net: ignore or skip known-flaky localhost Dial operations on macOS 10.12 builder

Fixes #22019
Fixes #32919

Change-Id: I60bf6c69b18c3e2d78b494e54adc958fe40134da
Reviewed-on: https://go-review.googlesource.com/c/go/+/202618
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/dial_test.go

@@ -639,9 +639,11 @@ func TestDialerLocalAddr(t *testing.T) {
 		}
 		c, err := d.Dial(tt.network, addr)
 		if err == nil && tt.error != nil || err != nil && tt.error == nil {
-			// On Darwin this occasionally times out.
-			// We don't know why. Issue #22019.
-			if runtime.GOOS == "darwin" && tt.error == nil && os.IsTimeout(err) {
+			// A suspected kernel bug in macOS 10.12 occasionally results in
+			// timeout errors when dialing address ::1. The errors have not
+			// been observed on newer versions of the OS, so we don't plan to work
+			// around them. See https://golang.org/issue/22019.
+			if tt.raddr == "::1" && os.Getenv("GO_BUILDER_NAME") == "darwin-amd64-10_12" && os.IsTimeout(err) {
 				t.Logf("ignoring timeout error on Darwin; see https://golang.org/issue/22019")
 			} else {
 				t.Errorf("%s %v->%s: got %v; want %v", tt.network, tt.laddr, tt.raddr, err, tt.error)

src/net/server_test.go

@@ -104,6 +104,14 @@ func TestTCPServer(t *testing.T) {
 				if perr := parseDialError(err); perr != nil {
 					t.Error(perr)
 				}
+				if tt.taddr == "::1" && os.Getenv("GO_BUILDER_NAME") == "darwin-amd64-10_12" && os.IsTimeout(err) {
+					// A suspected kernel bug in macOS 10.12 occasionally results in
+					// "i/o timeout" errors when dialing address ::1. The errors have not
+					// been observed on newer versions of the OS, so we don't plan to work
+					// around them. See https://golang.org/issue/32919.
+					t.Logf("ignoring error on known-flaky macOS 10.12 builder: %v", err)
+					continue
+				}
 				t.Fatal(err)
 			}
 			defer c.Close()

src/runtime/crash_test.go

@@ -435,6 +435,14 @@ func TestRecoverBeforePanicAfterGoexit(t *testing.T) {
 }
 
 func TestNetpollDeadlock(t *testing.T) {
+	if os.Getenv("GO_BUILDER_NAME") == "darwin-amd64-10_12" {
+		// A suspected kernel bug in macOS 10.12 occasionally results in
+		// an apparent deadlock when dialing localhost. The errors have not
+		// been observed on newer versions of the OS, so we don't plan to work
+		// around them. See https://golang.org/issue/22019.
+		testenv.SkipFlaky(t, 22019)
+	}
+
 	t.Parallel()
 	output := runTestProg(t, "testprognet", "NetpollDeadlock")
 	want := "done\n"