xtables: arptables accepts empty interface names

The empty string passed as interface name is simply ignored by legacy
arptables. Make the new common parser print a warning but accept it.
Calling xtables_parse_interface() with an empty string is safe.

Signed-off-by: Phil Sutter <phil@nwl.cc>

diff --git a/iptables/xtables.c b/iptables/xtables.c
index dc67affc19dbec42b666fdbb419bcbccb2cf77a3..075506f07dd5b762455fddc10715e367afb18ab0 100644 (file)
--- a/iptables/xtables.c
+++ b/iptables/xtables.c
@@ -260,6 +260,19 @@ list_rules(struct nft_handle *h, const char *chain, const char *table,
        return nft_cmd_rule_list_save(h, chain, table, rulenum, counters);
 }
 
+static void check_empty_interface(struct nft_handle *h, const char *arg)
+{
+       const char *msg = "Empty interface is likely to be undesired";
+
+       if (*arg != '\0')
+               return;
+
+       if (h->family != NFPROTO_ARP)
+               xtables_error(PARAMETER_PROBLEM, msg);
+
+       fprintf(stderr, "%s", msg);
+}
+
 void do_parse(struct nft_handle *h, int argc, char *argv[],
              struct nft_xt_cmd_parse *p, struct iptables_command_state *cs,
              struct xtables_args *args)
@@ -493,10 +506,7 @@ void do_parse(struct nft_handle *h, int argc, char *argv[],
 
 
                case 'i':
-                       if (*optarg == '\0')
-                               xtables_error(PARAMETER_PROBLEM,
-                                       "Empty interface is likely to be "
-                                       "undesired");
+                       check_empty_interface(h, optarg);
                        set_option(&cs->options, OPT_VIANAMEIN,
                                   &args->invflags, invert);
                        xtables_parse_interface(optarg,
@@ -505,10 +515,7 @@ void do_parse(struct nft_handle *h, int argc, char *argv[],
                        break;
 
                case 'o':
-                       if (*optarg == '\0')
-                               xtables_error(PARAMETER_PROBLEM,
-                                       "Empty interface is likely to be "
-                                       "undesired");
+                       check_empty_interface(h, optarg);
                        set_option(&cs->options, OPT_VIANAMEOUT,
                                   &args->invflags, invert);
                        xtables_parse_interface(optarg,