From 087a74e0731175d80de261f2688057fb8e0ec92e Mon Sep 17 00:00:00 2001
From: Antoine du Hamel <duhamelantoine1995@gmail.com>
Date: Wed, 8 Jul 2026 12:55:39 +0200
Subject: [PATCH] dns: stop using deprecated functions in `SetServers`

Signed-off-by: Antoine du Hamel <duhamelantoine1995@gmail.com>
---
 src/cares_wrap.cc         | 42 ++++++++++++---------------------------
 test/parallel/test-dns.js |  7 +++++--
 2 files changed, 18 insertions(+), 31 deletions(-)

diff --git a/src/cares_wrap.cc b/src/cares_wrap.cc
index 72f3d06fe07569..0f672897cd2b43 100644
--- a/src/cares_wrap.cc
+++ b/src/cares_wrap.cc
@@ -2110,15 +2110,9 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
 
   uint32_t len = arr->Length();
 
-  if (len == 0) {
-    int rv = ares_set_servers(channel->cares_channel(), nullptr);
-    return args.GetReturnValue().Set(rv);
-  }
-
-  std::vector<ares_addr_port_node> servers(len);
-  ares_addr_port_node* last = nullptr;
-
-  int err;
+  // An empty list clears all configured servers. ares_set_servers_ports_csv()
+  // treats an empty string as "blank all servers".
+  std::string csv;
 
   for (uint32_t i = 0; i < len; i++) {
     Local<Value> val;
@@ -2143,37 +2137,27 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
     node::Utf8Value ip(env->isolate(), ipValue);
     int port = portValue->Int32Value(env->context()).FromJust();
 
-    ares_addr_port_node* cur = &servers[i];
+    if (!csv.empty()) csv += ',';
 
-    cur->tcp_port = cur->udp_port = port;
+    // Incoming CSV format expected by c-ares: host[:port][,host[:port]]...
+    // IPv6 addresses must be wrapped in square brackets.
     switch (fam) {
       case 4:
-        cur->family = AF_INET;
-        err = uv_inet_pton(AF_INET, *ip, &cur->addr);
+        csv += *ip;
         break;
       case 6:
-        cur->family = AF_INET6;
-        err = uv_inet_pton(AF_INET6, *ip, &cur->addr);
+        csv += '[';
+        csv += *ip;
+        csv += ']';
         break;
       default:
         UNREACHABLE("Bad address family");
     }
-
-    if (err)
-      break;
-
-    cur->next = nullptr;
-
-    if (last != nullptr)
-      last->next = cur;
-
-    last = cur;
+    csv += ':';
+    csv += std::to_string(port);
   }
 
-  if (err == 0)
-    err = ares_set_servers_ports(channel->cares_channel(), servers.data());
-  else
-    err = ARES_EBADSTR;
+  int err = ares_set_servers_ports_csv(channel->cares_channel(), csv.c_str());
 
   if (err == ARES_SUCCESS)
     channel->set_is_servers_default(false);
diff --git a/test/parallel/test-dns.js b/test/parallel/test-dns.js
index d7c2efcbd16ee3..e885a700752e58 100644
--- a/test/parallel/test-dns.js
+++ b/test/parallel/test-dns.js
@@ -130,12 +130,15 @@ const portsExpected = [
   '4.4.4.4',
   '2001:4860:4860::8888',
   '103.238.225.181:666',
-  '[fe80::483a:5aff:fee6:1f04]:666',
-  'fe80::483a:5aff:fee6:1f04',
 ];
 dns.setServers(ports);
 assert.deepStrictEqual(dns.getServers(), portsExpected);
 
+// Link-local IPv6 addresses require a zone index (scope id) to be usable;
+// c-ares drops link-local servers configured without one.
+dns.setServers(['[fe80::483a:5aff:fee6:1f04]%eth0']);
+assert.deepStrictEqual(dns.getServers(), []);
+
 dns.setServers([]);
 assert.deepStrictEqual(dns.getServers(), []);