rename files dealing with low level conns to sys_conn

mock_batch_conn_test.go

@@ -1,5 +1,5 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: conn_oob.go
+// Source: sys_conn_oob.go
 
 // Package quic is a generated GoMock package.
 package quic

sys_conn.go

@@ -10,6 +10,7 @@ import (
 	"github.com/lucas-clemente/quic-go/internal/utils"
 )
 
+// connection is a connection that allow reading of a receivedPacket.
 type connection interface {
 	ReadPacket() (*receivedPacket, error)
 	WritePacket(b []byte, addr net.Addr, oob []byte) (int, error)
@@ -17,7 +18,8 @@ type connection interface {
 	io.Closer
 }
 
-// If the PacketConn passed to Dial or Listen satisfies this interface, quic-go will read the ECN bits from the IP header.
+// OOBCapablePacketConn is a connection that allows the reading of ECN bits from the IP header.
+// If the PacketConn passed to Dial or Listen satisfies this interface, quic-go will use it.
 // In this case, ReadMsgUDP() will be used instead of ReadFrom() to read packets.
 type OOBCapablePacketConn interface {
 	net.PacketConn
@@ -50,6 +52,11 @@ func wrapConn(pc net.PacketConn) (connection, error) {
 	return newConn(c)
 }
 
+// The basicConn is the most trivial implementation of a connection.
+// It reads a single packet from the underlying net.PacketConn.
+// It is used when
+// * the net.PacketConn is not a OOBCapablePacketConn, and
+// * when the OS doesn't support OOB.
 type basicConn struct {
 	net.PacketConn
 }