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.

Reviewed-by: Aaron Conole <aconole@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Link: https://patch.msgid.link/20240704085710.353845-4-amorenoz@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/psample/psample.c b/net/psample/psample.c
index b37488f426bc2ff9eb8e4aed548e8431436dbed9..1c76f3e48dcd98fc4f446d63389c2ebe5b6eb6c2 100644 (file)
--- 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) +