fragment: add fast path for in-order fragments

add fast path for in-order fragments

As the fragments are sent in order in most of OSes, such as Windows, Darwin and
FreeBSD, it is likely the new fragments are at the end of the inet_frag_queue.
In the fast path, we check if the skb at the end of the inet_frag_queue is the
prev we expect.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
----
 include/net/inet_frag.h |    1 +
 net/ipv4/ip_fragment.c  |   12 ++++++++++++
 net/ipv6/reassembly.c   |   11 +++++++++++
 3 files changed, 24 insertions(+)
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 39f2dc943908..16ff29a7bb30 100644
--- a/include/net/inet_frag.h
+++ b/include/net/inet_frag.h
@@ -20,6 +20,7 @@ struct inet_frag_queue {
 	atomic_t		refcnt;
 	struct timer_list	timer;      /* when will this queue expire? */
 	struct sk_buff		*fragments; /* list of received fragments */
+	struct sk_buff		*fragments_tail;
 	ktime_t			stamp;
 	int			len;        /* total length of orig datagram */
 	int			meat;