TUN-4597: Add a QUIC server skeleton

- Added a QUIC server to accept streams
- Unit test for this server also tests ALPN
- Temporary echo capability for HTTP ConnectionType

vendor/github.com/lucas-clemente/quic-go/conn.go

@@ -0,0 +1,65 @@
+package quic
+
+import (
+	"io"
+	"net"
+	"syscall"
+	"time"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+)
+
+type connection interface {
+	ReadPacket() (*receivedPacket, error)
+	WritePacket(b []byte, addr net.Addr, oob []byte) (int, error)
+	LocalAddr() net.Addr
+	io.Closer
+}
+
+// If the PacketConn passed to Dial or Listen satisfies this interface, quic-go will read the ECN bits from the IP header.
+// In this case, ReadMsgUDP() will be used instead of ReadFrom() to read packets.
+type OOBCapablePacketConn interface {
+	net.PacketConn
+	SyscallConn() (syscall.RawConn, error)
+	ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *net.UDPAddr, err error)
+	WriteMsgUDP(b, oob []byte, addr *net.UDPAddr) (n, oobn int, err error)
+}
+
+var _ OOBCapablePacketConn = &net.UDPConn{}
+
+func wrapConn(pc net.PacketConn) (connection, error) {
+	c, ok := pc.(OOBCapablePacketConn)
+	if !ok {
+		utils.DefaultLogger.Infof("PacketConn is not a net.UDPConn. Disabling optimizations possible on UDP connections.")
+		return &basicConn{PacketConn: pc}, nil
+	}
+	return newConn(c)
+}
+
+type basicConn struct {
+	net.PacketConn
+}
+
+var _ connection = &basicConn{}
+
+func (c *basicConn) ReadPacket() (*receivedPacket, error) {
+	buffer := getPacketBuffer()
+	// The packet size should not exceed protocol.MaxPacketBufferSize bytes
+	// If it does, we only read a truncated packet, which will then end up undecryptable
+	buffer.Data = buffer.Data[:protocol.MaxPacketBufferSize]
+	n, addr, err := c.PacketConn.ReadFrom(buffer.Data)
+	if err != nil {
+		return nil, err
+	}
+	return &receivedPacket{
+		remoteAddr: addr,
+		rcvTime:    time.Now(),
+		data:       buffer.Data[:n],
+		buffer:     buffer,
+	}, nil
+}
+
+func (c *basicConn) WritePacket(b []byte, addr net.Addr, _ []byte) (n int, err error) {
+	return c.PacketConn.WriteTo(b, addr)
+}