From 32d93cc4876fbc11dc5e428242186310a158b828 Mon Sep 17 00:00:00 2001
From: Aapo Talvensaari <aapo.talvensaari@gmail.com>
Date: Thu, 23 Jan 2025 14:58:56 +0000
Subject: [PATCH] chore(clustering): do not enable kong.sync.v2 when connecting
 dp is older than cp

Signed-off-by: Aapo Talvensaari <aapo.talvensaari@gmail.com>
---
 kong/clustering/rpc/manager.lua | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/kong/clustering/rpc/manager.lua b/kong/clustering/rpc/manager.lua
index fb40ace1a6e..1ca48dbe0d6 100644
--- a/kong/clustering/rpc/manager.lua
+++ b/kong/clustering/rpc/manager.lua
@@ -12,7 +12,8 @@ local callbacks = require("kong.clustering.rpc.callbacks")
 local clustering_tls = require("kong.clustering.tls")
 local constants = require("kong.constants")
 local table_isempty = require("table.isempty")
-local pl_tablex = require("pl.tablex")
+local table_clone = require("table.clone")
+local table_remove = table.remove
 local cjson = require("cjson.safe")
 local string_tools = require("kong.tools.string")
 
@@ -25,7 +26,7 @@ local ngx_log = ngx.log
 local ngx_exit = ngx.exit
 local ngx_time = ngx.time
 local exiting = ngx.worker.exiting
-local pl_tablex_makeset = pl_tablex.makeset
+local pl_tablex_makeset = require("pl.tablex").makeset
 local cjson_encode = cjson.encode
 local cjson_decode = cjson.decode
 local validate_client_cert = clustering_tls.validate_client_cert
@@ -188,10 +189,26 @@ function _M:_handle_meta_call(c, cert)
   assert(type(info.kong_hostname) == "string")
   assert(type(info.kong_conf) == "table")
 
+  local version = info.kong_version
+  local rpc_capabilities = self.callbacks:get_capabilities_list(version)
+  if KONG_VERSION > version  then
+    local delta_index
+    for i, rpc_capability in ipairs(rpc_capabilities) do
+      if rpc_capability == "kong.sync.v2" then
+        delta_index = i
+        break
+      end
+    end
+    if delta_index then
+      rpc_capabilities = table_clone(rpc_capabilities)
+      table_remove(rpc_capabilities, delta_index)
+    end
+  end
+
   local payload = {
     jsonrpc = jsonrpc.VERSION,
     result = {
-      rpc_capabilities = self.callbacks:get_capabilities_list(),
+      rpc_capabilities = rpc_capabilities,
       -- now we only support snappy
       rpc_frame_encoding = RPC_SNAPPY_FRAMED,
       },
@@ -239,7 +256,7 @@ function _M:_handle_meta_call(c, cert)
   -- store DP's ip addr
   self.client_info[node_id] = {
     ip = ngx_var.remote_addr,
-    version = info.kong_version,
+    version = version,
     labels = labels,
     cert_details = cert_details,
   }