UDT: Fix invalid initial packet sequence number when random number was a signed negative int

udt/packet/pktseq.go

@@ -1,5 +1,7 @@
 package packet
 
+import "math/rand"
+
 // PacketID represents a UDT packet ID sequence
 type PacketID struct {
 	Seq uint32
@@ -28,3 +30,8 @@ func (p PacketID) BlindDiff(rhs PacketID) int32 {
 	}
 	return int32(result)
 }
+
+// RandomPacketSequence returns a random packet sequence
+func RandomPacketSequence() PacketID {
+	return PacketID{rand.Uint32() & 0x7FFFFFFF}
+}

udt/udtsocket.go

@@ -2,7 +2,6 @@ package udt
 
 import (
 	"errors"
-	"math/rand"
 	"net"
 	"sync"
 	"syscall"
@@ -420,7 +419,7 @@ func newSocket(m *multiplexer, config *Config, sockID uint32, isServer bool, isD
 		maxFlowWinSize: maxFlowWinSize,
 		isDatagram:     isDatagram,
 		sockID:         sockID,
-		initPktSeq:     packet.PacketID{Seq: rand.Uint32()},
+		initPktSeq:     packet.RandomPacketSequence(),
 		messageIn:      make(chan []byte, 256),
 		messageOut:     make(chan sendMessage, 256),
 		recvEvent:      make(chan recvPktEvent, 256),