iotests/149: Skip on unsupported ciphers

Whenever qemu-img or qemu-io report that some cipher is unsupported,
skip the whole test, because that is probably because qemu has been
configured with the gnutls crypto backend.

We could taylor the algorithm list to what gnutls supports, but this is
a test that is run rather rarely anyway (because it requires
password-less sudo), and so it seems better and easier to skip it.  When
this test is intentionally run to check LUKS compatibility, it seems
better not to limit the algorithms but keep the list extensive.

Signed-off-by: Hanna Reitz <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Daniel P. Berrangé <[email protected]>

tests/qemu-iotests/149

@@ -230,6 +230,18 @@ def create_image(config, size_mb):
         fn.truncate(size_mb * 1024 * 1024)
 
 
+def check_cipher_support(config, output):
+    """Check the output of qemu-img or qemu-io for mention of the respective
+    cipher algorithm being unsupported, and if so, skip this test.
+    (Returns `output` for convenience.)"""
+
+    if 'Unsupported cipher algorithm' in output:
+        iotests.notrun('Unsupported cipher algorithm '
+                       f'{config.cipher}-{config.keylen}-{config.mode}; '
+                       'consider configuring qemu with a different crypto '
+                       'backend')
+    return output
+
 def qemu_img_create(config, size_mb):
     """Create and format a disk image with LUKS using qemu-img"""
 
@@ -253,7 +265,8 @@ def qemu_img_create(config, size_mb):
             "%dM" % size_mb]
 
     iotests.log("qemu-img " + " ".join(args), filters=[iotests.filter_test_dir])
-    iotests.log(iotests.qemu_img_pipe(*args), filters=[iotests.filter_test_dir])
+    iotests.log(check_cipher_support(config, iotests.qemu_img_pipe(*args)),
+                filters=[iotests.filter_test_dir])
 
 def qemu_io_image_args(config, dev=False):
     """Get the args for access an image or device with qemu-io"""
@@ -279,8 +292,8 @@ def qemu_io_write_pattern(config, pattern, offset_mb, size_mb, dev=False):
     args = ["-c", "write -P 0x%x %dM %dM" % (pattern, offset_mb, size_mb)]
     args.extend(qemu_io_image_args(config, dev))
     iotests.log("qemu-io " + " ".join(args), filters=[iotests.filter_test_dir])
-    iotests.log(iotests.qemu_io(*args), filters=[iotests.filter_test_dir,
-                                                 iotests.filter_qemu_io])
+    iotests.log(check_cipher_support(config, iotests.qemu_io(*args)),
+                filters=[iotests.filter_test_dir, iotests.filter_qemu_io])
 
 
 def qemu_io_read_pattern(config, pattern, offset_mb, size_mb, dev=False):
@@ -291,8 +304,8 @@ def qemu_io_read_pattern(config, pattern, offset_mb, size_mb, dev=False):
     args = ["-c", "read -P 0x%x %dM %dM" % (pattern, offset_mb, size_mb)]
     args.extend(qemu_io_image_args(config, dev))
     iotests.log("qemu-io " + " ".join(args), filters=[iotests.filter_test_dir])
-    iotests.log(iotests.qemu_io(*args), filters=[iotests.filter_test_dir,
-                                                 iotests.filter_qemu_io])
+    iotests.log(check_cipher_support(config, iotests.qemu_io(*args)),
+                filters=[iotests.filter_test_dir, iotests.filter_qemu_io])
 
 
 def test_once(config, qemu_img=False):