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>

2 files changed, 9 insertions, 13 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 751549ac0a84..7470c45d182d 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2214,10 +2214,6 @@ static inline struct page_frag *sk_page_frag(struct sock *sk)
 
 bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);
 
-int sk_alloc_sg(struct sock *sk, int len, struct scatterlist *sg,
-		int sg_start, int *sg_curr, unsigned int *sg_size,
-		int first_coalesce);
-
 /*
  *	Default write policy as shown to user space via poll/select/SIGIO
  */
diff --git a/include/net/tls.h b/include/net/tls.h
index 5e853835597e..3d22d8a59be7 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -39,6 +39,8 @@
 #include <linux/crypto.h>
 #include <linux/socket.h>
 #include <linux/tcp.h>
+#include <linux/skmsg.h>
+
 #include <net/tcp.h>
 #include <net/strparser.h>
 #include <crypto/aead.h>
@@ -103,15 +105,13 @@ struct tls_rec {
 	int tx_flags;
 	int inplace_crypto;
 
-	/* AAD | sg_plaintext_data | sg_tag */
-	struct scatterlist sg_plaintext_data[MAX_SKB_FRAGS + 1];
-	/* AAD | sg_encrypted_data (data contain overhead for hdr&iv&tag) */
-	struct scatterlist sg_encrypted_data[MAX_SKB_FRAGS + 1];
+	struct sk_msg msg_plaintext;
+	struct sk_msg msg_encrypted;
 
-	unsigned int sg_plaintext_size;
-	unsigned int sg_encrypted_size;
-	int sg_plaintext_num_elem;
-	int sg_encrypted_num_elem;
+	/* AAD | msg_plaintext.sg.data | sg_tag */
+	struct scatterlist sg_aead_in[2];
+	/* AAD | msg_encrypted.sg.data (data contains overhead for hdr & iv & tag) */
+	struct scatterlist sg_aead_out[2];
 
 	char aad_space[TLS_AAD_SPACE_SIZE];
 	struct aead_request aead_req;
@@ -223,8 +223,8 @@ struct tls_context {
 
 	unsigned long flags;
 	bool in_tcp_sendpages;
+	bool pending_open_record_frags;
 
-	u16 pending_open_record_frags;
 	int (*push_pending_record)(struct sock *sk, int flags);
 
 	void (*sk_write_space)(struct sock *sk);