Linux Virtualization - May 2018 - [PATCH V2 net-next 5/6] macvlan/macvtap: Add support for SCTP checksum offload.

On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich
wrote:
> Since we now have support for software CRC32c offload, turn it on
> for macvlan and macvtap devices so that guests can take advantage
> of offload SCTP checksums to the host or host hardware.
> 
> Signed-off-by: Vladislav Yasevich <vyasevic at redhat.com>
> ---
>  drivers/net/macvlan.c | 5 +++--
>  drivers/net/tap.c     | 8 +++++---
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 725f4b4..646b730 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -834,7 +834,7 @@ static struct lock_class_key
macvlan_netdev_addr_lock_key;
>  
>  #define ALWAYS_ON_OFFLOADS \
>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
>  
>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
>  
> @@ -842,7 +842,8 @@ static struct lock_class_key
macvlan_netdev_addr_lock_key;
>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST | \
>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
> +	 NETIF_F_SCTP_CRC)
>  
>  #define MACVLAN_STATE_MASK \
>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> index 9b6cb78..2c8512b 100644
> --- a/drivers/net/tap.c
> +++ b/drivers/net/tap.c
> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff
**pskb)
>  		 *	  check, we either support them all or none.
>  		 */
>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
> -		    !(features & NETIF_F_CSUM_MASK) &&
> -		    skb_checksum_help(skb))
> +		    skb_csum_hwoffload_help(skb, features))
>  			goto drop;
>  		if (ptr_ring_produce(&q->ring, skb))
>  			goto drop;
> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q, unsigned
long arg)
>  		}
>  	}
>  
> +	if (arg & TUN_F_SCTP_CSUM)
> +		feature_mask |= NETIF_F_SCTP_CRC;
> +
so this still affects TX, shouldn't this affect RX instead?

>  	/* tun/tap driver inverts the usage for TSO offloads, where
>  	 * setting the TSO bit means that the userspace wants to
>  	 * accept TSO frames and turning it off means that user space
> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned int
cmd,
>  	case TUNSETOFFLOAD:
>  		/* let the user check for future flags */
>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> -			    TUN_F_TSO_ECN | TUN_F_UFO))
> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
>  			return -EINVAL;
>  
>  		rtnl_lock();
> -- 
> 2.9.5

On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
> On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
>> Since we now have support for software CRC32c offload, turn it on
>> for macvlan and macvtap devices so that guests can take advantage
>> of offload SCTP checksums to the host or host hardware.
>>
>> Signed-off-by: Vladislav Yasevich <vyasevic at redhat.com>
>> ---
>>  drivers/net/macvlan.c | 5 +++--
>>  drivers/net/tap.c     | 8 +++++---
>>  2 files changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
>> index 725f4b4..646b730 100644
>> --- a/drivers/net/macvlan.c
>> +++ b/drivers/net/macvlan.c
>> @@ -834,7 +834,7 @@ static struct lock_class_key
macvlan_netdev_addr_lock_key;
>>  
>>  #define ALWAYS_ON_OFFLOADS \
>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
>> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
>> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
>>  
>>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
>>  
>> @@ -842,7 +842,8 @@ static struct lock_class_key
macvlan_netdev_addr_lock_key;
>>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA | NETIF_F_FRAGLIST |
\
>>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
>>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM | \
>> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
>> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
>> +	 NETIF_F_SCTP_CRC)
>>  
>>  #define MACVLAN_STATE_MASK \
>>  	((1<<__LINK_STATE_NOCARRIER) | (1<<__LINK_STATE_DORMANT))
>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
>> index 9b6cb78..2c8512b 100644
>> --- a/drivers/net/tap.c
>> +++ b/drivers/net/tap.c
>> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct sk_buff
**pskb)
>>  		 *	  check, we either support them all or none.
>>  		 */
>>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
>> -		    !(features & NETIF_F_CSUM_MASK) &&
>> -		    skb_checksum_help(skb))
>> +		    skb_csum_hwoffload_help(skb, features))
>>  			goto drop;
>>  		if (ptr_ring_produce(&q->ring, skb))
>>  			goto drop;
>> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q,
unsigned long arg)
>>  		}
>>  	}
>>  
>> +	if (arg & TUN_F_SCTP_CSUM)
>> +		feature_mask |= NETIF_F_SCTP_CRC;
>> +
> 
> so this still affects TX, shouldn't this affect RX instead?
There is no bit to set on the RX path just like there is no bit to set on the RX
patch
for TUN_F_CSUM.

We only invert TSO offloads, not checksum offloads as the comment below states.
For checksum,  macvtap has to compute the checksum itself in tap_handle_frame()
above.
It uses tx feature bits to see if needs do to the checksum.

If you think we need another flag to macvtap to control RXCSUM, that would need
to be
separate and cover standard TCP checksum as well.

-vlad
> 
> 
>>  	/* tun/tap driver inverts the usage for TSO offloads, where
>>  	 * setting the TSO bit means that the userspace wants to
>>  	 * accept TSO frames and turning it off means that user space
>> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file, unsigned
int cmd,
>>  	case TUNSETOFFLOAD:
>>  		/* let the user check for future flags */
>>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
>> -			    TUN_F_TSO_ECN | TUN_F_UFO))
>> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
>>  			return -EINVAL;
>>  
>>  		rtnl_lock();
>> -- 
>> 2.9.5

On Wed, May 02, 2018 at 09:27:00AM -0400, Vlad Yasevich
wrote:
> On 05/01/2018 11:24 PM, Michael S. Tsirkin wrote:
> > On Tue, May 01, 2018 at 10:07:38PM -0400, Vladislav Yasevich wrote:
> >> Since we now have support for software CRC32c offload, turn it on
> >> for macvlan and macvtap devices so that guests can take advantage
> >> of offload SCTP checksums to the host or host hardware.
> >>
> >> Signed-off-by: Vladislav Yasevich <vyasevic at redhat.com>
> >> ---
> >>  drivers/net/macvlan.c | 5 +++--
> >>  drivers/net/tap.c     | 8 +++++---
> >>  2 files changed, 8 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> >> index 725f4b4..646b730 100644
> >> --- a/drivers/net/macvlan.c
> >> +++ b/drivers/net/macvlan.c
> >> @@ -834,7 +834,7 @@ static struct lock_class_key
macvlan_netdev_addr_lock_key;
> >>  
> >>  #define ALWAYS_ON_OFFLOADS \
> >>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_GSO_SOFTWARE | \
> >> -	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL)
> >> +	 NETIF_F_GSO_ROBUST | NETIF_F_GSO_ENCAP_ALL | NETIF_F_SCTP_CRC)
> >>  
> >>  #define ALWAYS_ON_FEATURES (ALWAYS_ON_OFFLOADS | NETIF_F_LLTX)
> >>  
> >> @@ -842,7 +842,8 @@ static struct lock_class_key
macvlan_netdev_addr_lock_key;
> >>  	(NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_HIGHDMA |
NETIF_F_FRAGLIST | \
> >>  	 NETIF_F_GSO | NETIF_F_TSO | NETIF_F_LRO | \
> >>  	 NETIF_F_TSO_ECN | NETIF_F_TSO6 | NETIF_F_GRO | NETIF_F_RXCSUM |
\
> >> -	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER)
> >> +	 NETIF_F_HW_VLAN_CTAG_FILTER | NETIF_F_HW_VLAN_STAG_FILTER | \
> >> +	 NETIF_F_SCTP_CRC)
> >>  
> >>  #define MACVLAN_STATE_MASK \
> >>  	((1<<__LINK_STATE_NOCARRIER) |
(1<<__LINK_STATE_DORMANT))
> >> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
> >> index 9b6cb78..2c8512b 100644
> >> --- a/drivers/net/tap.c
> >> +++ b/drivers/net/tap.c
> >> @@ -369,8 +369,7 @@ rx_handler_result_t tap_handle_frame(struct
sk_buff **pskb)
> >>  		 *	  check, we either support them all or none.
> >>  		 */
> >>  		if (skb->ip_summed == CHECKSUM_PARTIAL &&
> >> -		    !(features & NETIF_F_CSUM_MASK) &&
> >> -		    skb_checksum_help(skb))
> >> +		    skb_csum_hwoffload_help(skb, features))
> >>  			goto drop;
> >>  		if (ptr_ring_produce(&q->ring, skb))
> >>  			goto drop;
> >> @@ -945,6 +944,9 @@ static int set_offload(struct tap_queue *q,
unsigned long arg)
> >>  		}
> >>  	}
> >>  
> >> +	if (arg & TUN_F_SCTP_CSUM)
> >> +		feature_mask |= NETIF_F_SCTP_CRC;
> >> +
> > 
> > so this still affects TX, shouldn't this affect RX instead?
> 
> There is no bit to set on the RX path just like there is no bit to set on
the RX patch
> for TUN_F_CSUM.
> 
> We only invert TSO offloads, not checksum offloads as the comment below
states.
> For checksum,  macvtap has to compute the checksum itself in
tap_handle_frame() above.
> It uses tx feature bits to see if needs do to the checksum.
> 
> If you think we need another flag to macvtap to control RXCSUM, that would
need to be
> separate and cover standard TCP checksum as well.
> 
> -vlad
Confused. What is the meaning of TUN_F_SCTP_CSUM? I assume this is
a way for userspace to tell tun device: "I can handle
packets without SCTP checksum, pls send them my way".

Now what is the implication for macvtap? And why  are
you setting NETIF_F_SCTP_CRC which is a flag
that affects packets sent by guest to host?

> > 
> > 
> >>  	/* tun/tap driver inverts the usage for TSO offloads, where
> >>  	 * setting the TSO bit means that the userspace wants to
> >>  	 * accept TSO frames and turning it off means that user space
> >> @@ -1077,7 +1079,7 @@ static long tap_ioctl(struct file *file,
unsigned int cmd,
> >>  	case TUNSETOFFLOAD:
> >>  		/* let the user check for future flags */
> >>  		if (arg & ~(TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6 |
> >> -			    TUN_F_TSO_ECN | TUN_F_UFO))
> >> +			    TUN_F_TSO_ECN | TUN_F_UFO | TUN_F_SCTP_CSUM))
> >>  			return -EINVAL;
> >>  
> >>  		rtnl_lock();
> >> -- 
> >> 2.9.5