dnsdist: Also lookup the cache for UDP answers for DoH

diff --git a/pdns/dnsdist.cc b/pdns/dnsdist.cc
index e64620ed876614347dd2d27ae860aef9d8c22014..16bde52b517aac30f45aff9c869412255e0e33ea 100644 (file)
--- a/pdns/dnsdist.cc
+++ b/pdns/dnsdist.cc
@@ -1198,7 +1198,7 @@ ProcessQueryResult processQuery(DNSQuestion& dq, ClientState& cs, LocalHolders&
       // we need ECS parsing (parseECS) to be true so we can be sure that the initial incoming query did not have an existing
       // ECS option, which would make it unsuitable for the zero-scope feature.
       if (dq.packetCache && !dq.skipCache && (!selectedBackend || !selectedBackend->disableZeroScope) && dq.packetCache->isECSParsingEnabled()) {
-        if (dq.packetCache->get(dq, dq.getHeader()->id, &dq.cacheKeyNoECS, dq.subnet, dq.dnssecOK, !dq.overTCP() || dq.getProtocol() == dnsdist::Protocol::DoH, allowExpired)) {
+        if (dq.packetCache->get(dq, dq.getHeader()->id, &dq.cacheKeyNoECS, dq.subnet, dq.dnssecOK, !dq.overTCP(), allowExpired)) {
 
           if (!prepareOutgoingResponse(holders, cs, dq, true)) {
             return ProcessQueryResult::Drop;
@@ -1220,7 +1220,7 @@ ProcessQueryResult processQuery(DNSQuestion& dq, ClientState& cs, LocalHolders&
     }
 
     if (dq.packetCache && !dq.skipCache) {
-      if (dq.packetCache->get(dq, dq.getHeader()->id, &dq.cacheKey, dq.subnet, dq.dnssecOK, !dq.overTCP() || dq.getProtocol() == dnsdist::Protocol::DoH, allowExpired)) {
+      if (dq.packetCache->get(dq, dq.getHeader()->id, &dq.cacheKey, dq.subnet, dq.dnssecOK, !dq.overTCP(), allowExpired)) {
 
         restoreFlags(dq.getHeader(), dq.origFlags);
 
@@ -1230,6 +1230,23 @@ ProcessQueryResult processQuery(DNSQuestion& dq, ClientState& cs, LocalHolders&
 
         return ProcessQueryResult::SendAnswer;
       }
+      else if (dq.protocol == dnsdist::Protocol::DoH) {
+        /* do a second-lookup for UDP responses */
+        uint32_t udpCacheKey = 0;
+        /* we need to do a copy to be able to restore the query on a TC=1 cached answer */
+        PacketBuffer initialQuery(dq.getData());
+        if (dq.packetCache->get(dq, dq.getHeader()->id, &udpCacheKey, dq.subnet, dq.dnssecOK, true, allowExpired)) {
+          if (dq.getHeader()->tc == 0) {
+            if (!prepareOutgoingResponse(holders, cs, dq, true)) {
+              return ProcessQueryResult::Drop;
+            }
+
+            return ProcessQueryResult::SendAnswer;
+          }
+          dq.getMutableData() = std::move(initialQuery);
+        }
+      }
+
       ++g_stats.cacheMisses;
     }