Merge branch 'tls-rx-avoid-skb_cow_data'

Merge branch 'tls-rx-avoid-skb_cow_data'

Jakub Kicinski says:

====================
tls: rx: avoid skb_cow_data()

TLS calls skb_cow_data() on the skb it received from strparser
whenever it needs to hold onto the skb with the decrypted data.
(The alternative being decrypting directly to a user space buffer
in whic case the input skb doesn't get modified or used after.)
TLS needs the decrypted skb:
 - almost always with TLS 1.3 (unless the new NoPad is enabled);
 - when user space buffer is too small to fit the record;
 - when BPF sockmap is enabled.

Most of the time the skb we get out of strparser is a clone of
a 64kB data unit coalsced by GRO. To make things worse skb_cow_data()
tries to output a linear skb and allocates it with GFP_ATOMIC.
This occasionally fails even under moderate memory pressure.

This patch set rejigs the TLS Rx so that we don't expect decryption
in place. The decryption handlers return an skb which may or may not
be the skb from strparser. For TLS 1.3 this results in a 20-30%
performance improvement without NoPad enabled.

v2: rebase after ed00caf2bd5d ("net/tls: Check for errors in tls_device_init")
====================

Signed-off-by: David S. Miller <davem@davemloft.net>