netdev - Re: [PATCH net] i40e: report VF tx_dropped with tx_errors instead of tx

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Message-ID: <CAOftDsEnyXZa8arEGL5pRa-0RvfwS5Tv7eb-uhOzCUAZcUxoAQ@mail.gmail.com>
Date: Thu, 17 Jul 2025 12:46:28 -0400
From: Dennis Chen <dechen@...hat.com>
To: netdev@...r.kernel.org
Cc: anthony.l.nguyen@...el.com, przemyslaw.kitszel@...el.com, 
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH net] i40e: report VF tx_dropped with tx_errors instead of tx_discards

On Wed, Jun 18, 2025 at 3:52 PM Dennis Chen <dechen@...hat.com> wrote:
>
> Currently the tx_dropped field in VF stats is not updated correctly
> when reading stats from the PF. This is because it reads from
> i40e_eth_stats.tx_discards which seems to be unused for per VSI stats,
> as it is not updated by i40e_update_eth_stats() and the corresponding
> register, GLV_TDPC, is not implemented[1].
>
> Use i40e_eth_stats.tx_errors instead, which is actually updated by
> i40e_update_eth_stats() by reading from GLV_TEPC.
>
> To test, create a VF and try to send bad packets through it:
>
> $ echo 1 > /sys/class/net/enp2s0f0/device/sriov_numvfs
> $ cat test.py
> from scapy.all import *
>
> vlan_pkt = Ether(dst="ff:ff:ff:ff:ff:ff") / Dot1Q(vlan=999) / IP(dst="192.168.0.1") / ICMP()
> ttl_pkt = IP(dst="8.8.8.8", ttl=0) / ICMP()
>
> print("Send packet with bad VLAN tag")
> sendp(vlan_pkt, iface="enp2s0f0v0")
> print("Send packet with TTL=0")
> sendp(ttl_pkt, iface="enp2s0f0v0")
> $ ip -s link show dev enp2s0f0
> 16: enp2s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
>     link/ether 3c:ec:ef:b7:e0:ac brd ff:ff:ff:ff:ff:ff
>     RX:  bytes packets errors dropped  missed   mcast
>              0       0      0       0       0       0
>     TX:  bytes packets errors dropped carrier collsns
>              0       0      0       0       0       0
>     vf 0     link/ether e2:c6:fd:c1:1e:92 brd ff:ff:ff:ff:ff:ff, spoof checking on, link-state auto, trust off
>     RX: bytes  packets  mcast   bcast   dropped
>              0        0       0       0        0
>     TX: bytes  packets   dropped
>              0        0        0
> $ python test.py
> Send packet with bad VLAN tag
> .
> Sent 1 packets.
> Send packet with TTL=0
> .
> Sent 1 packets.
> $ ip -s link show dev enp2s0f0
> 16: enp2s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
>     link/ether 3c:ec:ef:b7:e0:ac brd ff:ff:ff:ff:ff:ff
>     RX:  bytes packets errors dropped  missed   mcast
>              0       0      0       0       0       0
>     TX:  bytes packets errors dropped carrier collsns
>              0       0      0       0       0       0
>     vf 0     link/ether e2:c6:fd:c1:1e:92 brd ff:ff:ff:ff:ff:ff, spoof checking on, link-state auto, trust off
>     RX: bytes  packets  mcast   bcast   dropped
>              0        0       0       0        0
>     TX: bytes  packets   dropped
>              0        0        0
>
> A packet with non-existent VLAN tag and a packet with TTL = 0 are sent,
> but tx_dropped is not incremented.
>
> After patch:
>
> $ ip -s link show dev enp2s0f0
> 19: enp2s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
>     link/ether 3c:ec:ef:b7:e0:ac brd ff:ff:ff:ff:ff:ff
>     RX:  bytes packets errors dropped  missed   mcast
>              0       0      0       0       0       0
>     TX:  bytes packets errors dropped carrier collsns
>              0       0      0       0       0       0
>     vf 0     link/ether 4a:b7:3d:37:f7:56 brd ff:ff:ff:ff:ff:ff, spoof checking on, link-state auto, trust off
>     RX: bytes  packets  mcast   bcast   dropped
>              0        0       0       0        0
>     TX: bytes  packets   dropped
>              0        0        2
>
> Fixes: dc645daef9af5bcbd9c ("i40e: implement VF stats NDO")
> Signed-off-by: Dennis Chen <dechen@...hat.com>
>     Link: https://www.intel.com/content/www/us/en/content-details/596333/intel-ethernet-controller-x710-tm4-at2-carlsville-datasheet.html
> ---
>  drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> index 88e6bef69342..2dbe38eb9494 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> @@ -5006,7 +5006,7 @@ int i40e_get_vf_stats(struct net_device *netdev, int vf_id,
>         vf_stats->broadcast  = stats->rx_broadcast;
>         vf_stats->multicast  = stats->rx_multicast;
>         vf_stats->rx_dropped = stats->rx_discards + stats->rx_discards_other;
> -       vf_stats->tx_dropped = stats->tx_discards;
> +       vf_stats->tx_dropped = stats->tx_errors;
>
>         return 0;
>  }
> --
> 2.49.0
>
Hello,

Any update here?


Dennis Chen