[B.A.T.M.A.N.] [PATCHv2 1/4] batman-adv: substitute tt_poss_change with a per-tt_entry flag

Antonio Quartulli
2012-09-23T20:38:34Z

tt_poss_change is a node-wide flag which tells whether the node is in a roaming
state (a client recently moved to/away from it) in order to let it apply special
re-routing rules. However this flag does not give a clear idea of the current
state because it is not possible to understand *which client* is actually
involved in the roaming. For this reason a better approach has been chosen:
instead of using a node-wide variable, the roaming state is now given by a
per-tt_entry ROAM flag which, in case of packet coming through the node, tells
the node whether the real destination is in roaming state or not.

With this flag change, batadv_check_unicast_ttvn() has also been rearranged in
order to better fit the new re-routing logic and to be much more readable.

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
---
originator.c | 1 -
routing.c | 156 +++++++++++++++++++++++++++++++++++-----------------
soft-interface.c | 1 -
translation-table.c | 43 ++++++++++-----
translation-table.h | 2 +
types.h | 8 ---
6 files changed, 138 insertions(+), 73 deletions(-)

diff --git a/originator.c b/originator.c
index d9c14b8..bf27edc 100644
--- a/originator.c
+++ b/originator.c
@@ -220,7 +220,6 @@ struct batadv_orig_node *batadv_get_orig_node(struct batadv_priv *bat_priv,
atomic_set(&orig_node->refcount, 2);

orig_node->tt_initialised = false;
- orig_node->tt_poss_change = false;
orig_node->bat_priv = bat_priv;
memcpy(orig_node->orig, addr, ETH_ALEN);
orig_node->router = NULL;
diff --git a/routing.c b/routing.c
index 44109cc..bc4814c 100644
--- a/routing.c
+++ b/routing.c
@@ -710,12 +710,6 @@ int batadv_recv_roam_adv(struct sk_buff *skb, struct batadv_hard_iface *recv_if)
BATADV_TT_CLIENT_ROAM,
atomic_read(&orig_node->last_ttvn) + 1);

- /* Roaming phase starts: I have new information but the ttvn has not
- * been incremented yet. This flag will make me check all the incoming
- * packets for the correct destination.
- */
- bat_priv->tt.poss_change = true;
-
batadv_orig_node_free_ref(orig_node);
out:
/* returning NET_RX_DROP will make the caller function kfree the skb */
@@ -898,6 +892,46 @@ out:
return ret;
}

+/**
+ * batadv_reroute_unicast_packet - update the unicast header for re-routing
+ * @bat_priv: the bat priv with all the soft interface information
+ * @unicast_packet: the unicast header to be updated
+ * @dst_addr: the payload destination
+ * @msg: the message to print explaining the reason of the requested re-route
+ *
+ * Search the global translation table for dst_addr and update the unicast
+ * header with the new corresponding information (originator address where the
+ * destination client currently is and its known TTVN)
+ *
+ * Returns true if the packet header has been updated, false otherwise
+ */
+static bool
+batadv_reroute_unicast_packet(struct batadv_priv *bat_priv,
+ struct batadv_unicast_packet *unicast_packet,
+ uint8_t *dst_addr)
+{
+ struct batadv_orig_node *orig_node = NULL;
+ bool ret = false;
+
+ orig_node = batadv_transtable_search(bat_priv, NULL, dst_addr);
+ if (!orig_node)
+ goto out;
+
+ if (batadv_compare_eth(orig_node->orig, unicast_packet->dest))
+ goto out;
+
+ /* update the packet header */
+ memcpy(unicast_packet->dest, orig_node->orig, ETH_ALEN);
+ unicast_packet->ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
+
+ ret = true;
+out:
+ if (orig_node)
+ batadv_orig_node_free_ref(orig_node);
+
+ return ret;
+}
+
static int batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
struct sk_buff *skb) {
uint8_t curr_ttvn;
@@ -905,7 +939,6 @@ static int batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
struct ethhdr *ethhdr;
struct batadv_hard_iface *primary_if;
struct batadv_unicast_packet *unicast_packet;
- bool tt_poss_change;
int is_old_ttvn;

/* check if there is enough data before accessing it */
@@ -917,65 +950,88 @@ static int batadv_check_unicast_ttvn(struct batadv_priv *bat_priv,
return 0;

unicast_packet = (struct batadv_unicast_packet *)skb->data;
+ ethhdr = (struct ethhdr *)(skb->data + sizeof(*unicast_packet));

- if (batadv_is_my_mac(unicast_packet->dest)) {
- tt_poss_change = bat_priv->tt.poss_change;
- curr_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
- } else {
+ /* check if the destination client was served by this node and it is now
+ * roaming. In this case, it means that the node has got a ROAM_ADV
+ * message and that it knows the new destination in the mesh to re-route
+ * the packet to
+ */
+ if (batadv_tt_local_client_is_roaming(bat_priv, ethhdr->h_dest)) {
+ if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
+ ethhdr->h_dest))
+ net_ratelimited_function(batadv_dbg, BATADV_DBG_TT,
+ bat_priv,
+ "Rerouting unicast packet to %pM (dst=%pM): Local Roaming\n",
+ unicast_packet->dest,
+ ethhdr->h_dest);
+ /* at this point the mesh destination should have been
+ * substituted with the originator address found in the global
+ * table. If not, let the packet go untouched anyway because
+ * there is nothing the node can do
+ */
+ return 1;
+ }
+
+ /* retrieve the TTVN known by this node for the packet destination. This
+ * value is used later to check if the node which sent (or re-routed
+ * last time) the packet had an updated information or not
+ */
+ curr_ttvn = (uint8_t)atomic_read(&bat_priv->tt.vn);
+ if (!batadv_is_my_mac(unicast_packet->dest)) {
orig_node = batadv_orig_hash_find(bat_priv,
unicast_packet->dest);
-
+ /* if it is not possible to find the orig_node representing the
+ * destination, the packet can immediately be dropped as it will
+ * not be possible to deliver it
+ */
if (!orig_node)
return 0;

curr_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
- tt_poss_change = orig_node->tt_poss_change;
batadv_orig_node_free_ref(orig_node);
}

- /* Check whether I have to reroute the packet */
+ /* check if the TTVN contained in the packet is fresher than what the
+ * node knows
+ */
is_old_ttvn = batadv_seq_before(unicast_packet->ttvn, curr_ttvn);
- if (is_old_ttvn || tt_poss_change) {
- /* check if there is enough data before accessing it */
- if (pskb_may_pull(skb, sizeof(struct batadv_unicast_packet) +
- ETH_HLEN) < 0)
- return 0;
+ if (!is_old_ttvn)
+ return 1;

- ethhdr = (struct ethhdr *)(skb->data + sizeof(*unicast_packet));
+ /* the packet was forged based on outdated network information. Its
+ * destination can possibly be updated and forwarded towards the new
+ * target host
+ */
+ if (batadv_reroute_unicast_packet(bat_priv, unicast_packet,
+ ethhdr->h_dest)) {
+ net_ratelimited_function(batadv_dbg, BATADV_DBG_TT, bat_priv,
+ "Rerouting unicast packet to %pM (dst=%pM): TTVN mismatch old_ttvn=%u new_ttvn=%u\n",
+ unicast_packet->dest, ethhdr->h_dest,
+ unicast_packet->ttvn, curr_ttvn);
+ return 1;
+ }

- /* we don't have an updated route for this client, so we should
- * not try to reroute the packet!!
- */
- if (batadv_tt_global_client_is_roaming(bat_priv,
- ethhdr->h_dest))
- return 1;
+ /* the packet has not been re-routed: either the destination is
+ * currently served by this node or there is no destination at all and
+ * it is possible to drop the packet
+ */
+ if (!batadv_is_my_client(bat_priv, ethhdr->h_dest))
+ return 0;

- orig_node = batadv_transtable_search(bat_priv, NULL,
- ethhdr->h_dest);
-
- if (!orig_node) {
- if (!batadv_is_my_client(bat_priv, ethhdr->h_dest))
- return 0;
- primary_if = batadv_primary_if_get_selected(bat_priv);
- if (!primary_if)
- return 0;
- memcpy(unicast_packet->dest,
- primary_if->net_dev->dev_addr, ETH_ALEN);
- batadv_hardif_free_ref(primary_if);
- } else {
- memcpy(unicast_packet->dest, orig_node->orig,
- ETH_ALEN);
- curr_ttvn = (uint8_t)atomic_read(&orig_node->last_ttvn);
- batadv_orig_node_free_ref(orig_node);
- }
+ /* update the header in order to let the packet be delivered to this
+ * node's soft interface
+ */
+ primary_if = batadv_primary_if_get_selected(bat_priv);
+ if (!primary_if)
+ return 0;

- net_ratelimited_function(batadv_dbg, BATADV_DBG_TT, bat_priv,
- "TTVN mismatch (old_ttvn %u new_ttvn %u)! Rerouting unicast packet (for %pM) to %pM\n",
- unicast_packet->ttvn, curr_ttvn,
- ethhdr->h_dest, unicast_packet->dest);
+ memcpy(unicast_packet->dest, primary_if->net_dev->dev_addr, ETH_ALEN);
+
+ batadv_hardif_free_ref(primary_if);
+
+ unicast_packet->ttvn = curr_ttvn;

- unicast_packet->ttvn = curr_ttvn;
- }
return 1;
}

diff --git a/soft-interface.c b/soft-interface.c
index 22bc651..ffc0e16 100644
--- a/soft-interface.c
+++ b/soft-interface.c
@@ -488,7 +488,6 @@ struct net_device *batadv_softif_create(const char *name)
#endif
bat_priv->tt.last_changeset = NULL;
bat_priv->tt.last_changeset_len = 0;
- bat_priv->tt.poss_change = false;

bat_priv->primary_if = NULL;
bat_priv->num_ifaces = 0;
diff --git a/translation-table.c b/translation-table.c
index a570d95..8227f99 100644
--- a/translation-table.c
+++ b/translation-table.c
@@ -306,8 +306,6 @@ void batadv_tt_local_add(struct net_device *soft_iface, const uint8_t *addr,
head = &tt_global_entry->orig_list;
rcu_read_lock();
hlist_for_each_entry_rcu(orig_entry, node, head, list) {
- orig_entry->orig_node->tt_poss_change = true;
-
batadv_send_roam_adv(bat_priv,
tt_global_entry->common.addr,
orig_entry->orig_node);
@@ -512,8 +510,11 @@ uint16_t batadv_tt_local_remove(struct batadv_priv *bat_priv,
curr_flags = tt_local_entry->common.flags;

flags = BATADV_TT_CLIENT_DEL;
- if (roaming)
+ if (roaming) {
flags |= BATADV_TT_CLIENT_ROAM;
+ /* mark the local client as ROAMed */
+ tt_local_entry->common.flags |= BATADV_TT_CLIENT_ROAM;
+ }

batadv_tt_local_set_pending(bat_priv, tt_local_entry, flags, message);

@@ -1996,10 +1997,6 @@ void batadv_handle_tt_response(struct batadv_priv *bat_priv,

/* Recalculate the CRC for this orig_node and store it */
orig_node->tt_crc = batadv_tt_global_crc(bat_priv, orig_node);
- /* Roaming phase is over: tables are in sync again. I can
- * unset the flag
- */
- orig_node->tt_poss_change = false;
out:
if (orig_node)
batadv_orig_node_free_ref(orig_node);
@@ -2290,7 +2287,6 @@ static int batadv_tt_commit_changes(struct batadv_priv *bat_priv,
batadv_dbg(BATADV_DBG_TT, bat_priv,
"Local changes committed, updating to ttvn %u\n",
(uint8_t)atomic_read(&bat_priv->tt.vn));
- bat_priv->tt.poss_change = false;

/* reset the sending counter */
atomic_set(&bat_priv->tt.ogm_append_cnt, BATADV_TT_OGM_APPEND_MAX);
@@ -2402,11 +2398,6 @@ void batadv_tt_update_orig(struct batadv_priv *bat_priv,
*/
if (orig_node->tt_crc != tt_crc)
goto request_table;
-
- /* Roaming phase is over: tables are in sync again. I can
- * unset the flag
- */
- orig_node->tt_poss_change = false;
} else {
/* if we missed more than one change or our tables are not
* in sync anymore -> request fresh tt data
@@ -2445,6 +2436,32 @@ out:
return ret;
}

+/**
+ * batadv_tt_local_client_is_roaming - tells whether the client is roaming
+ * @bat_priv: the bat priv with all the soft interface information
+ * @addr: the MAC address of the local client to query
+ *
+ * Returns true if the local client is known to be roaming (it is not served by
+ * this node anymore) or not. If yes, the client is still present in the table
+ * to keep the latter consistent with the node TTVN
+ */
+bool batadv_tt_local_client_is_roaming(struct batadv_priv *bat_priv,
+ uint8_t *addr)
+{
+ struct batadv_tt_local_entry *tt_local_entry;
+ bool ret = false;
+
+ tt_local_entry = batadv_tt_local_hash_find(bat_priv, addr);
+ if (!tt_local_entry)
+ goto out;
+
+ ret = !!(tt_local_entry->common.flags & BATADV_TT_CLIENT_ROAM);
+ batadv_tt_local_entry_free_ref(tt_local_entry);
+out:
+ return ret;
+
+}
+
bool batadv_tt_add_temporary_global_entry(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig_node,
const unsigned char *addr)
diff --git a/translation-table.h b/translation-table.h
index 9fa4fe4..46d4451 100644
--- a/translation-table.h
+++ b/translation-table.h
@@ -59,6 +59,8 @@ int batadv_tt_append_diff(struct batadv_priv *bat_priv,
int packet_min_len);
bool batadv_tt_global_client_is_roaming(struct batadv_priv *bat_priv,
uint8_t *addr);
+bool batadv_tt_local_client_is_roaming(struct batadv_priv *bat_priv,
+ uint8_t *addr);
bool batadv_tt_add_temporary_global_entry(struct batadv_priv *bat_priv,
struct batadv_orig_node *orig_node,
const unsigned char *addr);
diff --git a/types.h b/types.h
index 02d5f50..e84da10 100644
--- a/types.h
+++ b/types.h
@@ -87,13 +87,6 @@ struct batadv_orig_node {
spinlock_t tt_buff_lock; /* protects tt_buff */
atomic_t tt_size;
bool tt_initialised;
- /* The tt_poss_change flag is used to detect an ongoing roaming phase.
- * If true, then I sent a Roaming_adv to this orig_node and I have to
- * inspect every packet directed to it to check whether it is still
- * the true destination or not. This flag will be reset to false as
- * soon as I receive a new TTVN from this orig_node
- */
- bool tt_poss_change;
uint32_t last_real_seqno;
uint8_t last_ttl;
DECLARE_BITMAP(bcast_bits, BATADV_TQ_LOCAL_WINDOW_SIZE);
@@ -191,7 +184,6 @@ struct batadv_priv_tt {
atomic_t vn;
atomic_t ogm_append_cnt;
atomic_t local_changes;
- bool poss_change;
struct list_head changes_list;
struct batadv_hashtable *local_hash;
struct batadv_hashtable *global_hash;
--
1.7.12