[PATCH v2 1/4] ipv4: add option to drop unicast encapsulated in L2 multicast

[PATCH v2 1/4] ipv4: add option to drop unicast encapsulated in L2 multicast

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

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 IPv4 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.

Additionally, enabling this option provides compliance with a SHOULD
clause of RFC 1122.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 Documentation/networking/ip-sysctl.txt |  7 +++++++
 include/uapi/linux/ip.h                |  1 +
 net/ipv4/devinet.c                     |  2 ++
 net/ipv4/ip_input.c                    | 26 +++++++++++++++++++++++++-
 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 05915be86235..35c4c43dd8de 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1208,6 +1208,13 @@ promote_secondaries - BOOLEAN
 	promote a corresponding secondary IP address instead of
 	removing all the corresponding secondary IP addresses.
 
+drop_unicast_in_l2_multicast - BOOLEAN
+	Drop any unicast IP packets that are received in link-layer
+	multicast (or broadcast) frames.
+	This behavior (for multicast) is actually a SHOULD in RFC
+	1122, but is disabled by default for compatibility reasons.
+	Default: off (0)
+
 
 tag - INTEGER
 	Allows you to write a number, which can be used as required.
diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h
index 08f894d2ddbd..584834f7e95c 100644
--- a/include/uapi/linux/ip.h
+++ b/include/uapi/linux/ip.h
@@ -165,6 +165,7 @@ enum
 	IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL,
 	IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL,
 	IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
+	IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
 	__IPV4_DEVCONF_MAX
 };
 
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index cebd9d31e65a..dbbab28a52a4 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2192,6 +2192,8 @@ static struct devinet_sysctl_table {
 					      "promote_secondaries"),
 		DEVINET_SYSCTL_FLUSHING_ENTRY(ROUTE_LOCALNET,
 					      "route_localnet"),
+		DEVINET_SYSCTL_FLUSHING_ENTRY(DROP_UNICAST_IN_L2_MULTICAST,
+					      "drop_unicast_in_l2_multicast"),
 	},
 };
 
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index b1209b63381f..a442b6bd9441 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -359,8 +359,32 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 	rt = skb_rtable(skb);
 	if (rt->rt_type == RTN_MULTICAST) {
 		IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INMCAST, skb->len);
-	} else if (rt->rt_type == RTN_BROADCAST)
+	} else if (rt->rt_type == RTN_BROADCAST) {
 		IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INBCAST, skb->len);
+	} else {
+		struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
+
+		/* RFC 1122 3.3.6:
+		 *
+		 *   When a host sends a datagram to a link-layer broadcast
+		 *   address, the IP destination address MUST be a legal IP
+		 *   broadcast or IP multicast address.
+		 *
+		 *   A host SHOULD silently discard a datagram that is received
+		 *   via a link-layer broadcast (see Section 2.4) but does not
+		 *   specify an IP multicast or broadcast destination address.
+		 *
+		 * This doesn't explicitly say L2 *broadcast*, but broadcast is
+		 * in a way a form of multicast and the most common use case for
+		 * this is 802.11 protecting against cross-station spoofing (the
+		 * so-called "hole-196" attack) so do it for both.
+		 */
+		if (in_dev &&
+		    IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST) &&
+		    (skb->pkt_type == PACKET_BROADCAST ||
+		     skb->pkt_type == PACKET_MULTICAST))
+			goto drop;
+	}
 
 	return dst_input(skb);
 
-- 
2.6.2

[PATCH v2 2/4] ipv6: add option to drop unicast encapsulated in L2 multicast

[Johannes Berg]

From: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

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.

Signed-off-by: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 Documentation/networking/ip-sysctl.txt |  6 ++++++
 include/linux/ipv6.h                   |  1 +
 include/uapi/linux/ipv6.h              |  1 +
 net/ipv6/addrconf.c                    |  8 ++++++++
 net/ipv6/ip6_input.c                   | 10 ++++++++++
 5 files changed, 26 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 35c4c43dd8de..a2169651254e 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1660,6 +1660,12 @@ stable_secret - IPv6 address
 
 	By default the stable secret is unset.
 
+drop_unicast_in_l2_multicast - BOOLEAN
+	Drop any unicast IPv6 packets that are received in link-layer
+	multicast (or broadcast) frames.
+
+	By default this is turned off.
+
 icmp/*:
 ratelimit - INTEGER
 	Limit the maximal rates for sending ICMPv6 packets.
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 0ef2a97ccdb5..34317cb6a6fc 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
 };
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d72fa90d6feb..35f880bcf626 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4672,6 +4672,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
 	array[DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN] = cnf->ignore_routes_with_linkdown;
 	/* we omit DEVCONF_STABLE_SECRET for now */
 	array[DEVCONF_USE_OIF_ADDRS_ONLY] = cnf->use_oif_addrs_only;
+	array[DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] = cnf->drop_unicast_in_l2_multicast;
 }
 
 static inline size_t inet6_ifla6_size(void)
@@ -5734,6 +5735,13 @@ static struct addrconf_sysctl_table
 			.proc_handler	= addrconf_sysctl_ignore_routes_with_linkdown,
 		},
 		{
+			.procname	= "drop_unicast_in_l2_multicast",
+			.data		= &ipv6_devconf.drop_unicast_in_l2_multicast,
+			.maxlen		= sizeof(int),
+			.mode		= 0644,
+			.proc_handler	= proc_dointvec,
+		},
+		{
 			/* sentinel */
 		}
 	},
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 9075acf081dd..31ac3c56da4b 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -134,6 +134,16 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
 	    IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
 		goto err;
 
+	/* If enabled, drop unicast packets that were encapsulated in link-layer
+	 * multicast or broadcast to protected against the so-called "hole-196"
+	 * attack in 802.11 wireless.
+	 */
+	if (!ipv6_addr_is_multicast(&hdr->daddr) &&
+	    (skb->pkt_type == PACKET_BROADCAST ||
+	     skb->pkt_type == PACKET_MULTICAST) &&
+	    idev->cnf.drop_unicast_in_l2_multicast)
+		goto err;
+
 	/* RFC4291 2.7
 	 * Nodes must not originate a packet to a multicast address whose scope
 	 * field contains the reserved value 0; if such a packet is received, it
-- 
2.6.2

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[PATCH v2 3/4] ipv4: add option to drop gratuitous ARP packets

[Johannes Berg]

From: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

In certain 802.11 wireless deployments, there will be ARP proxies
that use knowledge of the network to correctly answer requests.
To prevent gratuitous ARP frames on the shared medium from being
a problem, on such deployments wireless needs to drop them.

Enable this by providing an option called "drop_gratuitous_arp".

Signed-off-by: Johannes Berg <johannes.berg-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 Documentation/networking/ip-sysctl.txt | 6 ++++++
 include/uapi/linux/ip.h                | 1 +
 net/ipv4/arp.c                         | 8 ++++++++
 net/ipv4/devinet.c                     | 2 ++
 4 files changed, 17 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index a2169651254e..428fb48a19fc 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1215,6 +1215,12 @@ drop_unicast_in_l2_multicast - BOOLEAN
 	1122, but is disabled by default for compatibility reasons.
 	Default: off (0)
 
+drop_gratuitous_arp - BOOLEAN
+	Drop all gratuitous ARP frames, for example if there's a known
+	good ARP proxy on the network and such frames need not be used
+	(or in the case of 802.11, must not be used to prevent attacks.)
+	Default: off (0)
+
 
 tag - INTEGER
 	Allows you to write a number, which can be used as required.
diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h
index 584834f7e95c..f291569768dd 100644
--- a/include/uapi/linux/ip.h
+++ b/include/uapi/linux/ip.h
@@ -166,6 +166,7 @@ enum
 	IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL,
 	IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
 	IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
+	IPV4_DEVCONF_DROP_GRATUITOUS_ARP,
 	__IPV4_DEVCONF_MAX
 };
 
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 59b3e0e8fd51..36006a59c7f0 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -735,6 +735,14 @@ static int arp_process(struct net *net, struct sock *sk, struct sk_buff *skb)
 	    (!IN_DEV_ROUTE_LOCALNET(in_dev) && ipv4_is_loopback(tip)))
 		goto out;
 
+ /*
+  *	For some 802.11 wireless deployments (and possibly other networks),
+  *	there will be an ARP proxy and gratuitous ARP frames are attacks
+  *	and thus should not be accepted.
+  */
+	if (IN_DEV_ORCONF(in_dev, DROP_GRATUITOUS_ARP) && sip == tip)
+		goto out;
+
 /*
  *     Special case: We must set Frame Relay source Q.922 address
  */
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index dbbab28a52a4..3d835313575e 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2185,6 +2185,8 @@ static struct devinet_sysctl_table {
 					"igmpv3_unsolicited_report_interval"),
 		DEVINET_SYSCTL_RW_ENTRY(IGNORE_ROUTES_WITH_LINKDOWN,
 					"ignore_routes_with_linkdown"),
+		DEVINET_SYSCTL_RW_ENTRY(DROP_GRATUITOUS_ARP,
+					"drop_gratuitous_arp"),
 
 		DEVINET_SYSCTL_FLUSHING_ENTRY(NOXFRM, "disable_xfrm"),
 		DEVINET_SYSCTL_FLUSHING_ENTRY(NOPOLICY, "disable_policy"),
-- 
2.6.2

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[PATCH v2 4/4] ipv6: add option to drop unsolicited neighbor advertisements

[Johannes Berg]

From: Johannes Berg <johannes.berg@intel.com>

In certain 802.11 wireless deployments, there will be NA proxies
that use knowledge of the network to correctly answer requests.
To prevent unsolicitd advertisements on the shared medium from
being a problem, on such deployments wireless needs to drop them.

Enable this by providing an option called "drop_unsolicited_na".

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 Documentation/networking/ip-sysctl.txt | 7 +++++++
 include/linux/ipv6.h                   | 1 +
 include/uapi/linux/ipv6.h              | 1 +
 net/ipv6/addrconf.c                    | 8 ++++++++
 net/ipv6/ndisc.c                       | 9 +++++++++
 5 files changed, 26 insertions(+)

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 428fb48a19fc..77992f1173c3 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1672,6 +1672,13 @@ drop_unicast_in_l2_multicast - BOOLEAN
 
 	By default this is turned off.
 
+drop_unsolicited_na - BOOLEAN
+	Drop all unsolicited neighbor advertisements, for example if there's
+	a known good NA proxy on the network and such frames need not be used
+	(or in the case of 802.11, must not be used to prevent attacks.)
+
+	By default this is turned off.
+
 icmp/*:
 ratelimit - INTEGER
 	Limit the maximal rates for sending ICMPv6 packets.
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 34317cb6a6fc..9231bfdc7c92 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -56,6 +56,7 @@ struct ipv6_devconf {
 	__s32           ndisc_notify;
 	__s32		suppress_frag_ndisc;
 	__s32		accept_ra_mtu;
+	__s32		drop_unsolicited_na;
 	struct ipv6_stable_secret {
 		bool initialized;
 		struct in6_addr secret;
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 4c413570efe8..ec117b65d5a5 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -175,6 +175,7 @@ enum {
 	DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
 	DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
 	DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
+	DEVCONF_DROP_UNSOLICITED_NA,
 	DEVCONF_MAX
 };
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 35f880bcf626..e7dd0a0c5126 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4673,6 +4673,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
 	/* we omit DEVCONF_STABLE_SECRET for now */
 	array[DEVCONF_USE_OIF_ADDRS_ONLY] = cnf->use_oif_addrs_only;
 	array[DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] = cnf->drop_unicast_in_l2_multicast;
+	array[DEVCONF_DROP_UNSOLICITED_NA] = cnf->drop_unsolicited_na;
 }
 
 static inline size_t inet6_ifla6_size(void)
@@ -5742,6 +5743,13 @@ static struct addrconf_sysctl_table
 			.proc_handler	= proc_dointvec,
 		},
 		{
+			.procname	= "drop_unsolicited_na",
+			.data		= &ipv6_devconf.drop_unsolicited_na,
+			.maxlen		= sizeof(int),
+			.mode		= 0644,
+			.proc_handler	= proc_dointvec,
+		},
+		{
 			/* sentinel */
 		}
 	},
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 3e0f855e1bea..0737bc23ea39 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -887,6 +887,7 @@ static void ndisc_recv_na(struct sk_buff *skb)
 				    offsetof(struct nd_msg, opt));
 	struct ndisc_options ndopts;
 	struct net_device *dev = skb->dev;
+	struct inet6_dev *idev = __in6_dev_get(dev);
 	struct inet6_ifaddr *ifp;
 	struct neighbour *neigh;
 
@@ -906,6 +907,14 @@ static void ndisc_recv_na(struct sk_buff *skb)
 		return;
 	}
 
+	/* For some 802.11 wireless deployments (and possibly other networks),
+	 * there will be a NA proxy and unsolicitd packets are attacks
+	 * and thus should not be accepted.
+	 */
+	if (idev && idev->cnf.drop_unsolicited_na &&
+	    !msg->icmph.icmp6_solicited)
+		return;
+
 	if (!ndisc_parse_options(msg->opt, ndoptlen, &ndopts)) {
 		ND_PRINTK(2, warn, "NS: invalid ND option\n");
 		return;
-- 
2.6.2

Re: [PATCH v2 1/4] ipv4: add option to drop unicast encapsulated in L2 multicast

[Julian Anastasov]

	Hello,

On Wed, 4 Nov 2015, Johannes Berg wrote:

> From: Johannes Berg <johannes.berg@intel.com>
> 
> 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 IPv4 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.
> 
> Additionally, enabling this option provides compliance with a SHOULD
> clause of RFC 1122.
> 
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>

	Patches 1 and 3 look correct to me,

Reviewed-by: Julian Anastasov <ja@ssi.bg>

	If the patches are lost in the merge window you
can also consider one minor optimization, see below...

> ---
>  Documentation/networking/ip-sysctl.txt |  7 +++++++
>  include/uapi/linux/ip.h                |  1 +
>  net/ipv4/devinet.c                     |  2 ++
>  net/ipv4/ip_input.c                    | 26 +++++++++++++++++++++++++-
>  4 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
> index 05915be86235..35c4c43dd8de 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -1208,6 +1208,13 @@ promote_secondaries - BOOLEAN
>  	promote a corresponding secondary IP address instead of
>  	removing all the corresponding secondary IP addresses.
>  
> +drop_unicast_in_l2_multicast - BOOLEAN
> +	Drop any unicast IP packets that are received in link-layer
> +	multicast (or broadcast) frames.
> +	This behavior (for multicast) is actually a SHOULD in RFC
> +	1122, but is disabled by default for compatibility reasons.
> +	Default: off (0)
> +
>  
>  tag - INTEGER
>  	Allows you to write a number, which can be used as required.
> diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h
> index 08f894d2ddbd..584834f7e95c 100644
> --- a/include/uapi/linux/ip.h
> +++ b/include/uapi/linux/ip.h
> @@ -165,6 +165,7 @@ enum
>  	IPV4_DEVCONF_IGMPV2_UNSOLICITED_REPORT_INTERVAL,
>  	IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL,
>  	IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
> +	IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
>  	__IPV4_DEVCONF_MAX
>  };
>  
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index cebd9d31e65a..dbbab28a52a4 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -2192,6 +2192,8 @@ static struct devinet_sysctl_table {
>  					      "promote_secondaries"),
>  		DEVINET_SYSCTL_FLUSHING_ENTRY(ROUTE_LOCALNET,
>  					      "route_localnet"),
> +		DEVINET_SYSCTL_FLUSHING_ENTRY(DROP_UNICAST_IN_L2_MULTICAST,
> +					      "drop_unicast_in_l2_multicast"),
>  	},
>  };
>  
> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index b1209b63381f..a442b6bd9441 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -359,8 +359,32 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
>  	rt = skb_rtable(skb);
>  	if (rt->rt_type == RTN_MULTICAST) {
>  		IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INMCAST, skb->len);
> -	} else if (rt->rt_type == RTN_BROADCAST)
> +	} else if (rt->rt_type == RTN_BROADCAST) {
>  		IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INBCAST, skb->len);
> +	} else {

	} else if (unlikely(skb->pkt_type != PACKET_HOST)) {

	May be such check can save some cycles because
it is more common to see PACKET_HOST packets...

> +		struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
> +
> +		/* RFC 1122 3.3.6:
> +		 *
> +		 *   When a host sends a datagram to a link-layer broadcast
> +		 *   address, the IP destination address MUST be a legal IP
> +		 *   broadcast or IP multicast address.
> +		 *
> +		 *   A host SHOULD silently discard a datagram that is received
> +		 *   via a link-layer broadcast (see Section 2.4) but does not
> +		 *   specify an IP multicast or broadcast destination address.
> +		 *
> +		 * This doesn't explicitly say L2 *broadcast*, but broadcast is
> +		 * in a way a form of multicast and the most common use case for
> +		 * this is 802.11 protecting against cross-station spoofing (the
> +		 * so-called "hole-196" attack) so do it for both.
> +		 */
> +		if (in_dev &&
> +		    IN_DEV_ORCONF(in_dev, DROP_UNICAST_IN_L2_MULTICAST) &&
> +		    (skb->pkt_type == PACKET_BROADCAST ||
> +		     skb->pkt_type == PACKET_MULTICAST))
> +			goto drop;
> +	}
>  
>  	return dst_input(skb);
>  
> -- 
> 2.6.2

Regards

--
Julian Anastasov <ja@ssi.bg>

Re: [PATCH v2 1/4] ipv4: add option to drop unicast encapsulated in L2 multicast

[Johannes Berg]

On Wed, 2015-11-04 at 22:59 +0200, Julian Anastasov wrote:
> 
>         Patches 1 and 3 look correct to me,
> 
> Reviewed-by: Julian Anastasov <ja-FgGsKACvmQM@public.gmane.org>

Thanks for checking!

>         If the patches are lost in the merge window you
> can also consider one minor optimization, see below...

Oh, yeah, they probably are - sorry Dave.

> > -     } else if (rt->rt_type == RTN_BROADCAST)
> > +     } else if (rt->rt_type == RTN_BROADCAST) {
> >               IP_UPD_PO_STATS_BH(net, IPSTATS_MIB_INBCAST, skb-
> >len);
> > +     } else {
> 
>         } else if (unlikely(skb->pkt_type != PACKET_HOST)) {
> 
>         May be such check can save some cycles because
> it is more common to see PACKET_HOST packets...

I had thought about that based on your earlier comments, but then I
didn't quite see the point. However, perhaps we could invert the check
below to check the pkt_type first, hoping it'll have some kind of cache
effect?

johannes
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Re: [PATCH v2 1/4] ipv4: add option to drop unicast encapsulated in L2 multicast

[Julian Anastasov]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 702 bytes --]


	Hello,

On Wed, 4 Nov 2015, Johannes Berg wrote:

> On Wed, 2015-11-04 at 22:59 +0200, Julian Anastasov wrote:
> > 
> >         } else if (unlikely(skb->pkt_type != PACKET_HOST)) {
> > 
> >         May be such check can save some cycles because
> > it is more common to see PACKET_HOST packets...
> 
> I had thought about that based on your earlier comments, but then I
> didn't quite see the point. However, perhaps we could invert the check
> below to check the pkt_type first, hoping it'll have some kind of cache
> effect?

	Yes, looks like it would be better if the checks
are reordered, the IN_DEV_* methods look more complex recently.

Regards

--
Julian Anastasov <ja@ssi.bg>