From 415eeebda4e294f7aacb59d7632daed8646ea64d Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Fri, 11 Nov 2016 09:59:58 +1100
Subject: [PATCH] add --ipv6only=no test

---
 bin/tests/system/feature-test.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/bin/tests/system/feature-test.c b/bin/tests/system/feature-test.c
index 77452cc6cc..8ccc8bf34b 100644
--- a/bin/tests/system/feature-test.c
+++ b/bin/tests/system/feature-test.c
@@ -15,6 +15,7 @@
 
 #include <isc/print.h>
 #include <isc/util.h>
+#include <isc/net.h>
 #include <dns/edns.h>
 
 #ifdef WIN32
@@ -33,15 +34,16 @@ static void
 usage() {
 	fprintf(stderr, "usage: feature-test <arg>\n");
 	fprintf(stderr, "args:\n");
-	fprintf(stderr, "	--enable-filter-aaaa\n");
 	fprintf(stderr, "	--edns-version\n");
+	fprintf(stderr, "	--enable-filter-aaaa\n");
 	fprintf(stderr, "	--gethostname\n");
 	fprintf(stderr, "	--gssapi\n");
 	fprintf(stderr, "	--have-dlopen\n");
 	fprintf(stderr, "	--have-geoip\n");
 	fprintf(stderr, "	--have-libxml2\n");
-	fprintf(stderr, "	--rpz-nsip\n");
+	fprintf(stderr, "	--ipv6only=no\n");
 	fprintf(stderr, "	--rpz-nsdname\n");
+	fprintf(stderr, "	--rpz-nsip\n");
 	fprintf(stderr, "	--with-idn\n");
 }
 
@@ -154,6 +156,25 @@ main(int argc, char **argv) {
 #endif
 	}
 
+	if (strcmp(argv[1], "--ipv6only=no") == 0) {
+#ifdef WIN32
+		return (0);
+#elif defined(IPPROTO_IPV6) && defined(IPV6_V6ONLY)
+		int s;
+		int n;
+		int v6only = -1;
+		ISC_SOCKADDR_LEN_T len = sizeof(v6only);
+
+		s = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+		n = getsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY,
+			       (void *)&v6only, &len);
+		close(s);
+		return ((n == 0 && v6only == 0) ? 0 : 1);
+#else
+		return (1);
+#endif
+	}
+
 	fprintf(stderr, "unknown arg: %s\n", argv[1]);
 	usage();
 	return (1);