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netfilter: nf_tables: add transaction helper functions

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Add some helper functions for building the genmask as preparation for
set transactions.

Also add a little documentation how this stuff actually works.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Patrick McHardy 2015-03-25 14:08:49 +00:00 committed by Pablo Neira Ayuso
parent b2832dd662
commit ea4bd995b0
3 changed files with 35 additions and 16 deletions
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28
include/net/netfilter/nf_tables.h
View File

@ -720,6 +720,34 @@ void nft_unregister_expr(struct nft_expr_type *);
#define MODULE_ALIAS_NFT_SET() \
MODULE_ALIAS("nft-set")
/*
* The gencursor defines two generations, the currently active and the
* next one. Objects contain a bitmask of 2 bits specifying the generations
* they're active in. A set bit means they're inactive in the generation
* represented by that bit.
*
* New objects start out as inactive in the current and active in the
* next generation. When committing the ruleset the bitmask is cleared,
* meaning they're active in all generations. When removing an object,
* it is set inactive in the next generation. After committing the ruleset,
* the objects are removed.
*/
static inline unsigned int nft_gencursor_next(const struct net *net)
{
return net->nft.gencursor + 1 == 1 ? 1 : 0;
}
static inline u8 nft_genmask_next(const struct net *net)
{
return 1 << nft_gencursor_next(net);
}
static inline u8 nft_genmask_cur(const struct net *net)
{
/* Use ACCESS_ONCE() to prevent refetching the value for atomicity */
return 1 << ACCESS_ONCE(net->nft.gencursor);
}
/**
* struct nft_trans - nf_tables object update in transaction
*

17
net/netfilter/nf_tables_api.c
View File

@ -198,36 +198,31 @@ static int nft_delchain(struct nft_ctx *ctx)
static inline bool
nft_rule_is_active(struct net *net, const struct nft_rule *rule)
{
return (rule->genmask & (1 << net->nft.gencursor)) == 0;
}
static inline int gencursor_next(struct net *net)
{
return net->nft.gencursor+1 == 1 ? 1 : 0;
return (rule->genmask & nft_genmask_cur(net)) == 0;
}
static inline int
nft_rule_is_active_next(struct net *net, const struct nft_rule *rule)
{
return (rule->genmask & (1 << gencursor_next(net))) == 0;
return (rule->genmask & nft_genmask_next(net)) == 0;
}
static inline void
nft_rule_activate_next(struct net *net, struct nft_rule *rule)
{
/* Now inactive, will be active in the future */
rule->genmask = (1 << net->nft.gencursor);
rule->genmask = nft_genmask_cur(net);
}
static inline void
nft_rule_deactivate_next(struct net *net, struct nft_rule *rule)
{
rule->genmask = (1 << gencursor_next(net));
rule->genmask = nft_genmask_next(net);
}
static inline void nft_rule_clear(struct net *net, struct nft_rule *rule)
{
rule->genmask &= ~(1 << gencursor_next(net));
rule->genmask &= ~nft_genmask_next(net);
}
static int
@ -3626,7 +3621,7 @@ static int nf_tables_commit(struct sk_buff *skb)
while (++net->nft.base_seq == 0);
/* A new generation has just started */
net->nft.gencursor = gencursor_next(net);
net->nft.gencursor = nft_gencursor_next(net);
/* Make sure all packets have left the previous generation before
* purging old rules.

6
net/netfilter/nf_tables_core.c
View File

@ -121,11 +121,7 @@ nft_do_chain(struct nft_pktinfo *pkt, const struct nf_hook_ops *ops)
struct nft_jumpstack jumpstack[NFT_JUMP_STACK_SIZE];
struct nft_stats *stats;
int rulenum;
/*
* Cache cursor to avoid problems in case that the cursor is updated
* while traversing the ruleset.
*/
unsigned int gencursor = ACCESS_ONCE(net->nft.gencursor);
unsigned int gencursor = nft_genmask_cur(net);
do_chain:
rulenum = 0;