macsec: don't increment counters for an unrelated SA

On RX, we shouldn't be incrementing the stats for an arbitrary SA in
case the actual SA hasn't been set up. Those counters are intended to
track packets for their respective AN when the SA isn't currently
configured. Due to the way MACsec is implemented, we don't keep
counters unless the SA is configured, so we can't track those packets,
and those counters will remain at 0.

The RXSC's stats keeps track of those packets without telling us which
AN they belonged to. We could add counters for non-existent SAs, and
then find a way to integrate them in the dump to userspace, but I
don't think it's worth the effort.

Fixes: 91ec9bd5 ("macsec: Fix traffic counters/statistics")
Reported-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/f5ac92aaa5b89343232615f4c03f9f95042c6aa0.1728657709.git.sd@queasysnail.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/macsec.c

@@ -154,19 +154,6 @@ static struct macsec_rx_sa *macsec_rxsa_get(struct macsec_rx_sa __rcu *ptr)
 	return sa;
 }
 
-static struct macsec_rx_sa *macsec_active_rxsa_get(struct macsec_rx_sc *rx_sc)
-{
-	struct macsec_rx_sa *sa = NULL;
-	int an;
-
-	for (an = 0; an < MACSEC_NUM_AN; an++)	{
-		sa = macsec_rxsa_get(rx_sc->sa[an]);
-		if (sa)
-			break;
-	}
-	return sa;
-}
-
 static void free_rx_sc_rcu(struct rcu_head *head)
 {
 	struct macsec_rx_sc *rx_sc = container_of(head, struct macsec_rx_sc, rcu_head);
@@ -1208,15 +1195,12 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 		/* If validateFrames is Strict or the C bit in the
 		 * SecTAG is set, discard
 		 */
-		struct macsec_rx_sa *active_rx_sa = macsec_active_rxsa_get(rx_sc);
 		if (hdr->tci_an & MACSEC_TCI_C ||
 		    secy->validate_frames == MACSEC_VALIDATE_STRICT) {
 			u64_stats_update_begin(&rxsc_stats->syncp);
 			rxsc_stats->stats.InPktsNotUsingSA++;
 			u64_stats_update_end(&rxsc_stats->syncp);
 			DEV_STATS_INC(secy->netdev, rx_errors);
-			if (active_rx_sa)
-				this_cpu_inc(active_rx_sa->stats->InPktsNotUsingSA);
 			goto drop_nosa;
 		}
 
@@ -1226,8 +1210,6 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 		u64_stats_update_begin(&rxsc_stats->syncp);
 		rxsc_stats->stats.InPktsUnusedSA++;
 		u64_stats_update_end(&rxsc_stats->syncp);
-		if (active_rx_sa)
-			this_cpu_inc(active_rx_sa->stats->InPktsUnusedSA);
 		goto deliver;
 	}