inspect: Add drive naming hints

We currently use a heuristic to guess how drive names we find
referenced in the guest map to drive names in the appliance. If this
heuristic fails it can cause inspection to fail.

This change adds a new 'name' option to add_drive_opts, which allows
the user to explicitly pass the name of a drive to libguestfs if it is
known. This change also updates the fstab-parsing inspection code to
use this information if it is available.

generator/generator_actions.ml

@@ -1007,7 +1007,7 @@ be mountable but require special options.  Filesystems may
 not all belong to a single logical operating system
 (use C<guestfs_inspect_os> to look for OSes).");
 
-  ("add_drive_opts", (RErr, [String "filename"], [Bool "readonly"; String "format"; String "iface"]), -1, [FishAlias "add"],
+  ("add_drive_opts", (RErr, [String "filename"], [Bool "readonly"; String "format"; String "iface"; String "name"]), -1, [FishAlias "add"],
    [],
    "add an image to examine or modify",
    "\
@@ -1050,6 +1050,11 @@ this security hole.
 This rarely-used option lets you emulate the behaviour of the
 deprecated C<guestfs_add_drive_with_if> call (q.v.)
 
+=item C<name>
+
+The name the drive had in the original guest, e.g. /dev/sdb. This is used as a
+hint to the guest inspection process if it is available.
+
 =back");
 
   ("inspect_get_windows_systemroot", (RString "systemroot", [Device "root"], []), -1, [],

regressions/test-inspect-fstab.sh

@@ -49,15 +49,11 @@ $guestfish -a test1.img <<'EOF'
   upload test.fstab /etc/fstab
 EOF
 
-rm test.fstab
-
 # This will give a warning, but should not fail.
 $guestfish -a test1.img -i <<'EOF' | sort > test.output
   inspect-get-mountpoints /dev/VG/Root
 EOF
 
-rm test1.img
-
 if [ "$(cat test.output)" != "/: /dev/VG/Root
 /boot: /dev/vda1
 /nosuchfile: /dev/VG/LV1
@@ -67,4 +63,36 @@ if [ "$(cat test.output)" != "/: /dev/VG/Root
     exit 1
 fi
 
+# Test device name hints
+
+cat <<'EOF' > test.fstab
+/dev/VG/Root / ext2 default 0 0
+
+# Device name which requires a hint
+/dev/xvdg1 /boot ext2 default 0 0
+EOF
+
+$guestfish -a test1.img <<'EOF'
+  run
+  mount-options "" /dev/VG/Root /
+  upload test.fstab /etc/fstab
+EOF
+
+$guestfish <<'EOF' > test.output
+  add-drive-opts test1.img readonly:true name:xvdg
+  run
+  inspect-os
+  inspect-get-mountpoints /dev/VG/Root
+EOF
+
+if [ "$(cat test.output)" != "/dev/VG/Root
+/: /dev/VG/Root
+/boot: /dev/vda1" ]; then
+    echo "$0: error: unexpected output from inspect-get-mountpoints command"
+    cat test.output
+    exit 1
+fi
+
+rm test.fstab
+rm test1.img
 rm test.output

src/guestfs-internal.h

@@ -158,6 +158,7 @@ struct drive {
   int readonly;
   char *format;
   char *iface;
+  char *name;
   int use_cache_off;
 };
 

src/guestfs.c

@@ -1008,6 +1008,7 @@ guestfs___free_drives (struct drive **drives)
     free (i->path);
     free (i->format);
     free (i->iface);
+    free (i->name);
     free (i);
 
     i = next;

src/inspect_fs_unix.c

@@ -107,7 +107,7 @@ compile_regexps (void)
            "Scientific Linux.*release (\\d+)", 0);
   COMPILE (re_major_minor, "(\\d+)\\.(\\d+)", 0);
   COMPILE (re_aug_seq, "/\\d+$", 0);
-  COMPILE (re_xdev, "^/dev/(?:h|s|v|xv)d([a-z]+)(\\d*)$", 0);
+  COMPILE (re_xdev, "^/dev/(h|s|v|xv)d([a-z]+)(\\d*)$", 0);
   COMPILE (re_freebsd, "^/dev/ad(\\d+)s(\\d+)([a-z])$", 0);
   COMPILE (re_netbsd, "^NetBSD (\\d+)\\.(\\d+)", 0);
 }
@@ -817,7 +817,7 @@ static char *
 resolve_fstab_device (guestfs_h *g, const char *spec)
 {
   char *device = NULL;
-  char *slice, *disk, *part;
+  char *type, *slice, *disk, *part;
 
   if (STRPREFIX (spec, "/dev/mapper/")) {
     /* LVM2 does some strange munging on /dev/mapper paths for VGs and
@@ -832,33 +832,50 @@ resolve_fstab_device (guestfs_h *g, const char *spec)
      */
     device = guestfs_lvm_canonical_lv_name (g, spec);
   }
-  else if (match2 (g, spec, re_xdev, &disk, &part)) {
-    /* disk: ([a-z]+)
+  else if (match3 (g, spec, re_xdev, &type, &disk, &part)) {
+    /* type: (h|s|v|xv)
+     * disk: ([a-z]+)
      * part: (\d*) */
     char **devices = guestfs_list_devices (g);
     if (devices == NULL)
       return NULL;
 
-    /* Count how many disks the libguestfs appliance has */
-    size_t count;
-    for (count = 0; devices[count] != NULL; count++)
-      ;
+    /* Check any hints we were passed for a non-heuristic mapping */
+    char *name = safe_asprintf (g, "%sd%s", type, disk);
+    size_t i = 0;
+    struct drive *drive = g->drives;
+    while (drive) {
+      if (drive->name && STREQ(drive->name, name)) {
+        device = safe_asprintf (g, "%s%s", devices[i], part);
+        break;
+      }
 
-    /* Calculate the numerical index of the disk */
-    size_t i = disk[0] - 'a';
-    for (char *p = disk + 1; *p != '\0'; p++) {
-      i += 1; i *= 26;
-      i += *p - 'a';
-    }
-
-    /* Check the index makes sense wrt the number of disks the appliance has.
-     * If it does, map it to an appliance disk. */
-    if (i < count) {
-      size_t len = strlen (devices[i]) + strlen (part) + 1;
-      device = safe_malloc (g, len);
-      snprintf (device, len, "%s%s", devices[i], part);
+      i++; drive = drive->next;
+    }
+    free (name);
+
+    /* Guess the appliance device name if we didn't find a matching hint */
+    if (!device) {
+      /* Count how many disks the libguestfs appliance has */
+      size_t count;
+      for (count = 0; devices[count] != NULL; count++)
+        ;
+
+      /* Calculate the numerical index of the disk */
+      i = disk[0] - 'a';
+      for (char *p = disk + 1; *p != '\0'; p++) {
+        i += 1; i *= 26;
+        i += *p - 'a';
+      }
+
+      /* Check the index makes sense wrt the number of disks the appliance has.
+       * If it does, map it to an appliance disk. */
+      if (i < count) {
+        device = safe_asprintf (g, "%s%s", devices[i], part);
+      }
     }
 
+    free (type);
     free (disk);
     free (part);
     guestfs___free_string_list (devices);

src/launch.c

@@ -289,6 +289,7 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
   int readonly;
   char *format;
   char *iface;
+  char *name;
   int use_cache_off;
 
   if (strchr (filename, ',') != NULL) {
@@ -302,12 +303,15 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
            ? safe_strdup (g, optargs->format) : NULL;
   iface = optargs->bitmask & GUESTFS_ADD_DRIVE_OPTS_IFACE_BITMASK
           ? safe_strdup (g, optargs->iface) : safe_strdup (g, DRIVE_IF);
+  name = optargs->bitmask & GUESTFS_ADD_DRIVE_OPTS_NAME_BITMASK
+          ? safe_strdup (g, optargs->name) : NULL;
 
   if (format && !valid_format_iface (format)) {
     error (g, _("%s parameter is empty or contains disallowed characters"),
            "format");
     free (format);
     free (iface);
+    free (name);
     return -1;
   }
   if (!valid_format_iface (iface)) {
@@ -315,6 +319,7 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
            "iface");
     free (format);
     free (iface);
+    free (name);
     return -1;
   }
 
@@ -326,6 +331,7 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
   if (use_cache_off == -1) {
     free (format);
     free (iface);
+    free (name);
     return -1;
   }
 
@@ -334,6 +340,7 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
       perrorf (g, "%s", filename);
       free (format);
       free (iface);
+      free (name);
       return -1;
     }
   }
@@ -347,6 +354,7 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
   (*i)->readonly = readonly;
   (*i)->format = format;
   (*i)->iface = iface;
+  (*i)->name = name;
   (*i)->use_cache_off = use_cache_off;
 
   return 0;