[Intel-wired-lan] [Patch net] igb: pass the correct maxlen for eth_get_headlen()
Alexander Duyck
alexander.h.duyck at redhat.com
Thu Apr 23 19:45:21 UTC 2015
On 04/23/2015 12:30 PM, Cong Wang wrote:
> (Off-topic...)
>
> On Wed, Apr 22, 2015 at 4:23 PM, Cong Wang <cwang at twopensource.com> wrote:
>> The code looks correct to me now, except it is suspicious skb->len
>> is not updated after skb_copy_to_linear_data() while skb->tail is
>> advanced already. I need to think more before submitting a patch.
> I feel like we need the following patch, maybe skb->len is updated somewhere
> else by "skb->tail - skb->head", otherwise we are screwed?
Maybe in skb_add_rx_frag? You might take a look at it.
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index a0a9b1f..66e6fb6 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -6843,7 +6843,6 @@ static void igb_pull_tail(struct igb_ring *rx_ring,
> skb_frag_size_sub(frag, IGB_TS_HDR_LEN);
> frag->page_offset += IGB_TS_HDR_LEN;
> skb->data_len -= IGB_TS_HDR_LEN;
> - skb->len -= IGB_TS_HDR_LEN;
>
> /* move va to start of packet data */
> va += IGB_TS_HDR_LEN;
> @@ -6856,12 +6855,12 @@ static void igb_pull_tail(struct igb_ring *rx_ring,
>
> /* align pull length to size of long to optimize memcpy performance */
> skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));
> + __skb_put(skb, pull_len);
>
> /* update all of the pointers */
> skb_frag_size_sub(frag, pull_len);
> frag->page_offset += pull_len;
> skb->data_len -= pull_len;
> - skb->tail += pull_len;
> }
>
> /**
Seriously? Are you even reading the code? The fragment is already a
part of the skb, as such it is already included in skb->len. By
re-adding the header you are adding bytes that aren't there. All we
were doing is moving data from a fragment to the linear portion.
No offense but your starting to waste my time with these silly patch
ideas. The patches I submitted to intel-wired-lan fix the issue that
you found, and there aren't any new issues that it creates so the issue
is resolved. And like I said if you need to fix this in stable just
subtract IGB_TS_HDR_LEN from the header length scanned in
eth_get_headlen and it will resolve the issue you reported and that way
we can fix the issue and avoid pulling a fragment down to size 0.
- Alex
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