From: Florian Obser <florian@openbsd.org>
Subject: dig(1): Implement RESINFO (RFC 9606)
To: tech <tech@openbsd.org>
Date: Sun, 08 Dec 2024 09:20:13 +0100

RESINFO is just a weird spelling for txt:

| 4. Format of the Resolver Information
|
| The resolver information record uses the same format as DNS TXT records.

It can be tested thusly:

$ dig @resolver64.dns4all.eu resolver64.dns4all.eu RESINFO

; <<>> dig 9.10.8-P1 <<>> @resolver64.dns4all.eu resolver64.dns4all.eu RESINFO
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29370
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;resolver64.dns4all.eu.		IN	RESINFO

;; ANSWER SECTION:
resolver64.dns4all.eu.	2551	IN	RESINFO	"qnamemin temp-dnssecval temp-dns64 infourl=https://dns4all.eu"

;; Query time: 46 msec
;; SERVER: 2001:678:8::64#53(2001:678:8::64)
;; WHEN: Sun Dec 08 09:12:38 CET 2024
;; MSG SIZE  rcvd: 124


btw. I don't think dns4all.eu implements RESINFO correctly.

| The DNS client MUST set the Recursion Desired (RD) bit of the query to
| 0. The DNS client MUST discard the response if the AA flag in the
| response is set to 0, indicating that the DNS resolver is not
| authoritative for the response.

The answer does not have AA set and if I query with +norec I get
REFUSED. But never mind that, that's a problem on the server side.

OK?

diff --git lib/dns/include/dns/types.h lib/dns/include/dns/types.h
index 88dfe4fa312..0efc49d4927 100644
--- lib/dns/include/dns/types.h
+++ lib/dns/include/dns/types.h
@@ -150,6 +150,7 @@ enum {
 	dns_rdatatype_caa = 257,
 	dns_rdatatype_avc = 258,
 	dns_rdatatype_doa = 259,
+	dns_rdatatype_resinfo = 261,
 	dns_rdatatype_ta = 32768,
 	dns_rdatatype_dlv = 32769,
 	dns_rdatatype_keydata = 65533,
diff --git lib/dns/rdata.c lib/dns/rdata.c
index 395f3cf1262..e6d91c67df8 100644
--- lib/dns/rdata.c
+++ lib/dns/rdata.c
@@ -811,6 +811,7 @@ dns_rdatatype_fromtext(dns_rdatatype_t *typep, isc_textregion_t *source) {
 		{"ptr",		12},
 		{"px",		26},
 		{"reserved0",	0},
+		{"resinfo",	261},
 		{"rkey",	57},
 		{"rp",		17},
 		{"rrsig",	46},
@@ -1055,6 +1056,8 @@ dns_rdatatype_totext(dns_rdatatype_t type, isc_buffer_t *target) {
 		return (isc_str_tobuffer("AVC", target));
 	case 259:
 		return (isc_str_tobuffer("DOA", target));
+	case 261:
+		return (isc_str_tobuffer("RESINFO", target));
 	case 32768:
 		return (isc_str_tobuffer("TA", target));
 	case 32769:
diff --git lib/dns/rdata/generic/resinfo_261.c lib/dns/rdata/generic/resinfo_261.c
new file mode 100644
index 00000000000..6ad04d04f2d
--- /dev/null
+++ lib/dns/rdata/generic/resinfo_261.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* RFC 9606, based on txt_16.c */
+
+#ifndef RDATA_GENERIC_RESINFO_261_C
+#define RDATA_GENERIC_RESINFO_261_C
+
+static inline isc_result_t
+generic_totext_resinfo(ARGS_TOTEXT) {
+	isc_region_t region;
+
+	UNUSED(tctx);
+
+	dns_rdata_toregion(rdata, &region);
+
+	while (region.length > 0) {
+		RETERR(txt_totext(&region, 1, target));
+		if (region.length > 0)
+			RETERR(isc_str_tobuffer(" ", target));
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+static inline isc_result_t
+generic_fromwire_resinfo(ARGS_FROMWIRE) {
+	isc_result_t result;
+
+	UNUSED(type);
+	UNUSED(dctx);
+	UNUSED(rdclass);
+	UNUSED(options);
+
+	do {
+		result = txt_fromwire(source, target);
+		if (result != ISC_R_SUCCESS)
+			return (result);
+	} while (!buffer_empty(source));
+	return (ISC_R_SUCCESS);
+}
+
+static inline isc_result_t
+totext_resinfo(ARGS_TOTEXT) {
+
+	REQUIRE(rdata->type == dns_rdatatype_resinfo);
+
+	return (generic_totext_resinfo(rdata, tctx, target));
+}
+
+static inline isc_result_t
+fromwire_resinfo(ARGS_FROMWIRE) {
+
+	REQUIRE(type == dns_rdatatype_resinfo);
+
+	return (generic_fromwire_resinfo(rdclass, type, source, dctx, options,
+				     target));
+}
+
+static inline isc_result_t
+towire_resinfo(ARGS_TOWIRE) {
+
+	REQUIRE(rdata->type == dns_rdatatype_resinfo);
+
+	UNUSED(cctx);
+
+	return (isc_mem_tobuffer(target, rdata->data, rdata->length));
+}
+
+#endif	/* RDATA_GENERIC_RESINFO_261_C */

-- 
In my defence, I have been left unsupervised.