Re: [PATCH nf-next 1/2] netfilter: flowtable: retrieve stats on flow deletion

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Thu, Oct 29, 2026 at 12:25:21PM +0100, Lorenzo Bianconi wrote:
> > Retrieve stats too when deleting a flow from hardware. Apparently, the
> > existing approach is missing last stats sync with the conntrack entry.
> > Pass the stats object to the driver so it has a chance to populate it
> > at deletion time. Drivers need to be updated to use this new approach.
> > 
> > Reported-by: Valentin Berezhnoy <dreyksmail@gmail.com>
> > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> > ---
> >  net/netfilter/nf_flow_table_offload.c | 43 ++++++++++++++++-----------
> >  1 file changed, 26 insertions(+), 17 deletions(-)
> > 
> > diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
> > index 4365859220e6..53182323f73c 100644
> > --- a/net/netfilter/nf_flow_table_offload.c
> > +++ b/net/netfilter/nf_flow_table_offload.c
> > @@ -934,6 +934,27 @@ static int nf_flow_offload_tuple(struct nf_flowtable *flowtable,
> >  	return i;
> >  }
> >  
> > +static void flow_offload_update_stats(struct flow_offload_work *offload,
> > +				      struct flow_stats *stats)
> > +{
> > +	u64 lastused;
> > +
> > +	lastused = max_t(u64, stats[0].lastused, stats[1].lastused);
> > +	offload->flow->timeout = max_t(u64, offload->flow->timeout,
> > +				       lastused + flow_offload_get_timeout(offload->flow));
> > +
> > +	if (offload->flowtable->flags & NF_FLOWTABLE_COUNTER) {
> > +		if (stats[0].pkts)
> > +			nf_ct_acct_add(offload->flow->ct,
> > +				       FLOW_OFFLOAD_DIR_ORIGINAL,
> > +				       stats[0].pkts, stats[0].bytes);
> > +		if (stats[1].pkts)
> > +			nf_ct_acct_add(offload->flow->ct,
> > +				       FLOW_OFFLOAD_DIR_REPLY,
> > +				       stats[1].pkts, stats[1].bytes);
> > +	}
> > +}
> > +
> >  static int flow_offload_tuple_add(struct flow_offload_work *offload,
> >  				  struct nf_flow_rule *flow_rule,
> >  				  enum flow_offload_tuple_dir dir)
> > @@ -948,10 +969,13 @@ static int flow_offload_tuple_add(struct flow_offload_work *offload,
> >  static void flow_offload_tuple_del(struct flow_offload_work *offload,
> >  				   enum flow_offload_tuple_dir dir)
> >  {
> > +	struct flow_stats stats[FLOW_OFFLOAD_DIR_MAX] = {};
> > +
> >  	nf_flow_offload_tuple(offload->flowtable, offload->flow, NULL, dir,
> >  			      offload->flowtable->priority,
> > -			      FLOW_CLS_DESTROY, NULL,
> > +			      FLOW_CLS_DESTROY, stats,
> >  			      &offload->flowtable->flow_block.cb_list);
> 
> according to my understanding nf_flow_offload_tuple() copies the stats just if
> cmd is set to FLOW_CLS_STATS, right? Should we just check if stats is not NULL
> in nf_flow_offload_tuple() instead?

I posted a v2 with:

        if (cmd == FLOW_CLS_STATS ||
            cmd == FLOW_CLS_DESTROY)

but I can post a v3 with.

        if (stats)

instead as you suggest.

> Regards,
> Lorenzo
> 
> > +	flow_offload_update_stats(offload, stats);
> >  }
> >  
> >  static int flow_offload_rule_add(struct flow_offload_work *offload,
> > @@ -1011,27 +1035,12 @@ static void flow_offload_tuple_stats(struct flow_offload_work *offload,
> >  static void flow_offload_work_stats(struct flow_offload_work *offload)
> >  {
> >  	struct flow_stats stats[FLOW_OFFLOAD_DIR_MAX] = {};
> > -	u64 lastused;
> >  
> >  	flow_offload_tuple_stats(offload, FLOW_OFFLOAD_DIR_ORIGINAL, &stats[0]);
> >  	if (test_bit(NF_FLOW_HW_BIDIRECTIONAL, &offload->flow->flags))
> >  		flow_offload_tuple_stats(offload, FLOW_OFFLOAD_DIR_REPLY,
> >  					 &stats[1]);
> > -
> > -	lastused = max_t(u64, stats[0].lastused, stats[1].lastused);
> > -	offload->flow->timeout = max_t(u64, offload->flow->timeout,
> > -				       lastused + flow_offload_get_timeout(offload->flow));
> > -
> > -	if (offload->flowtable->flags & NF_FLOWTABLE_COUNTER) {
> > -		if (stats[0].pkts)
> > -			nf_ct_acct_add(offload->flow->ct,
> > -				       FLOW_OFFLOAD_DIR_ORIGINAL,
> > -				       stats[0].pkts, stats[0].bytes);
> > -		if (stats[1].pkts)
> > -			nf_ct_acct_add(offload->flow->ct,
> > -				       FLOW_OFFLOAD_DIR_REPLY,
> > -				       stats[1].pkts, stats[1].bytes);
> > -	}
> > +	flow_offload_update_stats(offload, stats);
> >  }
> >  
> >  static void flow_offload_work_handler(struct work_struct *work)
> > -- 
> > 2.47.3
> >