[Qemu-block] [PATCH v2] iotests: Do not rely on unavailable domains in 162

[Max Reitz]

There are some (mostly ISP-specific) name servers who will redirect
non-existing domains to special hosts. In this case, we will get a
different error message when trying to connect to such a host, which
breaks test 162.

162 needed this specific error message so it can confirm that qemu was
indeed trying to connect to the user-specified port. However, we can
also confirm this by setting up a local NBD server on exactly that port;
so we can fix the issue by doing just that.

Reported-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Max Reitz <address@hidden>
---
v2:
- Use a loop and random ports for starting qemu-nbd so we don't collide
  with ports which are already in use [Sascha]
---
 tests/qemu-iotests/162     | 25 +++++++++++++++++++++----
 tests/qemu-iotests/162.out |  2 +-
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/tests/qemu-iotests/162 b/tests/qemu-iotests/162
index 0b43ea3..c60a247 100755
--- a/tests/qemu-iotests/162
+++ b/tests/qemu-iotests/162
@@ -43,10 +43,27 @@ echo '=== NBD ==='
 $QEMU_IMG info 'json:{"driver": "nbd", "host": 42}'
 
 # And this should not treat @port as if it had not been specified
-# (We cannot use localhost with an invalid port here, but we need to use a
-#  non-existing domain, because otherwise the error message will not contain
-#  the port)
-$QEMU_IMG info 'json:{"driver": "nbd", "host": "does.not.exist.example.com", 
"port": 42}'
+# (We need to set up a server here, because the error message for "Connection
+#  refused" does not contain the destination port)
+
+# Launching qemu-nbd is done in a loop: We try to set up an NBD server on some
+# random port and continue until success, i.e. until we have found a port that
+# is not in use yet.
+while true; do
+    port=$((RANDOM + 32768))
+    $QEMU_NBD -p $port -f raw null-co:// &> /dev/null &
+    nbd_pid=$!
+    sleep 0.5
+
+    # Check whether the process is still alive
+    # (which is the case if the server has been created successfully)
+    if kill -0 $nbd_pid &> /dev/null; then
+        break
+    fi
+done
+
+$QEMU_IMG info "json:{'driver': 'nbd', 'host': 'localhost', 'port': $port}" \
+    | grep '^image' | sed -e "s/$port/PORT/"
 
 # This is a test for NBD's bdrv_refresh_filename() implementation: It expects
 # either host or path to be set, but it must not assume that they are set to
diff --git a/tests/qemu-iotests/162.out b/tests/qemu-iotests/162.out
index 9bba723..3c5be2c 100644
--- a/tests/qemu-iotests/162.out
+++ b/tests/qemu-iotests/162.out
@@ -2,7 +2,7 @@ QA output created by 162
 
 === NBD ===
 qemu-img: Could not open 'json:{"driver": "nbd", "host": 42}': Failed to 
connect socket: Invalid argument
-qemu-img: Could not open 'json:{"driver": "nbd", "host": 
"does.not.exist.example.com", "port": 42}': address resolution failed for 
does.not.exist.example.com:42: Name or service not known
+image: nbd://localhost:PORT
 image: nbd+unix://?socket=42
 
 === SSH ===
-- 
2.5.5