[B.A.T.M.A.N.] [PATCHv7 4/4] batman-adv: Add IPv4 link-local/IPv6-ll-all-nodes multicast support

Linus Lüssing
2013-07-03T22:03:22Z

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_HAS_NO_BRIDGE 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 and the BATADV_MCAST_LISTENER_ANNOUNCEMENT
flag are currently set and unset at the same time, so 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 | 170 ++++++++++++++++++++++++++++++++++++++++++++----------
packet.h | 1 +
soft-interface.c | 1 +
types.h | 1 +
5 files changed, 143 insertions(+), 31 deletions(-)

diff --git a/main.h b/main.h
index fe612d6..913bfd4 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/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 dee86ab..27781cc 100644
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -208,31 +208,61 @@ out:
}

/**
- * batadv_mcast_forw_mode - check on how to forward a multicast packet
- * @skb: The multicast packet to check
+ * 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
*
- * Return the forwarding mode as enum batadv_forw_mode.
+ * 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, then add
+ * 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
+ */
+ if (atomic_read(&bat_priv->mcast.num_has_bridge))
+ 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
+ *
+ * Check whether the given IPv6 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.
*/
-enum batadv_forw_mode
-batadv_mcast_forw_mode(struct sk_buff *skb, struct batadv_priv *bat_priv)
+static int batadv_mcast_forw_mode_check_ipv6(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->multicast_mode))
- 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;
+ if (!pskb_may_pull(skb, sizeof(struct ethhdr) + sizeof(*ip6hdr)))
+ return -ENOMEM;

ip6hdr = ipv6_hdr(skb);

@@ -241,18 +271,73 @@ batadv_mcast_forw_mode(struct sk_buff *skb, struct batadv_priv *bat_priv)
*/
if (IPV6_ADDR_MC_SCOPE(&ip6hdr->daddr) !=
IPV6_ADDR_SCOPE_LINKLOCAL)
- return BATADV_FORW_ALL;
+ return -EINVAL;

- /* We cannot snoop and therefore cannot optimize the
- * all-nodes-multicast address
+ /* With one bridge involved, we cannot be certain about
+ * link-local-all-nodes multicast listener announcements anymore
*/
- if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr))
+ if (ipv6_addr_is_ll_all_nodes(&ip6hdr->daddr) &&
+ atomic_read(&bat_priv->mcast.num_has_bridge))
+ return -EINVAL;
+
+ return 0;
+}
+
+/**
+ * batadv_mcast_forw_mode_check - check for optimized forwarding potential
+ * @skb: the multicast frame to check
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * Check whether the given multicast ethernet frame 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(struct sk_buff *skb,
+ struct batadv_priv *bat_priv)
+{
+ struct ethhdr *ethhdr = (struct ethhdr *)(skb->data);
+
+ if (!atomic_read(&bat_priv->multicast_mode))
+ return -EINVAL;
+
+ if (atomic_read(&bat_priv->mcast.num_no_mla))
+ 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:
+ return -EINVAL;
+ }
+}
+
+/**
+ * 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);
+ int ret;
+
+ ret = batadv_mcast_forw_mode_check(skb, bat_priv);
+ if (ret == -ENOMEM)
+ return BATADV_FORW_NONE;
+ else if (ret == -EINVAL)
return BATADV_FORW_ALL;

- count = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
+ ret = batadv_tt_global_hash_count(bat_priv, ethhdr->h_dest,
BATADV_NO_FLAGS);

- switch (count) {
+ switch (ret) {
case 0:
return BATADV_FORW_NONE;
case 1:
@@ -263,6 +348,28 @@ batadv_mcast_forw_mode(struct sk_buff *skb, struct batadv_priv *bat_priv)
}

/**
+ * batadv_mcast_tvlv_update_flag_counter - update the counter of a flag
+ * @flag: the flag we want to update counters for
+ * @flag_counter: the counter we might update
+ * @new_flags: the new capability bitset of a node
+ * @old_flags: the current, to be updated bitset of a node
+ *
+ * Update the given flag_counter with the help of the new flag information
+ * of a node to reflect how many nodes have the given flag unset.
+ */
+static void batadv_mcast_tvlv_update_flag_counter(uint8_t flag,
+ atomic_t *flag_counter,
+ uint8_t new_flags,
+ int old_flags)
+{
+ if (!(new_flags & flag) &&
+ (old_flags & flag || old_flags & BATADV_UNINIT_FLAGS))
+ atomic_inc(flag_counter);
+ else if (new_flags & flag && !(old_flags & flag))
+ atomic_dec(flag_counter);
+}
+
+/**
* 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
@@ -285,13 +392,14 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
(tvlv_value) && (tvlv_value_len == sizeof(mcast_flags)))
mcast_flags = *(uint8_t *)tvlv_value;

- if (!(mcast_flags & BATADV_MCAST_LISTENER_ANNOUNCEMENT) &&
- (orig->mcast_flags & BATADV_MCAST_LISTENER_ANNOUNCEMENT ||
- orig->mcast_flags & BATADV_UNINIT_FLAGS))
- atomic_inc(&bat_priv->mcast.num_no_mla);
- else if (mcast_flags & BATADV_MCAST_LISTENER_ANNOUNCEMENT &&
- !(orig->mcast_flags & BATADV_MCAST_LISTENER_ANNOUNCEMENT))
- atomic_dec(&bat_priv->mcast.num_no_mla);
+ batadv_mcast_tvlv_update_flag_counter(
+ BATADV_MCAST_LISTENER_ANNOUNCEMENT,
+ &bat_priv->mcast.num_no_mla,
+ mcast_flags, orig->mcast_flags);
+ batadv_mcast_tvlv_update_flag_counter(
+ BATADV_MCAST_HAS_NO_BRIDGE,
+ &bat_priv->mcast.num_has_bridge,
+ mcast_flags, orig->mcast_flags);

orig->mcast_flags = mcast_flags;
}
diff --git a/packet.h b/packet.h
index 1090977..d10dc17 100644
--- a/net/batman-adv/packet.h
+++ b/net/batman-adv/packet.h
@@ -94,6 +94,7 @@ enum batadv_icmp_packettype {
/* multicast capabilities */
enum batadv_mcast_flags {
BATADV_MCAST_LISTENER_ANNOUNCEMENT = BIT(0),
+ BATADV_MCAST_HAS_NO_BRIDGE = BIT(1),
};

/* tt data subtypes */
diff --git a/soft-interface.c b/soft-interface.c
index 8fad00e..73c0de1 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -663,6 +663,7 @@ static int batadv_softif_init_late(struct net_device *dev)
#ifdef CONFIG_BATMAN_ADV_MCAST
atomic_set(&bat_priv->multicast_mode, 1);
atomic_set(&bat_priv->mcast.num_no_mla, 0);
+ atomic_set(&bat_priv->mcast.num_has_bridge, 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 7535c69..4083746 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -508,6 +508,7 @@ struct batadv_priv_dat {
struct batadv_priv_mcast {
struct hlist_head mla_list;
atomic_t num_no_mla;
+ atomic_t num_has_bridge;
};
#endif

--
1.7.10.4