On Tue, Feb 04, 2014 at 01:46:37PM +0100, Florian Westphal wrote: > Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > On Tue, Feb 04, 2014 at 12:29:25AM +0100, Florian Westphal wrote: > > > Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx> wrote: > > > > diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c > > > > index 4d1fb5d..356bef5 100644 > > > > --- a/net/netfilter/nf_conntrack_core.c > > > > +++ b/net/netfilter/nf_conntrack_core.c > > > > @@ -448,7 +448,9 @@ nf_conntrack_hash_check_insert(struct nf_conn *ct) > > > > goto out; > > > > > > > > add_timer(&ct->timeout); > > > > - nf_conntrack_get(&ct->ct_general); > > > > + smp_wmb(); > > > > + /* The caller holds a reference to this object */ > > > > + atomic_set(&ct->ct_general.use, 2); > > > > > > What happens when the skb is dropped before confirmation? > > > > If you refer to the spot above, conntracks added via ctnetlink are > > always confirmed and the refcount will become 1 after insertion into > > the hashes. In the packet path, the refcount is 1 for unconfirmed > > conntracks, > > Right, sorry. I missed this. You only want to delay the init-to-1 > until the conntrack is inserted into the unconfirmed list. > > However, I think there is still a problem with the atomic_set to 2 > above. > > What about e.g. > Prerouting -> set refcnt to 1 > (clone) > (clone) > (refcnt is 3) > forward/postrouting -> confirmation (refcnt reset to two) > > I think this could happen at least with netfilter on-top-of bridge > when dealing with e.g. udp mcast. (i am looking at br_forward and > deliver_clone in particular). > > I think you could just leave hash_check_insert() alone? hash_check_insert() is only used by ctnetlink in the creation path for new conntracks. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
