Messages in this thread | | | From | Joe Stringer <> | Date | Thu, 4 Dec 2014 10:41:34 -0800 | Subject | Re: [PATCHv2 net] i40e: Implement ndo_gso_check() |
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On 2 December 2014 at 10:26, Jesse Gross <jesse@nicira.com> wrote: > On Mon, Dec 1, 2014 at 4:09 PM, Tom Herbert <therbert@google.com> wrote: >> On Mon, Dec 1, 2014 at 3:53 PM, Jesse Gross <jesse@nicira.com> wrote: >>> On Mon, Dec 1, 2014 at 3:47 PM, Tom Herbert <therbert@google.com> wrote: >>>> On Mon, Dec 1, 2014 at 3:35 PM, Joe Stringer <joestringer@nicira.com> wrote: >>>>> On 21 November 2014 at 09:59, Joe Stringer <joestringer@nicira.com> wrote: >>>>>> On 20 November 2014 16:19, Jesse Gross <jesse@nicira.com> wrote: >>>>>>> I don't know if we need to have the check at all for IPIP though - >>>>>>> after all the driver doesn't expose support for it all (actually it >>>>>>> doesn't expose GRE either). This raises kind of an interesting >>>>>>> question about the checks though - it's pretty easy to add support to >>>>>>> the driver for a new GSO type (and I imagine that people will be >>>>>>> adding GRE soon) and forget to update the check. >>>>>> >>>>>> If the check is more conservative, then testing would show that it's >>>>>> not working and lead people to figure out why (and update the check). >>>>> >>>>> More concretely, one suggestion would be something like following at >>>>> the start of each gso_check(): >>>>> >>>>> + const int supported = SKB_GSO_TCPV4 | SKB_GSO_TCPV6 | SKB_GSO_FCOE | >>>>> + SKB_GSO_UDP | SKB_GSO_UDP_TUNNEL; >>>>> + >>>>> + if (skb_shinfo(skb)->gso_type & ~supported) >>>>> + return false; >>>> >>>> This should already be handled by net_gso_ok. >>> >>> My original point wasn't so much that this isn't handled at the moment >>> but that it's easy to add a supported GSO type but then forget to >>> update this check - i.e. if a driver already supports UDP_TUNNEL and >>> adds support for GRE with the same constraints. It seems not entirely >>> ideal that this function is acting as a blacklist rather than a >>> whitelist. >> >> Agreed, it would be nice to have all the checking logic in one place. >> If all the drivers end up implementing ndo_gso_check then we could >> potentially get rid of the GSO types as features. This probably >> wouldn't be a bad thing since we already know that the features >> mechanism doesn't scale (for instance there's no way to indicate that >> certain combinations of GSO types are supported by a device). > > This crossed my mind and I agree that it's pretty clear that the > features mechanism isn't scaling very well. Presumably, the logical > extension of this is that each driver would have a function that looks > at a packet and returns a set of offload operations that it can > support rather than exposing a set of protocols. However, it seems > like it would probably result in a bunch of duplicate code in each > driver.
Given the discussion is still pretty open-ended, I've made the basic feedback changes for v3 and haven't tried to address the concern about forgetting to update this check when a driver adds support.
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