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/golang.org/x/net/internal/socket/rawconn.go

@@ -17,18 +17,45 @@ type Conn struct {
 	c       syscall.RawConn
 }
 
+// tcpConn is an interface implemented by net.TCPConn.
+// It can be used for interface assertions to check if a net.Conn is a TCP connection.
+type tcpConn interface {
+	SyscallConn() (syscall.RawConn, error)
+	SetLinger(int) error
+}
+
+var _ tcpConn = (*net.TCPConn)(nil)
+
+// udpConn is an interface implemented by net.UDPConn.
+// It can be used for interface assertions to check if a net.Conn is a UDP connection.
+type udpConn interface {
+	SyscallConn() (syscall.RawConn, error)
+	ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *net.UDPAddr, err error)
+}
+
+var _ udpConn = (*net.UDPConn)(nil)
+
+// ipConn is an interface implemented by net.IPConn.
+// It can be used for interface assertions to check if a net.Conn is an IP connection.
+type ipConn interface {
+	SyscallConn() (syscall.RawConn, error)
+	ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *net.IPAddr, err error)
+}
+
+var _ ipConn = (*net.IPConn)(nil)
+
 // NewConn returns a new raw connection.
 func NewConn(c net.Conn) (*Conn, error) {
 	var err error
 	var cc Conn
 	switch c := c.(type) {
-	case *net.TCPConn:
+	case tcpConn:
 		cc.network = "tcp"
 		cc.c, err = c.SyscallConn()
-	case *net.UDPConn:
+	case udpConn:
 		cc.network = "udp"
 		cc.c, err = c.SyscallConn()
-	case *net.IPConn:
+	case ipConn:
 		cc.network = "ip"
 		cc.c, err = c.SyscallConn()
 	default: