nbd: Improve error messages

This patch makes use of the Error object for nbd_receive_negotiate() so
that errors during negotiation look nicer.

Furthermore, this patch adds an additional error message if the received
magic was wrong, but would be correct for the other protocol version,
respectively: So if an export name was specified, but the NBD server
magic corresponds to an old handshake, this condition is explicitly
signaled to the user, and vice versa.

As these messages are now part of the "Could not open image" error
message, additional filtering has to be employed in iotest 083, which
this patch does as well.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 19 insertions, 35 deletions

diff --git a/tests/qemu-iotests/083 b/tests/qemu-iotests/083
index 991a9d9..1b2d3f1 100755
--- a/tests/qemu-iotests/083
+++ b/tests/qemu-iotests/083
@@ -56,7 +56,8 @@ filter_nbd() {
 	#
 	# Filter out the TCP port number since this changes between runs.
 	sed -e 's#^.*nbd\.c:.*##g' \
-	    -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g'
+	    -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g' \
+            -e 's#\(exportname=foo\|PORT\): Failed to .*$#\1#'
 }
 
 check_disconnect() {
diff --git a/tests/qemu-iotests/083.out b/tests/qemu-iotests/083.out
index fd397f4..8c1441b 100644
--- a/tests/qemu-iotests/083.out
+++ b/tests/qemu-iotests/083.out
@@ -1,62 +1,52 @@
 QA output created by 083
 === Check disconnect before neg1 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect after neg1 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect 8 neg1 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect 16 neg1 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect before export ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect after export ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect 4 export ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect 12 export ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect 16 export ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect before neg2 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect after neg2 ===
@@ -66,14 +56,12 @@ read failed: Input/output error
 
 === Check disconnect 8 neg2 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect 10 neg2 ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT:exportname=foo
 no file open, try 'help open'
 
 === Check disconnect before request ===
@@ -119,32 +107,27 @@ read 512/512 bytes at offset 0
 
 === Check disconnect before neg-classic ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT
 no file open, try 'help open'
 
 === Check disconnect 8 neg-classic ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT
 no file open, try 'help open'
 
 === Check disconnect 16 neg-classic ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT
 no file open, try 'help open'
 
 === Check disconnect 24 neg-classic ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT
 no file open, try 'help open'
 
 === Check disconnect 28 neg-classic ===
 
-
-qemu-io: can't open device nbd:127.0.0.1:PORT: Could not open image: Invalid argument
+qemu-io: can't open device nbd:127.0.0.1:PORT
 no file open, try 'help open'
 
 === Check disconnect after neg-classic ===