vlan: partially enable SIOCSHWTSTAMP in container

[ Upstream commit 731b73dba3 ]

Setting timestamp filter was explicitly disabled on vlan devices in
containers because it might affect other processes on the host. But it's
absolutely legit in case when real device is in the same namespace.

Fixes: 873017af77 ("vlan: disable SIOCSHWTSTAMP in container")
Signed-off-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/8021q/vlan_dev.c

@@ -365,7 +365,7 @@ static int vlan_dev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 
 	switch (cmd) {
 	case SIOCSHWTSTAMP:
-		if (!net_eq(dev_net(dev), &init_net))
+		if (!net_eq(dev_net(dev), dev_net(real_dev)))
 			break;
 		fallthrough;
 	case SIOCGMIIPHY: