net/http: ignore connection closes once done with the connection

Once the connection is put back into the idle pool, the request should
not take any action if the connection is closed.

Fixes #41600

Change-Id: I5e4ddcdc03cd44f5197ecfbe324638604961de84
Reviewed-on: https://go-review.googlesource.com/c/go/+/257818
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Trust: Damien Neil <dneil@google.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index 9086507d57..f22b798035 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -6433,3 +6433,54 @@ func TestErrorWriteLoopRace(t *testing.T) {
 		testTransportRace(req)
 	}
 }
+
+// Issue 41600
+// Test that a new request which uses the connection of an active request
+// cannot cause it to be canceled as well.
+func TestCancelRequestWhenSharingConnection(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, req *Request) {
+		w.Header().Add("Content-Length", "0")
+	}))
+	defer ts.Close()
+
+	client := ts.Client()
+	transport := client.Transport.(*Transport)
+	transport.MaxIdleConns = 1
+	transport.MaxConnsPerHost = 1
+
+	var wg sync.WaitGroup
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for ctx.Err() == nil {
+				reqctx, reqcancel := context.WithCancel(ctx)
+				go reqcancel()
+				req, _ := NewRequestWithContext(reqctx, "GET", ts.URL, nil)
+				res, err := client.Do(req)
+				if err == nil {
+					res.Body.Close()
+				}
+			}
+		}()
+	}
+
+	for ctx.Err() == nil {
+		req, _ := NewRequest("GET", ts.URL, nil)
+		if res, err := client.Do(req); err != nil {
+			t.Errorf("unexpected: %p %v", req, err)
+			break
+		} else {
+			res.Body.Close()
+		}
+	}
+
+	cancel()
+	wg.Wait()
+}