no longer switch to tcp mode for truncated NXDOMAIN results

Author: EmielBruijntjes

Makefile

@@ -3,7 +3,7 @@ INCLUDE_DIR             = ${PREFIX}/include
 LIBRARY_DIR             = ${PREFIX}/lib
 export LIBRARY_NAME		= dnscpp
 export SONAME			= 1.3
-export VERSION			= 1.3.3
+export VERSION			= 1.3.4
 
 all:
 		$(MAKE) -C src all

src/remotelookup.cpp

@@ -261,8 +261,12 @@ bool RemoteLookup::onReceived(const Ip &ip, const Response &response)
     if (!_query.matches(response)) return false;
 
     // if the response was not truncated, we can report it to userspace, we do this also
-    // when the response came from a TCP lookup and was still truncated
-    if (!response.truncated() || _connections > 0) return report(response);
+    // when the response came from a TCP lookup and was still truncated, or when the response
+    // contained an error (for error-responses we do not normally inspect the body, so who cares anyway?)
+    // (note: we ran into a dns-cpp error when switching to tcp-mode, but could not reproduce this
+    // in a test setup, the extra check for the rcode was added as workaround to avoid switching
+    // to tcp that often (in our case the switch only happened for truncated NXDOMAIN responses)
+    if (!response.truncated() || response.rcode() != 0 || _connections > 0) return report(response);
 
     // we can unsubscribe from all inbound udp sockets because we're no longer interested in those responses
     unsubscribe();

test/lookup.cpp

@@ -255,7 +255,7 @@ int main(int argc, const char *argv[])
         DNS::Context context(&myloop, config);
 
         // set the AD bit (but not the DO and CD bits)
-        context.bits(DNS::BIT_AD);
+        //context.bits(DNS::BIT_AD);
 
         // check usage
         if (argc != 3) throw std::runtime_error(std::string("usage: ") + argv[0] + " type value");