Merge remote-tracking branch 'origin/testing'

Eyal Birger says:

====================
When having many xfrm interfaces, the linear lookup of devices based on
if_id becomes costly.

The first patch refactors xfrmi_decode_session() to use the xi used in
the netdevice priv context instead of looking it up in the list based
on ifindex. This is needed in order to use if_id as the only key used
for xi lookup.

The second patch extends the existing infrastructure - which already
stores the xfrmi contexts in an array of lists - to use a hash of the
if_id.

Example benchmarks:
- running on a KVM based VM
- xfrm tunnel mode between two namespaces
- xfrm interface in one namespace (10.0.0.2)

Before this change set:

Single xfrm interface in namespace:
$ netperf -H 10.0.0.2 -l8 -I95,10 -t TCP_STREAM

MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.0.2 () port 0 AF_INET : +/-5.000% @ 95% conf.  : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

131072  16384  16384    8.00      298.36

After adding 400 xfrmi interfaces in the same namespace:

$ netperf -H 10.0.0.2 -l8 -I95,10 -t TCP_STREAM

MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.0.2 () port 0 AF_INET : +/-5.000% @ 95% conf.  : demo
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

131072  16384  16384    8.00      221.77

After this patchset there was no observed change after adding the
xfrmi interfaces.
====================

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>