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

[B.A.T.M.A.N.] [PATCH 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 entry
to the translation table.

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

Fixes: 9cbc67d9da47 ("batman-adv: change interface_rx to get orig node")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 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.] [PATCH 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 robust.

Fixes: 2d5b555644b2 ("batman-adv: send every DHCP packet as bat-unicast")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 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.] [PATCH 2/2] batman-adv: Use broadcast as fallback for gateway replies

[Sven Eckelmann]

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[....]
> 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?

Right now we have the problem that DHCP requests (broadcasts by the user) are
encapsulated by the gateway code in the wrong type of packet [1,2,3]. These
are the unicast packets (non-4addr) which cannot be used to create temporary
TT entries. This should be addressed by the first patch.

The second patch is currently only my bandaid (because I cannot patch all APs)
and I would be more than happy when this patch is not required. So I would not
object when this patch is rejected because it causes noise on the network.

For example gluon already accepted the first patch [4] and thus will hopefully
not require the second patch anymore with 2016.2.0 for clients doing their
DHCP Discover as broadcast.

Btw. the non-RFC version of the patch is here:

 https://patchwork.open-mesh.org/patch/16377/

I have taken the freedom to move the reply to this patch.


Kind regards,
	Sven

[1] https://patchwork.open-mesh.org/patch/16376/
[2] https://git.open-mesh.org/batman-adv.git/blob/a36b7a3b08f4cc7c41103aa4db176a11e965e068:/net/batman-adv/routing.c#l914
[3] https://git.open-mesh.org/batman-adv.git/blob/a36b7a3b08f4cc7c41103aa4db176a11e965e068:/net/batman-adv/soft-interface.c#l468
[4] https://github.com/freifunk-gluon/gluon/commit/93fe275000b65a4148d6a9713a030b0d30e6a9f1

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

[Antonio Quartulli]

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On Sun, Jun 12, 2016 at 10:43:19AM +0200, Sven Eckelmann wrote:
> 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 entry
> to the translation table.
> 
> Not doing it will make the batman-adv gateway server drop the DHCP response
> in many situations because it doesn't yet have the TT entry for the
> destination of the DHCP response.
> 
> Fixes: 9cbc67d9da47 ("batman-adv: change interface_rx to get orig node")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>

Acked-by: Antonio Quartulli <a@unstable.cc>


-- 
Antonio Quartulli

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

[Marek Lindner]

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On Sunday, June 12, 2016 10:43:19 Sven Eckelmann wrote:
> 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 entry
> to the translation table.
> 
> Not doing it will make the batman-adv gateway server drop the DHCP response
> in many situations because it doesn't yet have the TT entry for the
> destination of the DHCP response.
> 
> Fixes: 9cbc67d9da47 ("batman-adv: change interface_rx to get orig node")
> Signed-off-by: Sven Eckelmann <sven@narfation.org>
> ---
>  net/batman-adv/send.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Applied in revision 12c771d.

Thanks,
Marek

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