Display more information on DB version mismatch

https://fedorahosted.org/sssd/ticket/1589

Added check for determining, whether database version is higher or
lower than expected. To distinguish it from other errors it uses
following retun values (further used for appropriate error message):
EMEDIUMTYPE for lower version than expected
EUCLEAN for higher version than expected

When SSSD or one of it's tools fails on DB version mismatch, new error
message is showed suggesting how to proceed.

2 files changed, 64 insertions, 2 deletions

diff --git a/src/db/sysdb.c b/src/db/sysdb.c
index 9685163b..dda288f7 100644
--- a/src/db/sysdb.c
+++ b/src/db/sysdb.c
@@ -947,6 +947,38 @@ errno_t sysdb_add_to_domain(struct sss_domain_info *domain,
     return EOK;
 }
 
+/* Compare versions of sysdb, returns ERRNO accordingly */
+static errno_t
+sysdb_version_check(const char *expected,
+                    const char *received)
+{
+    int ret;
+    unsigned int exp_major, exp_minor, recv_major, recv_minor;
+
+    ret = sscanf(expected, "%u.%u", &exp_major, &exp_minor);
+    if (ret != 2) {
+        return EINVAL;
+    }
+    ret = sscanf(received, "%u.%u", &recv_major, &recv_minor);
+    if (ret != 2) {
+        return EINVAL;
+    }
+
+    if (recv_major > exp_major) {
+        return EUCLEAN;
+    } else if (recv_major < exp_major) {
+        return EMEDIUMTYPE;
+    }
+
+    if (recv_minor > exp_minor) {
+        return EUCLEAN;
+    } else if (recv_minor < exp_minor) {
+        return EMEDIUMTYPE;
+    }
+
+    return EOK;
+}
+
 int sysdb_domain_init_internal(TALLOC_CTX *mem_ctx,
                                struct sss_domain_info *domain,
                                const char *db_path,
@@ -1037,7 +1069,7 @@ int sysdb_domain_init_internal(TALLOC_CTX *mem_ctx,
             if (!allow_upgrade) {
                 DEBUG(0, ("Wrong DB version (got %s expected %s)\n",
                           version, SYSDB_VERSION));
-                ret = EINVAL;
+                ret = sysdb_version_check(SYSDB_VERSION, version);
                 goto done;
             }
 
@@ -1136,7 +1168,7 @@ int sysdb_domain_init_internal(TALLOC_CTX *mem_ctx,
 
         DEBUG(0,("Unknown DB version [%s], expected [%s] for domain %s!\n",
                  version?version:"not found", SYSDB_VERSION, domain->name));
-        ret = EINVAL;
+        ret = sysdb_version_check(SYSDB_VERSION, version);
         goto done;
     }
 
diff --git a/src/db/sysdb.h b/src/db/sysdb.h
index fb95c35c..c701717f 100644
--- a/src/db/sysdb.h
+++ b/src/db/sysdb.h
@@ -199,6 +199,36 @@
 #define SYSDB_MOD_DEL LDB_FLAG_MOD_DELETE
 #define SYSDB_MOD_REP LDB_FLAG_MOD_REPLACE
 
+/* sysdb version check macros */
+#define SYSDB_VERSION_ERROR_HINT \
+    ERROR("Removing cache files in "DB_PATH" should fix the issue, " \
+          "but note that removing cache files will also remove all of your " \
+          "cached credentials.\n")
+
+#define SYSDB_VERSION_LOWER_ERROR(ret) do { \
+    if (ret == EUCLEAN) { \
+        ERROR("Lower version of database is expected!\n"); \
+        SYSDB_VERSION_ERROR_HINT; \
+    } \
+} while(0)
+
+#define SYSDB_VERSION_HIGHER_ERROR(ret) do { \
+    if (ret == EMEDIUMTYPE) { \
+        ERROR("Higher version of database is expected!\n"); \
+        ERROR("In order to upgrade the database, you must run SSSD.\n"); \
+        SYSDB_VERSION_ERROR_HINT; \
+    } \
+} while(0)
+
+/* use this in daemons */
+#define SYSDB_VERSION_ERROR_DAEMON(ret) \
+    SYSDB_VERSION_LOWER_ERROR(ret)
+
+/* use this in tools */
+#define SYSDB_VERSION_ERROR(ret) \
+    SYSDB_VERSION_LOWER_ERROR(ret); \
+    SYSDB_VERSION_HIGHER_ERROR(ret)
+
 struct confdb_ctx;
 struct sysdb_ctx;