batman-adv: bcast: queue per interface, if needed

Currently we schedule a broadcast packet like:

3x: [ [(re-)queue] --> for(hard-if): maybe-transmit ]

The intention of queueing a broadcast packet multiple times is to
increase robustness for wireless interfaces. However on interfaces
which we only broadcast on once the queueing induces an unnecessary
penalty. This patch restructures the queueing to be performed on a per
interface basis:

for(hard-if):
- transmit
- if wireless: [queue] --> transmit --> [requeue] --> transmit

Next to the performance benefits on non-wireless interfaces this
should also make it easier to apply alternative strategies for
transmissions on wireless interfaces in the future (for instance sending
via unicast transmissions on wireless interfaces, without queueing in
batman-adv, if appropriate).
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

net/batman-adv/main.h

@@ -88,7 +88,6 @@
 /* number of packets to send for broadcasts on different interface types */
 #define BATADV_NUM_BCASTS_DEFAULT 1
 #define BATADV_NUM_BCASTS_WIRELESS 3
-#define BATADV_NUM_BCASTS_MAX 3
 
 /* length of the single packet used by the TP meter */
 #define BATADV_TP_PACKET_LEN ETH_DATA_LEN

net/batman-adv/routing.c

@@ -1182,9 +1182,9 @@ int batadv_recv_bcast_packet(struct sk_buff *skb,
 	struct batadv_bcast_packet *bcast_packet;
 	struct ethhdr *ethhdr;
 	int hdr_size = sizeof(*bcast_packet);
-	int ret = NET_RX_DROP;
 	s32 seq_diff;
 	u32 seqno;
+	int ret;
 
 	/* drop packet if it has not necessary minimum size */
 	if (unlikely(!pskb_may_pull(skb, hdr_size)))
@@ -1210,7 +1210,7 @@ int batadv_recv_bcast_packet(struct sk_buff *skb,
 	if (batadv_is_my_mac(bat_priv, bcast_packet->orig))
 		goto free_skb;
 
-	if (bcast_packet->ttl < 2)
+	if (bcast_packet->ttl-- < 2)
 		goto free_skb;
 
 	orig_node = batadv_orig_hash_find(bat_priv, bcast_packet->orig);
@@ -1249,7 +1249,9 @@ int batadv_recv_bcast_packet(struct sk_buff *skb,
 	batadv_skb_set_priority(skb, sizeof(struct batadv_bcast_packet));
 
 	/* rebroadcast packet */
-	batadv_add_bcast_packet_to_list(bat_priv, skb, 1, false);
+	ret = batadv_forw_bcast_packet(bat_priv, skb, 0, false);
+	if (ret == NETDEV_TX_BUSY)
+		goto free_skb;
 
 	/* don't hand the broadcast up if it is from an originator
 	 * from the same backbone.
@@ -1275,6 +1277,7 @@ int batadv_recv_bcast_packet(struct sk_buff *skb,
 	spin_unlock_bh(&orig_node->bcast_seqno_lock);
 free_skb:
 	kfree_skb(skb);
+	ret = NET_RX_DROP;
 out:
 	if (orig_node)
 		batadv_orig_node_put(orig_node);

net/batman-adv/send.h

@@ -39,10 +39,14 @@ int batadv_send_broadcast_skb(struct sk_buff *skb,
 			      struct batadv_hard_iface *hard_iface);
 int batadv_send_unicast_skb(struct sk_buff *skb,
 			    struct batadv_neigh_node *neigh_node);
-int batadv_add_bcast_packet_to_list(struct batadv_priv *bat_priv,
-				    const struct sk_buff *skb,
-				    unsigned long delay,
-				    bool own_packet);
+int batadv_forw_bcast_packet(struct batadv_priv *bat_priv,
+			     struct sk_buff *skb,
+			     unsigned long delay,
+			     bool own_packet);
+void batadv_send_bcast_packet(struct batadv_priv *bat_priv,
+			      struct sk_buff *skb,
+			      unsigned long delay,
+			      bool own_packet);
 void
 batadv_purge_outstanding_packets(struct batadv_priv *bat_priv,
 				 const struct batadv_hard_iface *hard_iface);

net/batman-adv/soft-interface.c

@@ -191,7 +191,7 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 	struct vlan_ethhdr *vhdr;
 	unsigned int header_len = 0;
 	int data_len = skb->len, ret;
-	unsigned long brd_delay = 1;
+	unsigned long brd_delay = 0;
 	bool do_bcast = false, client_added;
 	unsigned short vid;
 	u32 seqno;
@@ -330,7 +330,7 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 
 		bcast_packet = (struct batadv_bcast_packet *)skb->data;
 		bcast_packet->version = BATADV_COMPAT_VERSION;
-		bcast_packet->ttl = BATADV_TTL;
+		bcast_packet->ttl = BATADV_TTL - 1;
 
 		/* batman packet type: broadcast */
 		bcast_packet->packet_type = BATADV_BCAST;
@@ -346,13 +346,7 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb,
 		seqno = atomic_inc_return(&bat_priv->bcast_seqno);
 		bcast_packet->seqno = htonl(seqno);
 
-		batadv_add_bcast_packet_to_list(bat_priv, skb, brd_delay, true);
-
-		/* a copy is stored in the bcast list, therefore removing
-		 * the original skb.
-		 */
-		consume_skb(skb);
-
+		batadv_send_bcast_packet(bat_priv, skb, brd_delay, true);
 	/* unicast packet */
 	} else {
 		/* DHCP packets going to a server will use the GW feature */