[PATCH] fragment: add fast path

Changli Gao
2010-06-14T01:16:23Z

add fast path

As the fragments are usually in order, 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 | 17 +++++++++++++++++
net/ipv6/reassembly.c | 16 ++++++++++++++++
3 files changed, 34 insertions(+)
diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h
index 39f2dc9..16ff29a 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;
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 75347ea..d8c36d4 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -317,6 +317,7 @@ static int ip_frag_reinit(struct ipq *qp)
qp->q.len = 0;
qp->q.meat = 0;
qp->q.fragments = NULL;
+ qp->q.fragments_tail = NULL;
qp->iif = 0;

return 0;
@@ -389,6 +390,16 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
* in the chain of fragments so far. We must know where to put
* this fragment, right?
*/
+ prev = qp->q.fragments_tail;
+ if (prev) {
+ if (FRAG_CB(prev)->offset < offset) {
+ next = NULL;
+ goto found;
+ }
+ } else {
+ next = NULL;
+ goto found;
+ }
prev = NULL;
for (next = qp->q.fragments; next != NULL; next = next->next) {
if (FRAG_CB(next)->offset >= offset)
@@ -396,6 +407,7 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
prev = next;
}

+found:
/* We found where to put this one. Check for overlap with
* preceding fragment, and, if needed, align things so that
* any overlaps are eliminated.
@@ -454,6 +466,8 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)

/* Insert this fragment in the chain of fragments. */
skb->next = next;
+ if (!next)
+ qp->q.fragments_tail = skb;
if (prev)
prev->next = skb;
else
@@ -507,6 +521,8 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
goto out_nomem;

fp->next = head->next;
+ if (!fp->next)
+ qp->q.fragments_tail = fp;
prev->next = fp;

skb_morph(head, qp->q.fragments);
@@ -578,6 +594,7 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
iph->tot_len = htons(len);
IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
qp->q.fragments = NULL;
+ qp->q.fragments_tail = NULL;
return 0;

out_nomem:
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 6d4292f..dc15624 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -336,6 +336,16 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
* in the chain of fragments so far. We must know where to put
* this fragment, right?
*/
+ prev = fq->q.fragments_tail;
+ if (prev) {
+ if (FRAG6_CB(prev)->offset < offset) {
+ next = NULL;
+ goto found;
+ }
+ } else {
+ next = NULL;
+ goto found;
+ }
prev = NULL;
for(next = fq->q.fragments; next != NULL; next = next->next) {
if (FRAG6_CB(next)->offset >= offset)
@@ -343,6 +353,7 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
prev = next;
}

+found:
/* We found where to put this one. Check for overlap with
* preceding fragment, and, if needed, align things so that
* any overlaps are eliminated.
@@ -400,6 +411,8 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,

/* Insert this fragment in the chain of fragments. */
skb->next = next;
+ if (!next)
+ fq->q.fragments_tail = skb;
if (prev)
prev->next = skb;
else
@@ -466,6 +479,8 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
goto out_oom;

fp->next = head->next;
+ if (!fp->next)
+ fq->q.fragments_tail = fp;
prev->next = fp;

skb_morph(head, fq->q.fragments);
@@ -553,6 +568,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
IP6_INC_STATS_BH(net, __in6_dev_get(dev), IPSTATS_MIB_REASMOKS);
rcu_read_unlock();
fq->q.fragments = NULL;
+ fq->q.fragments_tail = NULL;
return 1;