[PATCH 4.14 112/146] ipv6: set all.accept_dad to 0 by default

Greg Kroah-Hartman
2018-01-01T14:50:01Z

From: Nicolas Dichtel <nicolas.dichtel@6wind.com>

[ Upstream commit 094009531612246d9e13f9e0c3ae2205d7f63a0a ]

With commits 35e015e1f577 and a2d3f3e33853, the global 'accept_dad' flag
is also taken into account (default value is 1). If either global or
per-interface flag is non-zero, DAD will be enabled on a given interface.

This is not backward compatible: before those patches, the user could
disable DAD just by setting the per-interface flag to 0. Now, the
user instead needs to set both flags to 0 to actually disable DAD.

Restore the previous behaviour by setting the default for the global
'accept_dad' flag to 0. This way, DAD is still enabled by default,
as per-interface flags are set to 1 on device creation, but setting
them to 0 is enough to disable DAD on a given interface.

- Before 35e015e1f57a7 and a2d3f3e33853:
global per-interface DAD enabled
[default] 1 1 yes
X 0 no
X 1 yes

- After 35e015e1f577 and a2d3f3e33853:
global per-interface DAD enabled
[default] 1 1 yes
0 0 no
0 1 yes
1 0 yes

- After this fix:
global per-interface DAD enabled
1 1 yes
0 0 no
[default] 0 1 yes
1 0 yes

Fixes: 35e015e1f577 ("ipv6: fix net.ipv6.conf.all interface DAD handlers")
Fixes: a2d3f3e33853 ("ipv6: fix net.ipv6.conf.all.accept_dad behaviour for real")
CC: Stefano Brivio <sbrivio@redhat.com>
CC: Matteo Croce <mcroce@redhat.com>
CC: Erik Kline <ek@google.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/addrconf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -231,7 +231,7 @@ static struct ipv6_devconf ipv6_devconf
.proxy_ndp = 0,
.accept_source_route = 0, /* we do not accept RH0 by default. */
.disable_ipv6 = 0,
- .accept_dad = 1,
+ .accept_dad = 0,
.suppress_frag_ndisc = 1,
.accept_ra_mtu = 1,
.stable_secret = {