[PATCH v2 net-next 02/16] net: dsa: allow drivers to request promiscuous mode on master

[Vladimir Oltean]

Currently DSA assumes that taggers don't mess with the destination MAC
address of the frames on RX. That is not always the case. Some DSA
headers are placed before the Ethernet header (ocelot), and others
simply mangle random bytes from the destination MAC address (sja1105
with its incl_srcpt option).

The DSA master goes to promiscuous mode automatically when the slave
devices go too (such as when enslaved to a bridge), but in standalone
mode this is a problem that needs to be dealt with.

So give drivers the possibility to signal that their tagging protocol
will get randomly dropped otherwise, and let DSA deal with fixing that.

Signed-off-by: Vladimir Oltean <vladimir.olt...@nxp.com>
---
 include/net/dsa.h |  7 +++++++
 net/dsa/master.c  | 21 ++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index d16057c5987a..70571b179d05 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -317,6 +317,13 @@ struct dsa_switch {
         */
        bool                    mtu_enforcement_ingress;
 
+       /* Some tagging protocols either mangle or shift the destination MAC
+        * address, in which case the DSA master would drop packets on ingress
+        * if what it understands out of the destination MAC address is not in
+        * its RX filter.
+        */
+       bool                    promisc_on_master;
+
        size_t num_ports;
 };
 
diff --git a/net/dsa/master.c b/net/dsa/master.c
index 61615ebc70e9..c12cbcdd54b1 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -259,6 +259,19 @@ static void dsa_netdev_ops_set(struct net_device *dev,
        dev->dsa_ptr->netdev_ops = ops;
 }
 
+static void dsa_master_set_promiscuity(struct net_device *dev, int inc)
+{
+       struct dsa_port *cpu_dp = dev->dsa_ptr;
+       struct dsa_switch *ds = cpu_dp->ds;
+
+       if (!ds->promisc_on_master)
+               return;
+
+       rtnl_lock();
+       dev_set_promiscuity(dev, inc);
+       rtnl_unlock();
+}
+
 static ssize_t tagging_show(struct device *d, struct device_attribute *attr,
                            char *buf)
 {
@@ -314,9 +327,12 @@ int dsa_master_setup(struct net_device *dev, struct 
dsa_port *cpu_dp)
        dev->dsa_ptr = cpu_dp;
        lockdep_set_class(&dev->addr_list_lock,
                          &dsa_master_addr_list_lock_key);
+
+       dsa_master_set_promiscuity(dev, 1);
+
        ret = dsa_master_ethtool_setup(dev);
        if (ret)
-               return ret;
+               goto out_err_reset_promisc;
 
        dsa_netdev_ops_set(dev, &dsa_netdev_ops);
 
@@ -329,6 +345,8 @@ int dsa_master_setup(struct net_device *dev, struct 
dsa_port *cpu_dp)
 out_err_ndo_teardown:
        dsa_netdev_ops_set(dev, NULL);
        dsa_master_ethtool_teardown(dev);
+out_err_reset_promisc:
+       dsa_master_set_promiscuity(dev, -1);
        return ret;
 }
 
@@ -338,6 +356,7 @@ void dsa_master_teardown(struct net_device *dev)
        dsa_netdev_ops_set(dev, NULL);
        dsa_master_ethtool_teardown(dev);
        dsa_master_reset_mtu(dev);
+       dsa_master_set_promiscuity(dev, -1);
 
        dev->dsa_ptr = NULL;
 
-- 
2.25.1