На 05.9.2010 г. 10:49, Eric Dumazet написа:

Le samedi 04 septembre 2010 à 22:34 +0200, Jarek Poplawski a écrit :

quoted

Hi again,

Just had a second look, and unless I miss something...

Plamen, could you test this patch, too? (Without removing the previous
one.)

Thanks,
Jarek P.

------------------->

[PATCH] gro: Re-fix different skb headrooms

The patch: "gro: fix different skb headrooms" in its part:
"2) allocate a minimal skb for head of frag_list" is buggy. The copied
skb has p->data set at the ip header at the moment, and skb_gro_offset
is the length of ip + tcp headers. So, after the change the length of
mac header is skipped. Later skb_set_mac_header() sets it into the
NET_SKB_PAD area (if it's long enough) and ip header is misaligned at
NET_SKB_PAD + NET_IP_ALIGN offset. There is no reason to assume the
original skb was wrongly allocated, so let's copy it as it was.

bugzilla : https://bugzilla.kernel.org/show_bug.cgi?id=16626
fixes commit: 3d3be4333fdf6faa080947b331a6a19bce1a4f57

Reported-by: Plamen Petrov<redacted>
Signed-off-by: Jarek Poplawski<redacted>
CC: Eric Dumazet<redacted>
---

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 26396ff..c83b421 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c

@@ -2706,7 +2706,7 @@ int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
  	} else if (skb_gro_len(p) != pinfo->gso_size)
  		return -E2BIG;

-	headroom = NET_SKB_PAD + NET_IP_ALIGN;
+	headroom = skb_headroom(p);
  	nskb = alloc_skb(headroom + skb_gro_offset(p), GFP_ATOMIC);
  	if (unlikely(!nskb))
  		return -ENOMEM;

You are right, thanks for reviewing this patch again :)

By the way, NET_IP_ALIGN is now 0 on x86, so technically speaking, your
patch un-aligns IP header on x86, but thats OK, since other arches might
want it being aligned, while x86 doesnt care.

Acked-by: Eric Dumazet<redacted>

Well, now that I'm back at work, I'm glad to report
that I tested both variants of the patch, and as Eric
points out - it works both ways.

So, which ever fits you guys better.

Thanks a lot!