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

From: Hannes Reinecke <hare@suse.de>
To: Jakub Kicinski <kuba@kernel.org>, Sagi Grimberg <sagi@grimberg.me>
Cc: Christoph Hellwig <hch@lst.de>,
	Boris Pismenny <borisp@nvidia.com>,
	john.fastabend@gmail.com, Paolo Abeni <pabeni@redhat.com>,
	Keith Busch <kbusch@kernel.org>,
	linux-nvme@lists.infradead.org,
	Chuck Lever <chuck.lever@oracle.com>,
	kernel-tls-handshake@lists.linux.dev,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH 10/18] nvme-tcp: fixup send workflow for kTLS
Date: Fri, 31 Mar 2023 08:03:00 +0200	[thread overview]
Message-ID: <7f057726-8777-2fd3-a207-b3cd96076cb9@suse.de> (raw)
In-Reply-To: <20230330224920.3a47fec9@kernel.org>

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@suse.de                              +49 911 74053 688
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