New API call iso_util_get_lfa_masks()

libisofs/fs_local.c

@@ -975,7 +975,7 @@ int iso_local_get_lfa_flags(char *disk_path, uint64_t *lfa_flags, int *max_bit,
     }
     if ((stbuf.st_mode & S_IFMT) == S_IFLNK && !(flag & 32))
         return 3;
-    ret= aaip_get_lfa_flags(disk_path, lfa_flags, max_bit, os_errno, 0);
+    ret = aaip_get_lfa_flags(disk_path, lfa_flags, max_bit, os_errno, 0);
     if(ret == 0)
         return ISO_AAIP_NOT_ENABLED;
     if (ret < 0)
@@ -986,8 +986,8 @@ int iso_local_get_lfa_flags(char *disk_path, uint64_t *lfa_flags, int *max_bit,
 
 /*
  * @param flag          Bitfield for control purposes
- *      bit0= do not try to set known superuser flags
+ *      bit0= do not try to change known superuser flags
- *      bit1= set only known chattr settable flags
+ *      bit1= change only known chattr settable flags
  *      bit5= in case of symbolic link: inquire link target
  * @return
  *      1 = ok, all lfa_flags bits were written
@@ -996,18 +996,14 @@ int iso_local_get_lfa_flags(char *disk_path, uint64_t *lfa_flags, int *max_bit,
  *     <0 = error
  */
 int iso_local_set_lfa_flags(char *disk_path, uint64_t lfa_flags, int max_bit,
-                            int *os_errno, int flag)
+                            uint64_t change_mask, int *os_errno, int flag)
 {
-    int ret;
+    int ret, old_max_bit;
     struct stat stbuf;
+    uint64_t known_user_mask, known_su_mask, non_settable, unknown, eff_flags;
 
-    /* chattr letters: User:         sucSdAmtDTCxPF
+    iso_util_get_lfa_masks(&known_user_mask, &known_su_mask, &non_settable,
-                       Superuser:    iaj 
+                           &unknown);
-                       Non-settable: Z(9)EI(13)heV(21)(22)N(31)
-    */
-    static uint64_t known_user_mask = 0x628384cf;
-    static uint64_t known_su_mask =   0x00004030;
-
     *os_errno = 0;
     if (flag & 32)
         ret = stat(disk_path, &stbuf);
@@ -1020,10 +1016,22 @@ int iso_local_set_lfa_flags(char *disk_path, uint64_t lfa_flags, int max_bit,
     if ((stbuf.st_mode & S_IFMT) == S_IFLNK && !(flag & 32))
         return 3;
     if (flag & 1)
-        lfa_flags &= ~known_su_mask;
+        change_mask &= ~known_su_mask;
     if (flag & 2)
-        lfa_flags &= known_user_mask | known_su_mask;
+        change_mask &= (known_user_mask | known_su_mask);
-    ret= aaip_set_lfa_flags(disk_path, lfa_flags, max_bit, os_errno, 0);
+    if (change_mask == ~((uint64_t) 0)) {
+        eff_flags = lfa_flags;
+    } else {
+        ret = aaip_get_lfa_flags(disk_path, &eff_flags, &old_max_bit, os_errno,
+                                 0);
+        if (ret == 0)
+            return ISO_AAIP_NOT_ENABLED;
+        if (ret < 0)
+            return ISO_AAIP_NO_GET_LOCAL;
+        eff_flags &= ~change_mask;
+        eff_flags |= (lfa_flags & change_mask);
+    }
+    ret= aaip_set_lfa_flags(disk_path, eff_flags, max_bit, os_errno, 0);
     if(ret == 0)
         return ISO_AAIP_NOT_ENABLED;
     if(ret < 0)

libisofs/libisofs.h

@@ -8089,10 +8089,15 @@ int iso_local_get_lfa_flags(char *disk_path, uint64_t *lfa_flags, int *max_bit,
  * @param os_errno
  *      Will get filled with errno if a system call fails.
  *      Else it will be filled with 0.
+ * @param change_mask
+ *      Tells which bits of lfa_flags are meant to change attribute flags
+ *      of the file. Submit ~((uint64_t) 0) if all bits may cause changes.
+ *      The set of changeable bits may further be restricted by bit0 and bit1
+ *      of parameter flag.
  * @param flag
  *      Bitfield for control purposes
- *      bit0= do not try to set known chattr superuser flags: iaj
+ *      bit0= do not try to change known chattr superuser flags: iaj
- *      bit1= set only known chattr settable flags: sucSiadAmjtDTCxPF
+ *      bit1= change only known chattr settable flags: sucSiadAmjtDTCxPF
  *      bit5= in case of symbolic link: operate on link target
  * @return
  *      1 = ok, all lfa_flags bits were written
@@ -8103,7 +8108,7 @@ int iso_local_get_lfa_flags(char *disk_path, uint64_t *lfa_flags, int *max_bit,
  * @since 1.5.8
  */
 int iso_local_set_lfa_flags(char *disk_path, uint64_t lfa_flags, int max_bit,
-                            int *os_errno, int flag);
+                            uint64_t change_mask, int *os_errno, int flag);
 
 
 /**
@@ -8152,6 +8157,34 @@ int iso_util_encode_lfa_flags(uint64_t lfa_flags, char **flags_text, int flag);
 int iso_util_decode_lfa_flags(char *flags_text, uint64_t *lfa_flags, int flag);
 
 
+/**
+ * Return the bit patterns of four classes of Linux-like file attribute flags.
+ * They were determined according to man 1 chattr and the source of lsattr
+ * in juli 2024. The symbolic strings and bit numbers are given here only
+ * for convenience. Decisive are the returned bit patterns.
+ *
+ * @param user_settable
+ *      The flag bits which are known to be user settable with chattr:
+ *        sucSdAmtDTCxPF
+ * @param su_settable
+ *      The flag bits which are known to be settable with chattr only by
+ *      bearers of various superuser powers:
+ *        iaj
+ * @param non_settable
+ *      The flags bits which are known to be not settable or not clearable
+ *      by chattr or only known to lsattr:
+ *        ZEIheVN
+ * @param unknown
+ *      The flags bits for which no symbolic letter is known. Some of them are
+ *      defined in <linux/fs.h> with sparse info, some not even that:
+ *        9, 13, 21, 22, 24, 26, 27, 31
+ *      
+ * @since 1.5.8
+ */
+void iso_util_get_lfa_masks(uint64_t *user_settable, uint64_t *su_settable,
+                            uint64_t *non_settable, uint64_t *unknown);
+ 
+
 /* Default in case that the compile environment has no macro PATH_MAX.
 */
 #define Libisofs_default_path_maX 4096

libisofs/libisofs.ver

@@ -392,5 +392,6 @@ iso_node_get_lfa_flags;
 iso_node_set_lfa_flags;
 iso_util_decode_lfa_flags;
 iso_util_encode_lfa_flags;
+iso_util_get_lfa_masks;
 } LIBISOFS6;
 

libisofs/util.c

@@ -2555,7 +2555,7 @@ int iso_util_encode_lfa_flags(uint64_t lfa_flags, char **flags_text, int flag)
             (*flags_text)[w++] = lfa_flag_letters[i];
         }
     }
-    flags_text[w] = 0;
+    (*flags_text)[w] = 0;
     if (was_unknown)
         return ISO_LFA_UNKNOWN_BIT;
     return ISO_SUCCESS;
@@ -2610,3 +2610,18 @@ int iso_util_decode_lfa_flags(char *flags_text, uint64_t *lfa_flags, int flag)
     return 1;
 }
 
+
+void iso_util_get_lfa_masks(uint64_t *user_settable, uint64_t *su_settable,
+                            uint64_t *non_settable, uint64_t *unknown)
+{
+    /* chattr letters: User settable     :  sucSdAmtDTCxPF
+                       Superuser settable:  iaj
+                       Non-settable      :  ZEIheVN
+                       unknown           :  9, 13, 21, 22, 24, 26, 27, >= 31 
+    */
+    *user_settable   = 0x628384cf;
+    *su_settable     = 0x00004030;
+    *non_settable    = 0x101c1900;
+    *unknown = 0xffffffff8d602200;
+}
+