feature, net/tshttpproxy: pull out support for using proxies as a feature

Saves 139 KB.

Also Synology support, which I saw had its own large-ish proxy parsing
support on Linux, but support for proxies without Synology proxy
support is reasonable, so I pulled that out as its own thing.

Updates #12614

Change-Id: I22de285a3def7be77fdcf23e2bec7c83c9655593
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

client/web/web.go

@@ -27,6 +27,7 @@ import (
 	"tailscale.com/envknob"
 	"tailscale.com/envknob/featureknob"
 	"tailscale.com/feature"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
@@ -496,6 +497,10 @@ func (s *Server) authorizeRequest(w http.ResponseWriter, r *http.Request) (ok bo
 	// Client using system-specific auth.
 	switch distro.Get() {
 	case distro.Synology:
+		if !buildfeatures.HasSynology {
+			// Synology support not built in.
+			return false
+		}
 		authorized, _ := authorizeSynology(r)
 		return authorized
 	case distro.QNAP:

clientupdate/distsign/distsign.go

@@ -55,7 +55,7 @@ import (
 
 	"github.com/hdevalence/ed25519consensus"
 	"golang.org/x/crypto/blake2s"
-	"tailscale.com/net/tshttpproxy"
+	"tailscale.com/feature"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/httpm"
 	"tailscale.com/util/must"
@@ -330,7 +330,7 @@ func fetch(url string, limit int64) ([]byte, error) {
 // limit bytes. On success, the returned value is a BLAKE2s hash of the file.
 func (c *Client) download(ctx context.Context, url, dst string, limit int64) ([]byte, int64, error) {
 	tr := http.DefaultTransport.(*http.Transport).Clone()
-	tr.Proxy = tshttpproxy.ProxyFromEnvironment
+	tr.Proxy = feature.HookProxyFromEnvironment.GetOrNil()
 	defer tr.CloseIdleConnections()
 	hc := &http.Client{Transport: tr}
 

cmd/derper/depaware.txt

@@ -2,16 +2,13 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
 
         filippo.io/edwards25519                                      from github.com/hdevalence/ed25519consensus
         filippo.io/edwards25519/field                                from filippo.io/edwards25519
-   W 💣 github.com/alexbrainman/sspi                                 from github.com/alexbrainman/sspi/internal/common+
-   W    github.com/alexbrainman/sspi/internal/common                 from github.com/alexbrainman/sspi/negotiate
-   W 💣 github.com/alexbrainman/sspi/negotiate                       from tailscale.com/net/tshttpproxy
         github.com/beorn7/perks/quantile                             from github.com/prometheus/client_golang/prometheus
      💣 github.com/cespare/xxhash/v2                                 from github.com/prometheus/client_golang/prometheus
         github.com/coder/websocket                                   from tailscale.com/cmd/derper+
         github.com/coder/websocket/internal/errd                     from github.com/coder/websocket
         github.com/coder/websocket/internal/util                     from github.com/coder/websocket
         github.com/coder/websocket/internal/xsync                    from github.com/coder/websocket
-   W 💣 github.com/dblohm7/wingoes                                   from tailscale.com/util/winutil+
+   W 💣 github.com/dblohm7/wingoes                                   from tailscale.com/util/winutil
         github.com/fxamacker/cbor/v2                                 from tailscale.com/tka
         github.com/go-json-experiment/json                           from tailscale.com/types/opt+
         github.com/go-json-experiment/json/internal                  from github.com/go-json-experiment/json+
@@ -89,7 +86,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/drive                                          from tailscale.com/client/local+
         tailscale.com/envknob                                        from tailscale.com/client/local+
         tailscale.com/feature                                        from tailscale.com/tsweb+
-        tailscale.com/feature/buildfeatures                          from tailscale.com/feature
+        tailscale.com/feature/buildfeatures                          from tailscale.com/feature+
         tailscale.com/health                                         from tailscale.com/net/tlsdial+
         tailscale.com/hostinfo                                       from tailscale.com/net/netmon+
         tailscale.com/ipn                                            from tailscale.com/client/local
@@ -113,7 +110,6 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/net/tlsdial                                    from tailscale.com/derp/derphttp
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/ipn+
-     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/derp/derphttp+
         tailscale.com/net/udprelay/status                            from tailscale.com/client/local
         tailscale.com/net/wsconn                                     from tailscale.com/cmd/derper
         tailscale.com/paths                                          from tailscale.com/client/local
@@ -146,7 +142,6 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/util/cibuild                                   from tailscale.com/health
         tailscale.com/util/clientmetric                              from tailscale.com/net/netmon+
         tailscale.com/util/cloudenv                                  from tailscale.com/hostinfo+
-   W    tailscale.com/util/cmpver                                    from tailscale.com/net/tshttpproxy
         tailscale.com/util/ctxkey                                    from tailscale.com/tsweb+
      💣 tailscale.com/util/deephash                                  from tailscale.com/util/syspolicy/setting
    L 💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
@@ -195,7 +190,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
    L    golang.org/x/net/bpf                                         from github.com/mdlayher/netlink+
         golang.org/x/net/dns/dnsmessage                              from net+
         golang.org/x/net/http/httpguts                               from net/http+
-        golang.org/x/net/http/httpproxy                              from net/http+
+        golang.org/x/net/http/httpproxy                              from net/http
         golang.org/x/net/http2/hpack                                 from net/http+
         golang.org/x/net/idna                                        from golang.org/x/crypto/acme/autocert+
         golang.org/x/net/internal/socks                              from golang.org/x/net/proxy

cmd/k8s-operator/depaware.txt

@@ -701,9 +701,11 @@ tailscale.com/cmd/k8s-operator dependencies: (generated by github.com/tailscale/
         tailscale.com/feature/buildfeatures                          from tailscale.com/wgengine/magicsock+
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/tsnet
         tailscale.com/feature/condregister/portmapper                from tailscale.com/tsnet
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/tsnet
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/syspolicy                              from tailscale.com/logpolicy
+        tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
         tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/client/web+
@@ -777,7 +779,7 @@ tailscale.com/cmd/k8s-operator dependencies: (generated by github.com/tailscale/
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/client/web+
         tailscale.com/net/tsdial                                     from tailscale.com/control/controlclient+
-     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/control/controlclient+
+     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/feature/useproxy
         tailscale.com/net/tstun                                      from tailscale.com/tsd+
         tailscale.com/net/udprelay/endpoint                          from tailscale.com/wgengine/magicsock
         tailscale.com/net/udprelay/status                            from tailscale.com/client/local

cmd/tailscale/cli/configure-synology-cert.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux && !ts_omit_acme
+//go:build linux && !ts_omit_acme && !ts_omit_synology
 
 package cli
 

cmd/tailscale/cli/debug.go

@@ -28,17 +28,17 @@ import (
 	"time"
 
 	"github.com/peterbourgon/ff/v3/ffcli"
-	"golang.org/x/net/http/httpproxy"
 	"golang.org/x/net/http2"
 	"tailscale.com/client/tailscale/apitype"
 	"tailscale.com/control/controlhttp"
+	"tailscale.com/feature"
+	_ "tailscale.com/feature/condregister/useproxy"
 	"tailscale.com/hostinfo"
 	"tailscale.com/internal/noiseconn"
 	"tailscale.com/ipn"
 	"tailscale.com/net/ace"
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsaddr"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/paths"
 	"tailscale.com/safesocket"
 	"tailscale.com/tailcfg"
@@ -992,15 +992,11 @@ func runTS2021(ctx context.Context, args []string) error {
 		if err != nil {
 			return err
 		}
-		envConf := httpproxy.FromEnvironment()
-		if *envConf == (httpproxy.Config{}) {
-			log.Printf("HTTP proxy env: (none)")
-		} else {
-			log.Printf("HTTP proxy env: %+v", envConf)
-		}
-		proxy, err := tshttpproxy.ProxyFromEnvironment(&http.Request{URL: u})
+		if proxyFromEnv, ok := feature.HookProxyFromEnvironment.GetOk(); ok {
+			proxy, err := proxyFromEnv(&http.Request{URL: u})
 			log.Printf("tshttpproxy.ProxyFromEnvironment = (%v, %v)", proxy, err)
 		}
+	}
 	machinePrivate := key.NewMachine()
 	var dialer net.Dialer
 

cmd/tailscale/depaware.txt

@@ -96,9 +96,11 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/feature/capture/dissector                      from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/condregister/portmapper                from tailscale.com/cmd/tailscale/cli
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/syspolicy                              from tailscale.com/cmd/tailscale/cli
+        tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
         tailscale.com/health                                         from tailscale.com/net/tlsdial+
         tailscale.com/health/healthmsg                               from tailscale.com/cmd/tailscale/cli
         tailscale.com/hostinfo                                       from tailscale.com/client/web+
@@ -130,7 +132,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/net/tlsdial                                    from tailscale.com/cmd/tailscale/cli+
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/client/web+
-     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/clientupdate/distsign+
+     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/feature/useproxy
         tailscale.com/net/udprelay/status                            from tailscale.com/client/local+
         tailscale.com/paths                                          from tailscale.com/client/local+
      💣 tailscale.com/safesocket                                     from tailscale.com/client/local+

cmd/tailscaled/debug.go

@@ -21,10 +21,11 @@ import (
 	"time"
 
 	"tailscale.com/derp/derphttp"
+	"tailscale.com/feature"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/health"
 	"tailscale.com/ipn"
 	"tailscale.com/net/netmon"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
 	"tailscale.com/util/eventbus"
@@ -124,10 +125,15 @@ func getURL(ctx context.Context, urlStr string) error {
 	if err != nil {
 		return fmt.Errorf("http.NewRequestWithContext: %v", err)
 	}
-	proxyURL, err := tshttpproxy.ProxyFromEnvironment(req)
+	var proxyURL *url.URL
+	if buildfeatures.HasUseProxy {
+		if proxyFromEnv, ok := feature.HookProxyFromEnvironment.GetOk(); ok {
+			proxyURL, err = proxyFromEnv(req)
 			if err != nil {
 				return fmt.Errorf("tshttpproxy.ProxyFromEnvironment: %v", err)
 			}
+		}
+	}
 	log.Printf("proxy: %v", proxyURL)
 	tr := &http.Transport{
 		Proxy:              func(*http.Request) (*url.URL, error) { return proxyURL, nil },
@@ -135,7 +141,10 @@ func getURL(ctx context.Context, urlStr string) error {
 		DisableKeepAlives:  true,
 	}
 	if proxyURL != nil {
-		auth, err := tshttpproxy.GetAuthHeader(proxyURL)
+		var auth string
+		if f, ok := feature.HookProxyGetAuthHeader.GetOk(); ok {
+			auth, err = f(proxyURL)
+		}
 		if err == nil && auth != "" {
 			tr.ProxyConnectHeader.Set("Proxy-Authorization", auth)
 		}

cmd/tailscaled/depaware-min.txt

@@ -57,6 +57,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/buildfeatures                          from tailscale.com/cmd/tailscaled+
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/feature/condregister
         tailscale.com/health                                         from tailscale.com/cmd/tailscaled+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/cmd/tailscaled+
@@ -110,7 +111,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/ipn+
         tailscale.com/net/tsdial                                     from tailscale.com/cmd/tailscaled+
-        tailscale.com/net/tshttpproxy                                from tailscale.com/cmd/tailscaled+
         tailscale.com/net/tstun                                      from tailscale.com/cmd/tailscaled+
         tailscale.com/net/udprelay/endpoint                          from tailscale.com/wgengine/magicsock
         tailscale.com/omit                                           from tailscale.com/ipn/conffile
@@ -219,7 +219,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/net/bpf                                         from github.com/mdlayher/genetlink+
         golang.org/x/net/dns/dnsmessage                              from net+
         golang.org/x/net/http/httpguts                               from golang.org/x/net/http2+
-        golang.org/x/net/http/httpproxy                              from net/http+
+        golang.org/x/net/http/httpproxy                              from net/http
         golang.org/x/net/http2                                       from tailscale.com/control/controlclient+
         golang.org/x/net/http2/hpack                                 from golang.org/x/net/http2+
         golang.org/x/net/icmp                                        from tailscale.com/net/ping

cmd/tailscaled/depaware-minbox.txt

@@ -78,6 +78,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister+
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/cmd/tailscale/cli+
         tailscale.com/health                                         from tailscale.com/cmd/tailscaled+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/cmd/tailscaled+
@@ -133,7 +134,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/ipn+
         tailscale.com/net/tsdial                                     from tailscale.com/cmd/tailscaled+
-        tailscale.com/net/tshttpproxy                                from tailscale.com/cmd/tailscaled+
         tailscale.com/net/tstun                                      from tailscale.com/cmd/tailscaled+
         tailscale.com/net/udprelay/endpoint                          from tailscale.com/wgengine/magicsock
         tailscale.com/net/udprelay/status                            from tailscale.com/client/local
@@ -246,7 +246,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/net/bpf                                         from github.com/mdlayher/genetlink+
         golang.org/x/net/dns/dnsmessage                              from net+
         golang.org/x/net/http/httpguts                               from golang.org/x/net/http2+
-        golang.org/x/net/http/httpproxy                              from net/http+
+        golang.org/x/net/http/httpproxy                              from net/http
         golang.org/x/net/http2                                       from tailscale.com/cmd/tailscale/cli+
         golang.org/x/net/http2/hpack                                 from golang.org/x/net/http2+
         golang.org/x/net/icmp                                        from tailscale.com/net/ping

cmd/tailscaled/depaware.txt

@@ -276,6 +276,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/clientupdate                           from tailscale.com/feature/condregister
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/feature/condregister
         tailscale.com/feature/debugportmapper                        from tailscale.com/feature/condregister
         tailscale.com/feature/doctor                                 from tailscale.com/feature/condregister
         tailscale.com/feature/drive                                  from tailscale.com/feature/condregister
@@ -289,6 +290,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/taildrop                               from tailscale.com/feature/condregister
    L    tailscale.com/feature/tap                                    from tailscale.com/feature/condregister
         tailscale.com/feature/tpm                                    from tailscale.com/feature/condregister
+        tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
         tailscale.com/feature/wakeonlan                              from tailscale.com/feature/condregister
         tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
@@ -357,7 +359,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/client/web+
         tailscale.com/net/tsdial                                     from tailscale.com/cmd/tailscaled+
-     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/clientupdate/distsign+
+     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/feature/useproxy
         tailscale.com/net/tstun                                      from tailscale.com/cmd/tailscaled+
         tailscale.com/net/udprelay                                   from tailscale.com/feature/relayserver
         tailscale.com/net/udprelay/endpoint                          from tailscale.com/feature/relayserver+

cmd/tailscaled/deps_test.go

@@ -222,3 +222,16 @@ func TestOmitGRO(t *testing.T) {
 		},
 	}.Check(t)
 }
+
+func TestOmitUseProxy(t *testing.T) {
+	deptest.DepChecker{
+		GOOS:   "linux",
+		GOARCH: "amd64",
+		Tags:   "ts_omit_useproxy,ts_include_cli",
+		OnDep: func(dep string) {
+			if strings.Contains(dep, "tshttproxy") {
+				t.Errorf("unexpected dep: %q", dep)
+			}
+		},
+	}.Check(t)
+}

cmd/tailscaled/proxy.go

@@ -17,10 +17,10 @@ import (
 	"net/http/httputil"
 	"strings"
 
+	"tailscale.com/feature"
 	"tailscale.com/net/proxymux"
 	"tailscale.com/net/socks5"
 	"tailscale.com/net/tsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/types/logger"
 )
 
@@ -104,7 +104,9 @@ func mkProxyStartFunc(socksListener, httpListener net.Listener) proxyStartFunc {
 			}()
 			addrs = append(addrs, socksListener.Addr().String())
 		}
-		tshttpproxy.SetSelfProxy(addrs...)
+		if set, ok := feature.HookProxySetSelfProxy.GetOk(); ok {
+			set(addrs...)
+		}
 	}
 }
 

cmd/tsidp/depaware.txt

@@ -143,9 +143,11 @@ tailscale.com/cmd/tsidp dependencies: (generated by github.com/tailscale/depawar
         tailscale.com/feature/buildfeatures                          from tailscale.com/wgengine/magicsock+
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/tsnet
         tailscale.com/feature/condregister/portmapper                from tailscale.com/tsnet
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/tsnet
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/syspolicy                              from tailscale.com/logpolicy
+        tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
         tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/client/web+
@@ -205,7 +207,7 @@ tailscale.com/cmd/tsidp dependencies: (generated by github.com/tailscale/depawar
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/client/web+
         tailscale.com/net/tsdial                                     from tailscale.com/control/controlclient+
-     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/control/controlclient+
+     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/feature/useproxy
         tailscale.com/net/tstun                                      from tailscale.com/tsd+
         tailscale.com/net/udprelay/endpoint                          from tailscale.com/wgengine/magicsock
         tailscale.com/net/udprelay/status                            from tailscale.com/client/local

control/controlclient/direct.go

@@ -42,7 +42,6 @@ import (
 	"tailscale.com/net/netx"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tempfork/httprec"
 	"tailscale.com/tka"
@@ -275,8 +274,12 @@ func NewDirect(opts Options) (*Direct, error) {
 	var interceptedDial *atomic.Bool
 	if httpc == nil {
 		tr := http.DefaultTransport.(*http.Transport).Clone()
-		tr.Proxy = tshttpproxy.ProxyFromEnvironment
-		tshttpproxy.SetTransportGetProxyConnectHeader(tr)
+		if buildfeatures.HasUseProxy {
+			tr.Proxy = feature.HookProxyFromEnvironment.GetOrNil()
+			if f, ok := feature.HookProxySetTransportGetProxyConnectHeader.GetOk(); ok {
+				f(tr)
+			}
+		}
 		tr.TLSClientConfig = tlsdial.Config(opts.HealthTracker, tr.TLSClientConfig)
 		var dialFunc netx.DialFunc
 		dialFunc, interceptedDial = makeScreenTimeDetectingDialFunc(opts.Dialer.SystemDial)

control/controlhttp/client.go

@@ -39,6 +39,8 @@ import (
 	"tailscale.com/control/controlbase"
 	"tailscale.com/control/controlhttp/controlhttpcommon"
 	"tailscale.com/envknob"
+	"tailscale.com/feature"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/health"
 	"tailscale.com/net/ace"
 	"tailscale.com/net/dnscache"
@@ -47,7 +49,6 @@ import (
 	"tailscale.com/net/netx"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tlsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstime"
@@ -81,7 +82,7 @@ func (a *Dialer) getProxyFunc() func(*http.Request) (*url.URL, error) {
 	if a.proxyFunc != nil {
 		return a.proxyFunc
 	}
-	return tshttpproxy.ProxyFromEnvironment
+	return feature.HookProxyFromEnvironment.GetOrNil()
 }
 
 // httpsFallbackDelay is how long we'll wait for a.HTTPPort to work before
@@ -463,8 +464,12 @@ func (a *Dialer) tryURLUpgrade(ctx context.Context, u *url.URL, optAddr netip.Ad
 		tr.Proxy = nil
 		tr.DialContext = dialer
 	} else {
+		if buildfeatures.HasUseProxy {
 			tr.Proxy = a.getProxyFunc()
-		tshttpproxy.SetTransportGetProxyConnectHeader(tr)
+			if set, ok := feature.HookProxySetTransportGetProxyConnectHeader.GetOk(); ok {
+				set(tr)
+			}
+		}
 		tr.DialContext = dnscache.Dialer(dialer, dns)
 	}
 	// Disable HTTP2, since h2 can't do protocol switching.

derp/derphttp/derphttp_client.go

@@ -32,6 +32,8 @@ import (
 	"tailscale.com/derp"
 	"tailscale.com/derp/derpconst"
 	"tailscale.com/envknob"
+	"tailscale.com/feature"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/health"
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/netmon"
@@ -39,7 +41,6 @@ import (
 	"tailscale.com/net/netx"
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tlsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstime"
@@ -734,9 +735,13 @@ func (c *Client) dialNode(ctx context.Context, n *tailcfg.DERPNode) (net.Conn, e
 			Path:   "/", // unused
 		},
 	}
-	if proxyURL, err := tshttpproxy.ProxyFromEnvironment(proxyReq); err == nil && proxyURL != nil {
+	if buildfeatures.HasUseProxy {
+		if proxyFromEnv, ok := feature.HookProxyFromEnvironment.GetOk(); ok {
+			if proxyURL, err := proxyFromEnv(proxyReq); err == nil && proxyURL != nil {
 				return c.dialNodeUsingProxy(ctx, n, proxyURL)
 			}
+		}
+	}
 
 	type res struct {
 		c   net.Conn
@@ -865,11 +870,15 @@ func (c *Client) dialNodeUsingProxy(ctx context.Context, n *tailcfg.DERPNode, pr
 	target := net.JoinHostPort(n.HostName, "443")
 
 	var authHeader string
-	if v, err := tshttpproxy.GetAuthHeader(pu); err != nil {
+	if buildfeatures.HasUseProxy {
+		if getAuthHeader, ok := feature.HookProxyGetAuthHeader.GetOk(); ok {
+			if v, err := getAuthHeader(pu); err != nil {
 				c.logf("derphttp: error getting proxy auth header for %v: %v", proxyURL, err)
 			} else if v != "" {
 				authHeader = fmt.Sprintf("Proxy-Authorization: %s\r\n", v)
 			}
+		}
+	}
 
 	if _, err := fmt.Fprintf(proxyConn, "CONNECT %s HTTP/1.1\r\nHost: %s\r\n%s\r\n", target, target, authHeader); err != nil {
 		if ctx.Err() != nil {

feature/buildfeatures/feature_outboundproxy_disabled.go

@@ -7,7 +7,7 @@
 
 package buildfeatures
 
-// HasOutboundProxy is whether the binary was built with support for modular feature "Outbound localhost HTTP/SOCK5 proxy support".
+// HasOutboundProxy is whether the binary was built with support for modular feature "Support running an outbound localhost HTTP/SOCK5 proxy support that sends traffic over Tailscale".
 // Specifically, it's whether the binary was NOT built with the "ts_omit_outboundproxy" build tag.
 // It's a const so it can be used for dead code elimination.
 const HasOutboundProxy = false

feature/buildfeatures/feature_outboundproxy_enabled.go

@@ -7,7 +7,7 @@
 
 package buildfeatures
 
-// HasOutboundProxy is whether the binary was built with support for modular feature "Outbound localhost HTTP/SOCK5 proxy support".
+// HasOutboundProxy is whether the binary was built with support for modular feature "Support running an outbound localhost HTTP/SOCK5 proxy support that sends traffic over Tailscale".
 // Specifically, it's whether the binary was NOT built with the "ts_omit_outboundproxy" build tag.
 // It's a const so it can be used for dead code elimination.
 const HasOutboundProxy = true

feature/buildfeatures/feature_synology_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_synology
+
+package buildfeatures
+
+// HasSynology is whether the binary was built with support for modular feature "Synology NAS integration (applies to Linux builds only)".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_synology" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasSynology = false

feature/buildfeatures/feature_synology_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_synology
+
+package buildfeatures
+
+// HasSynology is whether the binary was built with support for modular feature "Synology NAS integration (applies to Linux builds only)".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_synology" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasSynology = true

feature/buildfeatures/feature_useproxy_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_useproxy
+
+package buildfeatures
+
+// HasUseProxy is whether the binary was built with support for modular feature "Support using system proxies as specified by env vars or the system configuration to reach Tailscale servers.".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_useproxy" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasUseProxy = false

feature/buildfeatures/feature_useproxy_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_useproxy
+
+package buildfeatures
+
+// HasUseProxy is whether the binary was built with support for modular feature "Support using system proxies as specified by env vars or the system configuration to reach Tailscale servers.".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_useproxy" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasUseProxy = true

feature/condregister/condregister.go

@@ -6,9 +6,13 @@
 // to ensure all conditional features are registered.
 package condregister
 
+import (
 	// Portmapper is special in that the CLI also needs to link it in,
 	// so it's pulled out into its own package, rather than using a maybe_*.go
 	// file in condregister.
-import (
 	_ "tailscale.com/feature/condregister/portmapper"
+
+	// HTTP proxy support is also needed by the CLI, and tsnet, so it's its
+	// own package too.
+	_ "tailscale.com/feature/condregister/useproxy"
 )

feature/condregister/useproxy/doc.go

@@ -0,0 +1,6 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package useproxy registers support for using proxies
+// if it's not disabled via the ts_omit_useproxy build tag.
+package useproxy

feature/condregister/useproxy/useproxy.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !ts_omit_useproxy
+
+package useproxy
+
+import _ "tailscale.com/feature/useproxy"

feature/feature.go

@@ -50,7 +50,8 @@ func (h *Hook[Func]) Set(f Func) {
 }
 
 // Get returns the hook function, or panics if it hasn't been set.
-// Use IsSet to check if it's been set.
+// Use IsSet to check if it's been set, or use GetOrNil if you're
+// okay with a nil return value.
 func (h *Hook[Func]) Get() Func {
 	if !h.ok {
 		panic("Get on unset feature hook, without IsSet")
@@ -64,6 +65,11 @@ func (h *Hook[Func]) GetOk() (f Func, ok bool) {
 	return h.f, h.ok
 }
 
+// GetOrNil returns the hook function or nil if it hasn't been set.
+func (h *Hook[Func]) GetOrNil() Func {
+	return h.f
+}
+
 // Hooks is a slice of funcs.
 //
 // As opposed to a single Hook, this is meant to be used when

feature/featuretags/featuretags.go

@@ -121,7 +121,7 @@ var Features = map[FeatureTag]FeatureMeta{
 	"oauthkey": {"OAuthKey", "OAuth secret-to-authkey resolution support", nil},
 	"outboundproxy": {
 		Sym:  "OutboundProxy",
-		Desc: "Outbound localhost HTTP/SOCK5 proxy support",
+		Desc: "Support running an outbound localhost HTTP/SOCK5 proxy support that sends traffic over Tailscale",
 		Deps: []FeatureTag{"netstack"},
 	},
 	"osrouter": {
@@ -172,6 +172,10 @@ var Features = map[FeatureTag]FeatureMeta{
 		Desc: "Tailscale SSH support",
 		Deps: []FeatureTag{"dbus", "netstack"},
 	},
+	"synology": {
+		Sym:  "Synology",
+		Desc: "Synology NAS integration (applies to Linux builds only)",
+	},
 	"syspolicy": {"SystemPolicy", "System policy configuration (MDM) support", nil},
 	"systray": {
 		Sym:  "SysTray",
@@ -182,6 +186,10 @@ var Features = map[FeatureTag]FeatureMeta{
 	"tailnetlock": {"TailnetLock", "Tailnet Lock support", nil},
 	"tap":         {"Tap", "Experimental Layer 2 (ethernet) support", nil},
 	"tpm":         {"TPM", "TPM support", nil},
+	"useproxy": {
+		Sym:  "UseProxy",
+		Desc: "Support using system proxies as specified by env vars or the system configuration to reach Tailscale servers.",
+	},
 	"wakeonlan": {"WakeOnLAN", "Wake-on-LAN support", nil},
 	"webclient": {
 		Sym: "WebClient", Desc: "Web client support",

feature/hooks.go

@@ -3,6 +3,11 @@
 
 package feature
 
+import (
+	"net/http"
+	"net/url"
+)
+
 // HookCanAutoUpdate is a hook for the clientupdate package
 // to conditionally initialize.
 var HookCanAutoUpdate Hook[func() bool]
@@ -15,3 +20,23 @@ func CanAutoUpdate() bool {
 	}
 	return false
 }
+
+// HookProxyFromEnvironment is a hook for feature/useproxy to register
+// a function to use as http.ProxyFromEnvironment.
+var HookProxyFromEnvironment Hook[func(*http.Request) (*url.URL, error)]
+
+// HookProxyInvalidateCache is a hook for feature/useproxy to register
+// [tshttpproxy.InvalidateCache].
+var HookProxyInvalidateCache Hook[func()]
+
+// HookProxyGetAuthHeader is a hook for feature/useproxy to register
+// [tshttpproxy.GetAuthHeader].
+var HookProxyGetAuthHeader Hook[func(*url.URL) (string, error)]
+
+// HookProxySetSelfProxy is a hook for feature/useproxy to register
+// [tshttpproxy.SetSelfProxy].
+var HookProxySetSelfProxy Hook[func(...string)]
+
+// HookProxySetTransportGetProxyConnectHeader is a hook for feature/useproxy to register
+// [tshttpproxy.SetTransportGetProxyConnectHeader].
+var HookProxySetTransportGetProxyConnectHeader Hook[func(*http.Transport)]

feature/useproxy/useproxy.go

@@ -0,0 +1,18 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package useproxy registers support for using system proxies.
+package useproxy
+
+import (
+	"tailscale.com/feature"
+	"tailscale.com/net/tshttpproxy"
+)
+
+func init() {
+	feature.HookProxyFromEnvironment.Set(tshttpproxy.ProxyFromEnvironment)
+	feature.HookProxyInvalidateCache.Set(tshttpproxy.InvalidateCache)
+	feature.HookProxyGetAuthHeader.Set(tshttpproxy.GetAuthHeader)
+	feature.HookProxySetSelfProxy.Set(tshttpproxy.SetSelfProxy)
+	feature.HookProxySetTransportGetProxyConnectHeader.Set(tshttpproxy.SetTransportGetProxyConnectHeader)
+}

ipn/ipnlocal/cert.go

@@ -35,6 +35,7 @@ import (
 
 	"tailscale.com/atomicfile"
 	"tailscale.com/envknob"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/hostinfo"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
@@ -73,7 +74,7 @@ func (b *LocalBackend) certDir() (string, error) {
 	// As a workaround for Synology DSM6 not having a "var" directory, use the
 	// app's "etc" directory (on a small partition) to hold certs at least.
 	// See https://github.com/tailscale/tailscale/issues/4060#issuecomment-1186592251
-	if d == "" && runtime.GOOS == "linux" && distro.Get() == distro.Synology && distro.DSMVersion() == 6 {
+	if buildfeatures.HasSynology && d == "" && runtime.GOOS == "linux" && distro.Get() == distro.Synology && distro.DSMVersion() == 6 {
 		d = "/var/packages/Tailscale/etc" // base; we append "certs" below
 	}
 	if d == "" {

logpolicy/logpolicy.go

@@ -31,6 +31,7 @@ import (
 	"golang.org/x/term"
 	"tailscale.com/atomicfile"
 	"tailscale.com/envknob"
+	"tailscale.com/feature"
 	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/health"
 	"tailscale.com/hostinfo"
@@ -44,7 +45,6 @@ import (
 	"tailscale.com/net/netns"
 	"tailscale.com/net/netx"
 	"tailscale.com/net/tlsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/paths"
 	"tailscale.com/safesocket"
 	"tailscale.com/types/logger"
@@ -870,8 +870,12 @@ func (opts TransportOptions) New() http.RoundTripper {
 		tr.TLSClientConfig = opts.TLSClientConfig.Clone()
 	}
 
-	tr.Proxy = tshttpproxy.ProxyFromEnvironment
-	tshttpproxy.SetTransportGetProxyConnectHeader(tr)
+	if buildfeatures.HasUseProxy {
+		tr.Proxy = feature.HookProxyFromEnvironment.GetOrNil()
+		if set, ok := feature.HookProxySetTransportGetProxyConnectHeader.GetOk(); ok {
+			set(tr)
+		}
+	}
 
 	// We do our own zstd compression on uploads, and responses never contain any payload,
 	// so don't send "Accept-Encoding: gzip" to save a few bytes on the wire, since there

net/dnsfallback/dnsfallback.go

@@ -26,11 +26,11 @@ import (
 	"time"
 
 	"tailscale.com/atomicfile"
+	"tailscale.com/feature"
 	"tailscale.com/health"
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/tlsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/slicesx"
@@ -135,7 +135,7 @@ func bootstrapDNSMap(ctx context.Context, serverName string, serverIP netip.Addr
 	dialer := netns.NewDialer(logf, netMon)
 	tr := http.DefaultTransport.(*http.Transport).Clone()
 	tr.DisableKeepAlives = true // This transport is meant to be used once.
-	tr.Proxy = tshttpproxy.ProxyFromEnvironment
+	tr.Proxy = feature.HookProxyFromEnvironment.GetOrNil()
 	tr.DialContext = func(ctx context.Context, netw, addr string) (net.Conn, error) {
 		return dialer.DialContext(ctx, "tcp", net.JoinHostPort(serverIP.String(), "443"))
 	}

net/netmon/interfaces_windows.go

@@ -13,6 +13,7 @@ import (
 
 	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/tsconst"
 )
 
@@ -22,8 +23,10 @@ const (
 
 func init() {
 	likelyHomeRouterIP = likelyHomeRouterIPWindows
+	if buildfeatures.HasUseProxy {
 		getPAC = getPACWindows
 	}
+}
 
 func likelyHomeRouterIPWindows() (ret netip.Addr, _ netip.Addr, ok bool) {
 	rs, err := winipcfg.GetIPForwardTable2(windows.AF_INET)
@@ -244,6 +247,9 @@ const (
 )
 
 func getPACWindows() string {
+	if !buildfeatures.HasUseProxy {
+		return ""
+	}
 	var res *uint16
 	r, _, e := detectAutoProxyConfigURL.Call(
 		winHTTP_AUTO_DETECT_TYPE_DHCP|winHTTP_AUTO_DETECT_TYPE_DNS_A,

net/netmon/state.go

@@ -15,10 +15,11 @@ import (
 	"strings"
 
 	"tailscale.com/envknob"
+	"tailscale.com/feature"
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/hostinfo"
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/tsaddr"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/util/mak"
 )
 
@@ -501,14 +502,16 @@ func getState(optTSInterfaceName string) (*State, error) {
 		}
 	}
 
-	if s.AnyInterfaceUp() {
+	if buildfeatures.HasUseProxy && s.AnyInterfaceUp() {
 		req, err := http.NewRequest("GET", LoginEndpointForProxyDetermination, nil)
 		if err != nil {
 			return nil, err
 		}
-		if u, err := tshttpproxy.ProxyFromEnvironment(req); err == nil && u != nil {
+		if proxyFromEnv, ok := feature.HookProxyFromEnvironment.GetOk(); ok {
+			if u, err := proxyFromEnv(req); err == nil && u != nil {
 				s.HTTPProxy = u.String()
 			}
+		}
 		if getPAC != nil {
 			s.PAC = getPAC()
 		}

net/tshttpproxy/tshttpproxy_linux.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"net/url"
 
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/version/distro"
 )
 
@@ -17,7 +18,7 @@ func init() {
 }
 
 func linuxSysProxyFromEnv(req *http.Request) (*url.URL, error) {
-	if distro.Get() == distro.Synology {
+	if buildfeatures.HasSynology && distro.Get() == distro.Synology {
 		return synologyProxyFromConfigCached(req)
 	}
 	return nil, nil

tsnet/depaware.txt

@@ -139,9 +139,11 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         tailscale.com/feature/buildfeatures                          from tailscale.com/wgengine/magicsock+
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/tsnet
         tailscale.com/feature/condregister/portmapper                from tailscale.com/tsnet
+        tailscale.com/feature/condregister/useproxy                  from tailscale.com/tsnet
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/syspolicy                              from tailscale.com/logpolicy
+        tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
         tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/client/web+
@@ -201,7 +203,7 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         tailscale.com/net/tlsdial/blockblame                         from tailscale.com/net/tlsdial
         tailscale.com/net/tsaddr                                     from tailscale.com/client/web+
         tailscale.com/net/tsdial                                     from tailscale.com/control/controlclient+
-     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/control/controlclient+
+     💣 tailscale.com/net/tshttpproxy                                from tailscale.com/feature/useproxy
         tailscale.com/net/tstun                                      from tailscale.com/tsd+
         tailscale.com/net/udprelay/endpoint                          from tailscale.com/wgengine/magicsock
         tailscale.com/net/udprelay/status                            from tailscale.com/client/local

tsnet/tsnet.go

@@ -31,6 +31,7 @@ import (
 	"tailscale.com/envknob"
 	_ "tailscale.com/feature/condregister/oauthkey"
 	_ "tailscale.com/feature/condregister/portmapper"
+	_ "tailscale.com/feature/condregister/useproxy"
 	"tailscale.com/health"
 	"tailscale.com/hostinfo"
 	"tailscale.com/internal/client/tailscale"

tstest/integration/tailscaled_deps_test_darwin.go

@@ -36,7 +36,6 @@ import (
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
 	_ "tailscale.com/net/tsdial"
-	_ "tailscale.com/net/tshttpproxy"
 	_ "tailscale.com/net/tstun"
 	_ "tailscale.com/paths"
 	_ "tailscale.com/safesocket"

tstest/integration/tailscaled_deps_test_freebsd.go

@@ -36,7 +36,6 @@ import (
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
 	_ "tailscale.com/net/tsdial"
-	_ "tailscale.com/net/tshttpproxy"
 	_ "tailscale.com/net/tstun"
 	_ "tailscale.com/paths"
 	_ "tailscale.com/safesocket"

tstest/integration/tailscaled_deps_test_linux.go

@@ -36,7 +36,6 @@ import (
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
 	_ "tailscale.com/net/tsdial"
-	_ "tailscale.com/net/tshttpproxy"
 	_ "tailscale.com/net/tstun"
 	_ "tailscale.com/paths"
 	_ "tailscale.com/safesocket"

tstest/integration/tailscaled_deps_test_openbsd.go

@@ -36,7 +36,6 @@ import (
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
 	_ "tailscale.com/net/tsdial"
-	_ "tailscale.com/net/tshttpproxy"
 	_ "tailscale.com/net/tstun"
 	_ "tailscale.com/paths"
 	_ "tailscale.com/safesocket"

tstest/integration/tailscaled_deps_test_windows.go

@@ -46,7 +46,6 @@ import (
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
 	_ "tailscale.com/net/tsdial"
-	_ "tailscale.com/net/tshttpproxy"
 	_ "tailscale.com/net/tstun"
 	_ "tailscale.com/paths"
 	_ "tailscale.com/safesocket"

wgengine/netstack/netstack_userping.go

@@ -13,6 +13,7 @@ import (
 	"runtime"
 	"time"
 
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/version/distro"
 )
 
@@ -20,7 +21,7 @@ import (
 // CAP_NET_RAW from tailscaled's binary.
 var setAmbientCapsRaw func(*exec.Cmd)
 
-var isSynology = runtime.GOOS == "linux" && distro.Get() == distro.Synology
+var isSynology = runtime.GOOS == "linux" && buildfeatures.HasSynology && distro.Get() == distro.Synology
 
 // sendOutboundUserPing sends a non-privileged ICMP (or ICMPv6) ping to dstIP with the given timeout.
 func (ns *Impl) sendOutboundUserPing(dstIP netip.Addr, timeout time.Duration) error {
@@ -61,7 +62,7 @@ func (ns *Impl) sendOutboundUserPing(dstIP netip.Addr, timeout time.Duration) er
 			ping = "/bin/ping"
 		}
 		cmd := exec.Command(ping, "-c", "1", "-W", "3", dstIP.String())
-		if isSynology && os.Getuid() != 0 {
+		if buildfeatures.HasSynology && isSynology && os.Getuid() != 0 {
 			// On DSM7 we run as non-root and need to pass
 			// CAP_NET_RAW if our binary has it.
 			setAmbientCapsRaw(cmd)

wgengine/userspace.go

@@ -23,6 +23,7 @@ import (
 	"tailscale.com/control/controlknobs"
 	"tailscale.com/drive"
 	"tailscale.com/envknob"
+	"tailscale.com/feature"
 	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/health"
 	"tailscale.com/ipn/ipnstate"
@@ -35,7 +36,6 @@ import (
 	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/net/tsdial"
-	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/net/tstun"
 	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
@@ -559,7 +559,9 @@ func (e *userspaceEngine) consumeEventbusTopics(cli *eventbus.Client) func(*even
 			case <-cli.Done():
 				return
 			case changeDelta := <-changeDeltaSub.Events():
-				tshttpproxy.InvalidateCache()
+				if f, ok := feature.HookProxyInvalidateCache.GetOk(); ok {
+					f()
+				}
 				e.linkChange(&changeDelta)
 			}
 		}