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

On Fri, Jan 17, 2020 at 07:08:05PM +0530, Ayush Sawal wrote:

Hi steffen,

On 1/17/2020 5:47 PM, Steffen Klassert wrote:

quoted

On Fri, Jan 17, 2020 at 04:28:54PM +0530, Ayush Sawal wrote:

quoted

Hi steffen,

On 1/17/2020 12:34 PM, Steffen Klassert wrote:

quoted

On Fri, Jan 17, 2020 at 12:13:07PM +0530, Ayush Sawal wrote:

quoted

Hi Herbert,

On 1/17/2020 11:53 AM, Herbert Xu wrote:

quoted

On Thu, Jan 16, 2020 at 01:27:24PM +0530, Ayush Sawal wrote:

quoted

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.

I just did a test and I see the same behaviour. Seems like I was
mistaken, we actually fragment the ESP packets. The only case
where we do pre-encap fragmentation is IPv6 tunnel mode. But I
wonder if it would make sense to avoid to have ESP fragments on
the wire.