[B.A.T.M.A.N.] [RFC 1/2] batman-adv: Fix speedy join in gateway client mode

[B.A.T.M.A.N.] [RFC 1/2] batman-adv: Fix speedy join in gateway client mode

[Sven Eckelmann]

Speedy join only works when the received packet is either broadcast or an
4addr unicast packet. Thus packets converted from broadcast to unicast via
the gateway handling code have to be converted to 4addr packets to allow
the receiving gateway server to add the sender address as temporary node to
the translation table.

Not doing it will make batman-adv drop the DHCP response in many situations
because it doesn't yet have the TT entry for the destination of the DHCP
response.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
This is completely untested. The RFC was submitted to better explain a
problem to Antonio. This problems was noticed in real world setups but
these patches were not yet tested in these setups.

 net/batman-adv/send.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/send.c b/net/batman-adv/send.c
index 49836da..0e9445b 100644
--- a/net/batman-adv/send.c
+++ b/net/batman-adv/send.c
@@ -426,8 +426,8 @@ int batadv_send_skb_via_gw(struct batadv_priv *bat_priv, struct sk_buff *skb,
 	struct batadv_orig_node *orig_node;
 
 	orig_node = batadv_gw_get_selected_orig(bat_priv);
-	return batadv_send_skb_unicast(bat_priv, skb, BATADV_UNICAST, 0,
-				       orig_node, vid);
+	return batadv_send_skb_unicast(bat_priv, skb, BATADV_UNICAST_4ADDR,
+				       BATADV_P_DATA, orig_node, vid);
 }
 
 void batadv_forw_packet_free(struct batadv_forw_packet *forw_packet)
-- 
2.8.1

[B.A.T.M.A.N.] [RFC 2/2] batman-adv: Use broadcast as fallback for gateway replies

[Sven Eckelmann]

The replies from gateway server to gateway client are usually sent via
unicast packets. This only works when the destination address for the reply
is already known to the translation table. But usually the gateway replies
are in response to the first known contact from a device to the gateway
server. So it can happen that the TT entry was not yet created.

The gateway server has therefore use broadcast as fallback when the entry
is not yet known. This makes the first responses from a DHCP server to a
DHCP client more robost.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
This is completely untested. The RFC was submitted to better explain a
problem to Antonio. This problems was noticed in real world setups but
these patches were not yet tested in these setups.

 net/batman-adv/soft-interface.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 216ac03..5829695 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -297,6 +297,18 @@ send:
 			if (forw_mode == BATADV_FORW_SINGLE)
 				do_bcast = false;
 		}
+
+		/* DHCP to from server to client should use unicast when TT
+		 * entry is available and use broadcast as fallback
+		 */
+		if (!mcast_single_orig && dhcp_rcp == BATADV_DHCP_TO_CLIENT) {
+			mcast_single_orig = batadv_transtable_search(bat_priv,
+								     NULL,
+								     dst_hint,
+								     vid);
+			if (!mcast_single_orig)
+				do_bcast = true;
+		}
 	}
 
 	batadv_skb_set_priority(skb, 0);
-- 
2.8.1

Re: [B.A.T.M.A.N.] [RFC 2/2] batman-adv: Use broadcast as fallback for gateway replies

[Linus Lüssing]

On Sat, Jun 11, 2016 at 10:27:53PM +0200, Sven Eckelmann wrote:
> The replies from gateway server to gateway client are usually sent via
> unicast packets. This only works when the destination address for the reply
> is already known to the translation table. But usually the gateway replies
> are in response to the first known contact from a device to the gateway
> server. So it can happen that the TT entry was not yet created.
> 
> The gateway server has therefore use broadcast as fallback when the entry
> is not yet known. This makes the first responses from a DHCP server to a
> DHCP client more robost.
> 
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
> This is completely untested. The RFC was submitted to better explain a
> problem to Antonio. This problems was noticed in real world setups but
> these patches were not yet tested in these setups.

Hm, I'm wondering what kind of overhead implications this could
have in larger mesh networks.

Didn't TT support temporary entries? Could the gateway server
inject them into its global translation table after parsing an
incoming DHCP packet?