Re: [iptables PATCH v2 03/10] nft: cache: Introduce nft_cache_add_chain()

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Sep 23, 2020 at 07:48:42PM +0200, Phil Sutter wrote:
> This is a convenience function for adding a chain to cache, for now just
> a simple wrapper around nftnl_chain_list_add_tail().
> 
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
> Changes since v1:
> - Use the function in nft_chain_builtin_add() as well.
> ---
>  iptables/nft-cache.c | 12 +++++++++---
>  iptables/nft-cache.h |  3 +++
>  iptables/nft.c       | 16 +++++++---------
>  3 files changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/iptables/nft-cache.c b/iptables/nft-cache.c
> index b94766a751db4..a22e693320451 100644
> --- a/iptables/nft-cache.c
> +++ b/iptables/nft-cache.c
> @@ -165,6 +165,13 @@ static int fetch_table_cache(struct nft_handle *h)
>  	return 1;
>  }
>  
> +int nft_cache_add_chain(struct nft_handle *h, const struct builtin_table *t,
> +			struct nftnl_chain *c)
> +{
> +	nftnl_chain_list_add_tail(c, h->cache->table[t->type].chains);
> +	return 0;
> +}

This wrapper LGTM.

>  struct nftnl_chain_list_cb_data {
>  	struct nft_handle *h;
>  	const struct builtin_table *t;
> @@ -174,7 +181,6 @@ static int nftnl_chain_list_cb(const struct nlmsghdr *nlh, void *data)
>  {
>  	struct nftnl_chain_list_cb_data *d = data;
>  	const struct builtin_table *t = d->t;
> -	struct nftnl_chain_list *list;
>  	struct nft_handle *h = d->h;
>  	struct nftnl_chain *c;
>  	const char *tname;
> @@ -196,8 +202,8 @@ static int nftnl_chain_list_cb(const struct nlmsghdr *nlh, void *data)
>  		goto out;
>  	}
>  
> -	list = h->cache->table[t->type].chains;
> -	nftnl_chain_list_add_tail(c, list);
> +	if (nft_cache_add_chain(h, t, c))
> +		goto out;
>  
>  	return MNL_CB_OK;
>  out:
> diff --git a/iptables/nft-cache.h b/iptables/nft-cache.h
> index 76f9fbb6c8ccc..d97f8de255f02 100644
> --- a/iptables/nft-cache.h
> +++ b/iptables/nft-cache.h
> @@ -3,6 +3,7 @@
>  
>  struct nft_handle;
>  struct nft_cmd;
> +struct builtin_table;
>  
>  void nft_cache_level_set(struct nft_handle *h, int level,
>  			 const struct nft_cmd *cmd);
> @@ -12,6 +13,8 @@ void flush_chain_cache(struct nft_handle *h, const char *tablename);
>  int flush_rule_cache(struct nft_handle *h, const char *table,
>  		     struct nftnl_chain *c);
>  void nft_cache_build(struct nft_handle *h);
> +int nft_cache_add_chain(struct nft_handle *h, const struct builtin_table *t,
> +			struct nftnl_chain *c);
>  
>  struct nftnl_chain_list *
>  nft_chain_list_get(struct nft_handle *h, const char *table, const char *chain);
> diff --git a/iptables/nft.c b/iptables/nft.c
> index 4f40be2e60252..8e1a33ba69bf1 100644
> --- a/iptables/nft.c
> +++ b/iptables/nft.c
> @@ -695,7 +695,7 @@ static void nft_chain_builtin_add(struct nft_handle *h,
>  		return;
>  
>  	batch_chain_add(h, NFT_COMPAT_CHAIN_ADD, c);
> -	nftnl_chain_list_add_tail(c, h->cache->table[table->type].chains);
> +	nft_cache_add_chain(h, table, c);
>  }
>  
>  /* find if built-in table already exists */
> @@ -1696,7 +1696,7 @@ int nft_rule_flush(struct nft_handle *h, const char *chain, const char *table,
>  
>  int nft_chain_user_add(struct nft_handle *h, const char *chain, const char *table)
>  {
> -	struct nftnl_chain_list *list;
> +	const struct builtin_table *t;
>  	struct nftnl_chain *c;
>  	int ret;
>  
> @@ -1720,9 +1720,8 @@ int nft_chain_user_add(struct nft_handle *h, const char *chain, const char *tabl
>  
>  	ret = batch_chain_add(h, NFT_COMPAT_CHAIN_USER_ADD, c);
>  
> -	list = nft_chain_list_get(h, table, chain);
> -	if (list)
> -		nftnl_chain_list_add(c, list);
> +	t = nft_table_builtin_find(h, table);

I'd add here:

        assert(t);

just in case this is ever crashing here, let's make it nice.