tests: fix unix_passfd_dgram:rights_creds_payload after be1f485d7d6b

The test was failing due to the assert on lack of MSG_TRUNC flag in the
 output flags of recvmsg().
The code passed MSG_TRUNC, along with sufficient-size buffer to hold the
 message to-be-received to the recvmsg(), and expected MSG_TRUNC to be
 returned as well.

This is not exactly correct as a) MSG_TRUNC was not even a supported
 recvmsg() flag before be1f485d7d6b and b) it violates POSIX, as
 POSIX states it should be set only "If a message is too long to fit in
 the supplied buffers,".
The test was working before as the kernel copied input flags to the
 output flags. be1f485d7d6b changed that behaviour to clear MSG_TRUNC
 if it was present on the input.

Fix the test by checking POSIX-defined behaviour.

Discussed with:	glebius

1 files changed, 3 insertions, 5 deletions

diff --git a/tests/sys/kern/unix_passfd_test.c b/tests/sys/kern/unix_passfd_test.c
index dc017db4f1ce..49f4540bb9d0 100644
--- a/tests/sys/kern/unix_passfd_test.c
+++ b/tests/sys/kern/unix_passfd_test.c
@@ -255,9 +255,8 @@ recvfd_payload(int sockfd, int *recv_fd, void *buf, size_t buflen,
 	    "recvmsg: did not receive single-fd message");
 	ATF_REQUIRE_MSG(!localcreds(sockfd) || foundcreds,
 	    "recvmsg: expected credentials were not received");
-	if (recvmsg_flags & MSG_TRUNC)
-		ATF_REQUIRE_MSG(msghdr.msg_flags & MSG_TRUNC,
-		    "recvmsg: expected MSG_TRUNC missing");
+	ATF_REQUIRE_MSG((msghdr.msg_flags & MSG_TRUNC) == 0,
+	    "recvmsg: MSG_TRUNC is set while buffer is sufficient");
 }
 
 static void
@@ -584,8 +583,7 @@ ATF_TC_BODY(rights_creds_payload, tc)
 	ATF_REQUIRE_MSG((size_t)len == sendspace,
 	    "sendmsg: %zu bytes sent", len);
 	recvfd_payload(fd[1], &getfd, buf, len,
-	    CMSG_SPACE(SOCKCREDSIZE(CMGROUP_MAX)) + CMSG_SPACE(sizeof(int)),
-	    MSG_TRUNC);
+	    CMSG_SPACE(SOCKCREDSIZE(CMGROUP_MAX)) + CMSG_SPACE(sizeof(int)), 0);
 #endif
 
 	close(putfd);