http2: make Transport.IdleConnTimeout consider wall (not monotonic) time

This is the http2 version of CL 204797.

Updates golang/go#29308 (fixes once bundled into std)

Change-Id: I7cd97d38c941e9a8a62808e23b6533c72760f003
Reviewed-on: https://go-review.googlesource.com/c/net/+/208798
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

http2/transport.go

@@ -227,6 +227,7 @@ type ClientConn struct {
 	br              *bufio.Reader
 	fr              *Framer
 	lastActive      time.Time
+	lastIdle        time.Time // time last idle
 	// Settings from peer: (also guarded by mu)
 	maxFrameSize          uint32
 	maxConcurrentStreams  uint32
@@ -736,7 +737,8 @@ func (cc *ClientConn) idleStateLocked() (st clientConnIdleState) {
 	}
 
 	st.canTakeNewRequest = cc.goAway == nil && !cc.closed && !cc.closing && maxConcurrentOkay &&
-		int64(cc.nextStreamID)+2*int64(cc.pendingRequests) < math.MaxInt32
+		int64(cc.nextStreamID)+2*int64(cc.pendingRequests) < math.MaxInt32 &&
+		!cc.tooIdleLocked()
 	st.freshConn = cc.nextStreamID == 1 && st.canTakeNewRequest
 	return
 }
@@ -746,6 +748,16 @@ func (cc *ClientConn) canTakeNewRequestLocked() bool {
 	return st.canTakeNewRequest
 }
 
+// tooIdleLocked reports whether this connection has been been sitting idle
+// for too much wall time.
+func (cc *ClientConn) tooIdleLocked() bool {
+	// The Round(0) strips the monontonic clock reading so the
+	// times are compared based on their wall time. We don't want
+	// to reuse a connection that's been sitting idle during
+	// VM/laptop suspend if monotonic time was also frozen.
+	return cc.idleTimeout != 0 && !cc.lastIdle.IsZero() && time.Since(cc.lastIdle.Round(0)) > cc.idleTimeout
+}
+
 // onIdleTimeout is called from a time.AfterFunc goroutine. It will
 // only be called when we're idle, but because we're coming from a new
 // goroutine, there could be a new request coming in at the same time,
@@ -1150,6 +1162,7 @@ func (cc *ClientConn) awaitOpenSlotForRequest(req *http.Request) error {
 			}
 			return errClientConnUnusable
 		}
+		cc.lastIdle = time.Time{}
 		if int64(len(cc.streams))+1 <= int64(cc.maxConcurrentStreams) {
 			if waitingForConn != nil {
 				close(waitingForConn)
@@ -1638,6 +1651,7 @@ func (cc *ClientConn) streamByID(id uint32, andRemove bool) *clientStream {
 		delete(cc.streams, id)
 		if len(cc.streams) == 0 && cc.idleTimer != nil {
 			cc.idleTimer.Reset(cc.idleTimeout)
+			cc.lastIdle = time.Now()
 		}
 		close(cs.done)
 		// Wake up checkResetOrDone via clientStream.awaitFlowControl and

http2/transport_test.go

@@ -4483,3 +4483,41 @@ func testTransportBodyLargerThanSpecifiedContentLength(t *testing.T, body *chunk
 		t.Fatalf("expected %v, got %v", errReqBodyTooLong, err)
 	}
 }
+
+func TestClientConnTooIdle(t *testing.T) {
+	tests := []struct {
+		cc   func() *ClientConn
+		want bool
+	}{
+		{
+			func() *ClientConn {
+				return &ClientConn{idleTimeout: 5 * time.Second, lastIdle: time.Now().Add(-10 * time.Second)}
+			},
+			true,
+		},
+		{
+			func() *ClientConn {
+				return &ClientConn{idleTimeout: 5 * time.Second, lastIdle: time.Time{}}
+			},
+			false,
+		},
+		{
+			func() *ClientConn {
+				return &ClientConn{idleTimeout: 60 * time.Second, lastIdle: time.Now().Add(-10 * time.Second)}
+			},
+			false,
+		},
+		{
+			func() *ClientConn {
+				return &ClientConn{idleTimeout: 0, lastIdle: time.Now().Add(-10 * time.Second)}
+			},
+			false,
+		},
+	}
+	for i, tt := range tests {
+		got := tt.cc().tooIdleLocked()
+		if got != tt.want {
+			t.Errorf("%d. got %v; want %v", i, got, tt.want)
+		}
+	}
+}