[Tarantool-patches] [PATCH 2/2] raft: decode even invalid states of raft

[Cyrill Gorcunov]

We should never trust the request data it can
carry anything, thus lets make sure we're not
decoding some trash into a string.

Signed-off-by: Cyrill Gorcunov <gorcunov at gmail.com>
---
 src/box/lua/info.c |  2 +-
 src/box/raft.c     | 29 +++++++++++++++++++++--------
 src/box/raft.h     | 11 ++++++++++-
 3 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/src/box/lua/info.c b/src/box/lua/info.c
index cac3fd475..92d48c96c 100644
--- a/src/box/lua/info.c
+++ b/src/box/lua/info.c
@@ -582,7 +582,7 @@ static int
 lbox_info_election(struct lua_State *L)
 {
 	lua_createtable(L, 0, 4);
-	lua_pushstring(L, raft_state_strs[raft.state]);
+	lua_pushstring(L, raft_state_str(raft.state));
 	lua_setfield(L, -2, "state");
 	luaL_pushuint64(L, raft.volatile_term);
 	lua_setfield(L, -2, "term");
diff --git a/src/box/raft.c b/src/box/raft.c
index 9de77b0ec..44a76154f 100644
--- a/src/box/raft.c
+++ b/src/box/raft.c
@@ -44,13 +44,6 @@
  */
 #define RAFT_RANDOM_ELECTION_FACTOR 0.1
 
-const char *raft_state_strs[] = {
-	NULL,
-	"follower",
-	"candidate",
-	"leader",
-};
-
 /** Raft state of this instance. */
 struct raft raft = {
 	.leader = 0,
@@ -70,6 +63,26 @@ struct raft raft = {
 	.election_timeout = 5,
 };
 
+/**
+ * When decoding we should never trust that there
+ * is a valid data incomes.
+ */
+const char *
+raft_state_str(uint32_t state)
+{
+	static const char *str[] = {
+		[RAFT_STATE_NONE]	= "none",
+		[RAFT_STATE_FOLLOWER]	= "follower",
+		[RAFT_STATE_CANDIDATE]	= "candidate",
+		[RAFT_STATE_LEADER]	= "leader",
+	};
+
+	if (state < lengthof(str))
+		return str[state];
+
+	return "unknown";
+};
+
 /**
  * Check if Raft is completely synced with disk. Meaning all its critical values
  * are in WAL. Only in that state the node can become a leader or a candidate.
@@ -284,7 +297,7 @@ raft_request_to_string(const struct raft_request *req)
 	}
 	if (req->state != 0) {
 		rc = snprintf(pos, size, ", state: %s",
-			      raft_state_strs[req->state]);
+			      raft_state_str(req->state));
 		assert(rc >= 0);
 		pos += rc;
 		size -= rc;
diff --git a/src/box/raft.h b/src/box/raft.h
index be77a5473..3c007789b 100644
--- a/src/box/raft.h
+++ b/src/box/raft.h
@@ -70,6 +70,11 @@ struct raft_request;
 struct vclock;
 
 enum raft_state {
+	/**
+	 * Unknown state, never valid, for sequence completeness
+	 * and to print out wrong state from incoming packets.
+	 */
+	RAFT_STATE_NONE = 0,
 	/**
 	 * Can't write. Can only accept data from a leader. Node in this state
 	 * either monitors an existing leader, or there is an on-going election
@@ -86,7 +91,11 @@ enum raft_state {
 	RAFT_STATE_LEADER = 3,
 };
 
-extern const char *raft_state_strs[];
+/**
+ * Decode raft state into string representation.
+ */
+const char *
+raft_state_str(uint32_t state);
 
 struct raft {
 	/** Instance ID of leader of the current term. */
-- 
2.26.2