netfilter: nf_tables: add insert operation

This patch adds a new rule attribute NFTA_RULE_POSITION which is
used to store the position of a rule relatively to the others.
By providing a create command and specifying a position, the rule is
inserted after the rule with the handle equal to the provided
position.
Regarding notification, the position attribute is added to specify
the handle of the previous rule in append mode and the handle of
the next rule in the other case.

Signed-off-by: Eric Leblond <eric@regit.org>
---
 include/uapi/linux/netfilter/nf_tables.h |  1 +
 net/netfilter/nf_tables_api.c            | 47 +++++++++++++++++++++++++++++---
 2 files changed, 44 insertions(+), 4 deletions(-)

Hi Eric,

Thanks for this new round, some comments below:

On Sat, Jul 06, 2013 at 05:31:17PM +0200, Eric Leblond wrote:
> This patch adds a new rule attribute NFTA_RULE_POSITION which is
> used to store the position of a rule relatively to the others.
> By providing a create command and specifying a position, the rule is
> inserted after the rule with the handle equal to the provided
> position.
> Regarding notification, the position attribute is added to specify
> the handle of the previous rule in append mode and the handle of
> the next rule in the other case.
> 
> Signed-off-by: Eric Leblond <eric@regit.org>
> ---
>  include/uapi/linux/netfilter/nf_tables.h |  1 +
>  net/netfilter/nf_tables_api.c            | 47 +++++++++++++++++++++++++++++---
>  2 files changed, 44 insertions(+), 4 deletions(-)
> 
> diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> index d40a7f9..d9bf8ea 100644
> --- a/include/uapi/linux/netfilter/nf_tables.h
> +++ b/include/uapi/linux/netfilter/nf_tables.h
> @@ -143,6 +143,7 @@ enum nft_rule_attributes {
>  	NFTA_RULE_EXPRESSIONS,
>  	NFTA_RULE_FLAGS,
>  	NFTA_RULE_COMPAT,
> +	NFTA_RULE_POSITION,
>  	__NFTA_RULE_MAX
>  };
>  #define NFTA_RULE_MAX		(__NFTA_RULE_MAX - 1)
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index b00aca8..ce8a4f0 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -1267,6 +1267,7 @@ static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
>  	[NFTA_RULE_EXPRESSIONS]	= { .type = NLA_NESTED },
>  	[NFTA_RULE_FLAGS]	= { .type = NLA_U32 },
>  	[NFTA_RULE_COMPAT]	= { .type = NLA_NESTED },
> +	[NFTA_RULE_POSITION]	= { .type = NLA_U64 },
>  };
>  
>  static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> @@ -1279,6 +1280,7 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
>  	struct nfgenmsg *nfmsg;
>  	const struct nft_expr *expr, *next;
>  	struct nlattr *list;
> +	const struct nft_rule *prule;
>  
>  	event |= NFNL_SUBSYS_NFTABLES << 8;
>  	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
> @@ -1298,6 +1300,26 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
>  	if (nla_put_be64(skb, NFTA_RULE_HANDLE, cpu_to_be64(rule->handle)))
>  		goto nla_put_failure;
>  
> +	if (event & NLM_F_APPEND) {

This should be if (flags & NLM_F_APPEND)

> +		if ((rule->list.prev != LIST_POISON2) &&

You can use event instead to catch the deletion case:

if (event != NFT_MSG_DELRULE)

> +		    (rule->list.prev != &chain->rules)) {
> +			prule = list_entry(rule->list.prev,
> +					   struct nft_rule, list);
> +			if (nla_put_be64(skb, NFTA_RULE_POSITION,
> +					 cpu_to_be64(prule->handle)))
> +				goto nla_put_failure;
> +		}
> +	} else {
> +		if ((rule->list.next != LIST_POISON1) &&
> +		    (rule->list.next != &chain->rules)) {

You can use list_is_last instead of rule->list.next != &chain->rules.

Unfortunately, there is no list_is_first, but we could ask for
mainstream inclusion later on.

> +			prule = list_entry(rule->list.next,
> +					   struct nft_rule, list);
> +			if (nla_put_be64(skb, NFTA_RULE_POSITION,
> +					 cpu_to_be64(prule->handle)))
> +				goto nla_put_failure;
> +		}
> +	}
> +
>  	list = nla_nest_start(skb, NFTA_RULE_EXPRESSIONS);
>  	if (list == NULL)
>  		goto nla_put_failure;
> @@ -1537,7 +1559,7 @@ static int nf_tables_newrule(struct sock *nlsk, struct sk_buff *skb,
>  	int err, rem;
>  	bool create;
>  	u32 flags = 0;
> -	u64 handle;
> +	u64 handle, pos_handle;
>  
>  	create = nlh->nlmsg_flags & NLM_F_CREATE ? true : false;
>  
> @@ -1571,6 +1593,16 @@ static int nf_tables_newrule(struct sock *nlsk, struct sk_buff *skb,
>  		handle = nf_tables_alloc_handle(table);
>  	}
>  
> +	if (nla[NFTA_RULE_POSITION]) {
> +		pos_handle = be64_to_cpu(nla_get_be64(nla[NFTA_RULE_POSITION]));
> +		old_rule = __nf_tables_rule_lookup(chain, pos_handle);
> +		if (IS_ERR(old_rule))
> +			return PTR_ERR(old_rule);
> +
> +		if (! (nlh->nlmsg_flags & NLM_F_CREATE))
> +			return -EOPNOTSUPP;

Better this checking before the rule lookup.

> +	}
> +
>  	nft_ctx_init(&ctx, skb, nlh, afi, table, chain, nla);
>  
>  	n = 0;
> @@ -1625,9 +1657,16 @@ static int nf_tables_newrule(struct sock *nlsk, struct sk_buff *skb,
>  			nf_tables_rule_destroy(old_rule);
>  		}
>  	} else if (nlh->nlmsg_flags & NLM_F_APPEND)
> -		list_add_tail_rcu(&rule->list, &chain->rules);
> -	else
> -		list_add_rcu(&rule->list, &chain->rules);
> +		if (old_rule)
> +			list_add_rcu(&rule->list, &old_rule->list);
> +		else
> +			list_add_tail_rcu(&rule->list, &chain->rules);
> +	else {
> +		if (old_rule)
> +			list_add_tail_rcu(&rule->list, &old_rule->list);
> +		else
> +			list_add_rcu(&rule->list, &chain->rules);
> +	}
>  
>  	if (flags & NFT_RULE_F_COMMIT)
>  		list_add(&rule->dirty_list, &chain->dirty_rules);
> -- 
> 1.8.3.2
> 
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Hello Pablo,

Thanks for the review, here's an update version of the kernel
patch. A nftables patch on top of the one I've already provide
is also mandatory to have the insert operation working correctly.

BR,
--
Eric
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