netdev - Re: [PATCH 10/18] nvme-tcp: fixup send workflow for kTLS

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Date:   Fri, 31 Mar 2023 08:03:00 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Jakub Kicinski <kuba@...nel.org>, Sagi Grimberg <sagi@...mberg.me>
Cc:     Christoph Hellwig <hch@....de>, Boris Pismenny <borisp@...dia.com>,
        john.fastabend@...il.com, Paolo Abeni <pabeni@...hat.com>,
        Keith Busch <kbusch@...nel.org>,
        linux-nvme@...ts.infradead.org,
        Chuck Lever <chuck.lever@...cle.com>,
        kernel-tls-handshake@...ts.linux.dev,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH 10/18] nvme-tcp: fixup send workflow for kTLS

On 3/31/23 07:49, Jakub Kicinski wrote:
> On Thu, 30 Mar 2023 18:24:04 +0300 Sagi Grimberg wrote:
>>> kTLS does not support MSG_EOR flag for sendmsg(), and in general
>>> is really picky about invalid MSG_XXX flags.
>>
>> CC'ing TLS folks.
>>
>> Can't tls simply ignore MSG_EOR instead of consumers having to be
>> careful over it?
> 
> I think we can support EOR, I don't see any fundamental problem there.
> 
>>> So ensure that the MSG_EOR flags is blanked out for TLS, and that
>>> the MSG_SENDPAGE_LAST is only set if we actually do sendpage().
>>
>> You mean MSG_SENDPAGE_NOTLAST.
>>
>> It is also a bit annoying that a tls socket dictates different behavior
>> than a normal socket.
>>
>> The current logic is rather simple:
>> if more data comming:
>> 	flags = MSG_MORE | MSG_SENDPAGE_NOTLAST
>> else:
>> 	flags = MSG_EOR
>>
>> Would like to keep it that way for tls as well. Can someone
>> explain why this is a problem with tls?
> 
> Some of the flags are call specific, others may be internal to the
> networking stack (e.g. the DECRYPTED flag). Old protocols didn't do
> any validation because people coded more haphazardly in the 90s.
> This lack of validation is a major source of technical debt :(

A-ha. So what is the plan?
Should the stack validate flags?
And should the rules for validating be the same for all protocols?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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