unix/stream: fix EVFILT_WRITE after we did shutdown(2)

When fixing bug 286692, the change eafe5967ac558, that fixed a case when
peer side does close(), also had regressed a case when our side does
shutdown(SHUT_WR).  These actually are two independent code paths, and the
eafe5967ac558 shouldn't have touched the second block.  The removal of
'kn->kn_flags |= EV_EOF' was incorrect and the statement on original
behavior in the commit message was also incorrect.

Do not add back so_error setting, since I failed to find a test case that
would return anything but 0 in kevent.fflags when run on stable/14.

This was found with help of https://github.com/tokio-rs/mio.  Add a test
case into our test suite for that.

Fixes:	eafe5967ac558de142d91660e18e9238289890e3

Reviewed by:		markj
Differential Revision:	https://reviews.freebsd.org/D52327

2 files changed, 25 insertions, 3 deletions

diff --git a/sys/kern/uipc_usrreq.c b/sys/kern/uipc_usrreq.c
index 19870e989437..6138e543fae7 100644
--- a/sys/kern/uipc_usrreq.c
+++ b/sys/kern/uipc_usrreq.c
@@ -1807,9 +1807,7 @@ uipc_filt_sowrite(struct knote *kn, long hint)
 	kn->kn_data = uipc_stream_sbspace(&so2->so_rcv);
 
 	if (so2->so_rcv.sb_state & SBS_CANTRCVMORE) {
-		/*
-		 * XXXGL: maybe kn->kn_flags |= EV_EOF ?
-		 */
+		kn->kn_flags |= EV_EOF;
 		return (1);
 	} else if (kn->kn_sfflags & NOTE_LOWAT)
 		return (kn->kn_data >= kn->kn_sdata);
diff --git a/tests/sys/kern/unix_stream.c b/tests/sys/kern/unix_stream.c
index bb811f78f620..49d621dc5b0a 100644
--- a/tests/sys/kern/unix_stream.c
+++ b/tests/sys/kern/unix_stream.c
@@ -467,6 +467,29 @@ ATF_TC_BODY(peershutdown_wakeup_kevent, tc)
 	});
 }
 
+ATF_TC_WITHOUT_HEAD(ourshutdown_kevent);
+ATF_TC_BODY(ourshutdown_kevent, tc)
+{
+	struct kevent kev;
+	int sv[2], kq;
+
+	do_socketpair(sv);
+	ATF_REQUIRE(kq = kqueue());
+
+	EV_SET(&kev, sv[1], EVFILT_WRITE, EV_ADD, 0, 0, NULL);
+	ATF_REQUIRE(kevent(kq, &kev, 1, NULL, 0, NULL) == 0);
+
+	ATF_REQUIRE(shutdown(sv[1], SHUT_WR) == 0);
+
+	ATF_REQUIRE(kevent(kq, NULL, 0, &kev, 1, NULL) == 1);
+	ATF_REQUIRE(kev.ident == (uintptr_t)sv[1] &&
+	    kev.filter == EVFILT_WRITE &&
+	    kev.flags == EV_EOF);
+
+	close(sv[0]);
+	close(sv[1]);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 	ATF_TP_ADD_TC(tp, getpeereid);
@@ -482,6 +505,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, peershutdown_wakeup_select);
 	ATF_TP_ADD_TC(tp, peershutdown_wakeup_poll);
 	ATF_TP_ADD_TC(tp, peershutdown_wakeup_kevent);
+	ATF_TP_ADD_TC(tp, ourshutdown_kevent);
 
 	return atf_no_error();
 }