Thanks for reply.
On Wed, 2015-08-26 at 19:12 -0700, Eric Dumazet wrote:
On Thu, 2015-08-27 at 08:56 +0800, chenweil...@huawei.com wrote:
From: Weilong Chen <chenweil...@huawei.com>
When try to merge several skbs to prior one, if the frag_list is
used and the the last one is a small packet, once the condition
"len <= skb_tailroom(to)" is satisfied, we will get a wrong
packet!
This patch just check frag_lists before the condtion to prevent
this from happening.
Signed-off-by: Weilong Chen <chenweil...@huawei.com>
---
net/core/skbuff.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8a725cc..d08edcb 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff
*from,
if (skb_cloned(to))
return false;
+ if (skb_has_frag_list(to) || skb_has_frag_list(from))
+ return false;
+
if (len <= skb_tailroom(to)) {
if (len)
BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len));
@@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff
*from,
return true;
}
- if (skb_has_frag_list(to) || skb_has_frag_list(from))
- return false;
-
if (skb_headlen(from) != 0) {
struct page *page;
unsigned int offset;
Sigh.
No idea what problem you tried to solve.
This patch is not needed.
If (len <= skb_tailroom()), then it is obviously correct to copy_bits()
the bytes.
Hints :
- If @to has a fraglist, then skb_tailroom(to) is 0 so the copy can not
be done.
How to make sure it?
In my test, @to has a fraglist, but skb_tailroom(to) is not 0!
The test is about tipc, the function tipc_buf_append will merge 3 skbs
to one:
packet 1: len = 1420 skb_tailroom = 190
packet 2: len = 1420
packet 2 will be add to 1' fraglist, but not update skb_tailroom
packet 3: len = 60
Here's the error!
- If @from has a fraglist, it is not relevant as we copy it into @to and
will free @from.
This is going to be a FAQ
http://www.spinics.net/lists/netdev/msg315090.html
.
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