From 597e6d0e5d8823fd9f9cd9702c2c9e94e95237ff Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Mon, 14 Sep 2020 11:42:29 +0200
Subject: [PATCH] dnsdist: Use a counter for pipelined TCP queries

It turns out that collisions do happen with a random ID.
---
 pdns/dnsdistdist/dnsdist-tcp-downstream.cc |  2 +-
 regression-tests.dnsdist/test_OOOR.py      | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/pdns/dnsdistdist/dnsdist-tcp-downstream.cc b/pdns/dnsdistdist/dnsdist-tcp-downstream.cc
index 8b5e56e0bb..4fa155c55c 100644
--- a/pdns/dnsdistdist/dnsdist-tcp-downstream.cc
+++ b/pdns/dnsdistdist/dnsdist-tcp-downstream.cc
@@ -423,7 +423,7 @@ IOState TCPConnectionToBackend::handleResponse(std::shared_ptr<TCPConnectionToBa
 
     auto it = d_pendingResponses.find(queryId);
     if (it == d_pendingResponses.end()) {
-      DEBUGLOG("could not found any corresponding query for ID "<<queryId);
+      DEBUGLOG("could not find any corresponding query for ID "<<queryId<<". This is likely a duplicated ID over the same TCP connection, giving up!");
       notifyAllQueriesFailed(now);
       return IOState::Done;
     }
diff --git a/regression-tests.dnsdist/test_OOOR.py b/regression-tests.dnsdist/test_OOOR.py
index e2f2bc4d2e..ae1e457461 100644
--- a/regression-tests.dnsdist/test_OOOR.py
+++ b/regression-tests.dnsdist/test_OOOR.py
@@ -180,8 +180,11 @@ class TestOOORWithClientNotBackend(DNSDistTest):
 
         conn = self.openTCPConnection()
 
+        counter = 0
         for name in names:
             query = dns.message.make_query(name, 'A', 'IN', use_edns=False)
+            query.id = counter
+            counter = counter + 1
 
             self.sendTCPQueryOverConnection(conn, query)
 
@@ -212,8 +215,11 @@ class TestOOORWithClientNotBackend(DNSDistTest):
 
         conn = self.openTCPConnection()
 
+        counter = 0
         for name in names:
             query = dns.message.make_query(name, 'A', 'IN', use_edns=False)
+            query.id = counter
+            counter = counter + 1
 
             self.sendTCPQueryOverConnection(conn, query)
 
@@ -263,8 +269,11 @@ class TestOOORWithClientAndBackend(DNSDistTest):
 
         conn = self.openTCPConnection()
 
+        counter = 0
         for name in names:
             query = dns.message.make_query(name, 'A', 'IN', use_edns=False)
+            query.id = counter
+            counter = counter + 1
 
             self.sendTCPQueryOverConnection(conn, query)
 
@@ -293,8 +302,11 @@ class TestOOORWithClientAndBackend(DNSDistTest):
 
         conn = self.openTCPConnection()
 
+        counter = 0
         for name in names:
             query = dns.message.make_query(name, 'A', 'IN', use_edns=False)
+            query.id = counter
+            counter = counter + 1
 
             self.sendTCPQueryOverConnection(conn, query)
 
-- 
2.47.3