netdev - Re: [RFC PATCH 0/6] BOND TLS flags fixes

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Message-ID: <ee795e24-b430-a5f4-39c4-8586f2dc45a6@gmail.com>
Date:   Sun, 30 May 2021 13:49:09 +0300
From:   Tariq Toukan <ttoukan.linux@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Tariq Toukan <tariqt@...dia.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Moshe Shemesh <moshe@...dia.com>,
        Boris Pismenny <borisp@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Maxim Mikityanskiy <maximmi@...dia.com>
Subject: Re: [RFC PATCH 0/6] BOND TLS flags fixes



On 5/27/2021 8:56 PM, Jakub Kicinski wrote:
> On Thu, 27 May 2021 17:07:06 +0300 Tariq Toukan wrote:
>> On 5/27/2021 3:47 AM, Jakub Kicinski wrote:
>>> On Wed, 26 May 2021 12:57:41 +0300 Tariq Toukan wrote:
>>>> This RFC series suggests a solution for the following problem:
>>>>
>>>> Bond interface and lower interface are both up with TLS RX/TX offloads on.
>>>> TX/RX csum offload is turned off for the upper, hence RX/TX TLS is turned off
>>>> for it as well.
>>>> Yet, although it indicates that feature is disabled, new connections are still
>>>> offloaded by the lower, as Bond has no way to impact that:
>>>> Return value of bond_sk_get_lower_dev() is agnostic to this change.
>>>>
>>>> One way to solve this issue, is to bring back the Bond TLS operations callbacks,
>>>> i.e. provide implementation for struct tlsdev_ops in Bond.
>>>> This gives full control for the Bond over its features, making it aware of every
>>>> new TLS connection offload request.
>>>> This direction was proposed in the original Bond TLS implementation, but dropped
>>>> during ML review. Probably it's right to re-consider now.
>>>>
>>>> Here I suggest another solution, which requires generic changes out of the bond
>>>> driver.
>>>>
>>>> Fixes in patches 1 and 4 are needed anyway, independently to which solution
>>>> we choose. I'll probably submit them separately soon.
>>>
>>> No opinions here, semantics of bond features were always clear
>>> as mud to me. What does it mean that bond survived 20 years without
>>> rx-csum? And it so why would TLS offload be different from what one
>>> may presume the semantics of rx-csum are today?
>>
>> Advanced device offloads have basic logical dependencies, that are
>> applied for all kind of netdevs, agnostic to internal details of each
>> netdev.
>>
>> Nothing special with TLS really.
>> TLS device offload behaves similarly to TSO (needs HW_CSUM), and GRO_HW
>> (needs RXCSUM).
>> [...]
> 
> Right, the inter-dependency between features is obvious enough.
> What makes a feature be part of UPPER_DISABLES though?
> 

Regarding UPPER_DISABLES:
I propose using it here as an attempt to give the bond device some 
control over kTLS offloaded connections, to avoid cases where:
(*) UPPER.ktls_device_offload==OFF
(*) LOWER.ktls_device_offload==ON
(*) Newly created connections are offloaded!! Simply ignoring and 
bypassing the UPPER device state (this is how .ndo_sk_get_lower_dev works).

This is not my preferred solution though.
I think we should reconsider introducing bond implementation for "struct 
tlsdev_ops" callbacks, which gives bond interface full control and 
awareness to new TLS connections.