From: Daniel Kempenich <dan.kempenich@gmail.com>
Date: Fri, 27 Jan 2023 07:44:41 +0000 (+0100)
Subject: Allow evdns_base_new to succeed with no nameservers configured
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ebd7e8d7930df0ef9f11a23309c59cded735e7c4;p=libevent

Allow evdns_base_new to succeed with no nameservers configured

If resolv.conf has no nameservers, evdns_base_new can still succeed with
the default of using the name server from localhost matching the man
page documentation for resolv.conf.
---

diff --git a/evdns.c b/evdns.c
index 52e7ee62..05e515c0 100644
--- a/evdns.c
+++ b/evdns.c
@@ -4892,7 +4892,7 @@ evdns_base_new(struct event_base *event_base, int flags)
 #else
 		r = evdns_base_resolv_conf_parse(base, opts, "/etc/resolv.conf");
 #endif
-		if (r) {
+		if (r && (EVDNS_ERROR_NO_NAMESERVERS_CONFIGURED != r)) {
 			evdns_base_free_and_unlock(base, 0);
 			return NULL;
 		}
diff --git a/test/regress_dns.c b/test/regress_dns.c
index 4e247b34..e28ad52b 100644
--- a/test/regress_dns.c
+++ b/test/regress_dns.c
@@ -42,6 +42,9 @@
 #include <sys/queue.h>
 #ifndef _WIN32
 #include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 #include <signal.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
@@ -1218,6 +1221,39 @@ end:
 	if (dns)
 		evdns_base_free(dns, 0);
 }
+
+static void
+dns_nameservers_no_nameservers_configured_test(void *arg)
+{
+	struct basic_test_data *data = arg;
+	struct event_base *base = data->base;
+	struct evdns_base *dns = NULL;
+	int fd = -1;
+	char *tmpfilename = NULL;
+	const char filecontents[] = "# tmp empty resolv.conf\n";
+	const size_t filecontentssize = sizeof(filecontents);
+	int ok;
+	
+	fd = regress_make_tmpfile(filecontents, filecontentssize, &tmpfilename);
+	if (fd < 0)
+		tt_skip();
+
+	dns = evdns_base_new(base, 0);
+	tt_assert(dns);
+
+	ok = evdns_base_resolv_conf_parse(dns, DNS_OPTIONS_ALL, tmpfilename);
+	tt_int_op(ok, ==, EVDNS_ERROR_NO_NAMESERVERS_CONFIGURED);
+
+end:
+	if (fd != -1)
+		close(fd);
+	if (dns)
+		evdns_base_free(dns, 0);
+	if (tmpfilename) {
+		unlink(tmpfilename);
+		free(tmpfilename);
+	}
+}
 #endif
 
 /* === Test for bufferevent_socket_connect_hostname */
@@ -3007,6 +3043,8 @@ struct testcase_t dns_testcases[] = {
 #ifndef _WIN32
 	{ "nameservers_no_default", dns_nameservers_no_default_test,
 	  TT_FORK|TT_NEED_BASE, &basic_setup, NULL },
+	{ "no_nameservers_configured", dns_nameservers_no_nameservers_configured_test,
+	  TT_FORK|TT_NEED_BASE, &basic_setup, NULL },
 #endif
 
 	{ "getaddrinfo_async", test_getaddrinfo_async,
diff --git a/test/regress_main.c b/test/regress_main.c
index 489c74b7..a504d6ce 100644
--- a/test/regress_main.c
+++ b/test/regress_main.c
@@ -144,11 +144,11 @@ regress_make_tmpfile(const void *data, size_t datalen, char **filename_out)
 		return (-1);
 	if (write(fd, data, datalen) != (int)datalen) {
 		close(fd);
+		unlink(tmpfilename);
 		return (-1);
 	}
 	lseek(fd, 0, SEEK_SET);
-	/* remove it from the file system */
-	unlink(tmpfilename);
+	*filename_out = strdup(tmpfilename);
 	return (fd);
 #else
 	/* XXXX actually delete the file later */