net: dsa: sja1105: Limit use of incl_srcpt to bridge+vlan mode

The incl_srcpt setting makes the switch mangle the destination MACs of
multicast frames trapped to the CPU - a primitive tagging mechanism that
works even when we cannot use the 802.1Q software features.

The downside is that the two multicast MAC addresses that the switch
traps for L2 PTP (01-80-C2-00-00-0E and 01-1B-19-00-00-00) quickly turn
into a lot more, as the switch encodes the source port and switch id
into bytes 3 and 4 of the MAC. The resulting range of MAC addresses
would need to be installed manually into the DSA master port's multicast
MAC filter, and even then, most devices might not have a large enough
MAC filtering table.

As a result, only limit use of incl_srcpt to when it's strictly
necessary: when under a VLAN filtering bridge.  This fixes PTP in
non-bridged mode (standalone ports). Otherwise, PTP frames, as well as
metadata follow-up frames holding RX timestamps won't be received
because they will be blocked by the master port's MAC filter.
Linuxptp doesn't help, because it only requests the addition of the
unmodified PTP MACs to the multicast filter.
This issue is not seen in bridged mode because the master port is put in
promiscuous mode when the slave ports are enslaved to a bridge.
Therefore, there is no downside to having the incl_srcpt mechanism
active there.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index ecb54b828593..ea854ea903d1 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -392,11 +392,11 @@ static int sja1105_init_general_params(struct sja1105_private *priv)
 		.hostprio = 0,
 		.mac_fltres1 = SJA1105_LINKLOCAL_FILTER_A,
 		.mac_flt1    = SJA1105_LINKLOCAL_FILTER_A_MASK,
-		.incl_srcpt1 = true,
+		.incl_srcpt1 = false,
 		.send_meta1  = false,
 		.mac_fltres0 = SJA1105_LINKLOCAL_FILTER_B,
 		.mac_flt0    = SJA1105_LINKLOCAL_FILTER_B_MASK,
-		.incl_srcpt0 = true,
+		.incl_srcpt0 = false,
 		.send_meta0  = false,
 		/* The destination for traffic matching mac_fltres1 and
 		 * mac_fltres0 on all ports except host_port. Such traffic
@@ -1435,6 +1435,11 @@ static int sja1105_vlan_filtering(struct dsa_switch *ds, int port, bool enabled)
 	general_params->tpid = tpid;
 	/* EtherType used to identify inner tagged (C-tag) VLAN traffic */
 	general_params->tpid2 = tpid2;
+	/* When VLAN filtering is on, we need to at least be able to
+	 * decode management traffic through the "backup plan".
+	 */
+	general_params->incl_srcpt1 = enabled;
+	general_params->incl_srcpt0 = enabled;
 
 	rc = sja1105_static_config_reload(priv);
 	if (rc)