linux-kernel - Re: [PATCH net-next v7 03/10] net: psample: skip packet copy if no listeners

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Date: Mon, 01 Jul 2024 14:07:32 -0400
From: Aaron Conole <aconole@...hat.com>
To: Adrian Moreno <amorenoz@...hat.com>
Cc: netdev@...r.kernel.org,  echaudro@...hat.com,  horms@...nel.org,
  i.maximets@....org,  dev@...nvswitch.org,  Ido Schimmel
 <idosch@...dia.com>,  Yotam Gigi <yotam.gi@...il.com>,  "David S. Miller"
 <davem@...emloft.net>,  Eric Dumazet <edumazet@...gle.com>,  Jakub
 Kicinski <kuba@...nel.org>,  Paolo Abeni <pabeni@...hat.com>,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v7 03/10] net: psample: skip packet copy if no
 listeners

Adrian Moreno <amorenoz@...hat.com> writes:

> If nobody is listening on the multicast group, generating the sample,
> which involves copying packet data, seems completely unnecessary.
>
> Return fast in this case.
>
> Acked-by: Eelco Chaudron <echaudro@...hat.com>
> Reviewed-by: Ido Schimmel <idosch@...dia.com>
> Reviewed-by: Simon Horman <horms@...nel.org>
> Signed-off-by: Adrian Moreno <amorenoz@...hat.com>
> ---

Reviewed-by: Aaron Conole <aconole@...hat.com>

>  net/psample/psample.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/net/psample/psample.c b/net/psample/psample.c
> index b37488f426bc..1c76f3e48dcd 100644
> --- a/net/psample/psample.c
> +++ b/net/psample/psample.c
> @@ -376,6 +376,10 @@ void psample_sample_packet(struct psample_group *group, struct sk_buff *skb,
>  	void *data;
>  	int ret;
>  
> +	if (!genl_has_listeners(&psample_nl_family, group->net,
> +				PSAMPLE_NL_MCGRP_SAMPLE))
> +		return;
> +
>  	meta_len = (in_ifindex ? nla_total_size(sizeof(u16)) : 0) +
>  		   (out_ifindex ? nla_total_size(sizeof(u16)) : 0) +
>  		   (md->out_tc_valid ? nla_total_size(sizeof(u16)) : 0) +