From 953dc1ee667d747add03a7eb038c9805b18a9478 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Fri, 3 Mar 2023 14:04:16 +0100
Subject: [PATCH] dnsdist: Fall-back to non-XSK for too large responses

---
 pdns/dnsdist.cc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/pdns/dnsdist.cc b/pdns/dnsdist.cc
index 304cd0f99b..82ea4fc849 100644
--- a/pdns/dnsdist.cc
+++ b/pdns/dnsdist.cc
@@ -880,10 +880,20 @@ void responderThread(std::shared_ptr<DownstreamState> dss)
               return;
             }
             auto response = packet->clonePacketBuffer();
+            if (response.size() > packet->capacity()) {
+              /* fallback to sending the packet via normal socket */
+              ids->xskPacketHeader.reset();
+            }
             if (!processResponderPacket(dss, response, *localRespRuleActions, *localCacheInsertedRespRuleActions, std::move(*ids))) {
               xskInfo->sq.push(packet);
               return;
             }
+            if (response.size() > packet->capacity()) {
+              /* fallback to sending the packet via normal socket */
+              sendUDPResponse(ids->cs->udpFD, response, ids->delayMsec, ids->hopLocal, ids->hopRemote);
+              xskInfo->sq.push(packet);
+              return;
+            }
             packet->setHeader(*ids->xskPacketHeader);
             packet->setPayload(response);
             if (ids->delayMsec > 0) {
-- 
2.47.2