[v2] batman-adv: improve unicast packet (re)routing
Commit Message
In case of a client X roaming from a generic node A to another node B, it is
possible that a third node C gets A's OGM but not B's. At this point in time, if
C wants to send data to X it will send a unicast packet destined to A. The
packet header will contain A's last ttvn (C got A's OGM and so it knows it).
The packet will travel towards A without being intercepted because the ttvn
contained in its header is the newest for A.
Once A will receive the packet, A's state will not report to be in a "roaming
phase" (because, after a roaming, once A sends out its OGM, all the changes are
committed and the node is considered not to be in the roaming state anymore)
and it will match the ttvn carried by the packet. Therefore there is no reason
for A to try to alter the packet's route, thus dropping the packet because the
destination client is not there anymore.
However, C is well aware that it's routing information towards the client X is
outdated as it received an OGM from A saying that the client roamed away.
Thanks to this detail, this patch introduces a small change in behaviour: as
long as C is in the state of not knowing the new location of client X it will
forward the traffic to its last known location using ttvn-1 of the destination.
By using an older ttvn node A will be forced to re-route the packet.
Intermediate nodes are also allowed to update the packet's destination as long
as they have the information about the client's new location.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
---
- split a wrong two line assignment.
routing.c | 6 ++++++
translation-table.c | 18 ++++++++++++++++++
translation-table.h | 2 ++
unicast.c | 8 ++++++++
4 files changed, 34 insertions(+), 0 deletions(-)
Comments
On Friday, March 16, 2012 18:03:28 Antonio Quartulli wrote:
> In case of a client X roaming from a generic node A to another node B, it
> is possible that a third node C gets A's OGM but not B's. At this point in
> time, if C wants to send data to X it will send a unicast packet destined
> to A. The packet header will contain A's last ttvn (C got A's OGM and so
> it knows it).
>
> The packet will travel towards A without being intercepted because the ttvn
> contained in its header is the newest for A.
>
> Once A will receive the packet, A's state will not report to be in a
> "roaming phase" (because, after a roaming, once A sends out its OGM, all
> the changes are committed and the node is considered not to be in the
> roaming state anymore) and it will match the ttvn carried by the packet.
> Therefore there is no reason for A to try to alter the packet's route,
> thus dropping the packet because the destination client is not there
> anymore.
>
> However, C is well aware that it's routing information towards the client X
> is outdated as it received an OGM from A saying that the client roamed
> away. Thanks to this detail, this patch introduces a small change in
> behaviour: as long as C is in the state of not knowing the new location of
> client X it will forward the traffic to its last known location using
> ttvn-1 of the destination. By using an older ttvn node A will be forced to
> re-route the packet. Intermediate nodes are also allowed to update the
> packet's destination as long as they have the information about the
> client's new location.
Applied in revision b46c60b.
Thanks,
Marek
@@ -922,6 +922,12 @@ static int check_unicast_ttvn(struct bat_priv *bat_priv,
ethhdr = (struct ethhdr *)(skb->data +
sizeof(struct unicast_packet));
+
+ /* we don't have an updated route for this client, so we should
+ * not try to reroute the packet!! */
+ if (tt_global_client_is_roaming(bat_priv, ethhdr->h_dest))
+ return 1;
+
orig_node = transtable_search(bat_priv, NULL, ethhdr->h_dest);
if (!orig_node) {
@@ -2113,3 +2113,21 @@ request_table:
}
}
}
+
+/* returns true whether we know that the client has moved from its old
+ * originator to another one. This entry is kept is still kept for consistency
+ * purposes */
+bool tt_global_client_is_roaming(struct bat_priv *bat_priv, uint8_t *addr)
+{
+ bool ret = false;
+ struct tt_global_entry *tt_global_entry;
+ tt_global_entry = tt_global_hash_find(bat_priv, addr);
+
+ if (!tt_global_entry)
+ goto out;
+
+ ret = tt_global_entry->common.flags & TT_CLIENT_ROAM;
+ tt_global_entry_free_ref(tt_global_entry);
+out:
+ return ret;
+}
@@ -53,5 +53,7 @@ bool is_ap_isolated(struct bat_priv *bat_priv, uint8_t *src, uint8_t *dst);
void tt_update_orig(struct bat_priv *bat_priv, struct orig_node *orig_node,
const unsigned char *tt_buff, uint8_t tt_num_changes,
uint8_t ttvn, uint16_t tt_crc);
+bool tt_global_client_is_roaming(struct bat_priv *bat_priv, uint8_t *addr);
+
#endif /* _NET_BATMAN_ADV_TRANSLATION_TABLE_H_ */
@@ -392,6 +392,14 @@ find_router:
}
unicast_packet = (struct unicast_packet *)skb->data;
+
+ /* inform the destination ode that we are still missing a correct route
+ * for this client. The destination will receive this packet and will
+ * try to reroute it because the ttvn contained in the header is less
+ * than the current one */
+ if (tt_global_client_is_roaming(bat_priv, ethhdr->h_dest))
+ unicast_packet->ttvn = unicast_packet->ttvn - 1;
+
/* fragmentation mechanism only works for UNICAST (now) */
if (packet_type == BAT_UNICAST &&
atomic_read(&bat_priv->fragmentation) &&