syscall: remove use of IN_KUBERNETES in test, add a TODO to improve further

Updates #34956

Change-Id: I35c39f3afda7226eeae0fd6936f7ee0d5d6c025b
Reviewed-on: https://go-review.googlesource.com/c/go/+/201737
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/syscall/exec_linux_test.go

@@ -34,6 +34,14 @@ func isLXC() bool {
 }
 
 func skipInContainer(t *testing.T) {
+	// TODO: the callers of this func are using this func to skip
+	// tests when running as some sort of "fake root" that's uid 0
+	// but lacks certain Linux capabilities. Most of the Go builds
+	// run in privileged containers, though, where root is much
+	// closer (if not identical) to the real root. We should test
+	// for what we need exactly (which capabilities are active?),
+	// instead of just assuming "docker == bad". Then we'd get more test
+	// coverage on a bunch of builders too.
 	if isDocker() {
 		t.Skip("skip this test in Docker container")
 	}
@@ -341,14 +349,6 @@ func TestUnshareMountNameSpace(t *testing.T) {
 		t.Skip("kernel prohibits unshare in unprivileged process, unless using user namespace")
 	}
 
-	// When running under the Go continuous build, skip tests for
-	// now when under Kubernetes. (where things are root but not quite)
-	// Both of these are our own environment variables.
-	// See Issue 12815.
-	if os.Getenv("GO_BUILDER_NAME") != "" && os.Getenv("IN_KUBERNETES") == "1" {
-		t.Skip("skipping test on Kubernetes-based builders; see Issue 12815")
-	}
-
 	d, err := ioutil.TempDir("", "unshare")
 	if err != nil {
 		t.Fatalf("tempdir: %v", err)
@@ -391,14 +391,6 @@ func TestUnshareMountNameSpaceChroot(t *testing.T) {
 		t.Skip("kernel prohibits unshare in unprivileged process, unless using user namespace")
 	}
 
-	// When running under the Go continuous build, skip tests for
-	// now when under Kubernetes. (where things are root but not quite)
-	// Both of these are our own environment variables.
-	// See Issue 12815.
-	if os.Getenv("GO_BUILDER_NAME") != "" && os.Getenv("IN_KUBERNETES") == "1" {
-		t.Skip("skipping test on Kubernetes-based builders; see Issue 12815")
-	}
-
 	d, err := ioutil.TempDir("", "unshare")
 	if err != nil {
 		t.Fatalf("tempdir: %v", err)
@@ -586,14 +578,6 @@ func testAmbientCaps(t *testing.T, userns bool) {
 	skipInContainer(t)
 	mustSupportAmbientCaps(t)
 
-	// When running under the Go continuous build, skip tests for
-	// now when under Kubernetes. (where things are root but not quite)
-	// Both of these are our own environment variables.
-	// See Issue 12815.
-	if os.Getenv("GO_BUILDER_NAME") != "" && os.Getenv("IN_KUBERNETES") == "1" {
-		t.Skip("skipping test on Kubernetes-based builders; see Issue 12815")
-	}
-
 	skipUnprivilegedUserClone(t)
 
 	// skip on android, due to lack of lookup support