tests: Add a test of relative paths, to make sure we don't break them.

In some places we turn relative paths passed by the caller into
absolute paths: for example in the libvirt backend, all relative paths
to disk images have to be turned into absolute paths (by calling
realpath) because otherwise libvirt doesn't work.

This has the potential to break things, especially considering that
qemu uses the path passed to it in order to resolve the relative paths
of backing files.

For example consider the case where 'overlay' is a symbolic link to
/dev/dm-1, but /dev/dm-1 contains a qcow2 which references './backing'
as its backing file.  If we rewrote 'overlay' to '/dev/dm-1', then
qemu would try to look up '/dev/backing' for the backing file and
fail.

See also:

https://bugzilla.redhat.com/show_bug.cgi?id=1053684
https://www.redhat.com/archives/libguestfs/2014-January/thread.html#00087

Makefile.am

@@ -62,6 +62,7 @@ SUBDIRS += tests/http
 SUBDIRS += tests/syslinux
 SUBDIRS += tests/journal
 SUBDIRS += tests/fuzz
+SUBDIRS += tests/relative-paths
 SUBDIRS += tests/regressions
 endif
 

configure.ac

@@ -1767,6 +1767,7 @@ AC_CONFIG_FILES([Makefile
                  tests/protocol/Makefile
                  tests/qemu/Makefile
                  tests/regressions/Makefile
+                 tests/relative-paths/Makefile
                  tests/rsync/Makefile
                  tests/selinux/Makefile
                  tests/syslinux/Makefile

tests/relative-paths/Makefile.am

@@ -0,0 +1,37 @@
+# libguestfs
+# Copyright (C) 2014 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# Test relative paths to backing files.  Mainly this is a test that we
+# don't break this.
+#
+# See eg:
+# https://bugzilla.redhat.com/show_bug.cgi?id=1053684
+# https://www.redhat.com/archives/libguestfs/2014-January/thread.html#00087
+# (and more)
+
+include $(top_srcdir)/subdir-rules.mk
+
+TESTS = \
+	test-relative-paths.sh
+
+TESTS_ENVIRONMENT = $(top_builddir)/run --test
+
+check-valgrind:
+	$(MAKE) VG="$(top_builddir)/run @VG@" check
+
+EXTRA_DIST = \
+	$(TESTS)

tests/relative-paths/test-relative-paths.sh

@@ -0,0 +1,144 @@
+#!/bin/bash -
+# libguestfs
+# Copyright (C) 2014 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+set -e
+
+if [ -n "$SKIP_TEST_RELATIVE_PATHS_SH" ]; then
+    echo "$0: skipped (environment variable set)"
+    exit 77
+fi
+
+# UML doesn't support qcow2.  Conceivably there might be a similar
+# problem with UML COW images which would require a separate test.
+if [ "$($guestfish get-backend)" = "uml" ]; then
+    echo "$0: skipping test because uml backend does not support qcow2"
+    exit 77
+fi
+
+rm -f backing*
+rm -f overlay*
+rm -f link*
+rm -rf dir1
+
+# Set up a set of disk images involving relative paths.
+mkdir -p dir1/dir2
+
+# Regular overlay files.
+
+qemu-img create -f qcow2 backing1 10M
+qemu-img create -f qcow2 -b $(pwd)/backing1 overlay1
+
+qemu-img create -f qcow2 backing2 10M
+qemu-img create -f qcow2 -b backing2 overlay2
+
+qemu-img create -f qcow2 backing3 10M
+qemu-img create -f qcow2 -b ./backing3 overlay3
+
+qemu-img create -f qcow2 backing4 10M
+qemu-img create -f qcow2 -b ../../tests/relative-paths/backing4 overlay4
+
+qemu-img create -f qcow2 backing5 10M
+pushd dir1
+qemu-img create -f qcow2 -b ../backing5 overlay5
+popd
+
+qemu-img create -f qcow2 backing6 10M
+pushd dir1/dir2
+qemu-img create -f qcow2 -b ../../backing6 overlay6
+popd
+
+qemu-img create -f qcow2 dir1/backing7 10M
+qemu-img create -f qcow2 -b dir1/backing7 overlay7
+
+qemu-img create -f qcow2 dir1/dir2/backing8 10M
+qemu-img create -f qcow2 -b dir1/dir2/backing8 overlay8
+
+qemu-img create -f qcow2 dir1/dir2/backing9 10M
+pushd dir1
+qemu-img create -f qcow2 -b dir2/backing9 overlay9
+popd
+
+qemu-img create -f qcow2 dir1/backing10 10M
+pushd dir1/dir2
+qemu-img create -f qcow2 -b ../backing10 overlay10
+popd
+
+qemu-img create -f qcow2 dir1/backing11 10M
+pushd dir1
+qemu-img create -f qcow2 -b backing11 overlay11
+popd
+
+# Symbolic links.
+
+qemu-img create -f qcow2 backing12 10M
+qemu-img create -f qcow2 -b backing12 overlay12
+ln -s overlay12 link12
+
+qemu-img create -f qcow2 dir1/backing13 10M
+pushd dir1
+qemu-img create -f qcow2 -b backing13 overlay13
+popd
+ln -s dir1/overlay13 link13
+
+qemu-img create -f qcow2 dir1/dir2/backing14 10M
+pushd dir1
+qemu-img create -f qcow2 -b dir2/backing14 overlay14
+popd
+pushd dir1/dir2
+ln -s ../overlay14 link14
+popd
+
+qemu-img create -f qcow2 dir1/backing15 10M
+pushd dir1/dir2
+qemu-img create -f qcow2 -b ../backing15 overlay15
+popd
+pushd dir1
+ln -s dir2/overlay15 link15
+popd
+
+# Note that add-drive readonly/readwrite are substantially different
+# codepaths in most backends, so we should test each separately.
+for ro in readonly:true readonly:false; do
+    for prefix in "./" "" "$(pwd)/"; do
+        $VG ../../fish/guestfish <<EOF
+            add-drive ${prefix}overlay1            $ro format:qcow2
+            add-drive ${prefix}overlay2            $ro format:qcow2
+            add-drive ${prefix}overlay3            $ro format:qcow2
+            add-drive ${prefix}overlay4            $ro format:qcow2
+            add-drive ${prefix}dir1/overlay5       $ro format:qcow2
+            add-drive ${prefix}dir1/dir2/overlay6  $ro format:qcow2
+            add-drive ${prefix}overlay7            $ro format:qcow2
+            add-drive ${prefix}overlay8            $ro format:qcow2
+            add-drive ${prefix}dir1/overlay9       $ro format:qcow2
+            add-drive ${prefix}dir1/dir2/overlay10 $ro format:qcow2
+            add-drive ${prefix}dir1/overlay11      $ro format:qcow2
+            add-drive ${prefix}link12              $ro format:qcow2
+            add-drive ${prefix}link13              $ro format:qcow2
+            add-drive ${prefix}dir1/dir2/link14    $ro format:qcow2
+            add-drive ${prefix}dir1/link15         $ro format:qcow2
+            run
+            # Just forces the drives to be opened.
+            <! for n in a b c d e f g h i j k l m n o; do echo blockdev-getsize64 /dev/sd\$n; done
+EOF
+    done
+done
+
+rm -r dir1
+rm backing*
+rm overlay*
+rm link*