fix GetServers csv parser robustness for c-ares CSV output

Author: omghante

src/cares_wrap.cc

@@ -2163,29 +2163,57 @@ void GetServers(const FunctionCallbackInfo<Value>& args) {
     std::string entry = servers_str.substr(pos, comma - pos);
     pos = comma + 1;
 
+    // Trim whitespace just in case c-ares somehow adds it
+    size_t first = entry.find_first_not_of(" \t\r\n");
+    if (first == std::string::npos) continue;
+    size_t last = entry.find_last_not_of(" \t\r\n");
+    entry = entry.substr(first, (last - first + 1));
+    if (entry.empty()) continue;
+
     std::string host;
     int port = 53;  // default DNS port
 
-    if (!entry.empty() && entry[0] == '[') {
+    if (entry[0] == '[') {
       /* IPv6: [host]:port or [host] */
       auto bracket_end = entry.find(']');
       if (bracket_end != std::string::npos) {
         host = entry.substr(1, bracket_end - 1);
         if (bracket_end + 1 < entry.size() && entry[bracket_end + 1] == ':') {
-          port = std::stoi(entry.substr(bracket_end + 2));
+          try {
+            port = std::stoi(entry.substr(bracket_end + 2));
+          } catch (...) { /* ignore */
+          }
         }
+      } else {
+        host = entry;  // fallback if malformed
       }
     } else {
       /* IPv4: host:port or just host */
       auto colon = entry.rfind(':');
-      if (colon != std::string::npos) {
+      /* ensure colon isn't part of an IPv6 address accidentally output without
+       * brackets */
+      auto first_colon = entry.find(':');
+      if (colon != std::string::npos && colon == first_colon) {
         host = entry.substr(0, colon);
-        port = std::stoi(entry.substr(colon + 1));
+        try {
+          port = std::stoi(entry.substr(colon + 1));
+        } catch (...) { /* ignore */
+        }
       } else {
+        /* no port, or IPv6 addr without brackets */
         host = entry;
       }
     }
 
+    // Node.js expects IPv6 scope IDs to be preserved (if they were generated).
+    // The previous implementation dropped them since uv_inet_ntop ignores scope
+    // IDs. To match the previous strict behavior perfectly, we strip scope IDs
+    // (e.g. %lo0).
+    auto pct = host.find('%');
+    if (pct != std::string::npos) {
+      host = host.substr(0, pct);
+    }
+
     Local<Value> ret[] = {OneByteString(env->isolate(), host.c_str()),
                           Integer::New(env->isolate(), port)};