cmd/tailscale: refactor shared utility methods

Refactor two shared functions used by the tailscale cli,
calcAdvertiseRoutes and licensesURL. These are used by the web client as
well as other tailscale subcommands. The web client is being moved out
of the cli package, so move these two functions to new locations.

Updates tailscale/corp#13775

Signed-off-by: Will Norris <will@tailscale.com>

cmd/tailscale/cli/licenses.go

@@ -5,9 +5,9 @@ package cli
 
 import (
 	"context"
-	"runtime"
 
 	"github.com/peterbourgon/ff/v3/ffcli"
+	"tailscale.com/licenses"
 )
 
 var licensesCmd = &ffcli.Command{
@@ -18,27 +18,13 @@ var licensesCmd = &ffcli.Command{
 	Exec:       runLicenses,
 }
 
-// licensesURL returns the absolute URL containing open source license information for the current platform.
-func licensesURL() string {
-	switch runtime.GOOS {
-	case "android":
-		return "https://tailscale.com/licenses/android"
-	case "darwin", "ios":
-		return "https://tailscale.com/licenses/apple"
-	case "windows":
-		return "https://tailscale.com/licenses/windows"
-	default:
-		return "https://tailscale.com/licenses/tailscale"
-	}
-}
-
 func runLicenses(ctx context.Context, args []string) error {
-	licenses := licensesURL()
+	url := licenses.LicensesURL()
 	outln(`
 Tailscale wouldn't be possible without the contributions of thousands of open
 source developers. To see the open source packages included in Tailscale and
 their respective license information, visit:
 
-    ` + licenses)
+    ` + url)
 	return nil
 }

cmd/tailscale/cli/set.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/peterbourgon/ff/v3/ffcli"
 	"tailscale.com/ipn"
+	"tailscale.com/net/netutil"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/safesocket"
 )
@@ -159,11 +160,11 @@ func runSet(ctx context.Context, args []string) (retErr error) {
 // setArgs is the parsed command-line arguments.
 func calcAdvertiseRoutesForSet(advertiseExitNodeSet, advertiseRoutesSet bool, curPrefs *ipn.Prefs, setArgs setArgsT) (routes []netip.Prefix, err error) {
 	if advertiseExitNodeSet && advertiseRoutesSet {
-		return calcAdvertiseRoutes(setArgs.advertiseRoutes, setArgs.advertiseDefaultRoute)
+		return netutil.CalcAdvertiseRoutes(setArgs.advertiseRoutes, setArgs.advertiseDefaultRoute)
 
 	}
 	if advertiseRoutesSet {
-		return calcAdvertiseRoutes(setArgs.advertiseRoutes, curPrefs.AdvertisesExitNode())
+		return netutil.CalcAdvertiseRoutes(setArgs.advertiseRoutes, curPrefs.AdvertisesExitNode())
 	}
 	if advertiseExitNodeSet {
 		alreadyAdvertisesExitNode := curPrefs.AdvertisesExitNode()

cmd/tailscale/cli/up.go

@@ -6,7 +6,6 @@ package cli
 import (
 	"context"
 	"encoding/base64"
-	"encoding/binary"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -33,7 +32,7 @@ import (
 	"tailscale.com/health/healthmsg"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
-	"tailscale.com/net/tsaddr"
+	"tailscale.com/net/netutil"
 	"tailscale.com/safesocket"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
@@ -220,82 +219,6 @@ func warnf(format string, args ...any) {
 	printf("Warning: "+format+"\n", args...)
 }
 
-var (
-	ipv4default = netip.MustParsePrefix("0.0.0.0/0")
-	ipv6default = netip.MustParsePrefix("::/0")
-)
-
-func validateViaPrefix(ipp netip.Prefix) error {
-	if !tsaddr.IsViaPrefix(ipp) {
-		return fmt.Errorf("%v is not a 4-in-6 prefix", ipp)
-	}
-	if ipp.Bits() < (128 - 32) {
-		return fmt.Errorf("%v 4-in-6 prefix must be at least a /%v", ipp, 128-32)
-	}
-	a := ipp.Addr().As16()
-	// The first 64 bits of a are the via prefix.
-	// The next 32 bits are the "site ID".
-	// The last 32 bits are the IPv4.
-	// For now, we reserve the top 3 bytes of the site ID,
-	// and only allow users to use site IDs 0-255.
-	siteID := binary.BigEndian.Uint32(a[8:12])
-	if siteID > 0xFF {
-		return fmt.Errorf("route %v contains invalid site ID %08x; must be 0xff or less", ipp, siteID)
-	}
-	return nil
-}
-
-func calcAdvertiseRoutes(advertiseRoutes string, advertiseDefaultRoute bool) ([]netip.Prefix, error) {
-	routeMap := map[netip.Prefix]bool{}
-	if advertiseRoutes != "" {
-		var default4, default6 bool
-		advroutes := strings.Split(advertiseRoutes, ",")
-		for _, s := range advroutes {
-			ipp, err := netip.ParsePrefix(s)
-			if err != nil {
-				return nil, fmt.Errorf("%q is not a valid IP address or CIDR prefix", s)
-			}
-			if ipp != ipp.Masked() {
-				return nil, fmt.Errorf("%s has non-address bits set; expected %s", ipp, ipp.Masked())
-			}
-			if tsaddr.IsViaPrefix(ipp) {
-				if err := validateViaPrefix(ipp); err != nil {
-					return nil, err
-				}
-			}
-			if ipp == ipv4default {
-				default4 = true
-			} else if ipp == ipv6default {
-				default6 = true
-			}
-			routeMap[ipp] = true
-		}
-		if default4 && !default6 {
-			return nil, fmt.Errorf("%s advertised without its IPv6 counterpart, please also advertise %s", ipv4default, ipv6default)
-		} else if default6 && !default4 {
-			return nil, fmt.Errorf("%s advertised without its IPv4 counterpart, please also advertise %s", ipv6default, ipv4default)
-		}
-	}
-	if advertiseDefaultRoute {
-		routeMap[netip.MustParsePrefix("0.0.0.0/0")] = true
-		routeMap[netip.MustParsePrefix("::/0")] = true
-	}
-	if len(routeMap) == 0 {
-		return nil, nil
-	}
-	routes := make([]netip.Prefix, 0, len(routeMap))
-	for r := range routeMap {
-		routes = append(routes, r)
-	}
-	sort.Slice(routes, func(i, j int) bool {
-		if routes[i].Bits() != routes[j].Bits() {
-			return routes[i].Bits() < routes[j].Bits()
-		}
-		return routes[i].Addr().Less(routes[j].Addr())
-	})
-	return routes, nil
-}
-
 // prefsFromUpArgs returns the ipn.Prefs for the provided args.
 //
 // Note that the parameters upArgs and warnf are named intentionally
@@ -303,7 +226,7 @@ func calcAdvertiseRoutes(advertiseRoutes string, advertiseDefaultRoute bool) ([]
 // function exists for testing and should have no side effects or
 // outside interactions (e.g. no making Tailscale LocalAPI calls).
 func prefsFromUpArgs(upArgs upArgsT, warnf logger.Logf, st *ipnstate.Status, goos string) (*ipn.Prefs, error) {
-	routes, err := calcAdvertiseRoutes(upArgs.advertiseRoutes, upArgs.advertiseDefaultRoute)
+	routes, err := netutil.CalcAdvertiseRoutes(upArgs.advertiseRoutes, upArgs.advertiseDefaultRoute)
 	if err != nil {
 		return nil, err
 	}

cmd/tailscale/cli/web.go

@@ -28,6 +28,8 @@ import (
 	"tailscale.com/envknob"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/licenses"
+	"tailscale.com/net/netutil"
 	"tailscale.com/tailcfg"
 	"tailscale.com/util/cmpx"
 	"tailscale.com/util/groupmember"
@@ -385,7 +387,7 @@ func webHandler(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
-		routes, err := calcAdvertiseRoutes(postData.AdvertiseRoutes, postData.AdvertiseExitNode)
+		routes, err := netutil.CalcAdvertiseRoutes(postData.AdvertiseRoutes, postData.AdvertiseExitNode)
 		if err != nil {
 			w.WriteHeader(http.StatusInternalServerError)
 			json.NewEncoder(w).Encode(mi{"error": err.Error()})
@@ -437,7 +439,7 @@ func webHandler(w http.ResponseWriter, r *http.Request) {
 		Profile:      profile,
 		Status:       st.BackendState,
 		DeviceName:   deviceName,
-		LicensesURL:  licensesURL(),
+		LicensesURL:  licenses.LicensesURL(),
 		TUNMode:      st.TUN,
 		IsSynology:   distro.Get() == distro.Synology || envknob.Bool("TS_FAKE_SYNOLOGY"),
 		DSMVersion:   distro.DSMVersion(),

cmd/tailscale/depaware.txt

@@ -81,6 +81,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/hostinfo                                       from tailscale.com/net/interfaces+
         tailscale.com/ipn                                            from tailscale.com/cmd/tailscale/cli+
         tailscale.com/ipn/ipnstate                                   from tailscale.com/cmd/tailscale/cli+
+        tailscale.com/licenses                                       from tailscale.com/cmd/tailscale/cli
         tailscale.com/metrics                                        from tailscale.com/derp
         tailscale.com/net/dns/recursive                              from tailscale.com/net/dnsfallback
         tailscale.com/net/dnscache                                   from tailscale.com/derp/derphttp+

licenses/licenses.go

@@ -0,0 +1,21 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package licenses provides utilities for working with open source licenses.
+package licenses
+
+import "runtime"
+
+// LicensesURL returns the absolute URL containing open source license information for the current platform.
+func LicensesURL() string {
+	switch runtime.GOOS {
+	case "android":
+		return "https://tailscale.com/licenses/android"
+	case "darwin", "ios":
+		return "https://tailscale.com/licenses/apple"
+	case "windows":
+		return "https://tailscale.com/licenses/windows"
+	default:
+		return "https://tailscale.com/licenses/tailscale"
+	}
+}

net/netutil/routes.go

@@ -0,0 +1,93 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package netutil
+
+import (
+	"encoding/binary"
+	"fmt"
+	"net/netip"
+	"sort"
+	"strings"
+
+	"tailscale.com/net/tsaddr"
+)
+
+var (
+	ipv4default = netip.MustParsePrefix("0.0.0.0/0")
+	ipv6default = netip.MustParsePrefix("::/0")
+)
+
+func validateViaPrefix(ipp netip.Prefix) error {
+	if !tsaddr.IsViaPrefix(ipp) {
+		return fmt.Errorf("%v is not a 4-in-6 prefix", ipp)
+	}
+	if ipp.Bits() < (128 - 32) {
+		return fmt.Errorf("%v 4-in-6 prefix must be at least a /%v", ipp, 128-32)
+	}
+	a := ipp.Addr().As16()
+	// The first 64 bits of a are the via prefix.
+	// The next 32 bits are the "site ID".
+	// The last 32 bits are the IPv4.
+	// For now, we reserve the top 3 bytes of the site ID,
+	// and only allow users to use site IDs 0-255.
+	siteID := binary.BigEndian.Uint32(a[8:12])
+	if siteID > 0xFF {
+		return fmt.Errorf("route %v contains invalid site ID %08x; must be 0xff or less", ipp, siteID)
+	}
+	return nil
+}
+
+// CalcAdvertiseRoutes calculates the requested routes to be advertised by a node.
+// advertiseRoutes is the user-provided, comma-separated list of routes (IP addresses or CIDR prefixes) to advertise.
+// advertiseDefaultRoute indicates whether the node should act as an exit node and advertise default routes.
+func CalcAdvertiseRoutes(advertiseRoutes string, advertiseDefaultRoute bool) ([]netip.Prefix, error) {
+	routeMap := map[netip.Prefix]bool{}
+	if advertiseRoutes != "" {
+		var default4, default6 bool
+		advroutes := strings.Split(advertiseRoutes, ",")
+		for _, s := range advroutes {
+			ipp, err := netip.ParsePrefix(s)
+			if err != nil {
+				return nil, fmt.Errorf("%q is not a valid IP address or CIDR prefix", s)
+			}
+			if ipp != ipp.Masked() {
+				return nil, fmt.Errorf("%s has non-address bits set; expected %s", ipp, ipp.Masked())
+			}
+			if tsaddr.IsViaPrefix(ipp) {
+				if err := validateViaPrefix(ipp); err != nil {
+					return nil, err
+				}
+			}
+			if ipp == ipv4default {
+				default4 = true
+			} else if ipp == ipv6default {
+				default6 = true
+			}
+			routeMap[ipp] = true
+		}
+		if default4 && !default6 {
+			return nil, fmt.Errorf("%s advertised without its IPv6 counterpart, please also advertise %s", ipv4default, ipv6default)
+		} else if default6 && !default4 {
+			return nil, fmt.Errorf("%s advertised without its IPv4 counterpart, please also advertise %s", ipv6default, ipv4default)
+		}
+	}
+	if advertiseDefaultRoute {
+		routeMap[netip.MustParsePrefix("0.0.0.0/0")] = true
+		routeMap[netip.MustParsePrefix("::/0")] = true
+	}
+	if len(routeMap) == 0 {
+		return nil, nil
+	}
+	routes := make([]netip.Prefix, 0, len(routeMap))
+	for r := range routeMap {
+		routes = append(routes, r)
+	}
+	sort.Slice(routes, func(i, j int) bool {
+		if routes[i].Bits() != routes[j].Bits() {
+			return routes[i].Bits() < routes[j].Bits()
+		}
+		return routes[i].Addr().Less(routes[j].Addr())
+	})
+	return routes, nil
+}