move connection tracking into the Transport (#5113)

sys_conn.go

@@ -1,6 +1,7 @@
 package quic
 
 import (
+	"io"
 	"log"
 	"net"
 	"os"
@@ -13,6 +14,30 @@ import (
 	"github.com/quic-go/quic-go/internal/utils"
 )
 
+type connCapabilities struct {
+	// This connection has the Don't Fragment (DF) bit set.
+	// This means it makes to run DPLPMTUD.
+	DF bool
+	// GSO (Generic Segmentation Offload) supported
+	GSO bool
+	// ECN (Explicit Congestion Notifications) supported
+	ECN bool
+}
+
+// rawConn is a connection that allow reading of a receivedPackeh.
+type rawConn interface {
+	ReadPacket() (receivedPacket, error)
+	// WritePacket writes a packet on the wire.
+	// gsoSize is the size of a single packet, or 0 to disable GSO.
+	// It is invalid to set gsoSize if capabilities.GSO is not set.
+	WritePacket(b []byte, addr net.Addr, packetInfoOOB []byte, gsoSize uint16, ecn protocol.ECN) (int, error)
+	LocalAddr() net.Addr
+	SetReadDeadline(time.Time) error
+	io.Closer
+
+	capabilities() connCapabilities
+}
+
 // OOBCapablePacketConn is a connection that allows the reading of ECN bits from the IP header.
 // If the PacketConn passed to the [Transport] satisfies this interface, quic-go will use it.
 // In this case, ReadMsgUDP() will be used instead of ReadFrom() to read packets.