netdev - Re: Advertise maximum number of sg supported by driver in single request

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Date:   Fri, 17 Jan 2020 19:08:05 +0530
From:   Ayush Sawal <ayush.sawal@...cdesigners.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     ayush.sawal@...cdesigners.com,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-crypto@...r.kernel.org, manojmalviya@...lsio.com,
        Ayush Sawal <ayush.sawal@...lsio.com>, netdev@...r.kernel.org
Subject: Re: Advertise maximum number of sg supported by driver in single
 request

Hi steffen,

On 1/17/2020 5:47 PM, Steffen Klassert wrote:
> On Fri, Jan 17, 2020 at 04:28:54PM +0530, Ayush Sawal wrote:
>> Hi steffen,
>>
>> On 1/17/2020 12:34 PM, Steffen Klassert wrote:
>>> On Fri, Jan 17, 2020 at 12:13:07PM +0530, Ayush Sawal wrote:
>>>> Hi Herbert,
>>>>
>>>> On 1/17/2020 11:53 AM, Herbert Xu wrote:
>>>>> On Thu, Jan 16, 2020 at 01:27:24PM +0530, Ayush Sawal wrote:
>>>>>> The max data limit is 15 sgs where each sg contains data of mtu size .
>>>>>> we are running a netperf udp stream test over ipsec tunnel .The ipsec tunnel
>>>>>> is established between two hosts which are directly connected
>>>>> Are you actually getting 15-element SG lists from IPsec? What is
>>>>> generating an skb with 15-element SG lists?
>>>> we have established the ipsec tunnel in transport mode using ip xfrm.
>>>> and running traffic using netserver and netperf.
>>>>
>>>> In server side we are running
>>>> netserver -4
>>>> In client side we are running
>>>> "netperf -H <serverip> -p <port> -t UDP_STREAM  -Cc -- -m 21k"
>>>> where the packet size is 21k ,which is then fragmented into 15 ip fragments
>>>> each of mtu size.
>>> I'm lacking a bit of context here, but this should generate 15 IP
>>> packets that are encrypted one by one.
>> This is what i observed ,please correct me if i am wrong.
>> The packet when reaches esp_output(),is in socket buffer and based on the
>> number of frags ,sg is initialized  using
>> sg_init_table(sg,frags),where frags are 15 in our case.
> The packet should be IP fragmented before it enters esp_output()
> unless this is a UDP GSO packet. What kind of device do you use
> here? Is it a crypto accelerator or a NIC that can do ESP offloads?

We have device which works as a crypto accelerator . It just encrypts 
the packets and send it back to kernel.