tls: convert to generic sk_msg interface

Convert kTLS over to make use of sk_msg interface for plaintext and
encrypted scattergather data, so it reuses all the sk_msg helpers
and data structure which later on in a second step enables to glue
this to BPF.

This also allows to remove quite a bit of open coded helpers which
are covered by the sk_msg API. Recent changes in kTLs 80ece6a03aaf
("tls: Remove redundant vars from tls record structure") and
4e6d47206c32 ("tls: Add support for inplace records encryption")
changed the data path handling a bit; while we've kept the latter
optimization intact, we had to undo the former change to better
fit the sk_msg model, hence the sg_aead_in and sg_aead_out have
been brought back and are linked into the sk_msg sgs. Now the kTLS
record contains a msg_plaintext and msg_encrypted sk_msg each.

In the original code, the zerocopy_from_iter() has been used out
of TX but also RX path. For the strparser skb-based RX path,
we've left the zerocopy_from_iter() in decrypt_internal() mostly
untouched, meaning it has been moved into tls_setup_from_iter()
with charging logic removed (as not used from RX). Given RX path
is not based on sk_msg objects, we haven't pursued setting up a
dummy sk_msg to call into sk_msg_zerocopy_from_iter(), but it
could be an option to prusue in a later step.

Joint work with John.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 95678103c4a0..4e84b3c2eff8 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -102,6 +102,8 @@ struct sk_psock {
 
 int sk_msg_alloc(struct sock *sk, struct sk_msg *msg, int len,
 		 int elem_first_coalesce);
+int sk_msg_clone(struct sock *sk, struct sk_msg *dst, struct sk_msg *src,
+		 u32 off, u32 len);
 void sk_msg_trim(struct sock *sk, struct sk_msg *msg, int len);
 int sk_msg_free(struct sock *sk, struct sk_msg *msg);
 int sk_msg_free_nocharge(struct sock *sk, struct sk_msg *msg);