[Intel-wired-lan] [PATCH V2] ixgbe: Handle extended IPv6 headers in tx path

[Tom Herbert]

On Mon, Nov 16, 2015 at 4:26 PM, Mark D Rustad <mark.d.rustad at intel.com> wrote:
> Check for and handle IPv6 extended headers so that tx checksum
> offload can be done. Thanks to Tom Herbert for noticing this
> problem. Thanks to Alexander Duyck for recognizing problems with
> the first version of this patch.
>
> Reported-by: Tom Herbert <tom at herbertland.com>
> Signed-off-by: Mark Rustad <mark.d.rustad at intel.com>
> ---
> Changed in V2:
> - Use ipv6_skip_exthdr instead of ipv6_find_hdr
> - Move code into L3 processing and avoid any possible loop
> - Handle encapsulated IPv6 extended headers correctly
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |   19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index 1ffbe85eab7b..23f316a9ad5a 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -7229,6 +7229,8 @@ static void ixgbe_tx_csum(struct ixgbe_ring *tx_ring,
>                         struct tcphdr *tcphdr;
>                         u8 *raw;
>                 } transport_hdr;
> +               __be16 frag_off;
> +               int rc;
>
>                 if (skb->encapsulation) {
>                         network_hdr.raw = skb_inner_network_header(skb);
> @@ -7252,6 +7254,23 @@ static void ixgbe_tx_csum(struct ixgbe_ring *tx_ring,
>                 case 6:
>                         vlan_macip_lens |= transport_hdr.raw - network_hdr.raw;
>                         l4_hdr = network_hdr.ipv6->nexthdr;
> +                       if (likely((transport_hdr.raw - network_hdr.raw) ==
> +                                  sizeof(struct ipv6hdr)))
> +                               break;
> +                       rc = ipv6_skip_exthdr(skb, network_hdr.raw +
> +                                                  sizeof(struct ipv6hdr) -
> +                                                  skb->data,
> +                                             &l4_hdr, &frag_off);
> +                       if (rc < 0) {
> +                               if (unlikely(net_ratelimit())) {
> +                                       dev_warn(tx_ring->dev,
> +                                                "ipv6_skip_exthdr returned %d\n",
> +                                                rc);
> +                               }
> +                               break;
> +                       }
> +                       if (frag_off)
> +                               l4_hdr = 0;
>                         break;
>                 default:
>                         if (unlikely(net_ratelimit())) {
>

Failures should not result in dev_warn, just call skb_checksum_help
instead. Ignoring CHECKSUM_PARTIAL is guaranteed to be sending a bad
checksum!

The patch parses the extension headers and verifies the protocol is
supported (TCP, UDP, SCTP). But how does the device know the offset of
the transport header to perform the checksum? Is the device capable of
parsing the extension headers on transmit?

Thanks,
Tom