daemon/bindings/net: add interface name to link-local IPv6 addresses

1 files changed, 24 insertions, 1 deletions

diff --git a/daemon/bindings/net.c b/daemon/bindings/net.c
index ec9c822c..ff6a6c37 100644
--- a/daemon/bindings/net.c
+++ b/daemon/bindings/net.c
@@ -5,6 +5,7 @@
 #include "daemon/bindings/impl.h"
 
 #include "contrib/base64.h"
+#include "contrib/cleanup.h"
 #include "daemon/network.h"
 #include "daemon/tls.h"
 
@@ -303,6 +304,18 @@ static int net_close(lua_State *L)
 	return 1;
 }
 
+/** Check whether `addr` points to an `AF_INET6` address and whether the address
+ * is link-local. */
+static bool ip6_link_local(struct sockaddr_in6 *addr)
+{
+	if (addr->sin6_family != AF_INET6)
+		return false;
+
+	/* Link-local: https://tools.ietf.org/html/rfc4291#section-2.4 */
+	const uint8_t prefix[] = { 0xFE, 0x80 };
+	return kr_bitcmp((char *) addr->sin6_addr.s6_addr, (char *) prefix, 10) == 0;
+}
+
 /** List available interfaces. */
 static int net_interfaces(lua_State *L)
 {
@@ -333,7 +346,17 @@ static int net_interfaces(lua_State *L)
 		} else {
 			buf[0] = '\0';
 		}
-		lua_pushstring(L, buf);
+
+		if (ip6_link_local(&iface.address.address6)) {
+			/* Link-local IPv6: add %interface prefix */
+			auto_free char *str = NULL;
+			int ret = asprintf(&str, "%s%%%s", buf, iface.name);
+			kr_assert(ret > 0);
+			lua_pushstring(L, str);
+		} else {
+			lua_pushstring(L, buf);
+		}
+
 		lua_rawseti(L, -2, lua_objlen(L, -2) + 1);
 		lua_setfield(L, -2, "addr");