Re: [PATCH] net: dccp: delete redundant ackvec record in dccp_insert_options()

[Hangyu Hua]

On 21/2/2023 20:46, Eric Dumazet wrote:
> On Tue, Feb 21, 2023 at 10:22 AM Hangyu Hua <hbh25y@xxxxxxxxx> wrote:
> > A useless record can be insert into av_records when dccp_insert_options()
> > fails after dccp_insert_option_ackvec(). Repeated triggering may cause
> > av_records to have a lot of useless record with the same avr_ack_seqno.
> >
> > Fixes: 8b7b6c75c638 ("dccp: Integrate feature-negotiation insertion code")
> > Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> > ---
> >   net/dccp/options.c | 12 ++++++++++--
> >   1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/dccp/options.c b/net/dccp/options.c
> > index d24cad05001e..8aa4abeb15ea 100644
> > --- a/net/dccp/options.c
> > +++ b/net/dccp/options.c
> > @@ -549,6 +549,8 @@ static void dccp_insert_option_padding(struct sk_buff *skb)
> >   int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
> >   {
> >          struct dccp_sock *dp = dccp_sk(sk);
> > +       struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
> > +       struct dccp_ackvec_record *avr;
> >
> >          DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
> >
> > @@ -577,16 +579,22 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
> >
> >          if (dp->dccps_hc_rx_insert_options) {
> >                  if (ccid_hc_rx_insert_options(dp->dccps_hc_rx_ccid, sk, skb))
> > -                       return -1;
> > +                       goto delete_ackvec;
> >                  dp->dccps_hc_rx_insert_options = 0;
> >          }
> >
> >          if (dp->dccps_timestamp_echo != 0 &&
> >              dccp_insert_option_timestamp_echo(dp, NULL, skb))
> > -               return -1;
> > +               goto delete_ackvec;
> >
> >          dccp_insert_option_padding(skb);
> >          return 0;
> > +
> > +delete_ackvec:
> > +       avr = dccp_ackvec_lookup(&av->av_records, DCCP_SKB_CB(skb)->dccpd_seq);
>
> Why avr would be not NULL ?
>
> > +       list_del(&avr->avr_node);
> > +       kmem_cache_free(dccp_ackvec_record_slab, avr);
> > +       return -1;
> >   }
>
> Are you really using DCCP and/or how have you tested this patch ?
>
> net/dccp/ackvec.c:15:static struct kmem_cache *dccp_ackvec_record_slab;
>
> I doubt this patch has been compiled.
>
> I would rather mark DCCP deprecated and stop trying to fix it.

My bad. I will fix these problems.

Thanks,
Hangyu