netdev - [PATCH net-next v2 3/9] net: psample: skip packet copy if no listeners

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Date: Mon,  3 Jun 2024 20:56:37 +0200
From: Adrian Moreno <amorenoz@...hat.com>
To: netdev@...r.kernel.org
Cc: aconole@...hat.com,
	echaudro@...hat.com,
	horms@...nel.org,
	i.maximets@....org,
	dev@...nvswitch.org,
	Adrian Moreno <amorenoz@...hat.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: [PATCH net-next v2 3/9] net: psample: skip packet copy if no listeners

If nobody is listening on the multicast group, generating the sample,
which involves copying packet data, seems completely unnecessary.

Return fast in this case.

Signed-off-by: Adrian Moreno <amorenoz@...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) +
-- 
2.45.1