netns_linux: remove special handling for tests.

With netns handling localhost now, existing tests no longer
need special handling. The tests set up their connections to
localhost, and the connections work without fuss.

Remove the special handling for tests.

Also remove the hostinfo.TestCase support, since this was
the only use of it. It can be added back later if really
needed, but it would be better to try to make tests work
without special cases.

Signed-off-by: Denton Gentry <dgentry@tailscale.com>

cmd/tailscale/depaware.txt

@@ -22,7 +22,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/derp                                           from tailscale.com/derp/derphttp
         tailscale.com/derp/derphttp                                  from tailscale.com/net/netcheck
         tailscale.com/disco                                          from tailscale.com/derp
-        tailscale.com/hostinfo                                       from tailscale.com/net/interfaces+
+        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/metrics                                        from tailscale.com/derp

hostinfo/hostinfo.go

@@ -9,7 +9,6 @@
 package hostinfo
 
 import (
-	"flag"
 	"io"
 	"os"
 	"runtime"
@@ -29,7 +28,6 @@ const (
 	Heroku          = EnvType("hr")
 	AzureAppService = EnvType("az")
 	AWSFargate      = EnvType("fg")
-	TestCase        = EnvType("tc")
 )
 
 var envType atomic.Value // of EnvType
@@ -44,11 +42,6 @@ func GetEnvType() EnvType {
 }
 
 func getEnvType() EnvType {
-	// inTestCase needs to go first. If running tests in a container, we want
-	// the environment to be TestCase not the type of container.
-	if inTestCase() {
-		return TestCase
-	}
 	if inKnative() {
 		return KNative
 	}
@@ -91,13 +84,6 @@ func InContainer() bool {
 	return ret
 }
 
-func inTestCase() bool {
-	if flag.CommandLine.Lookup("test.v") != nil {
-		return true
-	}
-	return false
-}
-
 func inKnative() bool {
 	// https://cloud.google.com/run/docs/reference/container-contract#env-vars
 	if os.Getenv("K_REVISION") != "" && os.Getenv("K_CONFIGURATION") != "" &&

net/netns/netns_linux.go

@@ -15,7 +15,6 @@ import (
 	"syscall"
 
 	"golang.org/x/sys/unix"
-	"tailscale.com/hostinfo"
 	"tailscale.com/net/interfaces"
 )
 
@@ -75,14 +74,6 @@ func useSocketMark() bool {
 // ignoreErrors returns true if we should ignore setsocketopt errors in
 // this instance.
 func ignoreErrors() bool {
-	// If we're in a test, ignore errors. Assume the test knows
-	// what it's doing and will do its own skips or permission
-	// checks if it's setting up a world that needs netns to work.
-	// But by default, assume that tests don't need netns and it's
-	// harmless to ignore the sockopts failing.
-	if hostinfo.GetEnvType() == hostinfo.TestCase {
-		return true
-	}
 	if os.Getuid() != 0 {
 		// only root can manipulate these socket flags
 		return true
@@ -95,9 +86,6 @@ func ignoreErrors() bool {
 // It's intentionally the same signature as net.Dialer.Control
 // and net.ListenConfig.Control.
 func control(network, address string, c syscall.RawConn) error {
-	if hostinfo.GetEnvType() == hostinfo.TestCase {
-		return nil
-	}
 	if isLocalhost(address) {
 		// Don't bind to an interface for localhost connections.
 		return nil