netdev - [PATCH 2/2] vlan: Initialize dev->perm

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Date:   Mon, 24 Aug 2020 14:47:47 +0000
From:   Mira Ressel <aranea@...ah.de>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Mira Ressel <aranea@...ah.de>
Subject: [PATCH 2/2] vlan: Initialize dev->perm_addr

Set the perm_addr of vlan devices to that of their parent device.
Otherwise, it remains all zero, with the consequence that
ipv6_generate_stable_address() (which is used if the sysctl
net.ipv6.conf.DEV.addr_gen_mode is set to 2 or 3) assigns every vlan
interface on a host the same link-local address.

This has the added benefit of giving vlan devices the same link-local
address as their parent device, which is common practice, and indeed
precisely what happens automatically if the default eui64-based address
generation is used.

Signed-off-by: Mira Ressel <aranea@...ah.de>
---
 net/8021q/vlan_netlink.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/8021q/vlan_netlink.c b/net/8021q/vlan_netlink.c
index 0db85aeb119b..8c60d92b7717 100644
--- a/net/8021q/vlan_netlink.c
+++ b/net/8021q/vlan_netlink.c
@@ -182,6 +182,8 @@ static int vlan_newlink(struct net *src_net, struct net_device *dev,
 	else if (dev->mtu > max_mtu)
 		return -EINVAL;

+	memcpy(dev->perm_addr, real_dev->perm_addr, real_dev->addr_len);
+
 	err = vlan_changelink(dev, tb, data, extack);
 	if (!err)
 		err = register_vlan_dev(dev, extack);
-- 
2.25.4