From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Mon, 18 Feb 2019 12:07:14 +0000 (+0100)
Subject: Correctly interpret an empty AXFR response to an IXFR query
X-Git-Tag: auth-4.1.8~1^2
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2c4a96285bedaa738c98da53bc93c02967d74ae5;p=pdns

Correctly interpret an empty AXFR response to an IXFR query

(cherry picked from commit 98b3317609b2783d1bfd5da99edc81af28f4e1d6)
---

diff --git a/pdns/ixfr.cc b/pdns/ixfr.cc
index 74982b518..ab13446f8 100644
--- a/pdns/ixfr.cc
+++ b/pdns/ixfr.cc
@@ -59,6 +59,12 @@ vector<pair<vector<DNSRecord>, vector<DNSRecord> > > processIXFRRecords(const Co
     // the serial of this SOA record is the serial of the
     // zone before the removals and updates of this sequence
     if (sr->d_st.serial == masterSOA->d_st.serial) {
+      if (records.size() == 2) {
+        // if the entire update is two SOAs records with the same
+        // serial, this is actually an empty AXFR!
+        return {{remove, records}};
+      }
+
       // if it's the final SOA, there is nothing for us to see
       break;
     }
diff --git a/pdns/test-ixfr_cc.cc b/pdns/test-ixfr_cc.cc
index 63f4bdd95..95398e431 100644
--- a/pdns/test-ixfr_cc.cc
+++ b/pdns/test-ixfr_cc.cc
@@ -211,7 +211,14 @@ BOOST_AUTO_TEST_CASE(test_ixfr_same_serial) {
 
   auto ret = processIXFRRecords(master, zone, records, std::dynamic_pointer_cast<SOARecordContent>(masterSOA));
 
-  BOOST_CHECK_EQUAL(ret.size(), 0);
+  // this is actually an empty AXFR
+  BOOST_CHECK_EQUAL(ret.size(), 1);
+  // nothing in the deletion part then
+  BOOST_CHECK_EQUAL(ret.at(0).first.size(), 0);
+  // and the two SOAs in the addition part
+  BOOST_CHECK_EQUAL(ret.at(0).second.size(), 2);
+  BOOST_CHECK_EQUAL(ret.at(0).second.at(0).d_type, QType(QType::SOA).getCode());
+  BOOST_CHECK_EQUAL(ret.at(0).second.at(1).d_type, QType(QType::SOA).getCode());
 }
 
 BOOST_AUTO_TEST_CASE(test_ixfr_invalid_no_records) {