On 04/22/2015 10:45 AM, Cong Wang wrote: > The second parameter of eth_get_headlen() is the length of > the frame buffer, not the header length of skb. > > Cc: Jeff Kirsher <jeffrey.t.kirs...@intel.com> > Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com> > --- > drivers/net/ethernet/intel/igb/igb_main.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c > b/drivers/net/ethernet/intel/igb/igb_main.c > index a0a9b1f..7b3a370 100644 > --- a/drivers/net/ethernet/intel/igb/igb_main.c > +++ b/drivers/net/ethernet/intel/igb/igb_main.c > @@ -6852,7 +6852,9 @@ static void igb_pull_tail(struct igb_ring *rx_ring, > /* we need the header to contain the greater of either ETH_HLEN or > * 60 bytes if the skb->len is less than 60 for skb_pad. > */ > - pull_len = eth_get_headlen(va, IGB_RX_HDR_LEN); > + pull_len = eth_get_headlen(va, skb_frag_size(frag)); > + if (unlikely(pull_len > IGB_RX_HDR_LEN)) > + pull_len = IGB_RX_HDR_LEN; > > /* align pull length to size of long to optimize memcpy performance */ > skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long)));
You have this part right. The length represents the maximum length we are willing to traverse in the buffer. So if we 100% want to get the entire header regardless of what we can copy into then we could follow your approach. However, since the allocated space in the skb is only IGB_RX_HDR_LEN we only really want to traverse up to that length. Then that is all we copy out of the header. As a result we don't need the extra code for putting the upper limit on pull_len since that is factored in by passing IGB_RX_HDR_LEN as the maximum traversal length. - Alex -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
