Merge branch 'rndis_host-handle-bogus-mac-addresses-in-zte-rndis-devices'

Lech Perczak says:

====================
rndis_host: handle bogus MAC addresses in ZTE RNDIS devices

When porting support of ZTE MF286R to OpenWrt [1], it was discovered,
that its built-in LTE modem fails to adjust its target MAC address,
when a random MAC address is assigned to the interface, due to detection of
"locally-administered address" bit. This leads to dropping of ingress
trafficat the host. The modem uses RNDIS as its primary interface,
with some variants exposing both of them simultaneously.

Then it was discovered, that cdc_ether driver contains a fixup for that
exact issue, also appearing on CDC ECM interfaces.
I discussed how to proceed with that with Bjørn Mork at OpenWrt forum [3],
with the first approach would be to trust the locally-administered MAC
again, and add a quirk for the problematic ZTE devices, as suggested by
Kristian Evensen. before [4], but reusing the fixup from cdc_ether looks
like a safer and more generic solution.

Finally, according to Bjørn's suggestion. limit the scope of bogus MAC
addressdetection to ZTE devices, the same way as it is done in cdc_ether,
as this trait wasn't really observed outside of ZTE devices.
Do that for both flavours of RNDIS devices, with interface classes
02/02/ff and e0/01/03, as both types are reported by different modems.

[1] https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=7ac8da00609f42b8aba74b7efc6b0d055b7cef3e
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bfe9b9d2df669a57a95d641ed46eb018e204c6ce
[3] https://forum.openwrt.org/t/problem-with-modem-in-zte-mf286r/120988
[4] https://lore.kernel.org/all/CAKfDRXhDp3heiD75Lat7cr1JmY-kaJ-MS0tt7QXX=s8RFjbpUQ@mail.gmail.com/T/

Cc: Bjørn Mork <bjorn@mork.no>
Cc: Kristian Evensen <kristian.evensen@gmail.com>
Cc: Oliver Neukum <oliver@neukum.org>

v3: Fixed wrong identifier commit description and whitespace in patch 2.

v2: ensure that MAC fixup is applied to all Ethernet frames in RNDIS
batch, by introducing a driver flag, and integrating the fixup inside
rndis_rx_fixup().
====================

Link: https://lore.kernel.org/r/20220413014416.2306843-1-lech.perczak@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

4 files changed, 47 insertions, 5 deletions

diff --git a/drivers/net/usb/cdc_ether.c b/drivers/net/usb/cdc_ether.c
index 9b4dfa3001d6..2de09ad5bac0 100644
--- a/drivers/net/usb/cdc_ether.c
+++ b/drivers/net/usb/cdc_ether.c
@@ -479,7 +479,7 @@ static int usbnet_cdc_zte_bind(struct usbnet *dev, struct usb_interface *intf)
  * device MAC address has been updated). Always set MAC address to that of the
  * device.
  */
-static int usbnet_cdc_zte_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
+int usbnet_cdc_zte_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 {
 	if (skb->len < ETH_HLEN || !(skb->data[0] & 0x02))
 		return 1;
@@ -489,6 +489,7 @@ static int usbnet_cdc_zte_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 
 	return 1;
 }
+EXPORT_SYMBOL_GPL(usbnet_cdc_zte_rx_fixup);
 
 /* Ensure correct link state
  *
diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
index 247f58cb0f84..4e70dec30e5a 100644
--- a/drivers/net/usb/rndis_host.c
+++ b/drivers/net/usb/rndis_host.c
@@ -418,10 +418,7 @@ generic_rndis_bind(struct usbnet *dev, struct usb_interface *intf, int flags)
 		goto halt_fail_and_release;
 	}
 
-	if (bp[0] & 0x02)
-		eth_hw_addr_random(net);
-	else
-		eth_hw_addr_set(net, bp);
+	eth_hw_addr_set(net, bp);
 
 	/* set a nonzero filter to enable data transfers */
 	memset(u.set, 0, sizeof *u.set);
@@ -463,6 +460,16 @@ static int rndis_bind(struct usbnet *dev, struct usb_interface *intf)
 	return generic_rndis_bind(dev, intf, FLAG_RNDIS_PHYM_NOT_WIRELESS);
 }
 
+static int zte_rndis_bind(struct usbnet *dev, struct usb_interface *intf)
+{
+	int status = rndis_bind(dev, intf);
+
+	if (!status && (dev->net->dev_addr[0] & 0x02))
+		eth_hw_addr_random(dev->net);
+
+	return status;
+}
+
 void rndis_unbind(struct usbnet *dev, struct usb_interface *intf)
 {
 	struct rndis_halt	*halt;
@@ -485,10 +492,14 @@ EXPORT_SYMBOL_GPL(rndis_unbind);
  */
 int rndis_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 {
+	bool dst_mac_fixup;
+
 	/* This check is no longer done by usbnet */
 	if (skb->len < dev->net->hard_header_len)
 		return 0;
 
+	dst_mac_fixup = !!(dev->driver_info->data & RNDIS_DRIVER_DATA_DST_MAC_FIXUP);
+
 	/* peripheral may have batched packets to us... */
 	while (likely(skb->len)) {
 		struct rndis_data_hdr	*hdr = (void *)skb->data;
@@ -523,10 +534,17 @@ int rndis_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 			break;
 		skb_pull(skb, msg_len - sizeof *hdr);
 		skb_trim(skb2, data_len);
+
+		if (unlikely(dst_mac_fixup))
+			usbnet_cdc_zte_rx_fixup(dev, skb2);
+
 		usbnet_skb_return(dev, skb2);
 	}
 
 	/* caller will usbnet_skb_return the remaining packet */
+	if (unlikely(dst_mac_fixup))
+		usbnet_cdc_zte_rx_fixup(dev, skb);
+
 	return 1;
 }
 EXPORT_SYMBOL_GPL(rndis_rx_fixup);
@@ -600,6 +618,17 @@ static const struct driver_info	rndis_poll_status_info = {
 	.tx_fixup =	rndis_tx_fixup,
 };
 
+static const struct driver_info	zte_rndis_info = {
+	.description =	"ZTE RNDIS device",
+	.flags =	FLAG_ETHER | FLAG_POINTTOPOINT | FLAG_FRAMING_RN | FLAG_NO_SETINT,
+	.data =		RNDIS_DRIVER_DATA_DST_MAC_FIXUP,
+	.bind =		zte_rndis_bind,
+	.unbind =	rndis_unbind,
+	.status =	rndis_status,
+	.rx_fixup =	rndis_rx_fixup,
+	.tx_fixup =	rndis_tx_fixup,
+};
+
 /*-------------------------------------------------------------------------*/
 
 static const struct usb_device_id	products [] = {
@@ -614,6 +643,16 @@ static const struct usb_device_id	products [] = {
 				      USB_CLASS_COMM, 2 /* ACM */, 0x0ff),
 	.driver_info = (unsigned long)&rndis_info,
 }, {
+	/* ZTE WWAN modules */
+	USB_VENDOR_AND_INTERFACE_INFO(0x19d2,
+				      USB_CLASS_WIRELESS_CONTROLLER, 1, 3),
+	.driver_info = (unsigned long)&zte_rndis_info,
+}, {
+	/* ZTE WWAN modules, ACM flavour */
+	USB_VENDOR_AND_INTERFACE_INFO(0x19d2,
+				      USB_CLASS_COMM, 2 /* ACM */, 0x0ff),
+	.driver_info = (unsigned long)&zte_rndis_info,
+}, {
 	/* RNDIS is MSFT's un-official variant of CDC ACM */
 	USB_INTERFACE_INFO(USB_CLASS_COMM, 2 /* ACM */, 0x0ff),
 	.driver_info = (unsigned long) &rndis_info,
diff --git a/include/linux/usb/rndis_host.h b/include/linux/usb/rndis_host.h
index 809bccd08455..cc42db51bbba 100644
--- a/include/linux/usb/rndis_host.h
+++ b/include/linux/usb/rndis_host.h
@@ -197,6 +197,7 @@ struct rndis_keepalive_c {	/* IN (optionally OUT) */
 
 /* Flags for driver_info::data */
 #define RNDIS_DRIVER_DATA_POLL_STATUS	1	/* poll status before control */
+#define RNDIS_DRIVER_DATA_DST_MAC_FIXUP	2	/* device ignores configured MAC address */
 
 extern void rndis_status(struct usbnet *dev, struct urb *urb);
 extern int
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 8336e86ce606..1b4d72d5e891 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -214,6 +214,7 @@ extern int usbnet_ether_cdc_bind(struct usbnet *dev, struct usb_interface *intf)
 extern int usbnet_cdc_bind(struct usbnet *, struct usb_interface *);
 extern void usbnet_cdc_unbind(struct usbnet *, struct usb_interface *);
 extern void usbnet_cdc_status(struct usbnet *, struct urb *);
+extern int usbnet_cdc_zte_rx_fixup(struct usbnet *dev, struct sk_buff *skb);
 
 /* CDC and RNDIS support the same host-chosen packet filters for IN transfers */
 #define	DEFAULT_FILTER	(USB_CDC_PACKET_TYPE_BROADCAST \