netfilter: nf_tables: set element extended ACK reporting support

Report the element that causes problems via netlink extended ACK for set
element commands.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -5348,8 +5348,10 @@ static int nf_tables_getsetelem(struct sk_buff *skb,
 
 	nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
 		err = nft_get_set_elem(&ctx, set, attr);
-		if (err < 0)
+		if (err < 0) {
+			NL_SET_BAD_ATTR(extack, attr);
 			break;
+		}
 	}
 
 	return err;
@@ -6126,8 +6128,10 @@ static int nf_tables_newsetelem(struct sk_buff *skb,
 
 	nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
 		err = nft_add_set_elem(&ctx, set, attr, info->nlh->nlmsg_flags);
-		if (err < 0)
+		if (err < 0) {
+			NL_SET_BAD_ATTR(extack, attr);
 			return err;
+		}
 	}
 
 	if (nft_net->validate_state == NFT_VALIDATE_DO)
@@ -6397,8 +6401,10 @@ static int nf_tables_delsetelem(struct sk_buff *skb,
 
 	nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
 		err = nft_del_setelem(&ctx, set, attr);
-		if (err < 0)
+		if (err < 0) {
+			NL_SET_BAD_ATTR(extack, attr);
 			break;
+		}
 	}
 	return err;
 }