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-rw-r--r--common/rescue.c351
1 files changed, 351 insertions, 0 deletions
diff --git a/common/rescue.c b/common/rescue.c
new file mode 100644
index 0000000..7a85ebc
--- /dev/null
+++ b/common/rescue.c
@@ -0,0 +1,351 @@
+ /*
+ Unix SMB/CIFS implementation.
+
+ trivial database library, rescue attempt code.
+
+ Copyright (C) Rusty Russell 2012
+
+ ** NOTE! The following LGPL license applies to the tdb
+ ** library. This does NOT imply that all of Samba is released
+ ** under the LGPL
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 3 of the License, or (at your option) any later version.
+
+ This library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+#include "tdb_private.h"
+#include <assert.h>
+
+
+struct found {
+ tdb_off_t head; /* 0 -> invalid. */
+ struct tdb_record rec;
+ TDB_DATA key;
+ bool in_hash;
+ bool in_free;
+};
+
+struct found_table {
+ /* As an ordered array (by head offset). */
+ struct found *arr;
+ unsigned int num, max;
+};
+
+static bool looks_like_valid_record(struct tdb_context *tdb,
+ tdb_off_t off,
+ const struct tdb_record *rec,
+ TDB_DATA *key)
+{
+ unsigned int hval;
+
+ if (rec->magic != TDB_MAGIC)
+ return false;
+
+ if (rec->key_len + rec->data_len > rec->rec_len)
+ return false;
+
+ if (rec->rec_len % TDB_ALIGNMENT)
+ return false;
+
+ /* Next pointer must make some sense. */
+ if (rec->next > 0 && rec->next < TDB_DATA_START(tdb->hash_size))
+ return false;
+
+ if (tdb_oob(tdb, rec->next, sizeof(*rec), 1))
+ return false;
+
+ key->dsize = rec->key_len;
+ key->dptr = tdb_alloc_read(tdb, off + sizeof(*rec), key->dsize);
+ if (!key->dptr)
+ return false;
+
+ hval = tdb->hash_fn(key);
+ if (hval != rec->full_hash) {
+ free(key->dptr);
+ return false;
+ }
+
+ /* Caller frees up key->dptr */
+ return true;
+}
+
+static bool add_to_table(struct found_table *found,
+ tdb_off_t off,
+ struct tdb_record *rec,
+ TDB_DATA key)
+{
+ if (found->num + 1 > found->max) {
+ struct found *new;
+ found->max = (found->max ? found->max * 2 : 128);
+ new = realloc(found->arr, found->max * sizeof(found->arr[0]));
+ if (!new)
+ return false;
+ found->arr = new;
+ }
+
+ found->arr[found->num].head = off;
+ found->arr[found->num].rec = *rec;
+ found->arr[found->num].key = key;
+ found->arr[found->num].in_hash = false;
+ found->arr[found->num].in_free = false;
+
+ found->num++;
+ return true;
+}
+
+static bool walk_record(struct tdb_context *tdb,
+ const struct found *f,
+ void (*walk)(TDB_DATA, TDB_DATA, void *private_data),
+ void *private_data)
+{
+ TDB_DATA data;
+
+ data.dsize = f->rec.data_len;
+ data.dptr = tdb_alloc_read(tdb,
+ f->head + sizeof(f->rec) + f->rec.key_len,
+ data.dsize);
+ if (!data.dptr) {
+ if (tdb->ecode == TDB_ERR_OOM)
+ return false;
+ /* I/O errors are expected. */
+ return true;
+ }
+
+ walk(f->key, data, private_data);
+ free(data.dptr);
+ return true;
+}
+
+/* First entry which has offset >= this one. */
+static unsigned int find_entry(struct found_table *found, tdb_off_t off)
+{
+ unsigned int start = 0, end = found->num;
+
+ while (start < end) {
+ /* We can't overflow here. */
+ unsigned int mid = (start + end) / 2;
+
+ if (off < found->arr[mid].head) {
+ end = mid;
+ } else if (off > found->arr[mid].head) {
+ start = mid + 1;
+ } else {
+ return mid;
+ }
+ }
+
+ assert(start == end);
+ return end;
+}
+
+static void found_in_hashchain(struct found_table *found, tdb_off_t head)
+{
+ unsigned int match;
+
+ match = find_entry(found, head);
+ if (match < found->num && found->arr[match].head == head) {
+ found->arr[match].in_hash = true;
+ }
+}
+
+static void mark_free_area(struct found_table *found, tdb_off_t head,
+ tdb_len_t len)
+{
+ unsigned int match;
+
+ match = find_entry(found, head);
+ /* Mark everything within this free entry. */
+ while (match < found->num) {
+ if (found->arr[match].head >= head + len) {
+ break;
+ }
+ found->arr[match].in_free = true;
+ match++;
+ }
+}
+
+static int cmp_key(const void *a, const void *b)
+{
+ const struct found *fa = a, *fb = b;
+
+ if (fa->key.dsize < fb->key.dsize) {
+ return -1;
+ } else if (fa->key.dsize > fb->key.dsize) {
+ return 1;
+ }
+ return memcmp(fa->key.dptr, fb->key.dptr, fa->key.dsize);
+}
+
+static bool key_eq(TDB_DATA a, TDB_DATA b)
+{
+ return a.dsize == b.dsize
+ && memcmp(a.dptr, b.dptr, a.dsize) == 0;
+}
+
+static void free_table(struct found_table *found)
+{
+ unsigned int i;
+
+ for (i = 0; i < found->num; i++) {
+ free(found->arr[i].key.dptr);
+ }
+ free(found->arr);
+}
+
+static void logging_suppressed(struct tdb_context *tdb,
+ enum tdb_debug_level level, const char *fmt, ...)
+{
+}
+
+_PUBLIC_ int tdb_rescue(struct tdb_context *tdb,
+ void (*walk)(TDB_DATA, TDB_DATA, void *private_data),
+ void *private_data)
+{
+ struct found_table found = { NULL, 0, 0 };
+ tdb_off_t h, off, i;
+ tdb_log_func oldlog = tdb->log.log_fn;
+ struct tdb_record rec;
+ TDB_DATA key;
+ bool locked;
+
+ /* Read-only databases use no locking at all: it's best-effort.
+ * We may have a write lock already, so skip that case too. */
+ if (tdb->read_only || tdb->allrecord_lock.count != 0) {
+ locked = false;
+ } else {
+ if (tdb_lockall_read(tdb) == -1)
+ return -1;
+ locked = true;
+ }
+
+ /* Make sure we know true size of the underlying file. */
+ tdb_oob(tdb, tdb->map_size, 1, 1);
+
+ /* Suppress logging, since we anticipate errors. */
+ tdb->log.log_fn = logging_suppressed;
+
+ /* Now walk entire db looking for records. */
+ for (off = TDB_DATA_START(tdb->hash_size);
+ off < tdb->map_size;
+ off += TDB_ALIGNMENT) {
+ if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+ DOCONV()) == -1)
+ continue;
+
+ if (looks_like_valid_record(tdb, off, &rec, &key)) {
+ if (!add_to_table(&found, off, &rec, key)) {
+ goto oom;
+ }
+ }
+ }
+
+ /* Walk hash chains to positive vet. */
+ for (h = 0; h < 1+tdb->hash_size; h++) {
+ bool slow_chase = false;
+ tdb_off_t slow_off = FREELIST_TOP + h*sizeof(tdb_off_t);
+
+ if (tdb_ofs_read(tdb, FREELIST_TOP + h*sizeof(tdb_off_t),
+ &off) == -1)
+ continue;
+
+ while (off && off != slow_off) {
+ if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+ DOCONV()) != 0) {
+ break;
+ }
+
+ /* 0 is the free list, rest are hash chains. */
+ if (h == 0) {
+ /* Don't mark garbage as free. */
+ if (rec.magic != TDB_FREE_MAGIC) {
+ break;
+ }
+ mark_free_area(&found, off,
+ sizeof(rec) + rec.rec_len);
+ } else {
+ found_in_hashchain(&found, off);
+ }
+
+ off = rec.next;
+
+ /* Loop detection using second pointer at half-speed */
+ if (slow_chase) {
+ /* First entry happens to be next ptr */
+ tdb_ofs_read(tdb, slow_off, &slow_off);
+ }
+ slow_chase = !slow_chase;
+ }
+ }
+
+ /* Recovery area: must be marked as free, since it often has old
+ * records in there! */
+ if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &off) == 0 && off != 0) {
+ if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+ DOCONV()) == 0) {
+ mark_free_area(&found, off, sizeof(rec) + rec.rec_len);
+ }
+ }
+
+ /* Now sort by key! */
+ if (found.arr != NULL) {
+ qsort(found.arr, found.num, sizeof(found.arr[0]), cmp_key);
+ }
+
+ for (i = 0; (found.arr != NULL) && i < found.num; ) {
+ unsigned int num, num_in_hash = 0;
+
+ /* How many are identical? */
+ for (num = 0; num < found.num - i; num++) {
+ if (!key_eq(found.arr[i].key, found.arr[i+num].key)) {
+ break;
+ }
+ if (found.arr[i+num].in_hash) {
+ if (!walk_record(tdb, &found.arr[i+num],
+ walk, private_data))
+ goto oom;
+ num_in_hash++;
+ }
+ }
+ assert(num);
+
+ /* If none were in the hash, we print any not in free list. */
+ if (num_in_hash == 0) {
+ unsigned int j;
+
+ for (j = i; j < i + num; j++) {
+ if (!found.arr[j].in_free) {
+ if (!walk_record(tdb, &found.arr[j],
+ walk, private_data))
+ goto oom;
+ }
+ }
+ }
+
+ i += num;
+ }
+
+ tdb->log.log_fn = oldlog;
+ if (locked) {
+ tdb_unlockall_read(tdb);
+ }
+ return 0;
+
+oom:
+ tdb->log.log_fn = oldlog;
+ tdb->ecode = TDB_ERR_OOM;
+ TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_rescue: failed allocating\n"));
+ free_table(&found);
+ if (locked) {
+ tdb_unlockall_read(tdb);
+ }
+ return -1;
+}
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