[1386] EDNS TCP fallback disabled. NB: I still think it might be

	useful in DNSSEC situation when the resolver fully supports
	DNSSEC-aware clients.

ChangeLog

@@ -1,5 +1,6 @@
 xxx.	[bug]		dvv
-	resolver: EDNS fallback on FORMERR
+	resolver: If an upstream server responds with FORMERR to an EDNS query,
+	try querying it without EDNS.
 	(Trac #1386, git TBD)
 
 342.	[bug]		stephen

src/lib/resolve/recursive_query.cc

@@ -558,11 +558,9 @@ private:
             // see if it's a FORMERR and a potential EDNS problem
             if (incoming.getRcode() == Rcode::FORMERR()) {
                 if (protocol_ == IOFetch::UDP && edns_) {
-                    // try EDNS over TCP
-                    send(IOFetch::TCP, true);
-                    return (false);
-                } else if (protocol_ == IOFetch::TCP && edns_) {
-                    // try UDP, no EDNS
+                    // TODO: in case we absolutely need EDNS (i.e. for DNSSEC
+                    // aware queries), we might want to try TCP before we give
+                    // up. For now, just try UDP, no EDNS
                     send(IOFetch::UDP, false);
                     return (false);
                 }

src/lib/resolve/tests/recursive_query_unittest_3.cc

@@ -101,8 +101,7 @@ public:
     enum QueryStatus {
         NONE = 0,                   ///< Default
         EDNS_UDP = 1,               ///< EDNS query over UDP
-        EDNS_TCP = 2,               ///< EDNS query over TCP
-        NON_EDNS_UDP = 3,           ///< Non-EDNS query over UDP
+        NON_EDNS_UDP = 2,           ///< Non-EDNS query over UDP
         COMPLETE = 6                ///< Query is complete
     };
 
@@ -225,7 +224,7 @@ public:
             EXPECT_TRUE(query.getEDNS());
             // Return FORMERROR
             setFORMERR(message);
-            expected_ = EDNS_TCP;
+            expected_ = NON_EDNS_UDP;
             break;
 
         case NON_EDNS_UDP:
@@ -346,14 +345,7 @@ public:
 
         // Set up state-dependent bits:
         switch (expected_) {
-        case EDNS_TCP:
-            EXPECT_TRUE(query.getEDNS());
-            // Return FORMERROR
-            setFORMERR(message);
-            expected_ = NON_EDNS_UDP;
-            break;
-
-         default:
+        default:
             FAIL() << "TcpReceiveHandler called with unknown state";
         }