[B.A.T.M.A.N.] [PATCHv14 5/6] batman-adv: Add IPv4 link-local/IPv6-ll-all-nodes multicast support

Linus Lüssing
2014-02-15T16:47:53Z

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 won't be possible
to optimize 224.0.0.x and ff02::1 towards nodes with bridges, they will
always receive these ranges.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
---
main.c | 6 +++
main.h | 1 +
multicast.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++++++----
packet.h | 9 ++++
soft-interface.c | 1 +
types.h | 12 +++++
6 files changed, 156 insertions(+), 8 deletions(-)

diff --git a/main.c b/main.c
index 8f11b67..57b09fa 100644
--- a/main.c
+++ b/main.c
@@ -111,6 +111,9 @@ int batadv_mesh_init(struct net_device *soft_iface)
spin_lock_init(&bat_priv->tt.last_changeset_lock);
spin_lock_init(&bat_priv->tt.commit_lock);
spin_lock_init(&bat_priv->gw.list_lock);
+#ifdef CONFIG_BATMAN_ADV_MCAST
+ spin_lock_init(&bat_priv->mcast.want_lists_lock);
+#endif
spin_lock_init(&bat_priv->tvlv.container_list_lock);
spin_lock_init(&bat_priv->tvlv.handler_list_lock);
spin_lock_init(&bat_priv->softif_vlan_list_lock);
@@ -118,6 +121,9 @@ int batadv_mesh_init(struct net_device *soft_iface)
INIT_HLIST_HEAD(&bat_priv->forw_bat_list);
INIT_HLIST_HEAD(&bat_priv->forw_bcast_list);
INIT_HLIST_HEAD(&bat_priv->gw.list);
+#ifdef CONFIG_BATMAN_ADV_MCAST
+ INIT_HLIST_HEAD(&bat_priv->mcast.want_all_unsnoopables_list);
+#endif
INIT_LIST_HEAD(&bat_priv->tt.changes_list);
INIT_LIST_HEAD(&bat_priv->tt.req_list);
INIT_LIST_HEAD(&bat_priv->tt.roam_list);
diff --git a/main.h b/main.h
index dc6b4a2..a31da5a 100644
--- a/main.h
+++ b/main.h
@@ -177,6 +177,7 @@ 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 127ba50..ebfbf6e 100644
--- a/multicast.c
+++ b/multicast.c
@@ -272,9 +272,48 @@ out:
}

/**
+ * batadv_mcast_forw_mode_check_ipv4 - check for optimized forwarding potential
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the IPv4 packet to check
+ * @is_unsnoopable: stores whether the destination is snoopable
+ *
+ * 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 batadv_priv *bat_priv,
+ struct sk_buff *skb,
+ bool *is_unsnoopable)
+{
+ 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;
+
+ /* link-local multicast listeners behind a bridge are
+ * not snoopable (see RFC4541, section 2.1.2.2)
+ */
+ *is_unsnoopable = true;
+
+ return 0;
+}
+
+/**
* batadv_mcast_forw_mode_check_ipv6 - check for optimized forwarding potential
* @bat_priv: the bat priv with all the soft interface information
* @skb: the IPv6 packet to check
+ * @is_unsnoopable: stores whether the destination is snoopable
*
* Check whether the given IPv6 packet has the potential to
* be forwarded with a mode more optimal than classic flooding.
@@ -283,7 +322,8 @@ out:
* out of memory.
*/
static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
- struct sk_buff *skb)
+ struct sk_buff *skb,
+ bool *is_unsnoopable)
{
struct ipv6hdr *ip6hdr;

@@ -304,7 +344,7 @@ static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
* not snoopable (see RFC4541, section 3, paragraph 3)
*/
if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr))
- return -EINVAL;
+ *is_unsnoopable = true;

return 0;
}
@@ -313,6 +353,7 @@ static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
* batadv_mcast_forw_mode_check - check for optimized forwarding potential
* @bat_priv: the bat priv with all the soft interface information
* @skb: the multicast frame to check
+ * @is_unsnoopable: stores whether the destination is snoopable
*
* Check whether the given multicast ethernet frame has the potential to
* be forwarded with a mode more optimal than classic flooding.
@@ -321,7 +362,8 @@ static int batadv_mcast_forw_mode_check_ipv6(struct batadv_priv *bat_priv,
* out of memory.
*/
static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
- struct sk_buff *skb)
+ struct sk_buff *skb,
+ bool *is_unsnoopable)
{
struct ethhdr *ethhdr = eth_hdr(skb);

@@ -332,8 +374,12 @@ static int batadv_mcast_forw_mode_check(struct batadv_priv *bat_priv,
return -EINVAL;

switch (ntohs(ethhdr->h_proto)) {
+ case ETH_P_IP:
+ return batadv_mcast_forw_mode_check_ipv4(bat_priv, skb,
+ is_unsnoopable);
case ETH_P_IPV6:
- return batadv_mcast_forw_mode_check_ipv6(bat_priv, skb);
+ return batadv_mcast_forw_mode_check_ipv6(bat_priv, skb,
+ is_unsnoopable);
default:
return -EINVAL;
}
@@ -356,6 +402,33 @@ batadv_mcast_forw_tt_node_get(struct batadv_priv *bat_priv,
}

/**
+ * batadv_mcast_want_forw_unsnoop_node_get - get a node with an unsnoopable flag
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Return an orig_node which has the BATADV_MCAST_WANT_ALL_UNSNOOPABLES flag set
+ * and increase its refcount.
+ */
+static struct batadv_orig_node *
+batadv_mcast_forw_unsnoop_node_get(struct batadv_priv *bat_priv)
+{
+ struct batadv_orig_node *orig_node;
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(orig_node,
+ &bat_priv->mcast.want_all_unsnoopables_list,
+ mcast_want_all_unsnoopables_node) {
+ if (atomic_inc_not_zero(&orig_node->refcount))
+ goto unlock;
+ }
+
+ orig_node = NULL;
+
+unlock:
+ rcu_read_unlock();
+ return orig_node;
+}
+
+/**
* batadv_mcast_forw_mode - check on how to forward a multicast packet
* @bat_priv: the bat priv with all the soft interface information
* @skb: The multicast packet to check
@@ -370,9 +443,10 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
struct batadv_orig_node **orig)
{
struct ethhdr *ethhdr;
- int ret, tt_count;
+ bool is_unsnoopable = false;
+ int ret, tt_count, unsnoop_count, total_count;

- ret = batadv_mcast_forw_mode_check(bat_priv, skb);
+ ret = batadv_mcast_forw_mode_check(bat_priv, skb, &is_unsnoopable);
if (ret == -ENOMEM)
return BATADV_FORW_NONE;
else if (ret < 0)
@@ -382,10 +456,18 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,

tt_count = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
BATADV_NO_FLAGS);
+ unsnoop_count = !is_unsnoopable ? 0 :
+ atomic_read(&bat_priv->mcast.num_want_all_unsnoopables);

- switch (tt_count) {
+ total_count = tt_count + unsnoop_count;
+
+ switch (total_count) {
case 1:
- *orig = batadv_mcast_forw_tt_node_get(bat_priv, ethhdr);
+ if (tt_count)
+ *orig = batadv_mcast_forw_tt_node_get(bat_priv, ethhdr);
+ else if (unsnoop_count)
+ *orig = batadv_mcast_forw_unsnoop_node_get(bat_priv);
+
if (*orig)
return BATADV_FORW_SINGLE;

@@ -398,6 +480,39 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
}

/**
+ * batadv_mcast_want_unsnoop_update - update unsnoop counter and list
+ * @bat_priv: the bat priv with all the soft interface information
+ * @orig: the orig_node which multicast state might have changed of
+ * @mcast_flags: flags indicating the new multicast state
+ *
+ * If the BATADV_MCAST_WANT_ALL_UNSNOOPABLES flag of this originator,
+ * orig, has toggled then this method updates counter and list accordingly.
+ */
+static void batadv_mcast_want_unsnoop_update(struct batadv_priv *bat_priv,
+ struct batadv_orig_node *orig,
+ uint8_t mcast_flags)
+{
+ /* switched from flag unset to set */
+ if (mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES &&
+ !(orig->mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES)) {
+ atomic_inc(&bat_priv->mcast.num_want_all_unsnoopables);
+
+ spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+ hlist_add_head_rcu(&orig->mcast_want_all_unsnoopables_node,
+ &bat_priv->mcast.want_all_unsnoopables_list);
+ spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+ /* switched from flag set to unset */
+ } else if (!(mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) &&
+ orig->mcast_flags & BATADV_MCAST_WANT_ALL_UNSNOOPABLES) {
+ atomic_dec(&bat_priv->mcast.num_want_all_unsnoopables);
+
+ spin_lock_bh(&bat_priv->mcast.want_lists_lock);
+ hlist_del_rcu(&orig->mcast_want_all_unsnoopables_node);
+ spin_unlock_bh(&bat_priv->mcast.want_lists_lock);
+ }
+}
+
+/**
* batadv_mcast_tvlv_ogm_handler_v1 - process incoming multicast tvlv container
* @bat_priv: the bat priv with all the soft interface information
* @orig: the orig_node of the ogm
@@ -441,6 +556,8 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
(tvlv_value_len >= sizeof(mcast_flags)))
mcast_flags = *(uint8_t *)tvlv_value;

+ batadv_mcast_want_unsnoop_update(bat_priv, orig, mcast_flags);
+
orig->mcast_flags = mcast_flags;
}

@@ -477,4 +594,6 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)

if (!(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST))
atomic_dec(&bat_priv->mcast.num_disabled);
+
+ batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);
}
diff --git a/packet.h b/packet.h
index e8c483d..0aada24 100644
--- a/packet.h
+++ b/packet.h
@@ -89,6 +89,15 @@ 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 1a643fe..db6feca 100644
--- a/soft-interface.c
+++ b/soft-interface.c
@@ -710,6 +710,7 @@ static int batadv_softif_init_late(struct net_device *dev)
bat_priv->mcast.flags = BATADV_NO_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 c28fc4a..1a674cb 100644
--- a/types.h
+++ b/types.h
@@ -205,6 +205,8 @@ struct batadv_orig_bat_iv {
* @last_seen: time when last packet from this node was received
* @bcast_seqno_reset: time when the broadcast seqno window was reset
* @mcast_flags: multicast flags announced by the orig node
+ * @mcast_want_all_unsnoop_node: a list node for the
+ * mcast.want_all_unsnoopables list
* @capabilities: announced capabilities of this originator
* @capa_initialized: bitfield to remember whether a capability was initialized
* @last_ttvn: last seen translation table version number
@@ -249,6 +251,7 @@ struct batadv_orig_node {
unsigned long bcast_seqno_reset;
#ifdef CONFIG_BATMAN_ADV_MCAST
uint8_t mcast_flags;
+ struct hlist_node mcast_want_all_unsnoopables_node;
#endif
uint8_t capabilities;
uint8_t capa_initialized;
@@ -619,15 +622,24 @@ struct batadv_priv_dat {
/**
* struct batadv_priv_mcast - per mesh interface mcast data
* @mla_list: list of multicast addresses we are currently announcing via TT
+ * @want_all_unsnoopables_list: a list of orig_nodes wanting all unsnoopable
+ * multicast traffic
* @flags: the flags we have last sent in our mcast tvlv
* @enabled: whether the multicast tvlv is currently enabled
* @num_disabled: number of nodes that have no mcast tvlv
+ * @num_want_all_unsnoopables: number of nodes wanting unsnoopable IP traffic
+ * @want_lists_lock: lock for protecting modifications to mcast want lists
+ * (traversals are rcu-locked)
*/
struct batadv_priv_mcast {
struct hlist_head mla_list;
+ struct hlist_head want_all_unsnoopables_list;
uint8_t flags;
bool enabled;
atomic_t num_disabled;
+ atomic_t num_want_all_unsnoopables;
+ /* protects want_all_unsnoopables_list */
+ spinlock_t want_lists_lock;
};
#endif

--
1.7.10.4