net: virtual: Clear multicast bit when generating link address

echistyakov · kartben · commit dd6adc7cad9c · 2025-04-01T11:53:02.000+02:00
The least significant bit of the first octet of a MAC address is a
unicast/multicast bit. The bit should be cleared when generating a
random link address for a virtual interface. Any frames from such
interface/address will be dropped by the network as invalid if
the multicast bit is set.

Signed-off-by: Jack Chistyakov &lt;jack.chistyakov@outlook.com&gt;
diff --git a/subsys/net/l2/virtual/virtual.c b/subsys/net/l2/virtual/virtual.c
@@ -212,7 +212,8 @@ static void random_linkaddr(uint8_t *linkaddr, size_t len)
 {
 	sys_rand_get(linkaddr, len);
 
-	linkaddr[0] |= 0x02; /* force LAA bit */
+	linkaddr[0] |= 0x02;  /* force LAA bit */
+	linkaddr[0] &= ~0x01; /* clear multicast bit */
 }
 
 int net_virtual_interface_attach(struct net_if *virtual_iface,

Original file line number	Diff line number	Diff line change
`@@ -212,7 +212,8 @@ static void random_linkaddr(uint8_t *linkaddr, size_t len)`
`212`	`212`	`{`
`213`	`213`	`sys_rand_get(linkaddr, len);`
`214`	`214`
`215`		`- linkaddr[0] \|= 0x02; /* force LAA bit */`
	`215`	`+ linkaddr[0] \|= 0x02; /* force LAA bit */`
	`216`	`+ linkaddr[0] &= ~0x01; /* clear multicast bit */`
`216`	`217`	`}`
`217`	`218`
`218`	`219`	`int net_virtual_interface_attach(struct net_if *virtual_iface,`