src: add comment support for chains

This patch enables the user to specify a comment when adding a chain.

Relies on kernel space supporting userdata for chains.

> nft add table ip filter
> nft add chain ip filter input { comment "test"\; type filter hook input priority 0\; policy accept\; }
> list ruleset

table ip filter {
	chain input {
		comment "test"
		type filter hook input priority filter; policy accept;
	}
}

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

1 files changed, 11 insertions, 0 deletions

diff --git a/src/mnl.c b/src/mnl.c
index 6699b917..adb55d4d 100644
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -601,6 +601,7 @@ err:
 int mnl_nft_chain_add(struct netlink_ctx *ctx, struct cmd *cmd,
 		      unsigned int flags)
 {
+	struct nftnl_udata_buf *udbuf;
 	int priority, policy, i = 0;
 	struct nftnl_chain *nlc;
 	unsigned int ifname_len;
@@ -661,6 +662,16 @@ int mnl_nft_chain_add(struct netlink_ctx *ctx, struct cmd *cmd,
 
 			xfree(dev_array);
 		}
+		if (cmd->chain->comment) {
+			udbuf = nftnl_udata_buf_alloc(NFT_USERDATA_MAXLEN);
+			if (!udbuf)
+				memory_allocation_error();
+			if (!nftnl_udata_put_strz(udbuf, NFTNL_UDATA_CHAIN_COMMENT, cmd->chain->comment))
+				memory_allocation_error();
+			nftnl_chain_set_data(nlc, NFTNL_CHAIN_USERDATA, nftnl_udata_buf_data(udbuf),
+					     nftnl_udata_buf_len(udbuf));
+			nftnl_udata_buf_free(udbuf);
+		}
 	}
 	netlink_dump_chain(nlc, ctx);