[RFC,net-next,v2,2/2] bnxt: Use generic HBH removal helper in tx path

  Eric Dumazet implemented Big TCP that allowed bigger TSO/GRO packet sizes
for IPv6 traffic. See patch series:
'commit 89527be8d8d6 ("net: add IFLA_TSO_{MAX_SIZE|SEGS} attributes")'

This reduces the number of packets traversing the networking stack and
should usually improves performance. However, it also inserts a
temporary Hop-by-hop IPv6 extension header.

Using the HBH header removal method in the previous path, the extra header
be removed in bnxt drivers to allow it to send big TCP packets (bigger
TSO packets) as well.

Tested:
Compiled locally

To further test functional correctness, update the GSO/GRO limit on the
physical NIC:

ip link set eth0 gso_max_size 181000
ip link set eth0 gro_max_size 181000

Note that if there are bonding or ipvan devices on top of the physical
NIC, their GSO sizes need to be updated as well.

Then, IPv6/TCP packets with sizes larger than 64k can be observed.

Signed-off-by: Coco Li <lixiaoyan@google.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 4 ++++
 1 file changed, 4 insertions(+)
  

On Wed, Nov 23, 2022 at 11:16 AM Coco Li <lixiaoyan@google.com> wrote:
>
> Eric Dumazet implemented Big TCP that allowed bigger TSO/GRO packet sizes
> for IPv6 traffic. See patch series:
> 'commit 89527be8d8d6 ("net: add IFLA_TSO_{MAX_SIZE|SEGS} attributes")'
>
> This reduces the number of packets traversing the networking stack and
> should usually improves performance. However, it also inserts a
> temporary Hop-by-hop IPv6 extension header.
>
> Using the HBH header removal method in the previous path, the extra header
> be removed in bnxt drivers to allow it to send big TCP packets (bigger
> TSO packets) as well.
>
> Tested:
> Compiled locally
>
> To further test functional correctness, update the GSO/GRO limit on the
> physical NIC:
>
> ip link set eth0 gso_max_size 181000
> ip link set eth0 gro_max_size 181000
>
> Note that if there are bonding or ipvan devices on top of the physical
> NIC, their GSO sizes need to be updated as well.
>
> Then, IPv6/TCP packets with sizes larger than 64k can be observed.
>
> Signed-off-by: Coco Li <lixiaoyan@google.com>
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 0fe164b42c5d..2bfa5e9fb179 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -389,6 +389,9 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
>                         return NETDEV_TX_BUSY;
>         }
>
> +       if (unlikely(ipv6_hopopt_jumbo_remove(skb)))
> +               goto tx_free;
> +
>         length = skb->len;
>         len = skb_headlen(skb);
>         last_frag = skb_shinfo(skb)->nr_frags;
> @@ -13657,6 +13660,7 @@ static int bnxt_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>                 dev->features &= ~NETIF_F_LRO;
>         dev->priv_flags |= IFF_UNICAST_FLT;
>
> +       netif_set_tso_max_size(dev, GSO_MAX_SIZE);

Our chips can only transmit TSO packets up to 64K bytes, so I think
this won't work.
  

On Wed, Nov 23, 2022 at 11:42 AM Michael Chan <michael.chan@broadcom.com> wrote:
>
> On Wed, Nov 23, 2022 at 11:16 AM Coco Li <lixiaoyan@google.com> wrote:
> >
> > @@ -13657,6 +13660,7 @@ static int bnxt_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
> >                 dev->features &= ~NETIF_F_LRO;
> >         dev->priv_flags |= IFF_UNICAST_FLT;
> >
> > +       netif_set_tso_max_size(dev, GSO_MAX_SIZE);
>
> Our chips can only transmit TSO packets up to 64K bytes, so I think
> this won't work.

I wanted to double check with the hardware team but there's no one in
the office today.  I will confirm early next week.  Thanks.
  

On Wed, Nov 23, 2022 at 11:42 AM Michael Chan <michael.chan@broadcom.com> wrote:
>
> On Wed, Nov 23, 2022 at 11:16 AM Coco Li <lixiaoyan@google.com> wrote:
> >
> > Eric Dumazet implemented Big TCP that allowed bigger TSO/GRO packet sizes
> > for IPv6 traffic. See patch series:
> > 'commit 89527be8d8d6 ("net: add IFLA_TSO_{MAX_SIZE|SEGS} attributes")'
> >
> > This reduces the number of packets traversing the networking stack and
> > should usually improves performance. However, it also inserts a
> > temporary Hop-by-hop IPv6 extension header.
> >
> > Using the HBH header removal method in the previous path, the extra header
> > be removed in bnxt drivers to allow it to send big TCP packets (bigger
> > TSO packets) as well.
> >
> > Tested:
> > Compiled locally
> >
> > To further test functional correctness, update the GSO/GRO limit on the
> > physical NIC:
> >
> > ip link set eth0 gso_max_size 181000
> > ip link set eth0 gro_max_size 181000
> >
> > Note that if there are bonding or ipvan devices on top of the physical
> > NIC, their GSO sizes need to be updated as well.
> >
> > Then, IPv6/TCP packets with sizes larger than 64k can be observed.
> >
> > Signed-off-by: Coco Li <lixiaoyan@google.com>

I've confirmed with our hardware team that this is supported by our
chips, and I've tested it up to gso_max_size of 524280.  Thanks.

Tested-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
  

Great, thanks Michael! Will send a new version of the patch.

Best,
Coco Li


On Tue, Nov 29, 2022 at 12:59 AM Michael Chan <michael.chan@broadcom.com> wrote:
>
> On Wed, Nov 23, 2022 at 11:42 AM Michael Chan <michael.chan@broadcom.com> wrote:
> >
> > On Wed, Nov 23, 2022 at 11:16 AM Coco Li <lixiaoyan@google.com> wrote:
> > >
> > > Eric Dumazet implemented Big TCP that allowed bigger TSO/GRO packet sizes
> > > for IPv6 traffic. See patch series:
> > > 'commit 89527be8d8d6 ("net: add IFLA_TSO_{MAX_SIZE|SEGS} attributes")'
> > >
> > > This reduces the number of packets traversing the networking stack and
> > > should usually improves performance. However, it also inserts a
> > > temporary Hop-by-hop IPv6 extension header.
> > >
> > > Using the HBH header removal method in the previous path, the extra header
> > > be removed in bnxt drivers to allow it to send big TCP packets (bigger
> > > TSO packets) as well.
> > >
> > > Tested:
> > > Compiled locally
> > >
> > > To further test functional correctness, update the GSO/GRO limit on the
> > > physical NIC:
> > >
> > > ip link set eth0 gso_max_size 181000
> > > ip link set eth0 gro_max_size 181000
> > >
> > > Note that if there are bonding or ipvan devices on top of the physical
> > > NIC, their GSO sizes need to be updated as well.
> > >
> > > Then, IPv6/TCP packets with sizes larger than 64k can be observed.
> > >
> > > Signed-off-by: Coco Li <lixiaoyan@google.com>
>
> I've confirmed with our hardware team that this is supported by our
> chips, and I've tested it up to gso_max_size of 524280.  Thanks.
>
> Tested-by: Michael Chan <michael.chan@broadcom.com>
> Reviewed-by: Michael Chan <michael.chan@broadcom.com>
  

On Tue, Nov 29, 2022 at 9:29 AM Coco Li <lixiaoyan@google.com> wrote:
>
> Great, thanks Michael! Will send a new version of the patch.
>

I just realized one thing.  In bnxt_features_check() ->
bnxt_exthdr_check(), we check to make sure every extension header is
supported by the chip and the number of headers does not exceed what
the chip can support.  So to be more complete, I think we need to
exclude this from being counted.