I got massively confused this afternoon by this commit which defaults to
TCP for QTYPE=ANY queries.

https://source.isc.org/cgi-bin/gitweb.cgi?p=bind9.git;a=commitdiff;h=033a59090c5369f0d34951fdabfeedb60b5669ad

This is a sensible default, but I think it has made a confusing aspect of
dig even more confusing.

Until now, dig +notcp has been (for most purposes) a no-op. The thing that
makes it confusing is that it does not mean, as a newbie would expect,
that dig should not use TCP (except for the rather obscure IXFR).

In most cases where you want dig not to use TCP, you have to say dig
+ignore. However this does not mean "do not use TCP" for QTYPE=IXFR or
(now) for QTYPE=ANY.

The patch below harmonizes the behaviour of +notcp and +ignore. I haven't
done a full-on unification since that will probably be unhelpful for
experts.

---
 bin/dig/dig.c       | 12 ++++++++----
 bin/dig/dig.docbook |  9 +++++++++
 bin/dig/dighost.c   |  2 +-
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/bin/dig/dig.c b/bin/dig/dig.c
index 762ab01..fe775e4 100644
--- a/bin/dig/dig.c
+++ b/bin/dig/dig.c
@@ -1786,7 +1786,8 @@ dash_option(char *option, char *next, dig_lookup_t **lookup,
 				(*lookup)->ixfr_serial = serial;
 				(*lookup)->section_question = plusquest;
 				(*lookup)->comments = pluscomm;
-				if (!(*lookup)->tcp_mode_set)
+				if (!(*lookup)->tcp_mode_set &&
+				    !(*lookup)->ignore)
 					(*lookup)->tcp_mode = ISC_TRUE;
 			} else {
 				(*lookup)->rdtype = rdtype;
@@ -1796,7 +1797,8 @@ dash_option(char *option, char *next, dig_lookup_t **lookup,
 					(*lookup)->section_question = plusquest;
 					(*lookup)->comments = pluscomm;
 				} else if (rdtype == dns_rdatatype_any) {
-					if (!(*lookup)->tcp_mode_set)
+					if (!(*lookup)->tcp_mode_set &&
+					    !(*lookup)->ignore)
 						(*lookup)->tcp_mode = ISC_TRUE;
 				}
 				(*lookup)->ixfr_serial = ISC_FALSE;
@@ -2097,7 +2099,8 @@ parse_args(isc_boolean_t is_batchfile, isc_boolean_t config_only,
 						lookup->section_question =
 							plusquest;
 						lookup->comments = pluscomm;
-						if (!lookup->tcp_mode_set)
+						if (!lookup->tcp_mode_set &&
+						    !lookup->ignore)
 							lookup->tcp_mode = ISC_TRUE;
 					} else {
 						lookup->rdtype = rdtype;
@@ -2110,7 +2113,8 @@ parse_args(isc_boolean_t is_batchfile, isc_boolean_t config_only,
 						}
 						if (rdtype ==
 						    dns_rdatatype_any &&
-						    !lookup->tcp_mode_set)
+						    !lookup->tcp_mode_set &&
+						    !lookup->ignore)
 							lookup->tcp_mode = ISC_TRUE;
 						lookup->ixfr_serial = ISC_FALSE;
 					}
diff --git a/bin/dig/dig.docbook b/bin/dig/dig.docbook
index e262d24..87fc3d8 100644
--- a/bin/dig/dig.docbook
+++ b/bin/dig/dig.docbook
@@ -780,6 +780,10 @@
 	      Ignore truncation in UDP responses instead of retrying
 	      with TCP.  By default, TCP retries are performed.
 	    </para>
+	    <para>
+	      This option also disables the default use of TCP for ANY
+	      and IXFR query types.
+	    </para>
 	  </listitem>
 	</varlistentry>

@@ -1072,6 +1076,11 @@
 	      query is requested, in which case the default is TCP.
 	      AXFR queries always use TCP.
 	    </para>
+	    <para>
+	      <command>dig +notcp</command> ignores truncated UDP
+	      responses and does not retry with TCP, unless you also
+	      explicitly use the <literal>+noignore</literal> option.
+	    </para>
 	  </listitem>
 	</varlistentry>

diff --git a/bin/dig/dighost.c b/bin/dig/dighost.c
index 1030afc..f465c85 100644
--- a/bin/dig/dighost.c
+++ b/bin/dig/dighost.c
@@ -4012,7 +4012,7 @@ recv_done(isc_task_t *task, isc_event_t *event) {
 		return;
 	}
 	if ((msg->flags & DNS_MESSAGEFLAG_TC) != 0 &&
-	    !l->ignore && !l->tcp_mode) {
+	    !l->ignore && !l->tcp_mode && !l->tcp_mode_set) {
 		if (l->cookie == NULL && l->sendcookie && msg->opt != NULL)
 			process_opt(l, msg);
 		if (l->comments)
-- 
2.10.1.445.g3cdd5d1