netdev - Re: [Patch net] igb: pass the correct maxlen for eth_get

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Message-ID: <CAHA+R7OhbCSjggyb_Deq_jmoDWzEcR+=hhkKjyE9Pue7bXOmHg@mail.gmail.com>
Date:	Thu, 23 Apr 2015 12:30:06 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Alexander Duyck <alexander.duyck@...il.com>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	netdev <netdev@...r.kernel.org>,
	intel-wired-lan@...ts.osuosl.org,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [Patch net] igb: pass the correct maxlen for eth_get_headlen()

(Off-topic...)

On Wed, Apr 22, 2015 at 4:23 PM, Cong Wang <cwang@...pensource.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?

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;
 }

 /**
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