Staging: batman-adv: receive packets directly using skbs

This patch removes the (ugly and racy) packet receiving thread and the
kernel socket usage. Instead, packets are received directly by registering
the ethernet type and handling skbs instead of self-allocated buffers.

Some consequences and comments:

 * we don't copy the payload data when forwarding/sending/receiving data
   anymore. This should boost performance.
 * packets from/to different interfaces can be (theoretically) processed
   simultaneously. Only the big originator hash lock might be in the way.
 * no more polling or sleeping/wakeup/scheduling issues when receiving
   packets
 * this might introduce new race conditions.
 * aggregation and vis code still use packet buffers and are not (yet)
   converted.
 * all spinlocks were converted to irqsave/restore versions to solve
   some lifelock issues when preempted. This might be overkill, some
   of these locks might be reverted later.
 * skb copies are only done if neccesary to avoid overhead

performance differences:

 * we made some "benchmarks" with intel laptops.
 * bandwidth on Gigabit Ethernet increased from ~500 MBit/s to ~920 MBit/s
 * ping latency decresed from ~2ms to ~0.2 ms

I did some tests on my 9 node qemu environment and could confirm that
usual sending/receiving, forwarding, vis, batctl ping etc works.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Acked-by: Sven Eckelmann <sven.eckelmann@gmx.de>
Acked-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 60 insertions, 33 deletions

diff --git a/drivers/staging/batman-adv/send.c b/drivers/staging/batman-adv/send.c
index 49b1534..fd48f3f 100644
--- a/drivers/staging/batman-adv/send.c
+++ b/drivers/staging/batman-adv/send.c
@@ -23,6 +23,7 @@
 #include "send.h"
 #include "routing.h"
 #include "translation-table.h"
+#include "soft-interface.h"
 #include "hard-interface.h"
 #include "types.h"
 #include "vis.h"
@@ -58,51 +59,69 @@ static unsigned long forward_send_time(void)
 	return send_time;
 }
 
-/* sends a raw packet. */
-void send_raw_packet(unsigned char *pack_buff, int pack_buff_len,
-		     struct batman_if *batman_if, uint8_t *dst_addr)
+/* send out an already prepared packet to the given address via the
+ * specified batman interface */
+int send_skb_packet(struct sk_buff *skb,
+				struct batman_if *batman_if,
+				uint8_t *dst_addr)
 {
 	struct ethhdr *ethhdr;
-	struct sk_buff *skb;
-	int retval;
-	char *data;
 
 	if (batman_if->if_active != IF_ACTIVE)
-		return;
+		goto send_skb_err;
+
+	if (unlikely(!batman_if->net_dev))
+		goto send_skb_err;
 
 	if (!(batman_if->net_dev->flags & IFF_UP)) {
 		printk(KERN_WARNING
 		       "batman-adv:Interface %s is not up - can't send packet via that interface!\n",
 		       batman_if->dev);
-		return;
+		goto send_skb_err;
 	}
 
-	skb = dev_alloc_skb(pack_buff_len + sizeof(struct ethhdr));
-	if (!skb)
-		return;
-	data = skb_put(skb, pack_buff_len + sizeof(struct ethhdr));
+	/* push to the ethernet header. */
+	if (my_skb_push(skb, sizeof(struct ethhdr)) < 0)
+		goto send_skb_err;
 
-	memcpy(data + sizeof(struct ethhdr), pack_buff, pack_buff_len);
+	skb_reset_mac_header(skb);
 
-	ethhdr = (struct ethhdr *) data;
+	ethhdr = (struct ethhdr *) skb_mac_header(skb);
 	memcpy(ethhdr->h_source, batman_if->net_dev->dev_addr, ETH_ALEN);
 	memcpy(ethhdr->h_dest, dst_addr, ETH_ALEN);
 	ethhdr->h_proto = __constant_htons(ETH_P_BATMAN);
 
-	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, ETH_HLEN);
 	skb->priority = TC_PRIO_CONTROL;
 	skb->protocol = __constant_htons(ETH_P_BATMAN);
+
 	skb->dev = batman_if->net_dev;
 
 	/* dev_queue_xmit() returns a negative result on error.	 However on
 	 * congestion and traffic shaping, it drops and returns NET_XMIT_DROP
 	 * (which is > 0). This will not be treated as an error. */
-	retval = dev_queue_xmit(skb);
-	if (retval < 0)
-		printk(KERN_WARNING
-		       "batman-adv:Can't write to raw socket: %i\n",
-		       retval);
+
+	return dev_queue_xmit(skb);
+send_skb_err:
+	kfree_skb(skb);
+	return NET_XMIT_DROP;
+}
+
+/* sends a raw packet. */
+void send_raw_packet(unsigned char *pack_buff, int pack_buff_len,
+		     struct batman_if *batman_if, uint8_t *dst_addr)
+{
+	struct sk_buff *skb;
+	char *data;
+
+	skb = dev_alloc_skb(pack_buff_len + sizeof(struct ethhdr));
+	if (!skb)
+		return;
+	data = skb_put(skb, pack_buff_len + sizeof(struct ethhdr));
+	memcpy(data + sizeof(struct ethhdr), pack_buff, pack_buff_len);
+	/* pull back to the batman "network header" */
+	skb_pull(skb, sizeof(struct ethhdr));
+	send_skb_packet(skb, batman_if, dst_addr);
 }
 
 /* Send a packet to a given interface */
@@ -331,6 +350,8 @@ void schedule_forward_packet(struct orig_node *orig_node,
 
 static void forw_packet_free(struct forw_packet *forw_packet)
 {
+	if (forw_packet->skb)
+		kfree_skb(forw_packet->skb);
 	kfree(forw_packet->packet_buff);
 	kfree(forw_packet);
 }
@@ -353,7 +374,7 @@ static void _add_bcast_packet_to_list(struct forw_packet *forw_packet,
 			   send_time);
 }
 
-void add_bcast_packet_to_list(unsigned char *packet_buff, int packet_len)
+void add_bcast_packet_to_list(struct sk_buff *skb)
 {
 	struct forw_packet *forw_packet;
 
@@ -361,14 +382,16 @@ void add_bcast_packet_to_list(unsigned char *packet_buff, int packet_len)
 	if (!forw_packet)
 		return;
 
-	forw_packet->packet_buff = kmalloc(packet_len, GFP_ATOMIC);
-	if (!forw_packet->packet_buff) {
+	skb = skb_copy(skb, GFP_ATOMIC);
+	if (!skb) {
 		kfree(forw_packet);
 		return;
 	}
 
-	forw_packet->packet_len = packet_len;
-	memcpy(forw_packet->packet_buff, packet_buff, forw_packet->packet_len);
+	skb_reset_mac_header(skb);
+
+	forw_packet->skb = skb;
+	forw_packet->packet_buff = NULL;
 
 	/* how often did we send the bcast packet ? */
 	forw_packet->num_packets = 0;
@@ -384,6 +407,7 @@ void send_outstanding_bcast_packet(struct work_struct *work)
 	struct forw_packet *forw_packet =
 		container_of(delayed_work, struct forw_packet, delayed_work);
 	unsigned long flags;
+	struct sk_buff *skb1;
 
 	spin_lock_irqsave(&forw_bcast_list_lock, flags);
 	hlist_del(&forw_packet->list);
@@ -392,8 +416,10 @@ void send_outstanding_bcast_packet(struct work_struct *work)
 	/* rebroadcast packet */
 	rcu_read_lock();
 	list_for_each_entry_rcu(batman_if, &if_list, list) {
-		send_raw_packet(forw_packet->packet_buff,
-				forw_packet->packet_len,
+		/* send a copy of the saved skb */
+		skb1 = skb_copy(forw_packet->skb, GFP_ATOMIC);
+		if (skb1)
+			send_skb_packet(skb1,
 				batman_if, broadcastAddr);
 	}
 	rcu_read_unlock();
@@ -415,10 +441,11 @@ void send_outstanding_bat_packet(struct work_struct *work)
 		container_of(work, struct delayed_work, work);
 	struct forw_packet *forw_packet =
 		container_of(delayed_work, struct forw_packet, delayed_work);
+	unsigned long flags;
 
-	spin_lock(&forw_bat_list_lock);
+	spin_lock_irqsave(&forw_bat_list_lock, flags);
 	hlist_del(&forw_packet->list);
-	spin_unlock(&forw_bat_list_lock);
+	spin_unlock_irqrestore(&forw_bat_list_lock, flags);
 
 	send_packet(forw_packet);
 
@@ -459,18 +486,18 @@ void purge_outstanding_packets(void)
 	spin_unlock_irqrestore(&forw_bcast_list_lock, flags);
 
 	/* free batman packet list */
-	spin_lock(&forw_bat_list_lock);
+	spin_lock_irqsave(&forw_bat_list_lock, flags);
 	hlist_for_each_entry_safe(forw_packet, tmp_node, safe_tmp_node,
 				  &forw_bat_list, list) {
 
-		spin_unlock(&forw_bat_list_lock);
+		spin_unlock_irqrestore(&forw_bat_list_lock, flags);
 
 		/**
 		 * send_outstanding_bat_packet() will lock the list to
 		 * delete the item from the list
 		 */
 		cancel_delayed_work_sync(&forw_packet->delayed_work);
-		spin_lock(&forw_bat_list_lock);
+		spin_lock_irqsave(&forw_bat_list_lock, flags);
 	}
-	spin_unlock(&forw_bat_list_lock);
+	spin_unlock_irqrestore(&forw_bat_list_lock, flags);
 }