[v2] tests: allow qemu-iotests to be run against nbd backend

diff --git a/tests/qemu-iotests/common b/tests/qemu-iotests/common
index 1f6fdf5..195722e 100644
--- a/tests/qemu-iotests/common
+++ b/tests/qemu-iotests/common
@@ -136,6 +136,7 @@  check options
     -vmdk               test vmdk
     -rbd                test rbd
     -sheepdog           test sheepdog
+    -nbd                test nbd
     -xdiff		graphical mode diff
     -nocache		use O_DIRECT on backing file
     -misalign		misalign memory allocations
@@ -197,12 +198,14 @@  testlist options
 	    IMGPROTO=rbd
 	    xpand=false
 	    ;;
-
 	-sheepdog)
 	    IMGPROTO=sheepdog
 	    xpand=false
 	    ;;
-
+    -nbd)
+        IMGPROTO=nbd
+        xpand=false
+        ;;
 	-nocache)
 	    QEMU_IO_OPTIONS="$QEMU_IO_OPTIONS --nocache"
 	    xpand=false
@@ -350,9 +353,14 @@  fi
 
 [ "$QEMU" = "" ] && _fatal "qemu not found"
 [ "$QEMU_IMG" = "" ] && _fatal "qemu-img not found"
-[ "$QEMU_IO" = "" ] && _fatal "qemu-img not found"
+[ "$QEMU_IO" = "" ] && _fatal "qemu-io not found"
+
+if [ "$IMGPROTO" = "nbd" ] ; then
+    [ "$QEMU_NBD" = "" ] && _fatal "qemu-nbd not found"
+fi
 
 if $valgrind; then
     export REAL_QEMU_IO="$QEMU_IO_PROG"
     export QEMU_IO_PROG=valgrind_qemu_io
 fi
+
diff --git a/tests/qemu-iotests/common.config b/tests/qemu-iotests/common.config
index df082e7..08a3f10 100644
--- a/tests/qemu-iotests/common.config
+++ b/tests/qemu-iotests/common.config
@@ -90,21 +90,23 @@  export PS_ALL_FLAGS="-ef"
 if [ -z "$QEMU_PROG" ]; then
     export QEMU_PROG="`set_prog_path qemu`"
 fi
-[ "$QEMU_PROG" = "" ] && _fatal "qemu not found"
 
 if [ -z "$QEMU_IMG_PROG" ]; then
     export QEMU_IMG_PROG="`set_prog_path qemu-img`"
 fi
-[ "$QEMU_IMG_PROG" = "" ] && _fatal "qemu-img not found"
 
 if [ -z "$QEMU_IO_PROG" ]; then
     export QEMU_IO_PROG="`set_prog_path qemu-io`"
 fi
-[ "$QEMU_IO_PROG" = "" ] && _fatal "qemu-io not found"
+
+if [ -z "$QEMU_NBD_PROG" ]; then
+    export QEMU_NBD_PROG="`set_prog_path qemu-nbd`"
+fi
 
 export QEMU=$QEMU_PROG
-export QEMU_IMG=$QEMU_IMG_PROG 
+export QEMU_IMG=$QEMU_IMG_PROG
 export QEMU_IO="$QEMU_IO_PROG $QEMU_IO_OPTIONS"
+export QEMU_NBD=$QEMU_NBD_PROG
 
 [ -f /etc/qemu-iotest.config ]       && . /etc/qemu-iotest.config
 
diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index 334534f..aef5f52 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -49,6 +49,9 @@  umask 022
 
 if [ "$IMGPROTO" = "file" ]; then
     TEST_IMG=$TEST_DIR/t.$IMGFMT
+elif [ "$IMGPROTO" = "nbd" ]; then
+    TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
+    TEST_IMG="nbd:127.0.0.1:10810"
 else
     TEST_IMG=$IMGPROTO:$TEST_DIR/t.$IMGFMT
 fi
@@ -86,6 +89,13 @@  _make_test_img()
     local extra_img_options=""
     local image_size=$*
     local optstr=""
+    local img_name=""
+
+    if [ -n "$TEST_IMG_FILE" ]; then
+        img_name=$TEST_IMG_FILE
+    else
+        img_name=$TEST_IMG
+    fi
 
     if [ -n "$IMGOPTS" ]; then
         optstr=$(_optstr_add "$optstr" "$IMGOPTS")
@@ -104,7 +114,7 @@  _make_test_img()
     fi
 
     # XXX(hch): have global image options?
-    $QEMU_IMG create -f $IMGFMT $extra_img_options $TEST_IMG $image_size | \
+    $QEMU_IMG create -f $IMGFMT $extra_img_options $img_name $image_size | \
         sed -e "s#$IMGPROTO:$TEST_DIR#TEST_DIR#g" \
             -e "s#$TEST_DIR#TEST_DIR#g" \
             -e "s#$IMGFMT#IMGFMT#g" \
@@ -115,12 +125,23 @@  _make_test_img()
             -e "s# compat6=\\(on\\|off\\)##g" \
             -e "s# static=\\(on\\|off\\)##g" \
             -e "s# lazy_refcounts=\\(on\\|off\\)##g"
+
+    # Start an NBD server on the image file, which is what we'll be talking to
+    if [ $IMGPROTO = "nbd" ]; then
+        eval "$QEMU_NBD -v -t -b 127.0.0.1 -p 10810  $TEST_IMG_FILE &"
+        QEMU_NBD_PID=$!
+        sleep 1 # FIXME: qemu-nbd needs to be listening before we continue
+    fi
 }
 
 _cleanup_test_img()
 {
     case "$IMGPROTO" in
 
+        nbd)
+            kill $QEMU_NBD_PID
+            rm -f $TEST_IMG_FILE
+            ;;
         file)
             rm -f $TEST_DIR/t.$IMGFMT
             rm -f $TEST_DIR/t.$IMGFMT.orig