cli: upgrade to lucas-clemente/quic-go 0.23.0 (#449)

See https://github.com/ooni/probe/issues/1754 for a comprehensive description.

internal/quicx/quicx.go

@@ -0,0 +1,40 @@
+// Package quicx contains lucas-clemente/quic-go extensions.
+//
+// This code introduces the UDPLikeConn, whose documentation explain
+// why we need to introduce this new type. We could not put this
+// code inside an existing package because it's used (as of 20 Aug 2021)
+// by the netxlite package as well as by the netxmocks package.
+package quicx
+
+import (
+	"net"
+	"syscall"
+)
+
+// UDPLikeConn is a net.PacketConn with some extra functions
+// required to convince the QUIC library (lucas-clemente/quic-go)
+// to inflate the receive buffer of the connection.
+//
+// The QUIC library will treat this connection as a "dumb"
+// net.PacketConn, calling its ReadFrom and WriteTo methods
+// as opposed to more advanced methods that are available
+// under Linux and FreeBSD and improve the performance.
+//
+// It seems fine to avoid performance optimizations, because
+// they would complicate the implementation on our side and
+// our use cases (blocking and heavy throttling) do not seem
+// to require such optimizations.
+//
+// See https://github.com/ooni/probe/issues/1754 for a more
+// comprehensive discussion of UDPLikeConn.
+type UDPLikeConn interface {
+	// An UDPLikeConn is a net.PacketConn conn.
+	net.PacketConn
+
+	// SetReadBuffer allows setting the read buffer.
+	SetReadBuffer(bytes int) error
+
+	// SyscallConn returns a conn suitable for calling syscalls,
+	// which is also instrumental to setting the read buffer.
+	SyscallConn() (syscall.RawConn, error)
+}