On Thu, Jan 26, 2012 at 6:43 AM, Or Gerlitz <ogerl...@mellanox.com> wrote: > From: Shlomo Pongratz <shlo...@mellanox.com> > > The GRO flow makes a check in every layer to ensure the packets > are actually merged only if they match at all layers. > > The first GRO check, at L2 always fails for IPoIB, since it assumes > that all packets have 14 bytes of Ethernet link layer header. Using the > IPoIB header will not help here either, since its only four bytes. To > overcome this, the skb mac header pointer is set to an area within the > packet IB GRH headroom, such that later, the L2 check done by GRO > succeeds and it can move to checks at the network and transport layers.
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c > b/drivers/infiniband/ulp/ipoib/ipoib_ib.c > index 4115be5..89cfaf7 100644 > --- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c > +++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c > @@ -286,10 +287,20 @@ static void ipoib_ib_handle_rx_wc(struct net_device > *dev, struct ib_wc *wc) > else > skb->pkt_type = PACKET_MULTICAST; > > - skb_pull(skb, IB_GRH_BYTES); > + /* > + * GRO first does L2 compares (14 bytes). We must not let it start > from > + * the IPoIB header as ten octets of the IP header, containing fields > + * which vary from packet to packet will cause non-merging of packets. > + * from the same TCP stream. > + */ > + psgid = skb_pull(skb, offsetof(struct ib_grh, sgid)); > + /* if there's no GRH, that area could contain random data */ > + if (!(wc->wc_flags & IB_WC_GRH)) > + memset(psgid, 0, 16); > + skb_reset_mac_header(skb); > + skb_pull(skb, IB_GRH_BYTES - offsetof(struct ib_grh, sgid)); > > skb->protocol = ((struct ipoib_header *) skb->data)->proto; > - skb_reset_mac_header(skb); This seems like a really weird place to fix this. Wouldn't it make more sense to fix the GRO check to handle non-ethernet L2 headers? - R. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
