netdev - Re: [Intel-wired-lan] [PATCH V2 RFC 2/2] ixgbe: ixgbe_atr() compute l4_proto only if non-paged data has network/transport headers

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Date:   Mon, 17 Oct 2016 15:18:04 -0400
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        Netdev <netdev@...r.kernel.org>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>
Subject: Re: [Intel-wired-lan] [PATCH V2 RFC 2/2] ixgbe: ixgbe_atr() compute
 l4_proto only if non-paged data has network/transport headers

On (10/17/16 11:15), Alexander Duyck wrote:
> I would say you probably only need the first check here for skb->data
> and could probably skip the second part.  You will be testing for
> skb_tail_pointer in all the other tests you added so this check is
> redundant anyway.
> 
> Also you might want to go through and wrap these with unlikely() since
> most of these are exception cases.

Ok.. v3 will have this.

> >         /* Currently only IPv4/IPv6 with TCP is supported */
> >         switch (hdr.ipv4->version) {
> >         case IPVERSION:
> >                 /* access ihl as u8 to avoid unaligned access on ia64 */
> >                 hlen = (hdr.network[0] & 0x0F) << 2;
> > +               if (skb_tail_pointer(skb) < hdr.network + hlen +
> > +                                           sizeof(struct tcphdr))
> > +                       return;
> >                 l4_proto = hdr.ipv4->protocol;
> >                 break;
> >         case 6:
> >                 hlen = hdr.network - skb->data;
> > +               if (skb_tail_pointer(skb) < hdr.network + hlen +
> > +                                           sizeof(struct tcphdr))
> > +                       return;
> >                 l4_proto = ipv6_find_hdr(skb, &hlen, IPPROTO_TCP, NULL, NULL);
> >                 hlen -= hdr.network - skb->data;
> >                 break;
> 
> I believe one more check is needed after this block to verify the TCP
> header fields are present.
> 
> So you probably need to add a check for "skb_tail_pointer(skb) <
> (hdr.network + hlen + 20)".

But isnt that the same thing as the checks before l4_proto computation above?

--Sowmini