pass the maximum packet size from MTU discoverer to packet packer

mtu_discoverer.go

@@ -1,6 +1,7 @@
 package quic
 
 import (
+	"net"
 	"time"
 
 	"github.com/quic-go/quic-go/internal/ackhandler"
@@ -26,6 +27,20 @@ const (
 	mtuProbeDelay = 5
 )
 
+func getMaxPacketSize(addr net.Addr) protocol.ByteCount {
+	maxSize := protocol.ByteCount(protocol.MinInitialPacketSize)
+	// If this is not a UDP address, we don't know anything about the MTU.
+	// Use the minimum size of an Initial packet as the max packet size.
+	if udpAddr, ok := addr.(*net.UDPAddr); ok {
+		if utils.IsIPv4(udpAddr.IP) {
+			maxSize = protocol.InitialPacketSizeIPv4
+		} else {
+			maxSize = protocol.InitialPacketSizeIPv6
+		}
+	}
+	return maxSize
+}
+
 type mtuFinder struct {
 	lastProbeTime time.Time
 	probeInFlight bool