[B.A.T.M.A.N.] [PATCHv3 0/6] batman-adv: Optimizations for setups running dat and bla

[B.A.T.M.A.N.] [PATCHv3 0/6] batman-adv: Optimizations for setups running dat and bla

[Andreas Pape]

This patchset introduces optimizations for batman-adv in setups having several
gateways into a common (switched) Ethernet backbone network especially if dat
is additionally enabled.

Using the current implementation with bla and dat enabled, several problems
can be observed in a real setup:
1. Multiplication of ARP replies from dat enabled gateways and dat enabled
mesh nodes leading to an "ARP reply storm" in the common backbone network.
2. In rare corner cases bla does not fully prevent looping of unicast frames
in the direction Backbone --> mesh --> backbone and looping of multicast
frames in the direction mesh --> backbone --> mesh.
The latter can lead to temporary confusion in the switched backbone resulting
in packet loss and communication timeouts.

The observed problems are solved by introduction of additional rules for the
dat handling, bla packet forwarding and bla claiming/unclaiming of clients.

v3:

 - rebased patchset
 - moved snooping of ip addresses for dat speed up into separate function
 - removed "patch of a patch"
 - removed automatic claiming during check of a claim
 - fixed issues of the patchset not being compiled due to chosen batman
	options

Kind regards,
Andreas


..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
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[B.A.T.M.A.N.] [PATCHv3 1/6] batman-adv: prevent multiple ARP replies sent by gateways if dat enbled

[Andreas Pape]

If dat is enabled it must be made sure that only the backbone gw which has
claimed the remote destination for the ARP request answers the ARP request
directly if the MAC address is known due to the local dat table. This
prevents multiple ARP replies in a common backbone if more than one
gateway already knows the remote mac searched for in the ARP request.

Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/bridge_loop_avoidance.c |   49 ++++++++++++++++++++++++++++++++
 net/batman-adv/bridge_loop_avoidance.h |   11 +++++++
 net/batman-adv/distributed-arp-table.c |   15 ++++++++++
 3 files changed, 75 insertions(+), 0 deletions(-)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 748a9ea..2f46ce9 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -2045,3 +2045,52 @@ out:
 		batadv_hardif_put(primary_if);
 	return 0;
 }
+
+#ifdef CONFIG_BATMAN_ADV_DAT
+/**
+ * batadv_bla_handle_local_claim - check if address is claimed
+ *
+ * @bat_priv: the bat priv with all the soft interface information
+ * @addr: mac address of which the claim status is checked
+ * @vid: the VLAN ID
+ *
+ * addr is checked if this address is claimed by the local device itself.
+ *
+ * Return: true if bla is disabled or the mac is claimed by the device,
+ * false if the device addr is already claimed by another gateway
+ */
+bool batadv_bla_handle_local_claim(struct batadv_priv *bat_priv,
+				   u8 *addr, unsigned short vid)
+{
+	struct batadv_bla_claim search_claim;
+	struct batadv_bla_claim *claim = NULL;
+	struct batadv_hard_iface *primary_if = NULL;
+	bool ret = true;
+
+	if (!atomic_read(&bat_priv->bridge_loop_avoidance))
+		return ret;
+
+	primary_if = batadv_primary_if_get_selected(bat_priv);
+	if (!primary_if)
+		return ret;
+
+	/* First look if the mac address is claimed */
+	ether_addr_copy(search_claim.addr, addr);
+	search_claim.vid = vid;
+
+	claim = batadv_claim_hash_find(bat_priv, &search_claim);
+
+	/* If there is a claim and we are not owner of the claim,
+	 * return false.
+	 */
+	if (claim) {
+		if (!batadv_compare_eth(claim->backbone_gw->orig,
+					primary_if->net_dev->dev_addr))
+			ret = false;
+		batadv_claim_put(claim);
+	}
+
+	batadv_hardif_put(primary_if);
+	return ret;
+}
+#endif
diff --git a/net/batman-adv/bridge_loop_avoidance.h b/net/batman-adv/bridge_loop_avoidance.h
index 0f01dae..cc07be9 100644
--- a/net/batman-adv/bridge_loop_avoidance.h
+++ b/net/batman-adv/bridge_loop_avoidance.h
@@ -47,6 +47,10 @@ void batadv_bla_update_orig_address(struct batadv_priv *bat_priv,
 void batadv_bla_status_update(struct net_device *net_dev);
 int batadv_bla_init(struct batadv_priv *bat_priv);
 void batadv_bla_free(struct batadv_priv *bat_priv);
+#ifdef CONFIG_BATMAN_ADV_DAT
+bool batadv_bla_handle_local_claim(struct batadv_priv *bat_priv, u8 *addr,
+				   unsigned short vid);
+#endif

 #define BATADV_BLA_CRC_INIT	0
 #else /* ifdef CONFIG_BATMAN_ADV_BLA */
@@ -112,6 +116,13 @@ static inline void batadv_bla_free(struct batadv_priv *bat_priv)
 {
 }

+static inline
+bool batadv_bla_handle_local_claim(struct batadv_priv *bat_priv, u8 *addr,
+				   unsigned short vid)
+{
+	return true;
+}
+
 #endif /* ifdef CONFIG_BATMAN_ADV_BLA */

 #endif /* ifndef _NET_BATMAN_ADV_BLA_H_ */
diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 278800a..c11f035 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -48,6 +48,7 @@
 #include "originator.h"
 #include "send.h"
 #include "translation-table.h"
+#include "bridge_loop_avoidance.h"

 static void batadv_dat_purge(struct work_struct *work);

@@ -1003,6 +1004,20 @@ bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
 			goto out;
 		}

+		/* If BLA is enabled, only send ARP replies if we have claimed
+		 * the destination for the ARP request or if no one else of
+		 * the backbone gws belonging to our backbone has claimed the
+		 * destination.
+		 */
+		if (!batadv_bla_handle_local_claim(bat_priv,
+						   dat_entry->mac_addr, vid)) {
+			batadv_dbg(BATADV_DBG_DAT, bat_priv,
+				   "Device %pM claimed by another backbone gw. Don't send ARP reply!",
+				   dat_entry->mac_addr);
+			ret = true;
+			goto out;
+		}
+
 		skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src,
 				     bat_priv->soft_iface, ip_dst, hw_src,
 				     dat_entry->mac_addr, hw_src);
--
1.7.0.4



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
Geschäftsführer / Executive Board: Roland Bent, Dr. Martin Heubeck
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[B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Andreas Pape]

Speeding up dat address lookup is achieved by snooping all incoming ip
traffic. This especially increases the propability in bla setups that
a gateway into a common backbone network already has a fitting dat entry
to answer incoming ARP requests directly coming from the backbone
network thus further reducing ARP traffic in the mesh.

Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/distributed-arp-table.c |   50 ++++++++++++++++++++++++++++++++
 net/batman-adv/distributed-arp-table.h |    9 +++++-
 net/batman-adv/soft-interface.c        |    4 ++
 3 files changed, 62 insertions(+), 1 deletions(-)

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index c11f035..58cb488 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -27,6 +27,7 @@
 #include <linux/if_arp.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
+#include <linux/ip.h>
 #include <linux/in.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
@@ -362,6 +363,55 @@ out:
 		batadv_dat_entry_put(dat_entry);
 }

+/**
+ * batadv_dat_entry_check - check and update a dat entry
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: socket buffer
+ * @vid: VLAN identifier
+ *
+ * snoops incoming socket buffer for dat cache updates, if dat is enabled.
+ * Can be called from other modules.
+ */
+void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			    unsigned short vid)
+{
+	struct vlan_ethhdr *vhdr = NULL, tmp_vhdr;
+	struct ethhdr *ethhdr = NULL;
+	struct iphdr *iphdr = NULL, tmp_iphdr;
+
+	if (!atomic_read(&bat_priv->distributed_arp_table))
+		return;
+
+	ethhdr = eth_hdr(skb);
+
+	switch (ntohs(ethhdr->h_proto)) {
+	case ETH_P_IP:
+		iphdr = skb_header_pointer(skb, ETH_HLEN, sizeof(tmp_iphdr),
+					   &tmp_iphdr);
+		break;
+	case ETH_P_8021Q:
+		vhdr = skb_header_pointer(skb, 0, sizeof(tmp_vhdr),
+					  &tmp_vhdr);
+		if (!vhdr)
+			break;
+		if (ntohs(vhdr->h_vlan_encapsulated_proto) == ETH_P_IP) {
+			iphdr = skb_header_pointer(skb, sizeof(tmp_vhdr),
+						   sizeof(tmp_iphdr),
+						   &tmp_iphdr);
+		}
+		break;
+	}
+
+	if (iphdr) {
+		batadv_dbg(BATADV_DBG_DAT, bat_priv,
+			   "Snooped IP address: %pI4 %pM (vid: %d)\n",
+			   &iphdr->saddr, ethhdr->h_source,
+			   BATADV_PRINT_VID(vid));
+		batadv_dat_entry_add(bat_priv, iphdr->saddr,
+				     ethhdr->h_source, vid);
+	}
+}
+
 #ifdef CONFIG_BATMAN_ADV_DEBUG

 /**
diff --git a/net/batman-adv/distributed-arp-table.h b/net/batman-adv/distributed-arp-table.h
index 813ecea..cf1b93c 100644
--- a/net/batman-adv/distributed-arp-table.h
+++ b/net/batman-adv/distributed-arp-table.h
@@ -80,7 +80,8 @@ batadv_dat_init_own_addr(struct batadv_priv *bat_priv,
 int batadv_dat_init(struct batadv_priv *bat_priv);
 void batadv_dat_free(struct batadv_priv *bat_priv);
 int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset);
-
+void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			    unsigned short vid);
 /**
  * batadv_dat_inc_counter - increment the correct DAT packet counter
  * @bat_priv: the bat priv with all the soft interface information
@@ -173,6 +174,12 @@ static inline void batadv_dat_inc_counter(struct batadv_priv *bat_priv,
 {
 }

+static inline
+void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			    unsigned short vid)
+{
+}
+
 #endif /* CONFIG_BATMAN_ADV_DAT */

 #endif /* _NET_BATMAN_ADV_DISTRIBUTED_ARP_TABLE_H_ */
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 81665b1..1f1742a 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -28,6 +28,7 @@
 #include <linux/fs.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
+#include <linux/ip.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/kref.h>
@@ -442,6 +443,9 @@ void batadv_interface_rx(struct net_device *soft_iface,
 		goto dropped;
 	}

+	/* Snoop incoming traffic for dat update */
+	batadv_dat_entry_check(bat_priv, skb, vid);
+
 	/* skb->dev & skb->pkt_type are set here */
 	skb->protocol = eth_type_trans(skb, soft_iface);

--
1.7.0.4



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
Geschäftsführer / Executive Board: Roland Bent, Dr. Martin Heubeck
___________________________________________________________________
Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren, jegliche anderweitige Verwendung sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.
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[B.A.T.M.A.N.] [PATCHv3 3/6] batman-adv: prevent duplication of ARP replies when DAT is used

[Andreas Pape]

If none of the backbone gateways in a bla setup has already knowledge of
the mac address searched for in an incoming ARP request from the backbone
an address resolution via the DHT of DAT is started. The gateway can send
several ARP requests to different DHT nodes and therefore can get several
replies. This patch assures that not all of the possible ARP replies are
returned to the backbone by checking the local DAT cache of the gateway.
If there is an entry in the local cache the gateway has already learned
the requested address and there is no need to forward the additional reply
to the backbone.
Furthermore it is checked if this gateway has claimed the source of the ARP
reply and only forwards it to the backbone if it has claimed the source or
if there is no claim at all.

Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/distributed-arp-table.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 58cb488..f025c69 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -1239,6 +1239,7 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
 	__be32 ip_src, ip_dst;
 	u8 *hw_src, *hw_dst;
 	bool dropped = false;
+	struct batadv_dat_entry *dat_entry = NULL;
 	unsigned short vid;

 	if (!atomic_read(&bat_priv->distributed_arp_table))
@@ -1258,12 +1259,41 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
 	hw_dst = batadv_arp_hw_dst(skb, hdr_size);
 	ip_dst = batadv_arp_ip_dst(skb, hdr_size);

+	/* If ip_dst is already in cache and has the right mac address,
+	 * drop this frame if this ARP reply is destined for us because it's
+	 * most probably an ARP reply generated by another node of the DHT.
+	 * We have most probably received already a reply earlier. Delivering
+	 * this frame would lead to doubled receive of an ARP reply.
+	 */
+	dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_src, vid);
+	if ((dat_entry) && (batadv_compare_eth(hw_src, dat_entry->mac_addr))) {
+		batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP reply removed: ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; dat_entry: %pM-%pI4\n",
+			   hw_src, &ip_src, hw_dst, &ip_dst,
+			   dat_entry->mac_addr,	&dat_entry->ip);
+		dropped = true;
+		goto out;
+	}
+
 	/* Update our internal cache with both the IP addresses the node got
 	 * within the ARP reply
 	 */
 	batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);
 	batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

+	/* If BLA is enabled, only forward ARP replies if we have claimed the
+	 * source of the ARP reply or if no one else of the same backbone has
+	 * already claimed that client. This prevents that different gateways
+	 * to the same backbone all forward the ARP reply leading to multiple
+	 * replies in the backbone.
+	 */
+	if (!batadv_bla_handle_local_claim(bat_priv, hw_src, vid)) {
+		batadv_dbg(BATADV_DBG_DAT, bat_priv,
+			   "Device %pM claimed by another backbone gw. Drop ARP reply.\n",
+			   hw_src);
+		dropped = true;
+		goto out;
+	}
+
 	/* if this REPLY is directed to a client of mine, let's deliver the
 	 * packet to the interface
 	 */
@@ -1276,6 +1306,8 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
 out:
 	if (dropped)
 		kfree_skb(skb);
+	if (dat_entry)
+		batadv_dat_entry_put(dat_entry);
 	/* if dropped == false -> deliver to the interface */
 	return dropped;
 }
--
1.7.0.4



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
Geschäftsführer / Executive Board: Roland Bent, Dr. Martin Heubeck
___________________________________________________________________
Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren, jegliche anderweitige Verwendung sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.
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[B.A.T.M.A.N.] [PATCHv3 4/6] batman-adv: drop unicast packets from other backbone gw

[Andreas Pape]

Additional dropping of unicast packets received from another backbone gw of
the same backbone network before being forwarded to the same backbone again
is necessary. It was observed in a test setup that in rare cases these
frames lead to looping unicast traffic backbone->mesh->backbone.

Acked-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/routing.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index ae850f2..1ef0735 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -864,9 +864,11 @@ int batadv_recv_unicast_packet(struct sk_buff *skb,
 	int check, hdr_size = sizeof(*unicast_packet);
 	enum batadv_subtype subtype;
 	bool is4addr;
+	struct ethhdr *ethhdr;

 	unicast_packet = (struct batadv_unicast_packet *)skb->data;
 	unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data;
+	ethhdr = eth_hdr(skb);

 	is4addr = unicast_packet->packet_type == BATADV_UNICAST_4ADDR;
 	/* the caller function should have already pulled 2 bytes */
@@ -906,6 +908,20 @@ int batadv_recv_unicast_packet(struct sk_buff *skb,
 			}
 		}

+		/* If this is a unicast packet from another backgone gw,
+		 * drop it.
+		 */
+		orig_addr = ethhdr->h_source;
+		orig_node = batadv_orig_hash_find(bat_priv, orig_addr);
+		if (orig_node &&
+		    batadv_bla_is_backbone_gw(skb, orig_node, hdr_size)) {
+			batadv_dbg(BATADV_DBG_BLA, bat_priv,
+				   "Dropped unicast pkt received from another backbone gw %pM.\n",
+				   orig_addr);
+			batadv_orig_node_put(orig_node);
+			return NET_RX_DROP;
+		}
+
 		if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb,
 							  hdr_size))
 			goto rx_success;
--
1.7.0.4



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
Geschäftsführer / Executive Board: Roland Bent, Dr. Martin Heubeck
___________________________________________________________________
Diese E-Mail enthält vertrauliche und/oder rechtlich geschützte Informationen. Wenn Sie nicht der richtige Adressat sind oder diese E-Mail irrtümlich erhalten haben, informieren Sie bitte sofort den Absender und vernichten Sie diese Mail. Das unerlaubte Kopieren, jegliche anderweitige Verwendung sowie die unbefugte Weitergabe dieser Mail ist nicht gestattet.
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[B.A.T.M.A.N.] [PATCHv3 5/6] batman-adv: changed debug messages for easier bla debugging

[Andreas Pape]

Some of the bla debug messages are extended and additional messages are
added for easier bla debugging. Some debug messages introduced with the
dat changes in prior patches of this patch series have been changed to
be more compliant to other existing debug messages.

Acked-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/bridge_loop_avoidance.c |   18 ++++++++++++++----
 net/batman-adv/routing.c               |    2 +-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 2f46ce9..c426327 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -715,8 +715,8 @@ static void batadv_bla_add_claim(struct batadv_priv *bat_priv,
 			goto claim_free_ref;

 		batadv_dbg(BATADV_DBG_BLA, bat_priv,
-			   "bla_add_claim(): changing ownership for %pM, vid %d\n",
-			   mac, BATADV_PRINT_VID(vid));
+			   "bla_add_claim(): changing ownership for %pM, vid %d to gw %pM\n",
+			   mac, BATADV_PRINT_VID(vid), backbone_gw->orig);

 		spin_lock_bh(&claim->backbone_gw->crc_lock);
 		claim->backbone_gw->crc ^= crc16(0, claim->addr, ETH_ALEN);
@@ -1240,10 +1240,13 @@ static void batadv_bla_purge_claims(struct batadv_priv *bat_priv,
 				continue;

 			batadv_dbg(BATADV_DBG_BLA, bat_priv,
-				   "bla_purge_claims(): %pM, vid %d, time out\n",
+				   "bla_purge_claims(): timed out.\n");
+
+purge_now:
+			batadv_dbg(BATADV_DBG_BLA, bat_priv,
+				   "bla_purge_claims(): %pM, vid %d\n",
 				   claim->addr, claim->vid);

-purge_now:
 			batadv_handle_unclaim(bat_priv, primary_if,
 					      claim->backbone_gw->orig,
 					      claim->addr, claim->vid);
@@ -1787,6 +1790,13 @@ bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		/* possible optimization: race for a claim */
 		/* No claim exists yet, claim it for us!
 		 */
+
+		batadv_dbg(BATADV_DBG_BLA, bat_priv,
+			   "bla_rx(): Unclaimed MAC %pM found. Claim it. Local: %s\n",
+			   ethhdr->h_source,
+			   batadv_is_my_client(bat_priv,
+					       ethhdr->h_source, vid) ?
+			   "yes" : "no");
 		batadv_handle_claim(bat_priv, primary_if,
 				    primary_if->net_dev->dev_addr,
 				    ethhdr->h_source, vid);
diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 1ef0735..99186da 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -916,7 +916,7 @@ int batadv_recv_unicast_packet(struct sk_buff *skb,
 		if (orig_node &&
 		    batadv_bla_is_backbone_gw(skb, orig_node, hdr_size)) {
 			batadv_dbg(BATADV_DBG_BLA, bat_priv,
-				   "Dropped unicast pkt received from another backbone gw %pM.\n",
+				   "recv_unicast_packet(): Dropped unicast pkt received from another backbone gw %pM.\n",
 				   orig_addr);
 			batadv_orig_node_put(orig_node);
 			return NET_RX_DROP;
--
1.7.0.4



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[B.A.T.M.A.N.] [PATCHv3 6/6] batman-adv: handle race condition for claims between gateways

[Andreas Pape]

Consider the following situation which has been found in a test setup:
Gateway B has claimed client C and gateway A has the same backbone
network as B. C sends a broad- or multicast to B and directly after
this packet decides to send another packet to A due to a better TQ
value. B will forward the broad-/multicast into the backbone as it is
the responsible gw and after that A will claim C as it has been
chosen by C as the best gateway. If it now happens that A claims C
before it has received the broad-/multicast forwarded by B (due to
backbone topology or due to some delay in B when forwarding the
packet) we get a critical situation: in the current code A will
immediately unclaim C when receiving the multicast due to the
roaming client scenario although the position of C has not changed
in the mesh. If this happens the multi-/broadcast forwarded by B
will be sent back into the mesh by A and we have looping packets
until one of the gateways claims C again.
In order to prevent this, unclaiming of a client due to the roaming
client scenario is only done after a certain time is expired after
the last claim of the client. 100 ms are used here, which should be
slow enough for big backbones and slow gateways but fast enough not
to break the roaming client use case.

Acked-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/bridge_loop_avoidance.c |   20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index c426327..0790cbc 100644
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -1904,10 +1904,22 @@ bool batadv_bla_tx(struct batadv_priv *bat_priv, struct sk_buff *skb,
 		/* if yes, the client has roamed and we have
 		 * to unclaim it.
 		 */
-		batadv_handle_unclaim(bat_priv, primary_if,
-				      primary_if->net_dev->dev_addr,
-				      ethhdr->h_source, vid);
-		goto allow;
+		if (batadv_has_timed_out(claim->lasttime, 100)) {
+			/* only unclaim if the last claim entry is
+			 * older than 100 ms to make sure we really
+			 * have a roaming client here.
+			 */
+			batadv_dbg(BATADV_DBG_BLA, bat_priv, "bla_tx(): Roaming client %pM detected. Unclaim it.\n",
+				   ethhdr->h_source);
+			batadv_handle_unclaim(bat_priv, primary_if,
+					      primary_if->net_dev->dev_addr,
+					      ethhdr->h_source, vid);
+			goto allow;
+		} else {
+			batadv_dbg(BATADV_DBG_BLA, bat_priv, "bla_tx(): Race for claim %pM detected. Drop packet.\n",
+				   ethhdr->h_source);
+			goto handled;
+		}
 	}

 	/* check if it is a multicast/broadcast frame */
--
1.7.0.4



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

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Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Sven Eckelmann]

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On Friday 06 May 2016 10:58:23 Andreas Pape wrote:
> diff --git a/net/batman-adv/soft-interface.c
> b/net/batman-adv/soft-interface.c index 81665b1..1f1742a 100644
> --- a/net/batman-adv/soft-interface.c
> +++ b/net/batman-adv/soft-interface.c
> @@ -28,6 +28,7 @@
>  #include <linux/fs.h>
>  #include <linux/if_ether.h>
>  #include <linux/if_vlan.h>
> +#include <linux/ip.h>
>  #include <linux/jiffies.h>
>  #include <linux/kernel.h>
>  #include <linux/kref.h>

Haven't really looked at your patchset but was just interested in this new 
function. But I didn't came to look at it because I saw this weird include. 
Doesn't seem to make sense here at all when you look at the rest of the 
changes in this file:

> @@ -442,6 +443,9 @@ void batadv_interface_rx(struct net_device *soft_iface,
>  		goto dropped;
>  	}
> 
> +	/* Snoop incoming traffic for dat update */
> +	batadv_dat_entry_check(bat_priv, skb, vid);
> +
>  	/* skb->dev & skb->pkt_type are set here */
>  	skb->protocol = eth_type_trans(skb, soft_iface);

Kind regards,
	Sven

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Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Sven Eckelmann]

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Hi,

just some ideas (maybe not all of them are good):

[...]
> +       ethhdr = eth_hdr(skb);
> +
> +       switch (ntohs(ethhdr->h_proto)) {
> +       case ETH_P_IP:
> +               iphdr = skb_header_pointer(skb, ETH_HLEN, sizeof(tmp_iphdr),
> +                                          &tmp_iphdr);
> +               break;
> +       case ETH_P_8021Q:
> +               vhdr = skb_header_pointer(skb, 0, sizeof(tmp_vhdr),
> +                                         &tmp_vhdr);
> +               if (!vhdr)
> +                       break;

Do we need to continue here when there is no vhdr? Maybe just return.

> +               if (ntohs(vhdr->h_vlan_encapsulated_proto) == ETH_P_IP) {

Maybe the check here could be inverted to just return when this is not ETH_P_IP

> +                       iphdr = skb_header_pointer(skb, sizeof(tmp_vhdr),
> +                                                  sizeof(tmp_iphdr),
> +                                                  &tmp_iphdr);
> +               }
> +               break;
> +       }
> +
> +       if (iphdr) {

You could just modify the check to:

if (!iphdr)
	return;

Kind regards,
	Sven

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Re: [B.A.T.M.A.N.] [PATCHv3 4/6] batman-adv: drop unicast packets from other backbone gw

[Sven Eckelmann]

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On Friday 06 May 2016 10:58:25 Andreas Pape wrote:
[...]
> +		/* If this is a unicast packet from another backgone gw,
> +		 * drop it.
> +		 */
> +		orig_addr = ethhdr->h_source;
> +		orig_node = batadv_orig_hash_find(bat_priv, orig_addr);

I think we already told this before: This is overwriting the previous
orig_node without freeing the reference. It most likely has also other weird
consequences. Here is the relevant code to better understand what it
overwrites:

		if (is4addr) {
			subtype = unicast_4addr_packet->subtype;
			batadv_dat_inc_counter(bat_priv, subtype);

			/* Only payload data should be considered for speedy
			 * join. For example, DAT also uses unicast 4addr
			 * types, but those packets should not be considered
			 * for speedy join, since the clients do not actually
			 * reside at the sending originator.
			 */
			if (subtype == BATADV_P_DATA) {
				orig_addr = unicast_4addr_packet->src;
				orig_node = batadv_orig_hash_find(bat_priv,
								  orig_addr);
			}
		}

		/* If this is a unicast packet from another backgone gw,
		 * drop it.
		 */
		orig_addr = ethhdr->h_source;
		orig_node = batadv_orig_hash_find(bat_priv, orig_addr);
		if (orig_node &&
		    batadv_bla_is_backbone_gw(skb, orig_node, hdr_size)) {
			batadv_dbg(BATADV_DBG_BLA, bat_priv,
				   "recv_unicast_packet(): Dropped unicast pkt received from another backbone gw %pM.\n",
				   orig_addr);
			batadv_orig_node_put(orig_node);
			return NET_RX_DROP;
		}

Kind regards,
	Sven

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Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
> Speeding up dat address lookup is achieved by snooping all incoming ip
> traffic. This especially increases the propability in bla setups that
> a gateway into a common backbone network already has a fitting dat entry
> to answer incoming ARP requests directly coming from the backbone
> network thus further reducing ARP traffic in the mesh.
> 
> Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
> ---

This patch looks interesting :). Currently we have quite some
ARP-requests from gateways to clients left in Freifunk setups (had
been asking Antonio about it just yesterday) and looks like this
patch could help here.

> +void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
> +			    unsigned short vid)
> +{
[...]
> +		batadv_dat_entry_add(bat_priv, iphdr->saddr,
> +				     ethhdr->h_source, vid);
> +	}
> +}

There is something in batadv_dat_entry_add() that makes me a
little worried:

----
	if (dat_entry) {
		if (!batadv_compare_eth(dat_entry->mac_addr,
					mac_addr))
			ether_addr_copy(dat_entry->mac_addr, mac_addr);
----

ether_addr_copy() isn't atomic, there is a race condition between
the update and any such check - like the one just above it.

This isn't really a bug of your patchset, but could make this race
condition much more likely. In the worst case, a fast IP packet
stream would create a constant rewrite and mostly broken
dat_entry->mac_addr.

Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
> +void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
> +			    unsigned short vid)
> +{
[...]
> +	if (iphdr) {
> +		batadv_dbg(BATADV_DBG_DAT, bat_priv,
> +			   "Snooped IP address: %pI4 %pM (vid: %d)\n",
> +			   &iphdr->saddr, ethhdr->h_source,
> +			   BATADV_PRINT_VID(vid));
> +		batadv_dat_entry_add(bat_priv, iphdr->saddr,
> +				     ethhdr->h_source, vid);
> +	}

Not sure whether it is necessary, or whether there is a check
somewhere later within DAT. But should we exclude some
iphdr->saddr or ethhdr->h_source addresses? For instance a
DHCPDISCOVER usually has a zero-ip address.

Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

> Not sure whether it is necessary, or whether there is a check
> somewhere later within DAT. But should we exclude some
> iphdr->saddr or ethhdr->h_source addresses? For instance a
> DHCPDISCOVER usually has a zero-ip address.

And speaking of DHCP, do you (or anyone else) know, whether a
dhcp-server (or its kernel) sends an ARP request before sending
a unicast DHCPOFFER? Or do dhcp-servers usually craft DHCPOFFERs
in userspace within their daemon including the ethernet header?

If the latter is the case, maybe we could/should dat-snoop the
ethernet+IP destination of such DHCPOFFERs in interface_rx(),
too?

Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

On Thu, May 19, 2016 at 09:33:12PM +0200, Linus Lüssing wrote:
> This isn't really a bug of your patchset, but could make this race
> condition much more likely. In the worst case, a fast IP packet
> stream would create a constant rewrite and mostly broken
> dat_entry->mac_addr.

Sorry, this was wrong of me. Assuming no address collision, then
this would result to up to one unnecessary ether_addr_copy() on
32bit but no broken dat_entry->mac_addr.

So shouldn't be an issue, sorry.

Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

On Thu, May 19, 2016 at 10:30:49PM +0200, Linus Lüssing wrote:
> > Not sure whether it is necessary, or whether there is a check
> > somewhere later within DAT. But should we exclude some
> > iphdr->saddr or ethhdr->h_source addresses? For instance a
> > DHCPDISCOVER usually has a zero-ip address.
> 
> And speaking of DHCP, do you (or anyone else) know, whether a
> dhcp-server (or its kernel) sends an ARP request before sending
> a unicast DHCPOFFER? Or do dhcp-servers usually craft DHCPOFFERs
> in userspace within their daemon including the ethernet header?
> 
> If the latter is the case, maybe we could/should dat-snoop the
> ethernet+IP destination of such DHCPOFFERs in interface_rx(),
> too?

Did a quick try in VMs with two standard Debian unstable machines
using isc-dhcp-client and -server. Also enabled "ping-check false"
on the dhcp-server.

Then I do not see any ARP messages, I just see four DHCP packets (see
below). And "ip neigh" stays empty.

So it seems that at least the isc-dhcp-server can assemble raw
packets, including the ethernet frame (*).


So the DHCPOFFER's ethernet and IP destinations on a
batadv_interface_tx() (sorry, wrongly wrote _rx() above) would
give us an even earlier opportunity to feed DAT from.

Would that make sense to do so?



(*): Though looking at the code of isc-dhcpd, there seem to be
compile-time options for two more, different send_packet() functions
which do not always do that.


-----

tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
22:32:03.379281 02:04:64:a4:39:e2 (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 342: (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
    0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 02:04:64:a4:39:e2 (oui Unknown), length 300, xid 0x17feeb29, Flags [none]
          Client-Ethernet-Address 02:04:64:a4:39:e2 (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Discover
            Hostname Option 12, length 12: "Linus-Debian"
            Parameter-Request Option 55, length 13:
              Subnet-Mask, BR, Time-Zone, Default-Gateway
              Domain-Name, Domain-Name-Server, Option 119, Hostname
              Netbios-Name-Server, Netbios-Scope, MTU, Classless-Static-Route
              NTP
22:32:03.385454 02:04:64:a4:39:c3 (oui Unknown) > 02:04:64:a4:39:e2 (oui Unknown), ethertype IPv4 (0x0800), length 342: (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
    192.168.123.1.bootps > 192.168.123.50.bootpc: BOOTP/DHCP, Reply, length 300, xid 0x17feeb29, Flags [none]
          Your-IP 192.168.123.50
          Client-Ethernet-Address 02:04:64:a4:39:e2 (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Offer
            Server-ID Option 54, length 4: 192.168.123.1
            Lease-Time Option 51, length 4: 600
            Subnet-Mask Option 1, length 4: 255.255.255.0
            Default-Gateway Option 3, length 4: 192.168.123.1
            Domain-Name-Server Option 6, length 4: 192.168.123.1
22:32:03.386571 02:04:64:a4:39:e2 (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 342: (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
    0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 02:04:64:a4:39:e2 (oui Unknown), length 300, xid 0x17feeb29, Flags [none]
          Client-Ethernet-Address 02:04:64:a4:39:e2 (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: Request
            Server-ID Option 54, length 4: 192.168.123.1
            Requested-IP Option 50, length 4: 192.168.123.50
            Hostname Option 12, length 12: "Linus-Debian"
            Parameter-Request Option 55, length 13:
              Subnet-Mask, BR, Time-Zone, Default-Gateway
              Domain-Name, Domain-Name-Server, Option 119, Hostname
              Netbios-Name-Server, Netbios-Scope, MTU, Classless-Static-Route
              NTP
22:32:03.398683 02:04:64:a4:39:c3 (oui Unknown) > 02:04:64:a4:39:e2 (oui Unknown), ethertype IPv4 (0x0800), length 342: (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)
    192.168.123.1.bootps > 192.168.123.50.bootpc: BOOTP/DHCP, Reply, length 300, xid 0x17feeb29, Flags [none]
          Your-IP 192.168.123.50
          Client-Ethernet-Address 02:04:64:a4:39:e2 (oui Unknown)
          Vendor-rfc1048 Extensions
            Magic Cookie 0x63825363
            DHCP-Message Option 53, length 1: ACK
            Server-ID Option 54, length 4: 192.168.123.1
            Lease-Time Option 51, length 4: 600
            Subnet-Mask Option 1, length 4: 255.255.255.0
            Default-Gateway Option 3, length 4: 192.168.123.1
            Domain-Name-Server Option 6, length 4: 192.168.123.1
-----

Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

On Thu, May 19, 2016 at 10:30:49PM +0200, Linus Lüssing wrote:
> Or do dhcp-servers usually craft DHCPOFFERs
> in userspace within their daemon including the ethernet header?

Just noticed, they have to. The dhcp-server has to fill in the
ethernet destination as the kernel cannot provide it via ARP yet
- because the dhcp-client has no IP address yet :).

[B.A.T.M.A.N.] Antwort: Re: [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Andreas Pape]

"B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org> schrieb am
19.05.2016 21:45:53:

> Von: Linus Lüssing <linus.luessing@c0d3.blue>
> An: The list for a Better Approach To Mobile Ad-hoc Networking
> <b.a.t.m.a.n@lists.open-mesh.org>
> Datum: 19.05.2016 21:47
> Betreff: Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat
> by snooping received ip traffic
> Gesendet von: "B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org>
>
> On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
> > +void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct
> sk_buff *skb,
> > +             unsigned short vid)
> > +{
> [...]
> > +   if (iphdr) {
> > +      batadv_dbg(BATADV_DBG_DAT, bat_priv,
> > +            "Snooped IP address: %pI4 %pM (vid: %d)\n",
> > +            &iphdr->saddr, ethhdr->h_source,
> > +            BATADV_PRINT_VID(vid));
> > +      batadv_dat_entry_add(bat_priv, iphdr->saddr,
> > +                 ethhdr->h_source, vid);
> > +   }
>
> Not sure whether it is necessary, or whether there is a check
> somewhere later within DAT. But should we exclude some
> iphdr->saddr or ethhdr->h_source addresses? For instance a
> DHCPDISCOVER usually has a zero-ip address.

I think you have a good point here. Excluding especially
ip addresses like zero-ip address seems reasonable. Although
I think that this isn't a problem as long as no one is sending
arp requests for such ip addresses, filling the dat table with
unreasonable entries isn't a smart idea either. I will add some
additional tests here for reasonable ip addresses for the next
version of the patchset.

Thanks and regards,
Andreas



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
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Re: [B.A.T.M.A.N.] Antwort: Re: [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Antonio Quartulli]

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On Fri, May 20, 2016 at 01:32:35PM +0200, Andreas Pape wrote:
> "B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org> schrieb am
> 19.05.2016 21:45:53:
> 
> > Von: Linus Lüssing <linus.luessing@c0d3.blue>
> > An: The list for a Better Approach To Mobile Ad-hoc Networking
> > <b.a.t.m.a.n@lists.open-mesh.org>
> > Datum: 19.05.2016 21:47
> > Betreff: Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat
> > by snooping received ip traffic
> > Gesendet von: "B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org>
> >
> > On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
> > > +void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct
> > sk_buff *skb,
> > > +             unsigned short vid)
> > > +{
> > [...]
> > > +   if (iphdr) {
> > > +      batadv_dbg(BATADV_DBG_DAT, bat_priv,
> > > +            "Snooped IP address: %pI4 %pM (vid: %d)\n",
> > > +            &iphdr->saddr, ethhdr->h_source,
> > > +            BATADV_PRINT_VID(vid));
> > > +      batadv_dat_entry_add(bat_priv, iphdr->saddr,
> > > +                 ethhdr->h_source, vid);
> > > +   }
> >
> > Not sure whether it is necessary, or whether there is a check
> > somewhere later within DAT. But should we exclude some
> > iphdr->saddr or ethhdr->h_source addresses? For instance a
> > DHCPDISCOVER usually has a zero-ip address.
> 
> I think you have a good point here. Excluding especially
> ip addresses like zero-ip address seems reasonable. Although
> I think that this isn't a problem as long as no one is sending
> arp requests for such ip addresses, filling the dat table with
> unreasonable entries isn't a smart idea either. I will add some
> additional tests here for reasonable ip addresses for the next
> version of the patchset.

We already have some checks in the snooping functions that are performed when
calling batadv_arp_get_type(). Aren't those enough ?

Cheers,


-- 
Antonio Quartulli

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Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Antonio Quartulli]

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On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
> Speeding up dat address lookup is achieved by snooping all incoming ip
> traffic. This especially increases the propability in bla setups that
> a gateway into a common backbone network already has a fitting dat entry
> to answer incoming ARP requests directly coming from the backbone
> network thus further reducing ARP traffic in the mesh.

Any IP packet can't be sent if an ARP "handshake" has not been performed. This
means that when you are snooping an IP packet you have already snooped an ARP
packet slightly before. In which case do we really win something ?

On top of that, don't you think that snooping *every* packet will badly affect
the performance ? Have you tried measuring the difference ?


Cheers,

-- 
Antonio Quartulli

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Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Andreas Pape]

"B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org> schrieb am
20.05.2016 15:51:38:

> Von: Antonio Quartulli <a@unstable.cc>
> An: The list for a Better Approach To Mobile Ad-hoc Networking
> <b.a.t.m.a.n@lists.open-mesh.org>
> Datum: 20.05.2016 15:52
> Betreff: Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat
> by snooping received ip traffic
> Gesendet von: "B.A.T.M.A.N" <b.a.t.m.a.n-bounces@lists.open-mesh.org>
>
> On Fri, May 06, 2016 at 10:58:23AM +0200, Andreas Pape wrote:
> > Speeding up dat address lookup is achieved by snooping all incoming ip
> > traffic. This especially increases the propability in bla setups that
> > a gateway into a common backbone network already has a fitting dat
entry
> > to answer incoming ARP requests directly coming from the backbone
> > network thus further reducing ARP traffic in the mesh.
>
> Any IP packet can't be sent if an ARP "handshake" has not been
performed. This
> means that when you are snooping an IP packet you have already snooped
an ARP
> packet slightly before. In which case do we really win something ?
>
In case of a static mesh ("static" in terms of non-moving mesh nodes and
when the mesh nodes almost always use the same backbone gateways for a
common
wired backbone) we gain nothing by snooping every packet.
The idea came up when I started experimenting with more dynamic setups
where the mesh nodes move around with several gateways into a common
wired backbone. In this case routing becomes more dynamically and it is
not assured that the traffic from/for a mesh node is always routed via
the same gateway which has already snooped the arp traffic.

> On top of that, don't you think that snooping *every* packet will badly
affect
> the performance ? Have you tried measuring the difference ?
>
I'm aware that this has an impact. I can try to measure the difference
using
my devices but these results of course are related to the hardware I use.
I'm lacking experience if such results can be used to generalize a
conclusion.

On the other hand this "feature" was not the root cause to post this
patchset. More important for me is the prevention of the "arp reply
storms" and the temporary loops between backbone network and the mesh
because this generates trouble in my application.
If it increases the propability for acceptance I don't care to remove
the ip source address snooping from the patchset.

Best regards,
Andreas




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Re: [B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Linus Lüssing]

Hi,

On IRC, Matthias just pointed out another, conceptual issue with
this patch:

It snoops routed traffic, too. So we would end up with DAT entries
for every internet host as well :(.

Regards, Linus