batman-adv would forward OGMs from non-besthops while replacing the the TQ
and TTL values with the values from the best hop. In certain corner cases
this leads to a temporary routing loop.
This patch changes this behavior: Only packets from best next hops are
forwarded - TQ and TTL values won't be replaced anymore. However, the protocol
needs to rebroadcast OGMs from single hop neighbors regardless of whether or
not they are the best hop. To handle this case a new flag is introduced to
alert neighboring nodes about the forwarded OGM that is not from my best
next hop. It is to be discarded by all nodes except for the one originating
the OGM.
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Daniele Furlan <daniele.furlan@gmail.com>
Tested-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
The coming protocol changes also will have a part called "OGM". That
makes it necessary to introduce a distinction in the code base.
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Using BATMAN_OGM_LEN leaves one with the impression that this is
the full packet size which is not the case. Therefore the variable
is renamed.
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
This second version of the bridge loop avoidance for batman-adv
avoids loops between the mesh and a backbone (usually a LAN).
By connecting multiple batman-adv mesh nodes to the same ethernet
segment a loop can be created when the soft-interface is bridged
into that ethernet segment. A simple visualization of the loop
involving the most common case - a LAN as ethernet segment:
node1 <-- LAN --> node2
| |
wifi <-- mesh --> wifi
Packets from the LAN (e.g. ARP broadcasts) will circle forever from
node1 or node2 over the mesh back into the LAN.
With this patch, batman recognizes backbone gateways, nodes which are
part of the mesh and backbone/LAN at the same time. Each backbone
gateway "claims" clients from within the mesh to handle them
exclusively. By restricting that only responsible backbone gateways
may handle their claimed clients traffic, loops are effectively
avoided.
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
In packet.h the numeric constant 6 is used instead of the more portable ETH_ALEN
define. This patch substitute any hardcoded value with such define.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Acked-by: Sven Eckelmann <sven@narfation.org>
All batman-adv packets have a common 3 byte header. It can be used to share
some code between different code paths, but it was never explicit stated that
this header has to be always the same for all packets. Therefore, new code
changes always have the problem that they may accidently introduce regressions
by moving some elements around.
A new structure is introduced that contains the common header and makes it
easier visible that these 3 bytes have to be the same for all on-wire packets.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
The follow-up routing code changes are going to introduce additional
routing packet types which make this distinction necessary.
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Clients connected through a 802.11 device are now marked with the
TT_CLIENT_WIFI flag. This flag is also advertised with the tt
announcement.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
To keep transtable consistency among all the nodes, an originator must
not send not yet announced clients within a full table TT_RESPONSE.
Instead, deleted client have to be kept in the table in order to be sent
within an immediate TT_RESPONSE. In this way all the nodes in the
network will always provide the same response for the same request.
All the modification are committed at the next ttvn increment event.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
The tt_local_entry structure now has a 'flags' field. This helps to
unify the flags format to all the client related structures (tt_global_entry
and tt_change). The 'never_purge' field is now encoded in the 'flags' one.
To optimise the usage of this field, its length has been increased to 16bit
in order to use the eight leading bits (from 0 to 7) to store flags that
have to be sent on the wire, while the eight ending ones are used for local
computation only.
Moreover 'enum tt_change_flags' is now called 'enum tt_client_flags' and the
defined values apply to the tt_local_entry, tt_global_entry and the tt_change
'flags' field.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
With the current client announcement implementation, in case of roaming,
an update is triggered on the new AP serving the client. At that point
the new information is spread around by means of the OGM broadcasting
mechanism. Until this operations is not executed, no node is able to
correctly route traffic towards the client. This obviously causes packet
drops and introduces a delay in the time needed by the client to recover
its connections.
A new packet type called ROAMING_ADVERTISEMENT is added to account this
issue.
This message is sent in case of roaming from the new AP serving the
client to the old one and will contain the client MAC address. In this
way an out-of-OGM update is immediately committed, so that the old node
can update its global translation table. Traffic reaching this node will
then be redirected to the correct destination utilising the fresher
information. Thus reducing the packet drops and the connection recovery
delay.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
The client announcement mechanism informs every mesh node in the network
of any connected non-mesh client, in order to find the path towards that
client from any given point in the mesh.
The old implementation was based on the simple idea of appending a data
buffer to each OGM containing all the client MAC addresses the node is
serving. All other nodes can populate their global translation tables
(table which links client MAC addresses to node addresses) using this
MAC address buffer and linking it to the node's address contained in the
OGM. A node that wants to contact a client has to lookup the node the
client is connected to and its address in the global translation table.
It is easy to understand that this implementation suffers from several
issues:
- big overhead (each and every OGM contains the entire list of
connected clients)
- high latencies for client route updates due to long OGM trip time and
OGM losses
The new implementation addresses these issues by appending client
changes (new client joined or a client left) to the OGM instead of
filling it with all the client addresses each time. In this way nodes
can modify their global tables by means of "updates", thus reducing the
overhead within the OGMs.
To keep the entire network in sync each node maintains a translation
table version number (ttvn) and a translation table checksum. These
values are spread with the OGM to allow all the network participants to
determine whether or not they need to update their translation table
information.
When a translation table lookup is performed in order to send a packet
to a client attached to another node, the destination's ttvn is added to
the payload packet. Forwarding nodes can compare the packet's ttvn with
their destination's ttvn (this node could have a fresher information
than the source) and re-route the packet if necessary. This greatly
reduces the packet loss of clients roaming from one AP to the next.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
The amount of duplicated code in the receive and routing code can be
reduced when all headers provide the packet type, version and ttl in the
same first bytes.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
CodingStyle "Chapter 12: Macros, Enums and RTL" recommends to use enums
for several related constants. Internal states can be used without
defining the actual value, but all values which are visible to the
outside must be defined as before. Normal values are assigned as usual
and flags are defined by shifts of a bit.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
It is slightly irritating that comments after a long line span over
multiple lines without any code. It is easier to put them before the
actual code and reduce the number of lines which the eye has to read.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
To be coherent, all the functions/variables/constants have been renamed
to the TranslationTable style
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
The routing algorithm must be able to decide if a fragment can be merged with
the missing part and still be passed to a forwarding interface. The fragments
can only differ by one byte in case that the original payload had an uneven
length. In that situation the sender has to inform all possible receivers that
the tail is one byte longer using the flag UNI_FRAG_LARGETAIL.
The combination of UNI_FRAG_LARGETAIL and UNI_FRAG_HEAD flag makes it possible
to calculate the correct length for even and uneven sized payloads.
The original formula missed to add the unicast header at all and forgot to
remove the fragment header of the second fragment. This made the results highly
unreliable and only useful for machines with large differences between the
configured MTUs.
Reported-by: Russell Senior <russell@personaltelco.net>
Reported-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Linux 2.6.21 defines different macros for __attribute__ which are also
used inside batman-adv. The next version of checkpatch.pl warns about
the usage of __attribute__((packed))).
Linux 2.6.33 defines an extra macro __always_unused which is used to
assist source code analyzers and can be used to removed the last
existing __attribute__ inside the source code.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
B.A.T.M.A.N. (better approach to mobile ad-hoc networking) is a routing
protocol for multi-hop ad-hoc mesh networks. The networks may be wired or
wireless. See http://www.open-mesh.org/ for more information and user space
tools.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Marek Lindner
Simon Wunderlich
Antonio Quartulli
Sven Eckelmann