net: report timeouts more aggressively in Accept in the fake implementation

This ensures that if the listener has already timed out when Accept
is called, Accept always returns an error instead of instantaneously
accepting a connection that was already pending.

For #17948.

Change-Id: Iabef7121590df3dcc2fe428429d7c2bc2bcb6cd5
Reviewed-on: https://go-review.googlesource.com/c/go/+/557438
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Damien Neil <dneil@google.com>

diff --git a/src/net/net_fake.go b/src/net/net_fake.go
index 60b52b79fd0e78a5b86cf33cf3c42cb0c944a39a..b7ecb391448a2c75c16bf2f7d28fc0cde00a5dd5 100644 (file)
--- a/src/net/net_fake.go
+++ b/src/net/net_fake.go
@@ -325,14 +325,27 @@ func (ffd *fakeNetFD) accept(laddr Addr) (*netFD, error) {
                incoming []*netFD
                ok       bool
        )
+       expired := ffd.readDeadline.Load().expired
        select {
-       case <-ffd.readDeadline.Load().expired:
+       case <-expired:
                return nil, os.ErrDeadlineExceeded
        case incoming, ok = <-ffd.incoming:
                if !ok {
                        return nil, ErrClosed
                }
+               select {
+               case <-expired:
+                       ffd.incoming <- incoming
+                       return nil, os.ErrDeadlineExceeded
+               default:
+               }
        case incoming, ok = <-ffd.incomingFull:
+               select {
+               case <-expired:
+                       ffd.incomingFull <- incoming
+                       return nil, os.ErrDeadlineExceeded
+               default:
+               }
        }
 
        peer := incoming[0]