all: use Go 1.20's errors.Join instead of our multierr package

Updates #7123

Change-Id: Ie9be6814831f661ad5636afcd51d063a0d7a907d
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

wgengine/netlog/netlog.go

@@ -10,6 +10,7 @@ package netlog
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -28,7 +29,6 @@ import (
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logid"
 	"tailscale.com/types/netlogtype"
-	"tailscale.com/util/multierr"
 	"tailscale.com/wgengine/router"
 )
 
@@ -272,5 +272,5 @@ func (nl *Logger) Shutdown(ctx context.Context) error {
 	nl.addrs = nil
 	nl.prefixes = nil
 
-	return multierr.New(err1, err2)
+	return errors.Join(err1, err2)
 }

wgengine/router/osrouter/ifconfig_windows.go

@@ -18,7 +18,6 @@ import (
 	"tailscale.com/net/netmon"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/net/tstun"
-	"tailscale.com/util/multierr"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/winnet"
 
@@ -831,5 +830,5 @@ func syncRoutes(ifc *winipcfg.IPAdapterAddresses, want []*routeData, dontDelete
 		}
 	}
 
-	return multierr.New(errs...)
+	return errors.Join(errs...)
 }

wgengine/router/osrouter/router_linux.go

@@ -32,7 +32,6 @@ import (
 	"tailscale.com/types/preftype"
 	"tailscale.com/util/eventbus"
 	"tailscale.com/util/linuxfw"
-	"tailscale.com/util/multierr"
 	"tailscale.com/version/distro"
 	"tailscale.com/wgengine/router"
 )
@@ -488,7 +487,7 @@ func (r *linuxRouter) Set(cfg *router.Config) error {
 		r.enableIPForwarding()
 	}
 
-	return multierr.New(errs...)
+	return errors.Join(errs...)
 }
 
 var dockerStatefulFilteringWarnable = health.Register(&health.Warnable{

wgengine/wgcfg/device.go

@@ -4,6 +4,7 @@
 package wgcfg
 
 import (
+	"errors"
 	"io"
 	"sort"
 
@@ -11,7 +12,6 @@ import (
 	"github.com/tailscale/wireguard-go/device"
 	"github.com/tailscale/wireguard-go/tun"
 	"tailscale.com/types/logger"
-	"tailscale.com/util/multierr"
 )
 
 // NewDevice returns a wireguard-go Device configured for Tailscale use.
@@ -31,7 +31,7 @@ func DeviceConfig(d *device.Device) (*Config, error) {
 	cfg, fromErr := FromUAPI(r)
 	r.Close()
 	getErr := <-errc
-	err := multierr.New(getErr, fromErr)
+	err := errors.Join(getErr, fromErr)
 	if err != nil {
 		return nil, err
 	}
@@ -64,5 +64,5 @@ func ReconfigDevice(d *device.Device, cfg *Config, logf logger.Logf) (err error)
 	toErr := cfg.ToUAPI(logf, w, prev)
 	w.Close()
 	setErr := <-errc
-	return multierr.New(setErr, toErr)
+	return errors.Join(setErr, toErr)
 }