tdb: add tdb_rescue()

This allows for an emergency best-effort dump.  It's a little better than
strings(1).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 176 insertions, 0 deletions

diff --git a/lib/tdb/test/run-rescue-find_entry.c b/lib/tdb/test/run-rescue-find_entry.c
new file mode 100644
index 0000000000..25f4f1c05f
--- /dev/null
+++ b/lib/tdb/test/run-rescue-find_entry.c
@@ -0,0 +1,50 @@
+#include "../common/tdb_private.h"
+#include "../common/io.c"
+#include "../common/tdb.c"
+#include "../common/lock.c"
+#include "../common/freelist.c"
+#include "../common/traverse.c"
+#include "../common/transaction.c"
+#include "../common/error.c"
+#include "../common/open.c"
+#include "../common/check.c"
+#include "../common/hash.c"
+#include "../common/rescue.c"
+#include "tap-interface.h"
+#include <stdlib.h>
+#include "logging.h"
+
+#define NUM 20
+
+/* Binary searches are deceptively simple: easy to screw up! */
+int main(int argc, char *argv[])
+{
+	unsigned int i, j, n;
+	struct found f[NUM+1];
+	struct found_table table;
+
+	/* Set up array for searching. */
+	for (i = 0; i < NUM+1; i++) {
+		f[i].head = i * 3;
+	}
+	table.arr = f;
+
+	for (i = 0; i < NUM; i++) {
+		table.num = i;
+		for (j = 0; j < (i + 2) * 3; j++) {
+			n = find_entry(&table, j);
+			ok1(n <= i);
+
+			/* If we were searching for something too large... */
+			if (j > i*3)
+				ok1(n == i);
+			else {
+				/* It must give us something after j */
+				ok1(f[n].head >= j);
+				ok1(n == 0 || f[n-1].head < j);
+			}
+		}
+	}
+
+	return exit_status();
+}
diff --git a/lib/tdb/test/run-rescue.c b/lib/tdb/test/run-rescue.c
new file mode 100644
index 0000000000..a26c493972
--- /dev/null
+++ b/lib/tdb/test/run-rescue.c
@@ -0,0 +1,126 @@
+#include "../common/tdb_private.h"
+#include "../common/io.c"
+#include "../common/tdb.c"
+#include "../common/lock.c"
+#include "../common/freelist.c"
+#include "../common/traverse.c"
+#include "../common/transaction.c"
+#include "../common/error.c"
+#include "../common/open.c"
+#include "../common/check.c"
+#include "../common/hash.c"
+#include "../common/rescue.c"
+#include "tap-interface.h"
+#include <stdlib.h>
+#include "logging.h"
+
+struct walk_data {
+	TDB_DATA key;
+	TDB_DATA data;
+	bool fail;
+	unsigned count;
+};
+
+static inline bool tdb_deq(TDB_DATA a, TDB_DATA b)
+{
+	return a.dsize == b.dsize && memcmp(a.dptr, b.dptr, a.dsize) == 0;
+}
+
+static inline TDB_DATA tdb_mkdata(const void *p, size_t len)
+{
+	TDB_DATA d;
+	d.dptr = (void *)p;
+	d.dsize = len;
+	return d;
+}
+
+static void walk(TDB_DATA key, TDB_DATA data, void *_wd)
+{
+	struct walk_data *wd = _wd;
+
+	if (!tdb_deq(key, wd->key)) {
+		wd->fail = true;
+	}
+
+	if (!tdb_deq(data, wd->data)) {
+		wd->fail = true;
+	}
+	wd->count++;
+}
+
+static void count_records(TDB_DATA key, TDB_DATA data, void *_wd)
+{
+	struct walk_data *wd = _wd;
+
+	if (!tdb_deq(key, wd->key) || !tdb_deq(data, wd->data))
+		diag("%.*s::%.*s\n",
+		     (int)key.dsize, key.dptr, (int)data.dsize, data.dptr);
+	wd->count++;
+}
+
+static void log_fn(struct tdb_context *tdb, enum tdb_debug_level level, const char *fmt, ...)
+{
+	unsigned int *count = tdb_get_logging_private(tdb);
+	(*count)++;
+}
+
+int main(int argc, char *argv[])
+{
+	struct tdb_context *tdb;
+	struct walk_data wd;
+	unsigned int i, size, log_count = 0;
+	struct tdb_logging_context log_ctx = { log_fn, &log_count };
+
+	plan_tests(8);
+	tdb = tdb_open_ex("run-rescue.tdb", 1, TDB_CLEAR_IF_FIRST,
+			  O_CREAT|O_TRUNC|O_RDWR, 0600, &log_ctx, NULL);
+
+	wd.key.dsize = strlen("hi");
+	wd.key.dptr = (void *)"hi";
+	wd.data.dsize = strlen("world");
+	wd.data.dptr = (void *)"world";
+	wd.count = 0;
+	wd.fail = false;
+
+	ok1(tdb_store(tdb, wd.key, wd.data, TDB_INSERT) == 0);
+
+	ok1(tdb_rescue(tdb, walk, &wd) == 0);
+	ok1(!wd.fail);
+	ok1(wd.count == 1);
+
+	/* Corrupt the database, walk should either get it or not. */
+	size = tdb->map_size;
+	for (i = sizeof(struct tdb_header); i < size; i++) {
+		char c;
+		if (tdb->methods->tdb_read(tdb, i, &c, 1, false) != 0)
+			fail("Reading offset %i", i);
+		if (tdb->methods->tdb_write(tdb, i, "X", 1) != 0)
+			fail("Writing X at offset %i", i);
+
+		wd.count = 0;
+		if (tdb_rescue(tdb, count_records, &wd) != 0) {
+			wd.fail = true;
+			break;
+		}
+		/* Could be 0 or 1. */
+		if (wd.count > 1) {
+			wd.fail = true;
+			break;
+		}
+		if (tdb->methods->tdb_write(tdb, i, &c, 1) != 0)
+			fail("Restoring offset %i", i);
+	}
+	ok1(log_count == 0);
+	ok1(!wd.fail);
+	tdb_close(tdb);
+
+	/* Now try our known-corrupt db. */
+	tdb = tdb_open_ex("test/tdb.corrupt", 1024, 0, O_RDWR, 0,
+			  &taplogctx, NULL);
+	wd.count = 0;
+	ok1(tdb_rescue(tdb, count_records, &wd) == 0);
+	ok1(wd.count == 1627);
+	tdb_close(tdb);
+
+	return exit_status();
+}