ipip: enable lockless xmits

IPIP tunnels can benefit from lockless xmits, using NETIF_F_LLTX

Bench on a 16 cpus machine (dual E5540 cpus), 16 threads sending
10000000 UDP frames via one ipip tunnel (size:200 bytes per frame)

Before patch :
real	2m53.321s
user	0m10.277s
sys	46m0.597s

After patch:
real	0m32.063s
user	0m9.237s
sys	8m16.255s

Last problem to solve is the contention on dst :

16118.00 28.3% __ip_route_output_key         vmlinux
 6135.00 10.8% dst_release                   vmlinux
 3220.00  5.6% ip_finish_output              vmlinux
 2149.00  3.8% ip_route_output_flow          vmlinux
 1575.00  2.8% ip_append_data                vmlinux
 1481.00  2.6% ip_push_pending_frames        vmlinux
 1349.00  2.4% __xfrm_lookup                 vmlinux
 1216.00  2.1% csum_partial_copy_generic     vmlinux
 1208.00  2.1% udp_sendmsg                   vmlinux

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 9e78f11da786..6ad46c28ede2 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -767,6 +767,7 @@ static void ipip_tunnel_setup(struct net_device *dev)
         dev->iflink             = 0;
         dev->addr_len           = 4;
         dev->features           |= NETIF_F_NETNS_LOCAL;
+        dev->features           |= NETIF_F_LLTX;
         dev->priv_flags         &= ~IFF_XMIT_DST_RELEASE;
 }