ZTS: avoid piping to special devices

As described in #11445, the kernel interface kernel_{read,write} no
longer act on special devices.  In the ZTS, zfs send and receive are
tested by piping to these devices, leading to spurious failures (for
positive tests) and may mask errors (for negative tests).

Until a more permanent mechanism to address this deficiency is
developed, clean up the output from the ZTS by avoiding directly piping
to or from /dev/null and /dev/zero.

For /dev/zero input, simply use a pipe: `cat </dev/zero |` .

However, for /dev/null output, the shell semantics for pipe failures
means that zfs send error codes will be masked by the successful
`| cat >/dev/null` command execution.  In that case, use a temporary
file under $TEST_BASE_DIR for output in favor.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Attila Fülöp <attila@fueloep.org>
Signed-off-by: Antonio Russo <aerusso@aerusso.net>
Closes #11478

contrib/pyzfs/libzfs_core/test/test_libzfs_core.py

@@ -154,8 +154,8 @@ def os_open(name, mode):
 
 @contextlib.contextmanager
 def dev_null():
-    with os_open('/dev/null', os.O_WRONLY) as fd:
+    with tempfile.TemporaryFile(suffix='.zstream') as fd:
-        yield fd
+        yield fd.fileno()
 
 
 @contextlib.contextmanager

tests/zfs-tests/tests/functional/cli_root/zfs_receive/zfs_receive_005_neg.ksh

@@ -82,8 +82,8 @@ log_must zfs snapshot $init_snap
 log_must eval "zfs send $init_snap > $full_bkup"
 
 log_note "'zfs receive' fails with invalid send streams."
-log_mustnot eval "zfs receive $rst_init_snap < /dev/zero"
+log_mustnot eval "cat </dev/zero | zfs receive $rst_init_snap"
-log_mustnot eval "zfs receive -d $rst_root </dev/zero"
+log_mustnot eval "cat </dev/zero | zfs receive -d $rst_root"
 
 log_must eval "zfs receive $rst_init_snap < $full_bkup"
 

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send-b.ksh

@@ -58,13 +58,13 @@ log_must zfs set "org.openzfs:snapprop=val" "$SENDFS@s1"
 # 2. Verify command line options interact with '-b' correctly
 typeset opts=("" "p" "Rp" "cew" "nv" "D" "DLPRcenpvw")
 for opt in ${opts[@]}; do
-	log_must eval "zfs send -b$opt $SENDFS@s1 > /dev/null"
+	log_must eval "zfs send -b$opt $SENDFS@s1 >$TEST_BASE_DIR/devnull"
-	log_must eval "zfs send -b$opt -i $SENDFS@s1 $SENDFS@s2 > /dev/null"
+	log_must eval "zfs send -b$opt -i $SENDFS@s1 $SENDFS@s2 >$TEST_BASE_DIR/devnull"
-	log_must eval "zfs send -b$opt -I $SENDFS@s1 $SENDFS@s2 > /dev/null"
+	log_must eval "zfs send -b$opt -I $SENDFS@s1 $SENDFS@s2 >$TEST_BASE_DIR/devnull"
 done
 for opt in ${opts[@]}; do
-	log_mustnot eval "zfs send -b$opt $SENDFS > /dev/null"
+	log_mustnot eval "zfs send -b$opt $SENDFS >$TEST_BASE_DIR/devnull"
-	log_mustnot eval "zfs send -b$opt $SENDFS#bm > /dev/null"
+	log_mustnot eval "zfs send -b$opt $SENDFS#bm >$TEST_BASE_DIR/devnull"
 done
 
 # Do 3..6 in a loop to verify various combination of "zfs send" options

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_003_pos.ksh

@@ -61,7 +61,7 @@ log_must zfs snapshot $snap2
 
 typeset -i i=0
 while (( i < ${#args[*]} )); do
-	log_must eval "zfs send -i ${args[i]} > /dev/null"
+	log_must eval "zfs send -i ${args[i]} >$TEST_BASE_DIR/devnull"
 
 	(( i += 1 ))
 done

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_004_neg.ksh

@@ -96,7 +96,7 @@ log_must zfs snapshot $snap3
 typeset -i i=0
 while (( i < ${#badargs[*]} ))
 do
-	log_mustnot eval "zfs send ${badargs[i]} >/dev/null"
+	log_mustnot eval "zfs send ${badargs[i]} >$TEST_BASE_DIR/devnull"
 
 	(( i = i + 1 ))
 done

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_005_pos.ksh

@@ -61,6 +61,6 @@ log_must zfs snapshot -r $TESTPOOL@snap
 log_must zpool export $TESTPOOL
 log_must zpool import -o readonly=on $TESTPOOL
 
-log_must eval "zfs send -R $TESTPOOL@snap >/dev/null"
+log_must eval "zfs send -R $TESTPOOL@snap >$TEST_BASE_DIR/devnull"
 
 log_pass "'zfs send -R' can send from read-only pools"

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_encrypted.ksh

@@ -62,15 +62,15 @@ log_must eval "echo $passphrase1 | zfs create -o encryption=on" \
 
 log_must zfs snapshot -r $snap
 
-log_must eval "zfs send $snap > /dev/null"
+log_must eval "zfs send $snap >$TEST_BASE_DIR/devnull"
-log_mustnot eval "zfs send -p $snap > /dev/null"
+log_mustnot eval "zfs send -p $snap >$TEST_BASE_DIR/devnull"
-log_mustnot eval "zfs send -R $snap > /dev/null"
+log_mustnot eval "zfs send -R $snap >$TEST_BASE_DIR/devnull"
 
 log_must zfs unmount $TESTPOOL/$TESTFS1
 log_must zfs unload-key $TESTPOOL/$TESTFS1
 
-log_mustnot eval "zfs send $snap > /dev/null"
+log_mustnot eval "zfs send $snap >$TEST_BASE_DIR/devnull"
-log_must eval "zfs send $TESTPOOL/$TESTFS1/child@snap > /dev/null"
+log_must eval "zfs send $TESTPOOL/$TESTFS1/child@snap >$TEST_BASE_DIR/devnull"
 
 log_pass "ZFS performs unencrypted sends of encrypted datasets, unless the" \
 	"'-p' or '-R' options are specified"

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_encrypted_unloaded.ksh

@@ -53,7 +53,7 @@ log_must eval "echo $passphrase | zfs create -o encryption=on" \
 log_must zfs snapshot $snap
 log_must zfs unmount $TESTPOOL/$TESTFS1
 log_must zfs unload-key $TESTPOOL/$TESTFS1
-log_mustnot eval "zfs send $snap > /dev/null"
+log_mustnot eval "zfs send $snap >$TEST_BASE_DIR/devnull"
 
 log_pass "ZFS does not perform unencrypted sends from encrypted datasets" \
 	"with unloaded keys."

tests/zfs-tests/tests/functional/cli_root/zfs_send/zfs_send_raw.ksh

@@ -59,21 +59,21 @@ log_must eval "echo $passphrase | zfs create -o encryption=on" \
 log_must zfs snapshot $snap
 log_must zfs snapshot $snap1
 
-log_must eval "zfs send -w $snap > /dev/null"
+log_must eval "zfs send -w $snap >$TEST_BASE_DIR/devnull"
-log_must eval "zfs send -w $snap1 > /dev/null"
+log_must eval "zfs send -w $snap1 >$TEST_BASE_DIR/devnull"
 
 log_note "Verify ZFS can perform raw sends with properties"
-log_must eval "zfs send -wp $snap > /dev/null"
+log_must eval "zfs send -wp $snap >$TEST_BASE_DIR/devnull"
-log_must eval "zfs send -wp $snap1 > /dev/null"
+log_must eval "zfs send -wp $snap1 >$TEST_BASE_DIR/devnull"
 
 log_note "Verify ZFS can perform raw replication sends"
-log_must eval "zfs send -wR $snap > /dev/null"
+log_must eval "zfs send -wR $snap >$TEST_BASE_DIR/devnull"
-log_must eval "zfs send -wR $snap1 > /dev/null"
+log_must eval "zfs send -wR $snap1 >$TEST_BASE_DIR/devnull"
 
 log_note "Verify ZFS can perform a raw send of an encrypted datasets with" \
 	"its key unloaded"
 log_must zfs unmount $TESTPOOL/$TESTFS1
 log_must zfs unload-key $TESTPOOL/$TESTFS1
-log_must eval "zfs send -w $snap1 > /dev/null"
+log_must eval "zfs send -w $snap1 >$TEST_BASE_DIR/devnull"
 
 log_pass "ZFS performs raw sends of datasets"

tests/zfs-tests/tests/functional/redacted_send/redacted_negative.ksh

@@ -45,11 +45,11 @@ log_must zfs snapshot $clone2@snap
 
 # Incompatible flags
 log_must zfs redact $sendfs@snap2 book $clone1@snap
-log_mustnot eval "zfs send -R --redact book $sendfs@snap2 >/dev/null"
+log_mustnot eval "zfs send -R --redact book $sendfs@snap2 >$TEST_BASE_DIR/devnull"
 
 typeset arg
 for arg in "$sendfs" "$clone1#book"; do
-	log_mustnot eval "zfs send --redact book $arg >/dev/null"
+	log_mustnot eval "zfs send --redact book $arg >$TEST_BASE_DIR/devnull"
 done
 
 # Bad redaction list arguments
@@ -58,7 +58,7 @@ log_mustnot zfs redact $sendfs@snap1 book
 log_mustnot zfs redact $sendfs#book1 book4 $clone1
 log_mustnot zfs redact $sendfs@snap1 book snap2 snap3
 log_mustnot zfs redact $sendfs@snap1 book @snap2 @snap3
-log_mustnot eval "zfs send --redact $sendfs#book $sendfs@snap >/dev/null"
+log_mustnot eval "zfs send --redact $sendfs#book $sendfs@snap >$TEST_BASE_DIR/devnull"
 
 # Redaction snapshots not a descendant of tosnap
 log_mustnot zfs redact $sendfs@snap2 book $sendfs@snap2
@@ -66,7 +66,7 @@ log_must zfs redact $sendfs@snap2 book2 $clone1@snap $clone2@snap
 log_must eval "zfs send --redact book2 $sendfs@snap2 >$stream"
 log_must zfs redact $sendfs@snap2 book3 $clone1@snap $clone2@snap
 log_must eval "zfs send -i $sendfs@snap1 --redact book3 $sendfs@snap2 \
-    >/dev/null"
+    >$TEST_BASE_DIR/devnull"
 log_mustnot zfs redact $sendfs@snap3 $sendfs@snap3 $clone1@snap
 
 # Full redacted sends of redacted datasets are not allowed.

tests/zfs-tests/tests/functional/redacted_send/redacted_resume.ksh

@@ -81,7 +81,7 @@ log_must eval "zfs send --redact book1 $sendfs@snap >$stream"
 dd if=$stream bs=64k count=1 | log_mustnot zfs receive -s $recvfs
 [[ "-" = $(get_prop receive_resume_token $recvfs) ]] && \
     log_fail "Receive token not found."
-log_mustnot eval "zfs send --saved --redact book1 $recvfs > /dev/null"
+log_mustnot eval "zfs send --saved --redact book1 $recvfs >$TEST_BASE_DIR/devnull"
 log_must zfs recv -A $recvfs
 log_must datasetnonexists $recvfs
 

tests/zfs-tests/tests/functional/removal/removal_with_send.ksh

@@ -28,7 +28,7 @@ function callback
 {
 	create_snapshot $TESTPOOL/$TESTFS $TESTSNAP
 	log_must ksh -c \
-	    "zfs send $TESTPOOL/$TESTFS@$TESTSNAP >/dev/null"
+	    "zfs send $TESTPOOL/$TESTFS@$TESTSNAP >$TEST_BASE_DIR/devnull"
 	return 0
 }
 

tests/zfs-tests/tests/functional/rsend/send_invalid.ksh

@@ -44,7 +44,7 @@ log_must zfs snap $testfs@snap0
 log_must zfs snap $testfs@snap1
 
 # Test bad send with the CLI
-log_mustnot eval "zfs send -i $testfs@snap1 $testfs@snap0 >/dev/null"
+log_mustnot eval "zfs send -i $testfs@snap1 $testfs@snap0 >$TEST_BASE_DIR/devnull"
 
 # Test bad send with libzfs/libzfs_core
 log_must badsend $testfs@snap0 $testfs@snap1

tests/zfs-tests/tests/functional/rsend/send_partial_dataset.ksh

@@ -103,7 +103,7 @@ set -A badargs \
 
 while (( i < ${#badargs[*]} ))
 do
-	log_mustnot eval "zfs send --saved ${badargs[i]} >/dev/null"
+	log_mustnot eval "zfs send --saved ${badargs[i]} >$TEST_BASE_DIR/devnull"
 	(( i = i + 1 ))
 done