[PATCH 1/3 v3] net: usb: r8152: Check used MAC passthrough address

[Aaron Ma <aaron.ma@canonical.com>]

When plugin multiple r8152 ethernet dongles to Lenovo Docks
or USB hub, MAC passthrough address from BIOS should be
checked if it had been used to avoid using on other dongles.

Currently builtin r8152 on Dock still can't be identified.
First detected r8152 will use the MAC passthrough address.

v2:
Skip builtin PCI MAC address which is share MAC address with
passthrough MAC.
Check thunderbolt based ethernet.

v3:
Add return value.

Fixes: f77b83b5bbab ("net: usb: r8152: Add MAC passthrough support for
more Lenovo Docks")
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
---
 drivers/net/usb/r8152.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index f9877a3e83ac..2483dc421dff 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -25,6 +25,7 @@
 #include <linux/atomic.h>
 #include <linux/acpi.h>
 #include <linux/firmware.h>
+#include <linux/pci.h>
 #include <crypto/hash.h>
 #include <linux/usb/r8152.h>
 
@@ -1605,6 +1606,7 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 	char *mac_obj_name;
 	acpi_object_type mac_obj_type;
 	int mac_strlen;
+	struct net_device *ndev;
 
 	if (tp->lenovo_macpassthru) {
 		mac_obj_name = "\\MACA";
@@ -1662,6 +1664,19 @@ static int vendor_mac_passthru_addr_read(struct r8152 *tp, struct sockaddr *sa)
 		ret = -EINVAL;
 		goto amacout;
 	}
+	rcu_read_lock();
+	for_each_netdev_rcu(&init_net, ndev) {
+		if (ndev->dev.parent && dev_is_pci(ndev->dev.parent) &&
+				!pci_is_thunderbolt_attached(to_pci_dev(ndev->dev.parent)))
+			continue;
+		if (strncmp(buf, ndev->dev_addr, 6) == 0) {
+			ret = -EINVAL;
+			rcu_read_unlock();
+			goto amacout;
+		}
+	}
+	rcu_read_unlock();
+
 	memcpy(sa->sa_data, buf, 6);
 	netif_info(tp, probe, tp->netdev,
 		   "Using pass-thru MAC addr %pM\n", sa->sa_data);
-- 
2.30.2