af_unix: Add test for consecutive consumed OOB.

Let's add a test case where consecutive concumed OOB skbs stay
at the head of the queue.

Without the previous patch, ioctl(SIOCATMARK) assertion fails.

Before:

  #  RUN           msg_oob.no_peek.ex_oob_ex_oob_oob ...
  # msg_oob.c:305:ex_oob_ex_oob_oob:Expected answ[0] (0) == oob_head (1)
  # ex_oob_ex_oob_oob: Test terminated by assertion
  #          FAIL  msg_oob.no_peek.ex_oob_ex_oob_oob
  not ok 12 msg_oob.no_peek.ex_oob_ex_oob_oob

After:

  #  RUN           msg_oob.no_peek.ex_oob_ex_oob_oob ...
  #            OK  msg_oob.no_peek.ex_oob_ex_oob_oob
  ok 12 msg_oob.no_peek.ex_oob_ex_oob_oob

Signed-off-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: q2ven

tools/testing/selftests/net/af_unix/msg_oob.c

@@ -548,6 +548,29 @@ TEST_F(msg_oob, ex_oob_oob)
 	siocatmarkpair(false);
 }
 
+TEST_F(msg_oob, ex_oob_ex_oob_oob)
+{
+	sendpair("x", 1, MSG_OOB);
+	epollpair(true);
+	siocatmarkpair(true);
+
+	recvpair("x", 1, 1, MSG_OOB);
+	epollpair(false);
+	siocatmarkpair(true);
+
+	sendpair("y", 1, MSG_OOB);
+	epollpair(true);
+	siocatmarkpair(true);
+
+	recvpair("y", 1, 1, MSG_OOB);
+	epollpair(false);
+	siocatmarkpair(true);
+
+	sendpair("z", 1, MSG_OOB);
+	epollpair(true);
+	siocatmarkpair(true);
+}
+
 TEST_F(msg_oob, ex_oob_ahead_break)
 {
 	sendpair("hello", 5, MSG_OOB);