From 3f4c5daa1555333d5c3eb0053a15943cae88145a Mon Sep 17 00:00:00 2001
From: Maisem Ali <maisem@tailscale.com>
Date: Wed, 11 Oct 2023 17:49:01 +0000
Subject: [PATCH] wgengine/netstack: remove SubnetRouterWrapper

It was used when we only supported subnet routers on linux
and would nil out the SubnetRoutes slice as no other router
worked with it, but now we support subnet routers on ~all platforms.

The field it was setting to nil is now only used for network logging
and nowhere else, so keep the field but drop the SubnetRouterWrapper
as it's not useful.

Updates #cleanup

Change-Id: Id03f9b6ec33e47ad643e7b66e07911945f25db79
Signed-off-by: Maisem Ali <maisem@tailscale.com>
---
 cmd/tailscaled/tailscaled.go               |  1 -
 wgengine/netstack/subnet_router_wrapper.go | 28 ----------------------
 wgengine/router/router.go                  |  7 +++++-
 wgengine/userspace_ext_test.go             |  3 +--
 4 files changed, 7 insertions(+), 32 deletions(-)
 delete mode 100644 wgengine/netstack/subnet_router_wrapper.go

diff --git a/cmd/tailscaled/tailscaled.go b/cmd/tailscaled/tailscaled.go
index 6279dc850..b78827fef 100644
--- a/cmd/tailscaled/tailscaled.go
+++ b/cmd/tailscaled/tailscaled.go
@@ -709,7 +709,6 @@ func tryEngine(logf logger.Logf, sys *tsd.System, name string) (onlyNetstack boo
 		conf.DNS = d
 		conf.Router = r
 		if handleSubnetsInNetstack() {
-			conf.Router = netstack.NewSubnetRouterWrapper(conf.Router)
 			netstackSubnetRouter = true
 		}
 		sys.Set(conf.Router)
diff --git a/wgengine/netstack/subnet_router_wrapper.go b/wgengine/netstack/subnet_router_wrapper.go
deleted file mode 100644
index 97eb6406f..000000000
--- a/wgengine/netstack/subnet_router_wrapper.go
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright (c) Tailscale Inc & AUTHORS
-// SPDX-License-Identifier: BSD-3-Clause
-
-package netstack
-
-import (
-	"tailscale.com/wgengine/router"
-)
-
-type subnetRouter struct {
-	router.Router
-}
-
-// NewSubnetRouterWrapper returns a Router wrapper that prevents the
-// underlying Router r from seeing any advertised subnet routes, as
-// netstack will handle them instead.
-func NewSubnetRouterWrapper(r router.Router) router.Router {
-	return &subnetRouter{
-		Router: r,
-	}
-}
-
-func (r *subnetRouter) Set(c *router.Config) error {
-	if c != nil {
-		c.SubnetRoutes = nil // netstack will handle
-	}
-	return r.Router.Set(c)
-}
diff --git a/wgengine/router/router.go b/wgengine/router/router.go
index 3c5497f42..da0b39739 100644
--- a/wgengine/router/router.go
+++ b/wgengine/router/router.go
@@ -80,8 +80,13 @@ type Config struct {
 	// callback. If zero, the MTU is unchanged.
 	NewMTU int
 
+	// SubnetRoutes is the list of subnets that this node is
+	// advertising to other Tailscale nodes.
+	// As of 2023-10-11, this field is only used for network
+	// flow logging and is otherwise ignored.
+	SubnetRoutes []netip.Prefix
+
 	// Linux-only things below, ignored on other platforms.
-	SubnetRoutes     []netip.Prefix         // subnets being advertised to other Tailscale nodes
 	SNATSubnetRoutes bool                   // SNAT traffic to local subnets
 	NetfilterMode    preftype.NetfilterMode // how much to manage netfilter rules
 	NetfilterKind    string                 // what kind of netfilter to use (nftables, iptables)
diff --git a/wgengine/userspace_ext_test.go b/wgengine/userspace_ext_test.go
index 4a3f6127c..5183d8f1b 100644
--- a/wgengine/userspace_ext_test.go
+++ b/wgengine/userspace_ext_test.go
@@ -12,7 +12,6 @@ import (
 	"tailscale.com/tstest"
 	"tailscale.com/types/logger"
 	"tailscale.com/wgengine"
-	"tailscale.com/wgengine/netstack"
 	"tailscale.com/wgengine/router"
 )
 
@@ -55,7 +54,7 @@ func TestIsNetstackRouter(t *testing.T) {
 			name: "hybrid_netstack",
 			conf: wgengine.Config{
 				Tun:    newFakeOSTUN(),
-				Router: netstack.NewSubnetRouterWrapper(newFakeOSRouter()),
+				Router: newFakeOSRouter(),
 			},
 			setNetstackRouter: true,
 			want:              true,