net/cdc_ncm: Fix multicast RX support for CDC NCM devices with ZLP

ZLP for DisplayLink ethernet devices was enabled in 6.0:
266c0190aee3 ("net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices").
The related driver_info should be the "same as cdc_ncm_info, but with
FLAG_SEND_ZLP". However, set_rx_mode that enables handling multicast
traffic was missing in the new cdc_ncm_zlp_info.

usbnet_cdc_update_filter rx mode was introduced in linux 5.9 with:
e10dcb1b6ba7 ("net: cdc_ncm: hook into set_rx_mode to admit multicast

Without this hook, multicast, and then IPv6 SLAAC, is broken.

Fixes: 266c0190aee3 ("net/cdc_ncm: Enable ZLP for DisplayLink ethernet devices")
Signed-off-by: Santiago Ruano Rincón <>
Signed-off-by: David S. Miller <>
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 8d5cbda..0897fdb 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1915,6 +1915,7 @@
 	.status = cdc_ncm_status,
 	.rx_fixup = cdc_ncm_rx_fixup,
 	.tx_fixup = cdc_ncm_tx_fixup,
+	.set_rx_mode = usbnet_cdc_update_filter,
 /* Same as cdc_ncm_info, but with FLAG_WWAN */