Add "+showbadvers" to dig and reset EDNS version

Add "+showbadvers" to display the BADVERS response similarly
to "+showbadcookie".  Additionally reset the EDNS version to
the requested version in "dig +trace" so that EDNS version
negotiation can be tested at all levels of the trace rather
that just when requesting the root nameservers.

bin/dig/dig.c

@@ -289,6 +289,7 @@ help(void) {
 	       "                                      form of answers - global "
 	       "option)\n"
 	       "                 +[no]showbadcookie  (Show BADCOOKIE message)\n"
+	       "                 +[no]showbadvers    (Show BADVERS message)\n"
 	       "                 +[no]showsearch     (Search with intermediate "
 	       "results)\n"
 	       "                 +[no]split=##       (Split hex/base64 fields "
@@ -1772,6 +1773,8 @@ plus_option(char *option, bool is_batchfile, bool *need_clone,
 						FULLCHECK("edns");
 						if (!state) {
 							lookup->edns = -1;
+							lookup->original_edns =
+								-1;
 							break;
 						}
 						if (value == NULL) {
@@ -1788,6 +1791,7 @@ plus_option(char *option, bool is_batchfile, bool *need_clone,
 							goto exit_or_usage;
 						}
 						lookup->edns = num;
+						lookup->original_edns = num;
 						break;
 					case 'f':
 						FULLCHECK("ednsflags");
@@ -2306,9 +2310,19 @@ plus_option(char *option, bool is_batchfile, bool *need_clone,
 			case 'w': /* showsearch */
 				switch (cmd[4]) {
 				case 'b':
+					switch (cmd[7]) {
+					case 'c':
 						FULLCHECK("showbadcookie");
 						lookup->showbadcookie = state;
 						break;
+					case 'v':
+						FULLCHECK("showbadvers");
+						lookup->showbadvers = state;
+						break;
+					default:
+						goto invalid_option;
+					}
+					break;
 				case 's':
 					FULLCHECK("showsearch");
 					if (!lookup->trace) {

bin/dig/dig.rst

@@ -614,6 +614,12 @@ abbreviation is unambiguous; for example, :option:`+cd` is equivalent to
    BADCOOKIE rcode before retrying the request or not. The default
    is to not show the messages.
 
+.. option:: +showbadvers, +noshowbadvers
+
+   This option toggles whether to show the message containing the
+   BADVERS rcode before retrying the request or not. The default
+   is to not show the messages.
+
 .. option:: +showsearch, +noshowsearch
 
    This option performs [or does not perform] a search showing intermediate results.

bin/dig/dighost.c

@@ -605,6 +605,7 @@ make_empty_lookup(void) {
 		.idnout = idnout,
 		.udpsize = -1,
 		.edns = -1,
+		.original_edns = -1,
 		.recurse = true,
 		.retries = tries,
 		.comments = true,
@@ -738,6 +739,7 @@ clone_lookup(dig_lookup_t *lookold, bool servers) {
 	}
 
 	looknew->showbadcookie = lookold->showbadcookie;
+	looknew->showbadvers = lookold->showbadvers;
 	looknew->sendcookie = lookold->sendcookie;
 	looknew->seenbadcookie = lookold->seenbadcookie;
 	looknew->badcookie = lookold->badcookie;
@@ -764,6 +766,7 @@ clone_lookup(dig_lookup_t *lookold, bool servers) {
 	looknew->idnout = lookold->idnout;
 	looknew->udpsize = lookold->udpsize;
 	looknew->edns = lookold->edns;
+	looknew->original_edns = lookold->original_edns;
 	looknew->recurse = lookold->recurse;
 	looknew->aaonly = lookold->aaonly;
 	looknew->adflag = lookold->adflag;
@@ -1938,6 +1941,7 @@ followup_lookup(dns_message_t *msg, dig_query_t *query, dns_section_t section) {
 				}
 				domain = dns_fixedname_name(&lookup->fdomain);
 				dns_name_copy(name, domain);
+				lookup->edns = lookup->original_edns;
 			}
 			debug("adding server %s", namestr);
 			num = getaddresses(lookup, namestr, &lresult);
@@ -2456,7 +2460,8 @@ setup_lookup(dig_lookup_t *lookup) {
 			lookup->udpsize = DEFAULT_EDNS_BUFSIZE;
 		}
 		if (lookup->edns < 0) {
-			lookup->edns = DEFAULT_EDNS_VERSION;
+			lookup->original_edns = lookup->edns =
+				DEFAULT_EDNS_VERSION;
 		}
 
 		if (lookup->nsid) {
@@ -4300,6 +4305,11 @@ recv_done(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
 	if (msg->rcode == dns_rcode_badvers && msg->opt != NULL &&
 	    (newedns = ednsvers(msg->opt)) < l->edns && l->ednsneg)
 	{
+		if (l->showbadvers) {
+			dighost_printmessage(query, &b, msg, true);
+			dighost_received(isc_buffer_usedlength(&b), &peer,
+					 query);
+		}
 		/*
 		 * Add minimum EDNS version required checks here if needed.
 		 */

bin/dig/dighost.h

@@ -117,8 +117,8 @@ struct dig_lookup {
 		section_answer, section_authority, section_question,
 		seenbadcookie, sendcookie, servfail_stops,
 		setqid, /*% use a speciied query ID */
-		showbadcookie, stats, tcflag, tcp_keepalive, tcp_mode,
-		tcp_mode_set, tls_mode, /*% connect using TLS */
+		showbadcookie, showbadvers, stats, tcflag, tcp_keepalive,
+		tcp_mode, tcp_mode_set, tls_mode, /*% connect using TLS */
 		trace,				  /*% dig +trace */
 		trace_root, /*% initial query for either +trace or +nssearch */
 		ttlunits, use_usec, waiting_connect, zflag;
@@ -148,6 +148,7 @@ struct dig_lookup {
 	int nsfound;
 	int16_t udpsize;
 	int16_t edns;
+	int16_t original_edns;
 	int16_t padding;
 	uint32_t ixfr_serial;
 	isc_buffer_t rdatabuf;