From bd168d57ffed1dc73cb000b301674ebb1b9fd5d2 Mon Sep 17 00:00:00 2001
From: Alejo Sanchez <alejo.sanchez@scylladb.com>
Date: Fri, 4 Jun 2021 08:25:30 -0400
Subject: [PATCH] raft: fix vote reply handling in prevote

Do not register a reply to prevote as a real vote

Found and authored by @kostja.

Signed-off-by: Alejo Sanchez <alejo.sanchez@scylladb.com>
Message-Id: <20210604122530.1975388-1-alejo.sanchez@scylladb.com>
---
 raft/fsm.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/raft/fsm.cc b/raft/fsm.cc
index 38d1304c0a..970d1f7c76 100644
--- a/raft/fsm.cc
+++ b/raft/fsm.cc
@@ -692,6 +692,10 @@ void fsm::request_vote_reply(server_id from, vote_reply&& reply) {
     logger.trace("{} received a {} vote from {}", _my_id, reply.vote_granted ? "yes" : "no", from);
 
     auto& state = std::get<candidate>(_state);
+    // Should not register a reply to prevote as a real vote
+    if (state.is_prevote != reply.is_prevote) {
+        return;
+    }
     state.votes.register_vote(from, reply.vote_granted);
 
     switch (state.votes.tally_votes()) {