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netfilter: prefer extension check to pointer check

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The pointer check usually results in a 'false positive': its likely
that the ctnetlink module is loaded but no event monitoring is enabled.

After recent change to autodetect ctnetlink usage and only allocate
the ecache extension if a listener is active, check if the extension
is present on a given conntrack.

If its not there, there is nothing to report and calls to the
notification framework can be elided.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2022-04-25 15:15:44 +02:00 committed by Pablo Neira Ayuso
parent 90d1daa458
commit 8edc813111
2 changed files with 16 additions and 17 deletions
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2
include/net/netfilter/nf_conntrack_core.h
View file

@ -60,7 +60,7 @@ static inline int nf_conntrack_confirm(struct sk_buff *skb)
if (ct) {
if (!nf_ct_is_confirmed(ct))
ret = __nf_conntrack_confirm(skb);
if (likely(ret == NF_ACCEPT))
if (ret == NF_ACCEPT && nf_ct_ecache_exist(ct))
nf_ct_deliver_cached_events(ct);
}
return ret;

31
include/net/netfilter/nf_conntrack_ecache.h
View file

@ -36,6 +36,15 @@ nf_ct_ecache_find(const struct nf_conn *ct)
#endif
}
static inline bool nf_ct_ecache_exist(const struct nf_conn *ct)
{
#ifdef CONFIG_NF_CONNTRACK_EVENTS
return nf_ct_ext_exist(ct, NF_CT_EXT_ECACHE);
#else
return false;
#endif
}
#ifdef CONFIG_NF_CONNTRACK_EVENTS
/* This structure is passed to event handler */
@ -108,30 +117,20 @@ nf_conntrack_event_report(enum ip_conntrack_events event, struct nf_conn *ct,
u32 portid, int report)
{
#ifdef CONFIG_NF_CONNTRACK_EVENTS
const struct net *net = nf_ct_net(ct);
if (!rcu_access_pointer(net->ct.nf_conntrack_event_cb))
return 0;
return nf_conntrack_eventmask_report(1 << event, ct, portid, report);
#else
return 0;
if (nf_ct_ecache_exist(ct))
return nf_conntrack_eventmask_report(1 << event, ct, portid, report);
#endif
return 0;
}
static inline int
nf_conntrack_event(enum ip_conntrack_events event, struct nf_conn *ct)
{
#ifdef CONFIG_NF_CONNTRACK_EVENTS
const struct net *net = nf_ct_net(ct);
if (!rcu_access_pointer(net->ct.nf_conntrack_event_cb))
return 0;
return nf_conntrack_eventmask_report(1 << event, ct, 0, 0);
#else
return 0;
if (nf_ct_ecache_exist(ct))
return nf_conntrack_eventmask_report(1 << event, ct, 0, 0);
#endif
return 0;
}
#ifdef CONFIG_NF_CONNTRACK_EVENTS