reexport: Add sqlite backend

The reexport database code is designed to support multiple ways
to store the state.
So far only SQlite is implemented.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Steve Dickson <steved@redhat.com>

2 files changed, 314 insertions, 0 deletions

diff --git a/support/reexport/backend_sqlite.c b/support/reexport/backend_sqlite.c
new file mode 100644
index 0000000..132f30c
--- /dev/null
+++ b/support/reexport/backend_sqlite.c
@@ -0,0 +1,267 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sqlite3.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/random.h>
+#include <unistd.h>
+
+#include "conffile.h"
+#include "reexport_backend.h"
+#include "xlog.h"
+
+#define REEXPDB_DBFILE NFS_STATEDIR "/reexpdb.sqlite3"
+#define REEXPDB_DBFILE_WAIT_USEC (5000)
+
+static sqlite3 *db;
+static int init_done;
+
+static int prng_init(void)
+{
+	int seed;
+
+	if (getrandom(&seed, sizeof(seed), 0) != sizeof(seed)) {
+		xlog(L_ERROR, "Unable to obtain seed for PRNG via getrandom()");
+		return -1;
+	}
+
+	srand(seed);
+	return 0;
+}
+
+static void wait_for_dbaccess(void)
+{
+	usleep(REEXPDB_DBFILE_WAIT_USEC + (rand() % REEXPDB_DBFILE_WAIT_USEC));
+}
+
+static bool sqlite_plug_init(void)
+{
+	char *sqlerr;
+	int ret;
+
+	if (init_done)
+		return true;
+
+	if (prng_init() != 0)
+		return false;
+
+	ret = sqlite3_open_v2(conf_get_str_with_def("reexport", "sqlitedb", REEXPDB_DBFILE),
+			      &db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX,
+			      NULL);
+	if (ret != SQLITE_OK) {
+		xlog(L_ERROR, "Unable to open reexport database: %s", sqlite3_errstr(ret));
+		return false;
+	}
+
+again:
+	ret = sqlite3_exec(db, "CREATE TABLE IF NOT EXISTS fsidnums (num INTEGER PRIMARY KEY CHECK (num > 0 AND num < 4294967296), path TEXT UNIQUE); CREATE INDEX IF NOT EXISTS idx_ids_path ON fsidnums (path);", NULL, NULL, &sqlerr);
+	switch (ret) {
+	case SQLITE_OK:
+		init_done = 1;
+		ret = 0;
+		break;
+	case SQLITE_BUSY:
+	case SQLITE_LOCKED:
+		wait_for_dbaccess();
+		goto again;
+	default:
+		xlog(L_ERROR, "Unable to init reexport database: %s", sqlite3_errstr(ret));
+		sqlite3_free(sqlerr);
+		sqlite3_close_v2(db);
+		ret = -1;
+	}
+
+	return ret == 0 ? true : false;
+}
+
+static void sqlite_plug_destroy(void)
+{
+	if (!init_done)
+		return;
+
+	sqlite3_close_v2(db);
+}
+
+static bool get_fsidnum_by_path(char *path, uint32_t *fsidnum, bool *found)
+{
+	static const char fsidnum_by_path_sql[] = "SELECT num FROM fsidnums WHERE path = ?1;";
+	sqlite3_stmt *stmt = NULL;
+	bool success = false;
+	int ret;
+
+	*found = false;
+
+	ret = sqlite3_prepare_v2(db, fsidnum_by_path_sql, sizeof(fsidnum_by_path_sql), &stmt, NULL);
+	if (ret != SQLITE_OK) {
+		xlog(L_WARNING, "Unable to prepare SQL query '%s': %s", fsidnum_by_path_sql, sqlite3_errstr(ret));
+		goto out;
+	}
+
+	ret = sqlite3_bind_text(stmt, 1, path, -1, NULL);
+	if (ret != SQLITE_OK) {
+		xlog(L_WARNING, "Unable to bind SQL query '%s': %s", fsidnum_by_path_sql, sqlite3_errstr(ret));
+		goto out;
+	}
+
+again:
+	ret = sqlite3_step(stmt);
+	switch (ret) {
+	case SQLITE_ROW:
+		*fsidnum = sqlite3_column_int(stmt, 0);
+		success = true;
+		*found = true;
+		break;
+	case SQLITE_DONE:
+		/* No hit */
+		success = true;
+		*found = false;
+		break;
+	case SQLITE_BUSY:
+	case SQLITE_LOCKED:
+		wait_for_dbaccess();
+		goto again;
+	default:
+		xlog(L_WARNING, "Error while looking up '%s' in database: %s", path, sqlite3_errstr(ret));
+	}
+
+out:
+	sqlite3_finalize(stmt);
+	return success;
+}
+
+static bool sqlite_plug_path_by_fsidnum(uint32_t fsidnum, char **path, bool *found)
+{
+	static const char path_by_fsidnum_sql[] = "SELECT path FROM fsidnums WHERE num = ?1;";
+	sqlite3_stmt *stmt = NULL;
+	bool success = false;
+	int ret;
+
+	*found = false;
+
+	ret = sqlite3_prepare_v2(db, path_by_fsidnum_sql, sizeof(path_by_fsidnum_sql), &stmt, NULL);
+	if (ret != SQLITE_OK) {
+		xlog(L_WARNING, "Unable to prepare SQL query '%s': %s", path_by_fsidnum_sql, sqlite3_errstr(ret));
+		goto out;
+	}
+
+	ret = sqlite3_bind_int(stmt, 1, fsidnum);
+	if (ret != SQLITE_OK) {
+		xlog(L_WARNING, "Unable to bind SQL query '%s': %s", path_by_fsidnum_sql, sqlite3_errstr(ret));
+		goto out;
+	}
+
+again:
+	ret = sqlite3_step(stmt);
+	switch (ret) {
+	case SQLITE_ROW:
+		*path = strdup((char *)sqlite3_column_text(stmt, 0));
+		if (*path) {
+			*found = true;
+			success = true;
+		} else {
+			xlog(L_WARNING, "Out of memory");
+		}
+		break;
+	case SQLITE_DONE:
+		/* No hit */
+		*found = false;
+		success = true;
+		break;
+	case SQLITE_BUSY:
+	case SQLITE_LOCKED:
+		wait_for_dbaccess();
+		goto again;
+	default:
+		xlog(L_WARNING, "Error while looking up '%i' in database: %s", fsidnum, sqlite3_errstr(ret));
+	}
+
+out:
+	sqlite3_finalize(stmt);
+	return success;
+}
+
+static bool new_fsidnum_by_path(char *path, uint32_t *fsidnum)
+{
+	/*
+	 * This query is a little tricky. We use SQL to find and claim the smallest free fsid number.
+	 * To find a free fsid the fsidnums is left joined to itself but with an offset of 1.
+	 * Everything after the UNION statement is to handle the corner case where fsidnums
+	 * is empty. In this case we want 1 as first fsid number.
+	 */
+	static const char new_fsidnum_by_path_sql[] = "INSERT INTO fsidnums VALUES ((SELECT ids1.num + 1 FROM fsidnums AS ids1 LEFT JOIN fsidnums AS ids2 ON ids2.num = ids1.num + 1 WHERE ids2.num IS NULL UNION SELECT 1 WHERE NOT EXISTS (SELECT NULL FROM fsidnums WHERE num = 1) LIMIT 1), ?1) RETURNING num;";
+
+	sqlite3_stmt *stmt = NULL;
+	int ret, check = 0;
+	bool success = false;
+
+	ret = sqlite3_prepare_v2(db, new_fsidnum_by_path_sql, sizeof(new_fsidnum_by_path_sql), &stmt, NULL);
+	if (ret != SQLITE_OK) {
+		xlog(L_WARNING, "Unable to prepare SQL query '%s': %s", new_fsidnum_by_path_sql, sqlite3_errstr(ret));
+		goto out;
+	}
+
+	ret = sqlite3_bind_text(stmt, 1, path, -1, NULL);
+	if (ret != SQLITE_OK) {
+		xlog(L_WARNING, "Unable to bind SQL query '%s': %s", new_fsidnum_by_path_sql, sqlite3_errstr(ret));
+		goto out;
+	}
+
+again:
+	ret = sqlite3_step(stmt);
+	switch (ret) {
+	case SQLITE_ROW:
+		*fsidnum = sqlite3_column_int(stmt, 0);
+		success = true;
+		break;
+	case SQLITE_CONSTRAINT:
+		/* Maybe we lost the race against another writer and the path is now present. */
+		check = 1;
+		break;
+	case SQLITE_BUSY:
+	case SQLITE_LOCKED:
+		wait_for_dbaccess();
+		goto again;
+	default:
+		xlog(L_WARNING, "Error while looking up '%s' in database: %s", path, sqlite3_errstr(ret));
+	}
+
+out:
+	sqlite3_finalize(stmt);
+
+	if (check) {
+		bool found = false;
+
+		get_fsidnum_by_path(path, fsidnum, &found);
+		if (!found)
+			xlog(L_WARNING, "SQLITE_CONSTRAINT error while inserting '%s' in database", path);
+	}
+
+	return success;
+}
+
+static bool sqlite_plug_fsidnum_by_path(char *path, uint32_t *fsidnum, int may_create, bool *found)
+{
+	bool success;
+
+	success = get_fsidnum_by_path(path, fsidnum, found);
+	if (success) {
+		if (!*found && may_create) {
+			success = new_fsidnum_by_path(path, fsidnum);
+			if (success)
+				*found = true;
+		}
+	}
+
+	return success;
+}
+
+struct reexpdb_backend_plugin sqlite_plug_ops = {
+	.fsidnum_by_path = sqlite_plug_fsidnum_by_path,
+	.path_by_fsidnum = sqlite_plug_path_by_fsidnum,
+	.initdb = sqlite_plug_init,
+	.destroydb = sqlite_plug_destroy,
+};
diff --git a/support/reexport/reexport_backend.h b/support/reexport/reexport_backend.h
new file mode 100644
index 0000000..4940f06
--- /dev/null
+++ b/support/reexport/reexport_backend.h
@@ -0,0 +1,47 @@
+#ifndef REEXPORT_BACKEND_H
+#define REEXPORT_BACKEND_H
+
+extern struct reexpdb_backend_plugin sqlite_plug_ops;
+
+struct reexpdb_backend_plugin {
+	/*
+	 * Find or allocate a fsidnum for a given path.
+	 *
+	 * @path: Path to look for
+	 * @fsidnum: Pointer to an uint32_t variable
+	 * @may_create: If non-zero, a fsidnum will be allocated if none was found
+	 *
+	 * Returns true if either an fsidnum was found or successfully allocated,
+	 * false otherwise.
+	 * On success, the fsidnum will be stored into @fsidnum.
+	 * Upon errors, false is returned and errors are logged.
+	 */
+	bool (*fsidnum_by_path)(char *path, uint32_t *fsidnum, int may_create, bool *found);
+
+	/*
+	 * Lookup path by a given fsidnum
+	 *
+	 * @fsidnum: fsidnum to look for
+	 * @path: address of a char pointer
+	 *
+	 * Returns true if a path was found, false otherwise.
+	 * Upon errors, false is returned and errors are logged.
+	 * In case of success, the function returns the found path
+	 * via @path, @path will point to a freshly allocated buffer
+	 * which is free()'able.
+	 */
+	bool (*path_by_fsidnum)(uint32_t fsidnum, char **path, bool *found);
+
+	/*
+	 * Init database connection, can get called multiple times.
+	 * Returns true on success, false otherwise.
+	 */
+	bool (*initdb)(void);
+
+	/*
+	 * Undoes initdb().
+	 */
+	void (*destroydb)(void);
+};
+
+#endif /* REEXPORT_BACKEND_H */