tls: rx: don't report text length from the bowels of decrypt
We plumb pointer to chunk all the way to the decryption method.
It's set to the length of the text when decrypt_skb_update()
returns.
I think the code is written this way because original TLS
implementation passed &chunk to zerocopy_from_iter() and this
was carried forward as the code gotten more complex, without
any refactoring.
The fix for peek() introduced a new variable - to_decrypt
which for all practical purposes is what chunk is going to
get set to. Spare ourselves the pointer passing, use to_decrypt.
Use this opportunity to clean things up a little further.
Note that chunk / to_decrypt was mostly needed for the async
path, since the sync path would access rxm->full_len (decryption
transforms full_len from record size to text size). Use the
right source of truth more explicitly.
We have three cases:
- async - it's TLS 1.2 only, so chunk == to_decrypt, but we
need the min() because to_decrypt is a whole record
and we don't want to underflow len. Note that we can't
handle partial record by falling back to sync as it
would introduce reordering against records in flight.
- zc - again, TLS 1.2 only for now, so chunk == to_decrypt,
we don't do zc if len < to_decrypt, no need to check again.
- normal - it already handles chunk > len, we can factor out the
assignment to rxm->full_len and share it with zc.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>