netdev - Re: [PATCH net-next] udp: add drop count for packets in udp_prod

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Message-ID: <CANn89iKwmhmAOConHjNP7XxVLghaJJgU4gDSH+To8Q1V67Jv0Q@mail.gmail.com>
Date: Wed, 28 Jan 2026 12:43:51 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Mahdi Faramarzpour <mahdifrmx@...il.com>
Cc: netdev@...r.kernel.org, willemdebruijn.kernel@...il.com, 
	davem@...emloft.net, dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com, 
	horms@...nel.org, kshitiz.bartariya@...omail.in
Subject: Re: [PATCH net-next] udp: add drop count for packets in udp_prod_queue

On Wed, Jan 28, 2026 at 8:03 AM Mahdi Faramarzpour <mahdifrmx@...il.com> wrote:
>
> This commit adds SNMP drop count increment for the packets in
> per NUMA queues which were introduced in commit b650bf0977d3
> ("udp: remove busylock and add per NUMA queues"). note that SNMP
> counters are incremented currently by the caller for skb. And
> that these skbs on the intermediate queue cannot be counted
> there so need similar logic in their error path.
>
> Signed-off-by: Mahdi Faramarzpour <mahdifrmx@...il.com>
> ---
> v6:
>   - increasing a single counter based on socket family
> v5: https://lore.kernel.org/netdev/20260122185357.50922-1-mahdifrmx@gmail.com/
>   - check if drop counts are non-zero before increasing countrers
> v4: https://lore.kernel.org/netdev/20260108102950.49417-1-mahdifrmx@gmail.com/
>   - move all changes to unlikely(to_drop) branch
> v3: https://lore.kernel.org/netdev/20260105114732.140719-1-mahdifrmx@gmail.com/
>   - remove the unreachable UDP_MIB_RCVBUFERRORS code
> v2: https://lore.kernel.org/netdev/20260105071218.10785-1-mahdifrmx@gmail.com/
>   - change ENOMEM to ENOBUFS
> v1: https://lore.kernel.org/netdev/20260104105732.427691-1-mahdifrmx@gmail.com/
> ---
>  net/ipv4/udp.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index ffe074cb5..dd302f5fb 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1797,10 +1797,13 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
>                         skb = to_drop;
>                         to_drop = skb->next;
>                         skb_mark_not_on_list(skb);
> -                       /* TODO: update SNMP values. */
>                         sk_skb_reason_drop(sk, skb, SKB_DROP_REASON_PROTO_MEM);
>                 }
>                 numa_drop_add(&udp_sk(sk)->drop_counters, nb);
> +               SNMP_ADD_STATS(__UDPX_MIB(sk, (sk->sk_family == PF_INET)),
> +                              UDP_MIB_MEMERRORS, nb);
> +               SNMP_ADD_STATS(__UDPX_MIB(sk, (sk->sk_family == PF_INET)),
> +                              UDP_MIB_INERRORS, nb);
>         }

Hmm.. I have not followed your prior attempts, sorry for coming late.

Note that an UDP AF_INET6 socket for which ipv6_only_sock(sk) is false
can receive
IPv4 and IPv6 UDP packets, if bound to any addresses.

The to_drop list could contain a mix of IPv4 and IPv6 packets.

Ideally we should track SNMP values in the proper space (Ipv4 , IPv6).

See IPV6_V6ONLY and /proc/sys/net/ipv6/bindv6only for reference.