Index: asr/asr.c
===================================================================
RCS file: /cvs/src/lib/libc/asr/asr.c,v
retrieving revision 1.68
diff -u -p -r1.68 asr.c
--- asr/asr.c	20 Jan 2022 14:18:10 -0000	1.68
+++ asr/asr.c	1 Mar 2024 06:57:11 -0000
@@ -528,6 +528,7 @@ asr_ctx_create(void)
 		return (NULL);
 
 	ac->ac_options = RES_RECURSE | RES_DEFNAMES | RES_DNSRCH;
+	ac->ac_rdomain = -1; /* we don't care by default */
 	ac->ac_refcount = 1;
 	ac->ac_ndots = 1;
 	ac->ac_family[0] = AF_INET;
@@ -594,12 +595,32 @@ pass0(char **tok, int n, struct asr_ctx 
 	int		 i, j, d;
 	const char	*e;
 	struct sockaddr_storage	ss;
+	int rdomain;
+	const char *errstr;
 
 	if (!strcmp(tok[0], "nameserver")) {
 		if (ac->ac_nscount == ASR_MAXNS)
 			return;
-		if (n != 2)
+		switch (n) {
+		case 4:
+			if (strcmp(tok[2], "rdomain") != 0)
+				return;
+
+			if (ac->ac_rdomain == -1)
+				ac->ac_rdomain = getrtable();
+
+			rdomain = strtonum(tok[3], 0, INT_MAX, &errstr);
+			if (errstr != NULL)
+				return;
+
+			if (ac->ac_rdomain != rdomain)
+				return;
+			/* FALLTHROUGH */
+		case 2:
+			break;
+		default:
 			return;
+		}
 		if (asr_parse_nameserver((struct sockaddr *)&ss, tok[1]))
 			return;
 		if ((ac->ac_ns[ac->ac_nscount] = calloc(1, ss.ss_len)) == NULL)
Index: asr/asr_private.h
===================================================================
RCS file: /cvs/src/lib/libc/asr/asr_private.h,v
retrieving revision 1.49
diff -u -p -r1.49 asr_private.h
--- asr/asr_private.h	20 Nov 2023 12:15:16 -0000	1.49
+++ asr/asr_private.h	1 Mar 2024 06:57:11 -0000
@@ -121,6 +121,7 @@ enum async_type {
 #define	ASR_DB_DNS	'b'
 
 struct asr_ctx {
+	int		 ac_rdomain;
 	int		 ac_refcount;
 	int		 ac_options;
 	int		 ac_ndots;