safesocket: remove the IPN protocol support

Updates #6417

Change-Id: I78908633de842d83b2cc8b10a864a0f88ab1b113
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/message.go

@@ -1,41 +0,0 @@
-// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package ipn
-
-import (
-	"context"
-
-	"tailscale.com/envknob"
-	"tailscale.com/version"
-)
-
-type readOnlyContextKey struct{}
-
-// IsReadonlyContext reports whether ctx is a read-only context, as currently used
-// by Unix non-root users running the "tailscale" CLI command. They can run "status",
-// but not much else.
-func IsReadonlyContext(ctx context.Context) bool {
-	return ctx.Value(readOnlyContextKey{}) != nil
-}
-
-// ReadonlyContextOf returns ctx wrapped with a context value that
-// will make IsReadonlyContext reports true.
-func ReadonlyContextOf(ctx context.Context) context.Context {
-	if IsReadonlyContext(ctx) {
-		return ctx
-	}
-	return context.WithValue(ctx, readOnlyContextKey{}, readOnlyContextKey{})
-}
-
-// IPCVersion returns version.Long usually, unless TS_DEBUG_FAKE_IPC_VERSION is
-// set, in which it contains that value. This is only used for weird development
-// cases when testing mismatched versions and you want the client to act like it's
-// compatible with the server.
-func IPCVersion() string {
-	if v := envknob.String("TS_DEBUG_FAKE_IPC_VERSION"); v != "" {
-		return v
-	}
-	return version.Long
-}