netdev - Re: [PATCH nf-next 5/9] netfilter: conntrack: small refactoring of conntrack seq

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Date:	Wed, 4 May 2016 00:28:54 +0200
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Florian Westphal <fw@...len.de>
Cc:	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH nf-next 5/9] netfilter: conntrack: small refactoring of
 conntrack seq_printf

On Tue, May 03, 2016 at 08:12:50PM +0200, Pablo Neira Ayuso wrote:
> On Thu, Apr 28, 2016 at 07:13:44PM +0200, Florian Westphal wrote:
> > The iteration process is lockless, so we test if the conntrack object is
> > eligible for printing (e.g. is AF_INET) after obtaining the reference
> > count.
> > 
> > Once we put all conntracks into same hash table we might see more
> > entries that need to be skipped.
> > 
> > So add a helper and first perform the test in a lockless fashion
> > for fast skip.
> > 
> > Once we obtain the reference count, just repeat the check.
> > 
> > Signed-off-by: Florian Westphal <fw@...len.de>
> > ---
> >  .../netfilter/nf_conntrack_l3proto_ipv4_compat.c   | 24 +++++++++++++++++-----
> >  1 file changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
> > index f0dfe92..483cf79 100644
> > --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
> > +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4_compat.c
> > @@ -114,6 +114,19 @@ static inline void ct_show_secctx(struct seq_file *s, const struct nf_conn *ct)
> >  }
> >  #endif
> >  
> > +static bool ct_seq_should_skip(const struct nf_conn *ct,
> > +			       const struct nf_conntrack_tuple_hash *hash)
> > +{
> > +	/* we only want to print DIR_ORIGINAL */
> > +	if (NF_CT_DIRECTION(hash))
> > +		return true;
> > +
> > +	if (nf_ct_l3num(ct) != AF_INET)
> > +		return true;
> > +
> > +	return false;
> > +}
> > +
> >  static int ct_seq_show(struct seq_file *s, void *v)
> >  {
> >  	struct nf_conntrack_tuple_hash *hash = v;
> > @@ -123,14 +136,15 @@ static int ct_seq_show(struct seq_file *s, void *v)
> >  	int ret = 0;
> >  
> >  	NF_CT_ASSERT(ct);
> > -	if (unlikely(!atomic_inc_not_zero(&ct->ct_general.use)))
> > +	if (ct_seq_should_skip(ct, hash))
> >  		return 0;
> >  
> > +	if (unlikely(!atomic_inc_not_zero(&ct->ct_general.use)))
> > +		return 0;
> >  
> > -	/* we only want to print DIR_ORIGINAL */
> > -	if (NF_CT_DIRECTION(hash))
> > -		goto release;
> > -	if (nf_ct_l3num(ct) != AF_INET)
> > +	/* check if we raced w. object reuse */
> > +	if (!nf_ct_is_confirmed(ct) ||
> 
> This refactoring includes this new check, is this intentional?

It seems this check was previously missing, I can just amend the
commit log with a couple of lines to document that this patch also
includes this missing check. No problem.