 			round:        10,
 		},
+		{
+			// check that values that overflow time.Duration still correctly register
+			// as timely when round relaxation applied.
+			name:         "message delay fixed to not overflow time.Duration",
+			proposalTime: genesisTime,
+			recvTime:     genesisTime.Add(4 * time.Nanosecond),
+			precision:    time.Nanosecond * 2,
+			msgDelay:     time.Nanosecond,
+			expectTimely: true,
+			round:        5000,
+		},
 	}
 
 	for _, testCase := range testCases {