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From:   Mira Ressel <aranea@aixah.de>
To:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        netdev@vger.kernel.org (open list:NETWORKING DRIVERS),
        linux-kernel@vger.kernel.org (open list)
Cc:     Mira Ressel <aranea@aixah.de>
Subject: [PATCH 1/2] veth: Initialize dev->perm_addr
Date:   Mon, 24 Aug 2020 14:38:26 +0000
Message-Id: <20200824143828.5964-1-aranea@aixah.de>
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Sender: linux-kernel-owner@vger.kernel.org
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Set the perm_addr of veth devices to whatever MAC has been assigned to
the 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 veth
interface on a host the same link-local address.

The new behaviour matches that of several other virtual interface types
(such as gre), and as far as I can tell, perm_addr isn't used by any
other code sites that are relevant to veth.

Signed-off-by: Mira Ressel <aranea@aixah.de>
---
 drivers/net/veth.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index e56cd562a664..af1a7cda6205 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -1342,6 +1342,8 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 	if (!ifmp || !tbp[IFLA_ADDRESS])
 		eth_hw_addr_random(peer);
 
+	memcpy(peer->perm_addr, peer->dev_addr, peer->addr_len);
+
 	if (ifmp && (dev->ifindex != 0))
 		peer->ifindex = ifmp->ifi_index;
 
@@ -1370,6 +1372,8 @@ static int veth_newlink(struct net *src_net, struct net_device *dev,
 	if (tb[IFLA_ADDRESS] == NULL)
 		eth_hw_addr_random(dev);
 
+	memcpy(dev->perm_addr, dev->dev_addr, dev->addr_len);
+
 	if (tb[IFLA_IFNAME])
 		nla_strlcpy(dev->name, tb[IFLA_IFNAME], IFNAMSIZ);
 	else
-- 
2.25.4