ipv6: add option to drop unicast encapsulated in L2 multicast

In order to solve a problem with 802.11, the so-called hole-196 attack,
add an option (sysctl) called "drop_unicast_in_l2_multicast" which, if
enabled, causes the stack to drop IPv6 unicast packets encapsulated in
link-layer multi- or broadcast frames. Such frames can (as an attack)
be created by any member of the same wireless network and transmitted
as valid encrypted frames since the symmetric key for broadcast frames
is shared between all stations.

Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 402753bccafa..4a4c1ae826cb 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -50,6 +50,7 @@ struct ipv6_devconf {
         __s32           mc_forwarding;
 #endif
         __s32           disable_ipv6;
+        __s32           drop_unicast_in_l2_multicast;
         __s32           accept_dad;
         __s32           force_tllao;
         __s32           ndisc_notify;
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 38b4fef20219..4c413570efe8 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -174,6 +174,7 @@ enum {
         DEVCONF_USE_OIF_ADDRS_ONLY,
         DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
         DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
+        DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
         DEVCONF_MAX
 };