Determine available address families (and monitor when this changes)

to configure libunbound accordingly. This way it no longer tries to
talk to IPv6 nameservers when only IPv4 is available and vice versa.
input deraadt
OK kn

1 files changed, 43 insertions, 8 deletions

diff --git a/sbin/unwind/resolver.c b/sbin/unwind/resolver.c
index c1e399b859a..49f51d8a9ab 100644
--- a/sbin/unwind/resolver.c
+++ b/sbin/unwind/resolver.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: resolver.c,v 1.136 2021/01/26 12:46:46 florian Exp $	*/
+/*	$OpenBSD: resolver.c,v 1.137 2021/01/27 08:30:50 florian Exp $	*/
 
 /*
  * Copyright (c) 2018 Florian Obser <florian@openbsd.org>
@@ -230,6 +230,7 @@ struct key_cache		*unified_key_cache;
 struct val_neg_cache		*unified_neg_cache;
 
 int				 dns64_present;
+int				 available_afs = HAVE_IPV4 | HAVE_IPV6;
 
 static const char * const	 as112_zones[] = {
 	/* RFC1918 */
@@ -462,13 +463,13 @@ resolver_imsg_compose_frontend(int type, pid_t pid, void *data,
 void
 resolver_dispatch_frontend(int fd, short event, void *bula)
 {
-	struct imsgev			*iev = bula;
-	struct imsgbuf			*ibuf;
-	struct imsg			 imsg;
-	struct query_imsg		*query_imsg;
-	ssize_t				 n;
-	int				 shut = 0, verbose, i;
-	char				*ta;
+	struct imsgev		*iev = bula;
+	struct imsgbuf		*ibuf;
+	struct imsg		 imsg;
+	struct query_imsg	*query_imsg;
+	ssize_t			 n;
+	int			 shut = 0, verbose, i, new_available_afs;
+	char			*ta;
 
 	ibuf = &iev->ibuf;
 
@@ -567,6 +568,18 @@ resolver_dispatch_frontend(int fd, short event, void *bula)
 			replace_autoconf_forwarders((struct
 			    imsg_rdns_proposal *)imsg.data);
 			break;
+		case IMSG_CHANGE_AFS:
+			if (IMSG_DATA_SIZE(imsg) !=
+			    sizeof(new_available_afs))
+				fatalx("%s: IMSG_CHANGE_AFS wrong length: %lu",
+				    __func__, IMSG_DATA_SIZE(imsg));
+			memcpy(&new_available_afs, imsg.data,
+			    sizeof(new_available_afs));
+			if (new_available_afs != available_afs) {
+				available_afs = new_available_afs;
+				restart_ub_resolvers();
+			}
+			break;
 		default:
 			log_debug("%s: unexpected imsg %d", __func__,
 			    imsg.hdr.type);
@@ -1253,6 +1266,28 @@ create_resolver(enum uw_resolver_type type)
 			}
 		}
 
+		if (!(available_afs & HAVE_IPV4)) {
+			if((err = ub_ctx_set_option(res->ctx, "do-ip4:",
+			    "no")) != 0) {
+				ub_ctx_delete(res->ctx);
+				free(res);
+				log_warnx("error setting do-ip4: no: %s",
+				    ub_strerror(err));
+				return (NULL);
+			}
+		}
+
+		if (!(available_afs & HAVE_IPV6)) {
+			if((err = ub_ctx_set_option(res->ctx, "do-ip6:",
+			    "no")) != 0) {
+				ub_ctx_delete(res->ctx);
+				free(res);
+				log_warnx("error setting do-ip6: no: %s",
+				    ub_strerror(err));
+				return (NULL);
+			}
+		}
+
 		if (!log_getdebug()) {
 			if((err = ub_ctx_set_option(res->ctx, "use-syslog:",
 			    "no")) != 0) {