src: add comment support when adding tables

Adds userdata building logic if a comment is specified when creating a
new table. Adds netlink userdata parsing callback function.

Relies on kernel supporting userdata for nft_table.

Example:

> nft add table ip x { comment "test"\; }
> nft list ruleset

table ip x {
	comment "test"
}

Signed-off-by: Jose M. Guisado Gomez <guigom@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/rule.c b/src/rule.c
index a925d844..2c4b5dbe 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -1324,6 +1324,8 @@ void table_free(struct table *table)
 
 	if (--table->refcnt > 0)
 		return;
+	if (table->comment)
+		xfree(table->comment);
 	list_for_each_entry_safe(chain, next, &table->chains, list)
 		chain_free(chain);
 	list_for_each_entry_safe(chain, next, &table->chain_bindings, list)
@@ -1422,6 +1424,9 @@ static void table_print(const struct table *table, struct output_ctx *octx)
 	nft_print(octx, "\n");
 	table_print_options(table, &delim, octx);
 
+	if (table->comment)
+		nft_print(octx, "\tcomment \"%s\"\n", table->comment);
+
 	list_for_each_entry(obj, &table->objs, list) {
 		nft_print(octx, "%s", delim);
 		obj_print(obj, octx);