From 1365807195bf3a2d14b8c5559b456a2e0215da43 Mon Sep 17 00:00:00 2001
From: Rafael Buchbinder <r-bk@users.noreply.github.com>
Date: Wed, 17 Oct 2018 09:48:28 +0300
Subject: [PATCH] pdns-recursor: properly handle exceptions thrown from
 lua-recursor4

directResolve function is used by lua-recursor4 in various callbacks. As
a result an exception thrown from this function is caught in generic
exception handlers at the end of startDoResolve (pdns_recursor).
Specifically, ImmediateServFailException is caught in the catch-all
exception handler, which obscures the origin of the error.

This commit adds handling of all exceptions inside directResolve and
converts them to error code (-1). This way, an exception in this
function is handled properly in startDoResolve and ServFail is sent
downstream.

To clarify, in case of exception the return DNSRecord vector is cleared
to make sure that old behavior is preserved, when in case of exception
the vector was not referenced in any way.
---
 pdns/syncres.cc | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/pdns/syncres.cc b/pdns/syncres.cc
index ec3cf531b..f90a5c2cd 100644
--- a/pdns/syncres.cc
+++ b/pdns/syncres.cc
@@ -2902,7 +2902,26 @@ int directResolve(const DNSName& qname, const QType& qtype, int qclass, vector<D
   gettimeofday(&now, 0);
 
   SyncRes sr(now);
-  int res = sr.beginResolve(qname, QType(qtype), qclass, ret); 
+  int res = -1;
+  try {
+    res = sr.beginResolve(qname, QType(qtype), qclass, ret);
+  }
+  catch(const PDNSException& e) {
+    g_log<<Logger::Error<<"Failed to resolve "<<qname.toLogString()<<", got pdns exception: "<<e.reason<<endl;
+    ret.clear();
+  }
+  catch(const ImmediateServFailException& e) {
+    g_log<<Logger::Error<<"Failed to resolve "<<qname.toLogString()<<", got ImmediateServFailException: "<<e.reason<<endl;
+    ret.clear();
+  }
+  catch(const std::exception& e) {
+    g_log<<Logger::Error<<"Failed to resolve "<<qname.toLogString()<<", got STL error: "<<e.what()<<endl;
+    ret.clear();
+  }
+  catch(...) {
+    g_log<<Logger::Error<<"Failed to resolve "<<qname.toLogString()<<", got an exception"<<endl;
+    ret.clear();
+  }
   
   return res;
 }
-- 
2.49.0