net: unblock plan9 TCP Read calls after socket close

Fixes #7782
Fixes #9554
Updates #7237 (original metabug, before we switched to specific bugs)
Updates #11932 (plan9 still doesn't have net I/O deadline support)

Change-Id: I96f311b88b1501d884ebc008fd31ad2cf1e16d75
Reviewed-on: https://go-review.googlesource.com/15941Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David du Colombier <0intro@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/dial_test.go

@@ -509,6 +509,9 @@ func TestDialerFallbackDelay(t *testing.T) {
 }
 
 func TestDialSerialAsyncSpuriousConnection(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping on plan9; no deadline support, golang.org/issue/11932")
+	}
 	ln, err := newLocalListener("tcp")
 	if err != nil {
 		t.Fatal(err)

src/net/fd_plan9.go

@@ -171,6 +171,14 @@ func (fd *netFD) Close() error {
 	if !fd.ok() {
 		return syscall.EINVAL
 	}
+	if fd.net == "tcp" {
+		// The following line is required to unblock Reads.
+		// For some reason, WriteString returns an error:
+		// "write /net/tcp/39/listen: inappropriate use of fd"
+		// But without it, Reads on dead conns hang forever.
+		// See Issue 9554.
+		fd.ctl.WriteString("hangup")
+	}
 	err := fd.ctl.Close()
 	if fd.data != nil {
 		if err1 := fd.data.Close(); err1 != nil && err == nil {

src/net/http/httputil/reverseproxy_test.go

@@ -14,7 +14,6 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"reflect"
-	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -226,9 +225,6 @@ func TestReverseProxyFlushInterval(t *testing.T) {
 }
 
 func TestReverseProxyCancelation(t *testing.T) {
-	if runtime.GOOS == "plan9" {
-		t.Skip("skipping test; see https://golang.org/issue/9554")
-	}
 	const backendResponse = "I am the backend"
 
 	reqInFlight := make(chan struct{})

src/net/http/serve_test.go

@@ -26,6 +26,7 @@ import (
 	"os/exec"
 	"reflect"
 	"runtime"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -2980,6 +2981,7 @@ func TestServerConnState(t *testing.T) {
 		if _, err := io.WriteString(c, "BOGUS REQUEST\r\n\r\n"); err != nil {
 			t.Fatal(err)
 		}
+		c.Read(make([]byte, 1)) // block until server hangs up on us
 		c.Close()
 	}
 
@@ -3013,9 +3015,14 @@ func TestServerConnState(t *testing.T) {
 	}
 	logString := func(m map[int][]ConnState) string {
 		var b bytes.Buffer
-		for id, l := range m {
+		var keys []int
+		for id := range m {
+			keys = append(keys, id)
+		}
+		sort.Ints(keys)
+		for _, id := range keys {
 			fmt.Fprintf(&b, "Conn %d: ", id)
-			for _, s := range l {
+			for _, s := range m[id] {
 				fmt.Fprintf(&b, "%s ", s)
 			}
 			b.WriteString("\n")

src/net/http/transport_test.go

@@ -874,9 +874,6 @@ func TestTransportGzipShort(t *testing.T) {
 
 // tests that persistent goroutine connections shut down when no longer desired.
 func TestTransportPersistConnLeak(t *testing.T) {
-	if runtime.GOOS == "plan9" {
-		t.Skip("skipping test; see https://golang.org/issue/7237")
-	}
 	defer afterTest(t)
 	gotReqCh := make(chan bool)
 	unblockCh := make(chan bool)
@@ -943,9 +940,6 @@ func TestTransportPersistConnLeak(t *testing.T) {
 // golang.org/issue/4531: Transport leaks goroutines when
 // request.ContentLength is explicitly short
 func TestTransportPersistConnLeakShortBody(t *testing.T) {
-	if runtime.GOOS == "plan9" {
-		t.Skip("skipping test; see https://golang.org/issue/7237")
-	}
 	defer afterTest(t)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 	}))
@@ -2291,15 +2285,28 @@ type errorReader struct {
 
 func (e errorReader) Read(p []byte) (int, error) { return 0, e.err }
 
+type plan9SleepReader struct{}
+
+func (plan9SleepReader) Read(p []byte) (int, error) {
+	if runtime.GOOS == "plan9" {
+		// After the fix to unblock TCP Reads in
+		// https://golang.org/cl/15941, this sleep is required
+		// on plan9 to make sure TCP Writes before an
+		// immediate TCP close go out on the wire.  On Plan 9,
+		// it seems that a hangup of a TCP connection with
+		// queued data doesn't send the queued data first.
+		// https://golang.org/issue/9554
+		time.Sleep(50 * time.Millisecond)
+	}
+	return 0, io.EOF
+}
+
 type closerFunc func() error
 
 func (f closerFunc) Close() error { return f() }
 
 // Issue 6981
 func TestTransportClosesBodyOnError(t *testing.T) {
-	if runtime.GOOS == "plan9" {
-		t.Skip("skipping test; see https://golang.org/issue/7782")
-	}
 	defer afterTest(t)
 	readBody := make(chan error, 1)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
@@ -2313,7 +2320,7 @@ func TestTransportClosesBodyOnError(t *testing.T) {
 		io.Reader
 		io.Closer
 	}{
-		io.MultiReader(io.LimitReader(neverEnding('x'), 1<<20), errorReader{fakeErr}),
+		io.MultiReader(io.LimitReader(neverEnding('x'), 1<<20), plan9SleepReader{}, errorReader{fakeErr}),
 		closerFunc(func() error {
 			select {
 			case didClose <- true: