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, 39 insertions, 0 deletions

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index ae2b281c9c57..56a99d0c9aa0 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -73,6 +73,45 @@ int sk_msg_alloc(struct sock *sk, struct sk_msg *msg, int len,
 }
 EXPORT_SYMBOL_GPL(sk_msg_alloc);
 
+int sk_msg_clone(struct sock *sk, struct sk_msg *dst, struct sk_msg *src,
+		 u32 off, u32 len)
+{
+	int i = src->sg.start;
+	struct scatterlist *sge = sk_msg_elem(src, i);
+	u32 sge_len, sge_off;
+
+	if (sk_msg_full(dst))
+		return -ENOSPC;
+
+	while (off) {
+		if (sge->length > off)
+			break;
+		off -= sge->length;
+		sk_msg_iter_var_next(i);
+		if (i == src->sg.end && off)
+			return -ENOSPC;
+		sge = sk_msg_elem(src, i);
+	}
+
+	while (len) {
+		sge_len = sge->length - off;
+		sge_off = sge->offset + off;
+		if (sge_len > len)
+			sge_len = len;
+		off = 0;
+		len -= sge_len;
+		sk_msg_page_add(dst, sg_page(sge), sge_len, sge_off);
+		sk_mem_charge(sk, sge_len);
+		sk_msg_iter_var_next(i);
+		if (i == src->sg.end && len)
+			return -ENOSPC;
+		sge = sk_msg_elem(src, i);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sk_msg_clone);
+
 void sk_msg_return_zero(struct sock *sk, struct sk_msg *msg, int bytes)
 {
 	int i = msg->sg.start;