From 3bea87e36f630842aeeda6be887f21dd899fa679 Mon Sep 17 00:00:00 2001
From: Kostas Kyrimis <kostas@dragonflydb.io>
Date: Mon, 24 Jul 2023 15:08:24 +0300
Subject: [PATCH] fix(VersionMonitor): improper version update to older version
 (#1577)

Add correct version comparison between VersionMonitor and the dfly server
---
 src/server/dfly_main.cc | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/server/dfly_main.cc b/src/server/dfly_main.cc
index 1a32e69f6..94e09a748 100644
--- a/src/server/dfly_main.cc
+++ b/src/server/dfly_main.cc
@@ -3,6 +3,7 @@
 // See LICENSE for licensing terms.
 //
 
+#include "absl/strings/numbers.h"
 #ifdef NDEBUG
 #include <mimalloc-new-delete.h>
 #endif
@@ -161,9 +162,41 @@ struct VersionMonitor {
   }
 
  private:
+  bool IsVersionOutdated(std::string_view remote, std::string_view current) const;
   void RunTask(SSL_CTX* ssl_ctx);
 };
 
+bool VersionMonitor::IsVersionOutdated(const std::string_view remote,
+                                       const std::string_view current) const {
+  const std::vector<absl::string_view> remote_xyz = absl::StrSplit(remote, ".");
+  const std::vector<absl::string_view> current_xyz = absl::StrSplit(current, ".");
+  if (remote_xyz.size() != current_xyz.size()) {
+    LOG(WARNING) << "Can't compare Dragonfly version " << current << " to latest version "
+                 << remote;
+    return false;
+  }
+  const auto print_to_log = [](const std::string_view version, const absl::string_view part) {
+    LOG(WARNING) << "Can't parse " << version << " part of version " << part << " as a number";
+  };
+  for (size_t i = 0; i < remote_xyz.size(); ++i) {
+    size_t remote_x = 0;
+    if (!absl::SimpleAtoi(remote_xyz[i], &remote_x)) {
+      print_to_log(remote, remote_xyz[i]);
+      return false;
+    }
+    size_t current_x = 0;
+    if (!absl::SimpleAtoi(current_xyz[i], &current_x)) {
+      print_to_log(current, current_xyz[i]);
+      return false;
+    }
+    if (remote_x > current_x) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 void VersionMonitor::Run(ProactorPool* proactor_pool) {
   // Avoid running dev environments.
   bool is_dev_env = false;
@@ -205,8 +238,8 @@ void VersionMonitor::RunTask(SSL_CTX* ssl_ctx) {
     const std::optional<std::string> remote_version =
         GetRemoteVersion(my_pb, ssl_ctx, host_name, port, resource, version_header);
     if (remote_version) {
-      const std::string rv = remote_version.value();
-      if (rv != current_version) {
+      const std::string_view rv = remote_version.value();
+      if (IsVersionOutdated(rv, current_version)) {
         LOG_FIRST_N(INFO, 1) << "Your current version '" << current_version
                              << "' is not the latest version. A newer version '" << rv
                              << "' is now available. Please consider an update.";