nntp: prevent event_read from firing twice in a row

When a client starts pipelining requests to us which trigger
long responses, we need to keep socket readiness checks disabled
and only enable them when our socket rbuf is drained.

Failure to do this caused aborted clients with
"BUG: nested long response" when Danga::Socket calls event_read
for read-readiness after our "next_tick" sub fires in the
same event loop iteration.

Reported-by: Jonathan Corbet <corbet@lwn.net>

cf. https://public-inbox.org/meta/20181013124658.23b9f9d2@lwn.net/

1 files changed, 21 insertions, 0 deletions

diff --git a/t/nntpd.t b/t/nntpd.t
index 9c1d0762..ffed4376 100644
--- a/t/nntpd.t
+++ b/t/nntpd.t
@@ -252,6 +252,27 @@ EOF
                 ok($date <= $t1, 'valid date before stop');
         }
 
+        # pipelined requests:
+        {
+                my $nreq = 90;
+                syswrite($s, "GROUP $group\r\n");
+                my $res = <$s>;
+                my $rdr = fork;
+                if ($rdr == 0) {
+                        use POSIX qw(_exit);
+                        for (1..$nreq) {
+                                <$s> =~ /\A224 / or _exit(1);
+                                <$s> =~ /\A1/ or _exit(2);
+                                <$s> eq ".\r\n" or _exit(3);
+                        }
+                        _exit(0);
+                }
+                for (1..$nreq) {
+                        syswrite($s, "XOVER 1\r\n");
+                }
+                is($rdr, waitpid($rdr, 0), 'reader done');
+                is($? >> 8, 0, 'no errors');
+        }
         {
                 setsockopt($s, IPPROTO_TCP, TCP_NODELAY, 1);
                 syswrite($s, 'HDR List-id 1-');