linux-kernel - [PATCH net-next v1] r8152: allow userland to disable multicast

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Message-Id: <20220830045923.net-next.v1.1.I4fee0ac057083d4f848caf0fa3a9fd466fc374a0@changeid>
Date:   Tue, 30 Aug 2022 04:59:39 +0000
From:   Sven van Ashbrook <svenva@...omium.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Alex Levin <levinale@...gle.com>,
        Chithra Annegowda <chithraa@...gle.com>,
        Frank Gorgenyi <frankgor@...gle.com>,
        Sven van Ashbrook <svenva@...omium.org>,
        Aaron Ma <aaron.ma@...onical.com>,
        David Ober <dober6023@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Hao Chen <chenhao288@...ilicon.com>,
        Hayes Wang <hayeswang@...ltek.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jean-Francois Le Fillatre <jflf_kernel@....com>,
        Paolo Abeni <pabeni@...hat.com>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH net-next v1] r8152: allow userland to disable multicast

The rtl8152 driver does not disable multicasting when userspace asks
it to. For example:
 $ ifconfig eth0 -multicast -allmulti
 $ tcpdump -p -i eth0  # will still capture multicast frames

Fix by clearing the device multicast filter table when multicast and
allmulti are both unset.

Tested as follows:
- Set multicast on eth0 network interface
- verify that multicast packets are coming in:
  $ tcpdump -p -i eth0
- Clear multicast and allmulti on eth0 network interface
- verify that no more multicast packets are coming in:
  $ tcpdump -p -i eth0

Signed-off-by: Sven van Ashbrook <svenva@...omium.org>
---

 drivers/net/usb/r8152.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 688905ea0a6d..5e85b8bf9e87 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -2727,22 +2727,26 @@ static void _rtl8152_set_rx_mode(struct net_device *netdev)
 		ocp_data |= RCR_AM | RCR_AAP;
 		mc_filter[1] = 0xffffffff;
 		mc_filter[0] = 0xffffffff;
-	} else if ((netdev_mc_count(netdev) > multicast_filter_limit) ||
-		   (netdev->flags & IFF_ALLMULTI)) {
+	} else if ((netdev->flags & IFF_MULTICAST &&
+				netdev_mc_count(netdev) > multicast_filter_limit) ||
+			   (netdev->flags & IFF_ALLMULTI)) {
 		/* Too many to filter perfectly -- accept all multicasts. */
 		ocp_data |= RCR_AM;
 		mc_filter[1] = 0xffffffff;
 		mc_filter[0] = 0xffffffff;
 	} else {
-		struct netdev_hw_addr *ha;
-
 		mc_filter[1] = 0;
 		mc_filter[0] = 0;
-		netdev_for_each_mc_addr(ha, netdev) {
-			int bit_nr = ether_crc(ETH_ALEN, ha->addr) >> 26;
 
-			mc_filter[bit_nr >> 5] |= 1 << (bit_nr & 31);
-			ocp_data |= RCR_AM;
+		if (netdev->flags & IFF_MULTICAST) {
+			struct netdev_hw_addr *ha;
+
+			netdev_for_each_mc_addr(ha, netdev) {
+				int bit_nr = ether_crc(ETH_ALEN, ha->addr) >> 26;
+
+				mc_filter[bit_nr >> 5] |= 1 << (bit_nr & 31);
+				ocp_data |= RCR_AM;
+			}
 		}
 	}
 
-- 
2.37.2.672.g94769d06f0-goog