linux-kernel - [PATCH net-next 3/8] ipvlan: Handle rx mcast-ip and unicast eth

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Message-ID: <20251021144410.257905-4-skorodumov.dmitry@huawei.com>
Date: Tue, 21 Oct 2025 17:44:05 +0300
From: Dmitry Skorodumov <skorodumov.dmitry@...wei.com>
To: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <andrey.bokhanko@...wei.com>, Dmitry Skorodumov
	<skorodumov.dmitry@...wei.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH net-next 3/8] ipvlan: Handle rx mcast-ip and unicast eth

Some WiFi enfironments sometimes send mcast packets
with unicast eth_dst. Forcibly replace eth_dst to be bcast in this case
if bridge is in L2E mode.

Signed-off-by: Dmitry Skorodumov <skorodumov.dmitry@...wei.com>
---
 drivers/net/ipvlan/ipvlan_core.c | 57 ++++++++++++++++++++++++++++++--
 1 file changed, 55 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ipvlan/ipvlan_core.c b/drivers/net/ipvlan/ipvlan_core.c
index 9af0dcc307da..41059639f307 100644
--- a/drivers/net/ipvlan/ipvlan_core.c
+++ b/drivers/net/ipvlan/ipvlan_core.c
@@ -855,18 +855,69 @@ static rx_handler_result_t ipvlan_handle_mode_l3(struct sk_buff **pskb,
 	return ret;
 }
 
+static bool ipvlan_is_mcast(struct ipvl_port *port, void *lyr3h, int addr_type)
+{
+	switch (addr_type) {
+#if IS_ENABLED(CONFIG_IPV6)
+	/* ToDo: handle  ICMPV6*/
+	case IPVL_IPV6:
+		return !is_ipv6_usable(&((struct ipv6hdr *)lyr3h)->daddr);
+#endif
+	case IPVL_IPV4: {
+		/* Treat mcast, bcast and zero as multicast. */
+		__be32 i4addr = ((struct iphdr *)lyr3h)->daddr;
+
+		return !is_ipv4_usable(i4addr);
+	}
+	case IPVL_ARP: {
+		struct arphdr *arph;
+		unsigned char *arp_ptr;
+		__be32 i4addr;
+
+		arph = (struct arphdr *)lyr3h;
+		arp_ptr = (unsigned char *)(arph + 1);
+		arp_ptr += (2 * port->dev->addr_len) + 4;
+		i4addr = *(__be32 *)arp_ptr;
+		return !is_ipv4_usable(i4addr);
+	}
+	}
+	return false;
+}
+
+static bool ipvlan_is_l2_mcast(struct ipvl_port *port, struct sk_buff *skb,
+			       bool *need_eth_fix)
+{
+	void *lyr3h;
+	int addr_type;
+
+	/* In some wifi environments unicast dest address means nothing.
+	 * IP still can be a mcast and frame should be treated as mcast.
+	 */
+	*need_eth_fix = false;
+	if (is_multicast_ether_addr(eth_hdr(skb)->h_dest))
+		return true;
+
+	if (!ipvlan_is_learnable(port))
+		return false;
+
+	lyr3h = ipvlan_get_L3_hdr(port, skb, &addr_type);
+	*need_eth_fix = lyr3h && ipvlan_is_mcast(port, lyr3h, addr_type);
+
+	return *need_eth_fix;
+}
+
 static rx_handler_result_t ipvlan_handle_mode_l2(struct sk_buff **pskb,
 						 struct ipvl_port *port)
 {
 	struct sk_buff *skb = *pskb;
-	struct ethhdr *eth = eth_hdr(skb);
 	rx_handler_result_t ret = RX_HANDLER_PASS;
+	bool need_eth_fix;
 
 	/* Ignore already seen packets. */
 	if (ipvlan_is_skb_marked(skb, port->dev))
 		return RX_HANDLER_PASS;
 
-	if (is_multicast_ether_addr(eth->h_dest)) {
+	if (ipvlan_is_l2_mcast(port, skb, &need_eth_fix)) {
 		if (ipvlan_external_frame(skb, port)) {
 			/* External frames are queued for device local
 			 * distribution, but a copy is given to master
@@ -877,6 +928,8 @@ static rx_handler_result_t ipvlan_handle_mode_l2(struct sk_buff **pskb,
 			struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
 
 			if (nskb) {
+				if (need_eth_fix)
+					memset(eth_hdr(nskb)->h_dest, 0xff, ETH_ALEN);
 				ipvlan_mark_skb(skb, port->dev);
 				ipvlan_skb_crossing_ns(nskb, NULL);
 				ipvlan_multicast_enqueue(port, nskb, false);
-- 
2.25.1