On Wed, Apr 22, 2015 at 12:43 PM, Alexander Duyck <[email protected]> wrote: > 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 <[email protected]> >> Signed-off-by: Cong Wang <[email protected]> >> --- >> 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.
But the frag size could be smaller than IGB_RX_HDR_LEN which is the case this patch tries to fix. > > 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. That is why I put unlikely() there, even with tunnel headers we unlikely pull header longer than IGB_RX_HDR_LEN, the code is just for completeness. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
