* [RFC] Should skb->csum include 8021Q header for CHECKSUM_COMPLETE && NETIF_F_HW_VLAN_CTAG_RX
@ 2013-11-29 13:28 Thomas Graf
2013-11-29 19:08 ` Stephen Hemminger
0 siblings, 1 reply; 2+ messages in thread
From: Thomas Graf @ 2013-11-29 13:28 UTC (permalink / raw)
To: netdev
Hi
Given CHECKSUM_COMPLETE, is skb->csum supposed to include the
checksum of the VLAN header if the header was stripped by the
NIC?
The answer is clear for non accelerated VLAN: it covers all of
the packet without ethernet CRC.
For the accelerated path the answer is less clear after staring
at drivers. The stack currently only fixes the csum for the
software path.
We are seeing hw csum failure warnings for drivers like enic if
OVS pops a VLAN header that was previously stripped in hardware.
Should we force CHECKSUM_NONE like VXLAN does or are all drivers
guaranteed to include VLAN bits for CHECK_COMPLETE regardless of
acceleration?
Best,
Thomas
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [RFC] Should skb->csum include 8021Q header for CHECKSUM_COMPLETE && NETIF_F_HW_VLAN_CTAG_RX
2013-11-29 13:28 [RFC] Should skb->csum include 8021Q header for CHECKSUM_COMPLETE && NETIF_F_HW_VLAN_CTAG_RX Thomas Graf
@ 2013-11-29 19:08 ` Stephen Hemminger
0 siblings, 0 replies; 2+ messages in thread
From: Stephen Hemminger @ 2013-11-29 19:08 UTC (permalink / raw)
To: Thomas Graf; +Cc: netdev
On Fri, 29 Nov 2013 13:28:19 +0000
Thomas Graf <tgraf@suug.ch> wrote:
> Hi
>
> Given CHECKSUM_COMPLETE, is skb->csum supposed to include the
> checksum of the VLAN header if the header was stripped by the
> NIC?
>
> The answer is clear for non accelerated VLAN: it covers all of
> the packet without ethernet CRC.
>
> For the accelerated path the answer is less clear after staring
> at drivers. The stack currently only fixes the csum for the
> software path.
>
> We are seeing hw csum failure warnings for drivers like enic if
> OVS pops a VLAN header that was previously stripped in hardware.
> Should we force CHECKSUM_NONE like VXLAN does or are all drivers
> guaranteed to include VLAN bits for CHECK_COMPLETE regardless of
> acceleration?
>
> Best,
> Thomas
> --
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Most hardware is smart enough that if it strips the VLAN header,
it does not include it in the checksum.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2013-11-29 13:28 [RFC] Should skb->csum include 8021Q header for CHECKSUM_COMPLETE && NETIF_F_HW_VLAN_CTAG_RX Thomas Graf
2013-11-29 19:08 ` Stephen Hemminger
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