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

On 21/2/2023 20:46, Eric Dumazet wrote:

On Tue, Feb 21, 2023 at 10:22 AM Hangyu Hua [off-list ref] wrote:

quoted

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 <redacted>
---
  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 ?

quoted

+       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