all: cleanup unused code, part 1 (#10661)

Run `staticcheck` with `U1000` to find unused code. This cleans up about
a half of it. I'll do the other half separately to keep PRs manageable.

Updates #cleanup

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

tstest/archtest/archtest_test.go

@@ -14,7 +14,7 @@ import (
 func TestAlignedAtomicInt64(t *testing.T) {
 	type T struct {
 		A atomicbitops.Int64
-		x int32
+		_ int32
 		B atomicbitops.Int64
 	}
 

tstest/integration/vms/derive_bindhost_test.go

@@ -4,7 +4,6 @@
 package vms
 
 import (
-	"io"
 	"net/netip"
 	"runtime"
 	"testing"
@@ -43,9 +42,3 @@ func TestDeriveBindhost(t *testing.T) {
 	}
 	t.Log(deriveBindhost(t))
 }
-
-type nopWriteCloser struct {
-	io.Writer
-}
-
-func (nwc nopWriteCloser) Close() error { return nil }

tstest/integration/vms/vms_steps_test.go

@@ -19,8 +19,6 @@ import (
 	"golang.org/x/crypto/ssh"
 )
 
-const timeout = 15 * time.Second
-
 func retry(t *testing.T, fn func() error) {
 	t.Helper()
 	const tries = 3

tstest/natlab/natlab.go

@@ -442,16 +442,6 @@ func (m *Machine) forwardPacket(p *Packet, iif *Interface) {
 	oif.net.write(p)
 }
 
-func unspecOf(ip netip.Addr) netip.Addr {
-	if ip.Is4() {
-		return v4unspec
-	}
-	if ip.Is6() {
-		return v6unspec
-	}
-	panic(fmt.Sprintf("bogus IP %#v", ip))
-}
-
 // Attach adds an interface to a machine.
 //
 // The first interface added to a Machine becomes that machine's
@@ -572,19 +562,6 @@ func (m *Machine) interfaceForIP(ip netip.Addr) (*Interface, error) {
 	return nil, fmt.Errorf("no route found to %v", ip)
 }
 
-func (m *Machine) hasv6() bool {
-	m.mu.Lock()
-	defer m.mu.Unlock()
-	for _, f := range m.interfaces {
-		for _, ip := range f.ips {
-			if ip.Is6() {
-				return true
-			}
-		}
-	}
-	return false
-}
-
 func (m *Machine) pickEphemPort() (port uint16, err error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()