fix: make timestamps strictly increasing

peer/record.go

@@ -2,6 +2,7 @@ package peer
 
 import (
 	"fmt"
+	"sync"
 	"time"
 
 	pb "github.com/libp2p/go-libp2p-core/peer/pb"
@@ -125,9 +126,23 @@ func PeerRecordFromProtobuf(msg *pb.PeerRecord) (*PeerRecord, error) {
 	return record, nil
 }
 
+var (
+	lastTimestampMu sync.Mutex
+	lastTimestamp   uint64
+)
+
 // TimestampSeq is a helper to generate a timestamp-based sequence number for a PeerRecord.
 func TimestampSeq() uint64 {
-	return uint64(time.Now().UnixNano())
+	now := uint64(time.Now().UnixNano())
+	lastTimestampMu.Lock()
+	defer lastTimestampMu.Unlock()
+	// Not all clocks are strictly increasing, but we need these sequence numbers to be strictly
+	// increasing.
+	if now <= lastTimestamp {
+		now = lastTimestamp + 1
+	}
+	lastTimestamp = now
+	return now
 }
 
 // Domain is used when signing and validating PeerRecords contained in Envelopes.

peer/record_test.go

@@ -52,3 +52,16 @@ func TestSignedPeerRecordFromEnvelope(t *testing.T) {
 		}
 	})
 }
+
+// This is pretty much guaranteed to pass on Linux no matter how we implement it, but Windows has
+// low clock precision. This makes sure we never get a duplicate.
+func TestTimestampSeq(t *testing.T) {
+	var last uint64
+	for i := 0; i < 1000; i++ {
+		next := TimestampSeq()
+		if next <= last {
+			t.Errorf("non-increasing timestamp found: %d <= %d", next, last)
+		}
+		last = next
+	}
+}