[B.A.T.M.A.N.] [PATCHv5 3/3] batman-adv: Modified forwarding behaviour for multicast packets

Linus Lüssing
2013-06-14T09:02:05Z

With this patch a multicast packet is not always simply flooded anymore,
the bevahiour for the following cases is changed to reduce
unnecessary overhead:

If all nodes within the horizon of a certain node have signalized
multicast listener announcement capability
(BATADV_MCAST_LISTENER_ANNOUNCEMENT) then an IPv6 multicast packet
with a destination of IPv6 link-local scope coming from the upstream
of this node...

* ...is dropped if there is no according multicast listener in the
translation table,
* ...is forwarded via unicast if there is a single node with interested
multicast listeners
* ...and otherwise still gets flooded.

Signed-off-by: Linus Lüssing <linus.luessing@web.de>
---
distributed-arp-table.c | 2 +-
multicast.c | 56 +++++++++++++++++++++++++++++++++++++
multicast.h | 23 +++++++++++++++
send.c | 5 ++--
send.h | 9 +++---
soft-interface.c | 18 ++++++++++--
translation-table.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++
translation-table.h | 2 ++
8 files changed, 177 insertions(+), 9 deletions(-)

diff --git a/distributed-arp-table.c b/distributed-arp-table.c
index f2543c2..87248bb 100644
--- a/distributed-arp-table.c
+++ b/distributed-arp-table.c
@@ -1030,7 +1030,7 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
BATADV_P_DAT_CACHE_REPLY,
vid);
else
- err = batadv_send_skb_unicast(bat_priv, skb_new, vid);
+ err = batadv_send_skb_unicast(bat_priv, skb_new, vid, false);

if (!err) {
batadv_inc_counter(bat_priv, BATADV_CNT_DAT_CACHED_REPLY_TX);
diff --git a/multicast.c b/multicast.c
index 74fb19e..7a52a63 100644
--- a/multicast.c
+++ b/multicast.c
@@ -21,6 +21,7 @@
#include "originator.h"
#include "hard-interface.h"
#include "translation-table.h"
+#include "multicast.h"

struct batadv_hw_addr {
struct list_head list;
@@ -210,6 +211,61 @@ out:
}

/**
+ * batadv_mcast_forw_mode - check on how to forward a multicast packet
+ * @skb: The multicast packet to check
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Return the forwarding mode as enum batadv_forw_mode.
+ */
+enum batadv_forw_mode
+batadv_mcast_forw_mode(struct sk_buff *skb, struct batadv_priv *bat_priv)
+{
+ struct ethhdr *ethhdr = (struct ethhdr *)(skb->data);
+ struct ipv6hdr *ip6hdr;
+ int count;
+
+ if (!atomic_read(&bat_priv->mcast_group_awareness))
+ return BATADV_FORW_ALL;
+
+ if (atomic_read(&bat_priv->mcast.num_no_mla))
+ return BATADV_FORW_ALL;
+
+ if (ntohs(ethhdr->h_proto) != ETH_P_IPV6)
+ return BATADV_FORW_ALL;
+
+ /* We might fail due to out-of-memory -> drop it */
+ if (!pskb_may_pull(skb, sizeof(*ethhdr) + sizeof(*ip6hdr)))
+ return BATADV_FORW_NONE;
+
+ ip6hdr = ipv6_hdr(skb);
+
+ /* TODO: Implement Multicast Router Discovery, then add
+ * scope >= IPV6_ADDR_SCOPE_LINKLOCAL, too
+ */
+ if (IPV6_ADDR_MC_SCOPE(&ip6hdr->daddr) !=
+ IPV6_ADDR_SCOPE_LINKLOCAL)
+ return BATADV_FORW_ALL;
+
+ /* We cannot snoop and therefore cannot optimize the
+ * all-nodes-multicast address
+ */
+ if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr))
+ return BATADV_FORW_ALL;
+
+ count = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
+ BATADV_NO_FLAGS);
+
+ switch (count) {
+ case 0:
+ return BATADV_FORW_NONE;
+ case 1:
+ return BATADV_FORW_SINGLE;
+ default:
+ return BATADV_FORW_ALL;
+ }
+}
+
+/**
* 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
diff --git a/multicast.h b/multicast.h
index aa58e4b..7b291d5 100644
--- a/multicast.h
+++ b/multicast.h
@@ -20,10 +20,27 @@
#ifndef _NET_BATMAN_ADV_MULTICAST_H_
#define _NET_BATMAN_ADV_MULTICAST_H_

+/**
+ * batadv_forw_mode - the way a packet should be forwarded as
+ * @BATADV_FORW_ALL: forward the packet to all nodes
+ * (currently via classic flooding)
+ * @BATADV_FORW_SINGLE: forward the packet to a single node
+ * (currently via the BATMAN_IV unicast routing protocol)
+ * @BATADV_FORW_NONE: don't forward, drop it
+ */
+enum batadv_forw_mode {
+ BATADV_FORW_ALL,
+ BATADV_FORW_SINGLE,
+ BATADV_FORW_NONE,
+};
+
#ifdef CONFIG_BATMAN_ADV_MCAST_OPTIMIZATIONS

void batadv_mcast_mla_tt_update(struct batadv_priv *bat_priv);

+enum batadv_forw_mode
+batadv_mcast_forw_mode(struct sk_buff *skb, struct batadv_priv *bat_priv);
+
int batadv_mcast_init(struct batadv_priv *bat_priv);

void batadv_mcast_free(struct batadv_priv *bat_priv);
@@ -37,6 +54,12 @@ static inline void batadv_mcast_mla_tt_update(struct batadv_priv *bat_priv)
return;
}

+static inline enum batadv_forw_mode
+batadv_mcast_forw_mode(struct sk_buff *skb, struct batadv_priv *bat_priv)
+{
+ return BATADV_FORW_ALL;
+}
+
static inline int batadv_mcast_init(struct batadv_priv *bat_priv)
{
return 0;
diff --git a/send.c b/send.c
index b631355..68f65f1 100644
--- a/send.c
+++ b/send.c
@@ -242,13 +242,14 @@ out:
* @packet_subtype: the unicast 4addr packet subtype (only relevant for unicast
* 4addr packets)
* @vid: the vid to be used to search the translation table
+ * @forw_to_gw: whether to forward to a gateway (or via TT otherwise)
*
* Returns 1 in case of error or 0 otherwise.
*/
int batadv_send_skb_generic_unicast(struct batadv_priv *bat_priv,
struct sk_buff *skb, int packet_type,
int packet_subtype,
- unsigned short vid)
+ unsigned short vid, bool forw_to_gw)
{
struct ethhdr *ethhdr = (struct ethhdr *)skb->data;
struct batadv_unicast_packet *unicast_packet;
@@ -256,7 +257,7 @@ int batadv_send_skb_generic_unicast(struct batadv_priv *bat_priv,
int ret = NET_RX_DROP;

/* get routing information */
- if (is_multicast_ether_addr(ethhdr->h_dest))
+ if (forw_to_gw)
orig_node = batadv_gw_get_selected_orig(bat_priv);
else
/* check for tt host - increases orig_node refcount.
diff --git a/send.h b/send.h
index c030cb7..642f9fc 100644
--- a/send.h
+++ b/send.h
@@ -41,22 +41,23 @@ bool batadv_send_skb_prepare_unicast_4addr(struct batadv_priv *bat_priv,
int batadv_send_skb_generic_unicast(struct batadv_priv *bat_priv,
struct sk_buff *skb, int packet_type,
int packet_subtype,
- unsigned short vid);
+ unsigned short vid, bool forw_to_gw);

/**
* batadv_send_unicast_skb - send the skb encapsulated in a unicast packet
* @bat_priv: the bat priv with all the soft interface information
* @skb: the payload to send
* @vid: the vid to be used to search the translation table
+ * @forw_to_gw: whether to forward to a gateway (or via TT otherwise)
*
* Returns 1 in case of error or 0 otherwise.
*/
static inline int batadv_send_skb_unicast(struct batadv_priv *bat_priv,
struct sk_buff *skb,
- unsigned short vid)
+ unsigned short vid, bool forw_to_gw)
{
return batadv_send_skb_generic_unicast(bat_priv, skb, BATADV_UNICAST,
- 0, vid);
+ 0, vid, forw_to_gw);
}

/**
@@ -76,7 +77,7 @@ static inline int batadv_send_skb_unicast_4addr(struct batadv_priv *bat_priv,
{
return batadv_send_skb_generic_unicast(bat_priv, skb,
BATADV_UNICAST_4ADDR,
- packet_subtype, vid);
+ packet_subtype, vid, false);
}

#endif /* _NET_BATMAN_ADV_SEND_H_ */
diff --git a/soft-interface.c b/soft-interface.c
index 90d06c5..d91526f 100644
--- a/soft-interface.c
+++ b/soft-interface.c
@@ -34,6 +34,7 @@
#include <linux/ethtool.h>
#include <linux/etherdevice.h>
#include <linux/if_vlan.h>
+#include "multicast.h"
#include "bridge_loop_avoidance.h"
#include "network-coding.h"

@@ -169,6 +170,8 @@ static int batadv_interface_tx(struct sk_buff *skb,
bool do_bcast = false;
unsigned short vid;
uint32_t seqno;
+ enum batadv_forw_mode mode;
+ bool forw_to_gw = false;

if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
goto dropped;
@@ -226,13 +229,24 @@ static int batadv_interface_tx(struct sk_buff *skb,
* via unicast to their gateway
*/
ret = batadv_gw_is_dhcp_target(skb, &header_len);
- if (ret)
+ if (ret) {
do_bcast = false;
+ forw_to_gw = true;
+ }
break;
case BATADV_GW_MODE_OFF:
default:
break;
}
+
+ if (do_bcast && !is_broadcast_ether_addr(ethhdr->h_dest)) {
+ mode = batadv_mcast_forw_mode(skb, bat_priv);
+ if (mode == BATADV_FORW_NONE)
+ goto dropped;
+
+ if (mode == BATADV_FORW_SINGLE)
+ do_bcast = false;
+ }
}

/* ethernet packet should be broadcasted */
@@ -289,7 +303,7 @@ static int batadv_interface_tx(struct sk_buff *skb,

batadv_dat_snoop_outgoing_arp_reply(bat_priv, skb);

- ret = batadv_send_skb_unicast(bat_priv, skb, vid);
+ ret = batadv_send_skb_unicast(bat_priv, skb, vid, forw_to_gw);
if (ret != 0)
goto dropped_freed;
}
diff --git a/translation-table.c b/translation-table.c
index 18a2051..87287c7 100644
--- a/translation-table.c
+++ b/translation-table.c
@@ -125,6 +125,77 @@ batadv_tt_hash_find(struct batadv_hashtable *hash, const uint8_t *addr,
}

/**
+ * batadv_tt_orig_entries_count - count the number of originators
+ * @head: a list of originators
+ *
+ * Return the number of originator entries in the given list.
+ *
+ * The caller needs to hold the rcu_read_lock().
+ */
+static int batadv_tt_orig_entries_count(struct hlist_head *head)
+{
+ struct batadv_tt_orig_list_entry *orig_entry;
+ int count = 0;
+
+ hlist_for_each_entry_rcu(orig_entry, head, list) {
+ if (!atomic_read(&orig_entry->refcount))
+ continue;
+
+ count++;
+ }
+
+ return count;
+}
+
+/**
+ * batadv_tt_global_hash_count - count the number of orig entries
+ * @hash: hash table containing the tt entries
+ * @addr: the mac address of the client to count entries for
+ * @vid: VLAN identifier
+ *
+ * Return the number of originators advertising the given address/data
+ * (excluding ourself).
+ */
+int batadv_tt_global_hash_count(struct batadv_priv *bat_priv,
+ const uint8_t *addr, unsigned short vid)
+{
+ struct hlist_head *head, *orig_list;
+ struct batadv_tt_common_entry to_search, *tt_common_entry;
+ struct batadv_tt_global_entry *tt_global_entry;
+ uint32_t index;
+ int count = 0;
+
+ if (!bat_priv->tt.global_hash)
+ goto out;
+
+ memcpy(to_search.addr, addr, ETH_ALEN);
+ to_search.vid = vid;
+
+ index = batadv_choose_tt(&to_search, bat_priv->tt.global_hash->size);
+ head = &bat_priv->tt.global_hash->table[index];
+
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(tt_common_entry, head, hash_entry) {
+ if (!batadv_compare_eth(tt_common_entry, addr))
+ continue;
+
+ if (!atomic_read(&tt_common_entry->refcount))
+ continue;
+
+ tt_global_entry = container_of(tt_common_entry,
+ struct batadv_tt_global_entry,
+ common);
+ orig_list = &tt_global_entry->orig_list;
+ count = batadv_tt_orig_entries_count(orig_list);
+ break;
+ }
+ rcu_read_unlock();
+
+out:
+ return count;
+}
+
+/**
* batadv_tt_local_hash_find - search the local table for a given client
* @bat_priv: the bat priv with all the soft interface information
* @addr: the mac address of the client to look for
diff --git a/translation-table.h b/translation-table.h
index 1d9506d..3916ca8 100644
--- a/translation-table.h
+++ b/translation-table.h
@@ -31,6 +31,8 @@ int batadv_tt_global_seq_print_text(struct seq_file *seq, void *offset);
void batadv_tt_global_del_orig(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig_node,
const char *message);
+int batadv_tt_global_hash_count(struct batadv_priv *bat_priv,
+ const uint8_t *addr, unsigned short vid);
struct batadv_orig_node *batadv_transtable_search(struct batadv_priv *bat_priv,
const uint8_t *src,
const uint8_t *addr,
--
1.7.10.4