From 43eeadc142d01b88f08aed7f6a7aba69f9dd9666 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <rgacogne-github@coredump.fr>
Date: Thu, 26 Nov 2015 15:55:04 +0100
Subject: [PATCH] Drop truncated UDP messages caused by a small buffer.

When we receive a message too large for our buffer, recvmsg() will
truncate the content to fit the buffer and set the MSG_TRUNC flag.
There is no point in trying to parse this message because we will
choke during the parsing anyway.
---
 pdns/dnsdist.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pdns/dnsdist.cc b/pdns/dnsdist.cc
index fc72f8316d..d189d3f0ef 100644
--- a/pdns/dnsdist.cc
+++ b/pdns/dnsdist.cc
@@ -439,6 +439,13 @@ try
 	continue;
       }
 
+      if (msgh.msg_flags & MSG_TRUNC) {
+        /* message was too large for our buffer */
+        vinfolog("Dropping message too large for our buffer");
+        g_stats.nonCompliantQueries++;
+        continue;
+      }
+
       g_stats.queries++;
       if(!acl->match(remote)) {
 	vinfolog("Query from %s dropped because of ACL", remote.toStringWithPort());
-- 
2.47.2