[B.A.T.M.A.N.] [PATCHv9 4/5] batman-adv: Add IPv4 link-local/IPv6-ll-all-nodes multicast support

Linus Lüssing
2013-08-15T19:21:18Z

With this patch a node may additionally perform the dropping or
unicasting behaviour for a link-local IPv4 and link-local-all-nodes
IPv6 multicast packet, too.

The extra counter and BATADV_MCAST_WANT_ALL_UNSNOOPABLES flag is needed
because with a future bridge snooping support integration a node with a
bridge on top of its soft interface is not able to reliably detect its
multicast listeners for IPv4 link-local and the IPv6
link-local-all-nodes addresses anymore (see RFC4541, section 2.1.2.2
and section 3).

Even though this new flag does make "no difference" now, it'll ensure
a seamless integration of multicast bridge support without needing to
break compatibility later.

Also note, that even with multicast bridge support it will need only
one node with a bridge to disable optimizations for link-local IPv4
and IPv6-link-local-all-nodes multicast, resulting in flooding all
these packets again. So the 224.0.0.x address range and the ff02::1
address will never be a safe choice for multicast streaming etc. if
you do not control every node.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
---
main.h | 1 +
multicast.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
packet.h | 9 +++++++++
soft-interface.c | 1 +
types.h | 2 ++
5 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/main.h b/main.h
index 7225f63..0640dce 100644
--- a/main.h
+++ b/main.h
@@ -166,6 +166,7 @@ enum batadv_uev_type {
#include <linux/slab.h>
#include <net/sock.h> /* struct sock */
#include <net/addrconf.h> /* ipv6 address stuff */
+#include <linux/ip.h>
#include <net/rtnetlink.h>
#include <linux/jiffies.h>
#include <linux/seq_file.h>
diff --git a/multicast.c b/multicast.c
index 29cb929..ae7992a 100644
--- a/multicast.c
+++ b/multicast.c
@@ -266,6 +266,44 @@ out:
}

/**
+ * batadv_mcast_forw_mode_check_ipv4 - check for optimized forwarding potential
+ * @skb: the IPv4 packet to check
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Check whether the given IPv4 packet has the potential to
+ * be forwarded with a mode more optimal than classic flooding.
+ *
+ * If so then return 0. Otherwise -EINVAL is returned or -ENOMEM if we are
+ * out of memory.
+ */
+static int batadv_mcast_forw_mode_check_ipv4(struct sk_buff *skb,
+ struct batadv_priv *bat_priv)
+{
+ struct iphdr *iphdr;
+
+ /* We might fail due to out-of-memory -> drop it */
+ if (!pskb_may_pull(skb, sizeof(struct ethhdr) + sizeof(*iphdr)))
+ return -ENOMEM;
+
+ iphdr = ip_hdr(skb);
+
+ /* TODO: Implement Multicast Router Discovery (RFC4286),
+ * then allow scope > link local, too
+ */
+ if (!ipv4_is_local_multicast(iphdr->daddr))
+ return -EINVAL;
+
+ /* With one bridge involved, we cannot be certain about
+ * link-local multicast listener announcements anymore
+ * (see RFC4541, section 2.1.2.2)
+ */
+ if (atomic_read(&bat_priv->mcast.num_want_all_unsnoopables))
+ return -EINVAL;
+
+ return 0;
+}
+
+/**
* batadv_mcast_forw_mode_check_ipv6 - check for optimized forwarding potential
* @skb: the IPv6 packet to check
* @bat_priv: the bat priv with all the soft interface information
@@ -298,7 +336,8 @@ static int batadv_mcast_forw_mode_check_ipv6(struct sk_buff *skb,
* link-local-all-nodes multicast listener announcements anymore
* (see RFC4541, section 3, paragraph 3)
*/
- if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr))
+ if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr) &&
+ atomic_read(&bat_priv->mcast.num_want_all_unsnoopables))
return -EINVAL;

return 0;
@@ -327,6 +366,8 @@ static int batadv_mcast_forw_mode_check(struct sk_buff *skb,
return -EINVAL;

switch (ntohs(ethhdr->h_proto)) {
+ case ETH_P_IP:
+ return batadv_mcast_forw_mode_check_ipv4(skb, bat_priv);
case ETH_P_IPV6:
return batadv_mcast_forw_mode_check_ipv6(skb, bat_priv);
default:
@@ -418,6 +459,9 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
batadv_mcast_counter_update(BATADV_ORIG_CAPA_HAS_MCAST,
&bat_priv->mcast.num_disabled,
~orig->capabilities, ~old_capabilities);
+ batadv_mcast_counter_update(BATADV_MCAST_WANT_ALL_UNSNOOPABLES,
+ &bat_priv->mcast.num_want_all_unsnoopables,
+ mcast_flags, orig->mcast_flags);

orig->mcast_flags = mcast_flags;
}
@@ -457,4 +501,7 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
batadv_mcast_counter_update(BATADV_ORIG_CAPA_HAS_MCAST,
&bat_priv->mcast.num_disabled,
~BATADV_NO_FLAGS, ~orig->capabilities);
+ batadv_mcast_counter_update(BATADV_MCAST_WANT_ALL_UNSNOOPABLES,
+ &bat_priv->mcast.num_want_all_unsnoopables,
+ BATADV_NO_FLAGS, orig->mcast_flags);
}
diff --git a/packet.h b/packet.h
index c8cc1b2..5fc795f 100644
--- a/packet.h
+++ b/packet.h
@@ -91,6 +91,15 @@ enum batadv_icmp_packettype {
BATADV_PARAMETER_PROBLEM = 12,
};

+/**
+ * enum batadv_mcast_flags - flags for multicast capabilities and settings
+ * @BATADV_MCAST_WANT_ALL_UNSNOOPABLES: we want all packets destined for
+ * 224.0.0.0/24 or ff02::1
+ */
+enum batadv_mcast_flags {
+ BATADV_MCAST_WANT_ALL_UNSNOOPABLES = BIT(0),
+};
+
/* tt data subtypes */
#define BATADV_TT_DATA_TYPE_MASK 0x0F

diff --git a/soft-interface.c b/soft-interface.c
index 2ecf9a5..2967a43 100644
--- a/soft-interface.c
+++ b/soft-interface.c
@@ -677,6 +677,7 @@ static int batadv_softif_init_late(struct net_device *dev)
bat_priv->mcast.flags = BATADV_UNINIT_FLAGS;
atomic_set(&bat_priv->multicast_mode, 1);
atomic_set(&bat_priv->mcast.num_disabled, 0);
+ atomic_set(&bat_priv->mcast.num_want_all_unsnoopables, 0);
#endif
atomic_set(&bat_priv->gw_mode, BATADV_GW_MODE_OFF);
atomic_set(&bat_priv->gw_sel_class, 20);
diff --git a/types.h b/types.h
index aa17d09..1ce1793 100644
--- a/types.h
+++ b/types.h
@@ -550,11 +550,13 @@ struct batadv_priv_dat {
* @mla_list: list of multicast addresses we are currently announcing via TT
* @flags: the flags we have last sent in our mcast tvlv
* @num_disabled: number of nodes that have no mcast tvlv
+ * @num_want_all_unsnoopables: number of nodes wanting unsnoopable IP traffic
*/
struct batadv_priv_mcast {
struct hlist_head mla_list;
int flags;
atomic_t num_disabled;
+ atomic_t num_want_all_unsnoopables;
};
#endif

--
1.7.10.4