build_patches: reintroduce updated l2tp stats patch

Like in the earlier patch, this suppresses the integer overflow
warning for l2tp on 32 bit systems. However, like before, the
underlying counter variable is still a 32-bit integer, so the
traffic counters will just restart at zero after reaching
2^32 bytes = 4 GiB.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Tested-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Reviewed-by: Tobias Klaus <tk+ff@meskal.net>
Reviewed-by: Dominik Heidler <dominik@heidler.eu>

build_patches/openwrt/0004-ar71xx-4.4-l2tp-stats.patch

@@ -0,0 +1,41 @@
+--- target/linux/ar71xx/patches-4.4/fix-l2tp-stats-counter-overflow-on-32-bit-systems.patch	1970-01-01 01:00:00.000000000 +0100
++++ target/linux/ar71xx/patches-4.4/fix-l2tp-stats-counter-overflow-on-32-bit-systems.patch	2016-03-12 18:41:32.818602442 +0100
+@@ -0,0 +1,38 @@
++From 19b1c8733b99f13005f2d8918bce588f0b2556f8 Mon Sep 17 00:00:00 2001
++From: Dominik Heidler <dominik@heidler.eu>
++Date: Sat, 12 Mar 2016 18:37:42 +0100
++Subject: [PATCH] Fix l2tp stats couter on 32 Bit Systems
++
++---
++ net/l2tp/l2tp_eth.c | 9 +++++++++
++ 1 file changed, 9 insertions(+)
++
++diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
++index e253c26..a18c2ff 100644
++--- a/net/l2tp/l2tp_eth.c
+++++ b/net/l2tp/l2tp_eth.c
++@@ -111,12 +111,21 @@ static struct rtnl_link_stats64 *l2tp_eth_get_stats64(struct net_device *dev,
++ {
++ 	struct l2tp_eth *priv = netdev_priv(dev);
++ 
+++	#if BITS_PER_LONG == 64
++ 	stats->tx_bytes   = atomic_long_read(&priv->tx_bytes);
++ 	stats->tx_packets = atomic_long_read(&priv->tx_packets);
++ 	stats->tx_dropped = atomic_long_read(&priv->tx_dropped);
++ 	stats->rx_bytes   = atomic_long_read(&priv->rx_bytes);
++ 	stats->rx_packets = atomic_long_read(&priv->rx_packets);
++ 	stats->rx_errors  = atomic_long_read(&priv->rx_errors);
+++	#else
+++	stats->tx_bytes   = (unsigned long) atomic_long_read(&priv->tx_bytes);
+++	stats->tx_packets = (unsigned long) atomic_long_read(&priv->tx_packets);
+++	stats->tx_dropped = (unsigned long) atomic_long_read(&priv->tx_dropped);
+++	stats->rx_bytes   = (unsigned long) atomic_long_read(&priv->rx_bytes);
+++	stats->rx_packets = (unsigned long) atomic_long_read(&priv->rx_packets);
+++	stats->rx_errors  = (unsigned long) atomic_long_read(&priv->rx_errors);
+++	#endif
++ 	return stats;
++ }
++ 
++-- 
++2.7.2
++