[RFC PATCH] ipv6: Use dev_addr in stable-privacy address generation

["Bram Bonné" <brambonne@google.com>]

This patch extends the IN6_ADDR_GEN_MODE_STABLE_PRIVACY address
generation mode to use the software-defined MAC address (dev_addr)
rather than the permanent, hardware-defined MAC address (perm_addr) of
the interface when generating IPv6 link-local addresses.

This ensures that the IPv6 link-local address changes in line with the
MAC address when per-network MAC address randomization is used,
providing the expected privacy guarantees.

When no MAC address randomization is used, dev_addr corresponds to
perm_addr, and IN6_ADDR_GEN_MODE_STABLE_PRIVACY behaves as before.

When MAC address randomization is used, this makes the MAC address
fulfill the role of both the Net_Iface and the (optional) Network_ID
parameters in RFC7217.

Cc: Lorenzo Colitti <lorenzo@google.com>
Cc: Jeffrey Vanderstoep <jeffv@google.com>
Signed-off-by: Bram Bonné <brambonne@google.com>
---
 net/ipv6/addrconf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 5b9de773ce73..cd69a4331246 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3252,7 +3252,7 @@ static int ipv6_generate_stable_address(struct in6_addr *address,
 	sha_init(digest);
 	memset(&data, 0, sizeof(data));
 	memset(workspace, 0, sizeof(workspace));
-	memcpy(data.hwaddr, idev->dev->perm_addr, idev->dev->addr_len);
+	memcpy(data.hwaddr, idev->dev->dev_addr, idev->dev->addr_len);
 	data.prefix[0] = address->s6_addr32[0];
 	data.prefix[1] = address->s6_addr32[1];
 	data.secret = secret;
-- 
2.25.1.696.g5e7596f4ac-goog