From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Safonov Subject: Re: [PATCH] netfilter: conntrack: fix calculation of next bucket number in early_drop Date: Thu, 25 Oct 2018 05:52:53 +0100 Message-ID: References: <20181025034853.23573-1-vasilykh@arista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: stable@vger.kernel.org To: Vasily Khoruzhick , Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , "David S. Miller" , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20181025034853.23573-1-vasilykh@arista.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 10/25/18 4:48 AM, Vasily Khoruzhick wrote: > If there's no entry to drop in bucket that corresponds to the hash, > early_drop() should look for it in other buckets. But since it increments > hash instead of bucket number, it actually looks in the same bucket 8 > times: hsize is 16k by default (14 bits) and hash is 32-bit value, so > reciprocal_scale(hash, hsize) returns the same value for hash..hash+7 in > most cases. > > Fix it by increasing bucket number instead of hash and rename _hash > to bucket to avoid future confusion. > > Fixes: 3e86638e9a0b ("netfilter: conntrack: consider ct netns in early_drop logic") > Cc: # v4.7+ > Signed-off-by: Vasily Khoruzhick Nice work! Reviewed-by: Dmitry Safonov > --- > net/netfilter/nf_conntrack_core.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c > index ca1168d67fac..a04af246b184 100644 > --- a/net/netfilter/nf_conntrack_core.c > +++ b/net/netfilter/nf_conntrack_core.c > @@ -1073,19 +1073,22 @@ static unsigned int early_drop_list(struct net *net, > return drops; > } > > -static noinline int early_drop(struct net *net, unsigned int _hash) > +static noinline int early_drop(struct net *net, unsigned int hash) > { > unsigned int i; > > for (i = 0; i < NF_CT_EVICTION_RANGE; i++) { > struct hlist_nulls_head *ct_hash; > - unsigned int hash, hsize, drops; > + unsigned int bucket, hsize, drops; > > rcu_read_lock(); > nf_conntrack_get_ht(&ct_hash, &hsize); > - hash = reciprocal_scale(_hash++, hsize); > + if (!i) > + bucket = reciprocal_scale(hash, hsize); > + else > + bucket = (bucket + 1) % hsize; > > - drops = early_drop_list(net, &ct_hash[hash]); > + drops = early_drop_list(net, &ct_hash[bucket]); > rcu_read_unlock(); > > if (drops) { > -- Dima