Add a cdrom size checker for OVF ds to ds-identify

With a large size ISO file attached to iso dev, ds-identify might
grep it entirely if iso dev is ISO9660, it takes very long time to
start OS.

Resolve this by:

- Adding a checker to read the ISO size (from sysfs).  If
the size of the ISO filesystem is > 10MiB then the ISO will be
ignored (logged as oversized).

- Move the ovf vmware guest customization checker to be
ahead of cdrom ovf checker, so no need check the ISO size if vmware
guest customization is enabled.

LP: #1806701

2 files changed, 51 insertions, 13 deletions

diff --git a/tests/unittests/test_ds_identify.py b/tests/unittests/test_ds_identify.py
index 7575223f..587e6993 100644
--- a/tests/unittests/test_ds_identify.py
+++ b/tests/unittests/test_ds_identify.py
@@ -524,6 +524,30 @@ class TestDsIdentify(DsIdentifyBase):
             self._check_via_dict(
                 ovf_cdrom_by_label, rc=RC_FOUND, dslist=['OVF', DS_NONE])
 
+    def test_ovf_on_vmware_iso_found_by_cdrom_with_different_size(self):
+        """OVF is identified by well-known iso9660 labels."""
+        ovf_cdrom_with_size = copy.deepcopy(VALID_CFG['OVF'])
+
+        # Set cdrom size to 20480 (10MB in 512 byte units)
+        ovf_cdrom_with_size['files']['sys/class/block/sr0/size'] = '20480\n'
+        self._check_via_dict(
+            ovf_cdrom_with_size, rc=RC_NOT_FOUND, policy_dmi="disabled")
+
+        # Set cdrom size to 204800 (100MB in 512 byte units)
+        ovf_cdrom_with_size['files']['sys/class/block/sr0/size'] = '204800\n'
+        self._check_via_dict(
+            ovf_cdrom_with_size, rc=RC_NOT_FOUND, policy_dmi="disabled")
+
+        # Set cdrom size to 18432 (9MB in 512 byte units)
+        ovf_cdrom_with_size['files']['sys/class/block/sr0/size'] = '18432\n'
+        self._check_via_dict(
+            ovf_cdrom_with_size, rc=RC_FOUND, dslist=['OVF', DS_NONE])
+
+        # Set cdrom size to 2048 (1MB in 512 byte units)
+        ovf_cdrom_with_size['files']['sys/class/block/sr0/size'] = '2048\n'
+        self._check_via_dict(
+            ovf_cdrom_with_size, rc=RC_FOUND, dslist=['OVF', DS_NONE])
+
     def test_default_nocloud_as_vdb_iso9660(self):
         """NoCloud is found with iso9660 filesystem on non-cdrom disk."""
         self._test_ds_found('NoCloud')
@@ -815,6 +839,7 @@ VALID_CFG = {
         ],
         'files': {
             'dev/sr0': 'pretend ovf iso has ' + OVF_MATCH_STRING + '\n',
+            'sys/class/block/sr0/size': '2048\n',
         }
     },
     'OVF-guestinfo': {
diff --git a/tools/ds-identify b/tools/ds-identify
index e16708f6..0305e361 100755
--- a/tools/ds-identify
+++ b/tools/ds-identify
@@ -766,10 +766,34 @@ is_cdrom_ovf() {
         config-2|CONFIG-2|rd_rdfe_stable*|cidata|CIDATA) return 1;;
     esac
 
+    # skip device which size is 10MB or larger
+    local size="" sfile="${PATH_SYS_CLASS_BLOCK}/${dev##*/}/size"
+    [ -f "$sfile" ] || return 1
+    read size <"$sfile" || { warn "failed reading from $sfile"; return 1; }
+    # size is in 512 byte units. so convert to MB (integer division)
+    if [ $((size/2048)) -ge 10 ]; then
+        debug 2 "$dev: size $((size/2048))MB is considered too large for OVF"
+        return 1
+    fi
+
     local idstr="http://schemas.dmtf.org/ovf/environment/1"
     grep --quiet --ignore-case "$idstr" "${PATH_ROOT}$dev"
 }
 
+has_ovf_cdrom() {
+    # DI_ISO9660_DEVS is <device>=label,<device>=label2
+    # like /dev/sr0=OVF-TRANSPORT,/dev/other=with spaces
+    if [ "${DI_ISO9660_DEVS#${UNAVAILABLE}:}" = "${DI_ISO9660_DEVS}" ]; then
+        local oifs="$IFS"
+        # shellcheck disable=2086
+        { IFS=","; set -- ${DI_ISO9660_DEVS}; IFS="$oifs"; }
+        for tok in "$@"; do
+            is_cdrom_ovf "${tok%%=*}" "${tok#*=}" && return 0
+        done
+    fi
+    return 1
+}
+
 dscheck_OVF() {
     check_seed_dir ovf ovf-env.xml && return "${DS_FOUND}"
 
@@ -780,20 +804,9 @@ dscheck_OVF() {
 
     ovf_vmware_transport_guestinfo && return "${DS_FOUND}"
 
-    # DI_ISO9660_DEVS is <device>=label,<device>=label2
-    # like /dev/sr0=OVF-TRANSPORT,/dev/other=with spaces
-    if [ "${DI_ISO9660_DEVS#${UNAVAILABLE}:}" = "${DI_ISO9660_DEVS}" ]; then
-        local oifs="$IFS"
-        # shellcheck disable=2086
-        { IFS=","; set -- ${DI_ISO9660_DEVS}; IFS="$oifs"; }
-        for tok in "$@"; do
-            is_cdrom_ovf "${tok%%=*}" "${tok#*=}" && return $DS_FOUND
-        done
-    fi
+    has_ovf_cdrom && return "${DS_FOUND}"
 
-    if ovf_vmware_guest_customization; then
-        return ${DS_FOUND}
-    fi
+    ovf_vmware_guest_customization && return "${DS_FOUND}"
 
     return ${DS_NOT_FOUND}
 }