[PATCH net v2 2/4] tls: device: fix next-record sequence in core-driven RX resync

[Rishikesh Jethwani <rjethwani@purestorage.com>]

tls_device_core_ctrl_rx_resync() asks the device to resync at the next
record, passing rec_seq + 1 together with tcp_sk(sk)->copied_seq as that
record's TCP sequence. With the original strparser the current record
had already been read out of the TCP receive queue, so copied_seq was
the start of the next record.

The TLS-specific strparser leaves the record queued in its normal mode
until tls_strp_msg_consume(), so copied_seq is still the start of the
current record. The resync branch is taken when tcp_inq() does not
exceed the record length, i.e. typically when the current record is the
only data queued, and the device is told that record rec_seq + 1 begins
where record rec_seq begins. This can prevent hardware resynchronization
and keep subsequent records on the software decryption path. Further
resync attempts are made with backoff.

In copy mode copied_seq is already past the record, so the sequence is
correct there; the only exception is a FIN consumed along with the
record, after which no further record can follow.

Use the record start from tls_strp_msg_seq() plus the record length
instead. That is the start of the next record in both modes, so the
reported sequence no longer depends on which mode the strparser is in.

Only drivers using TLS_OFFLOAD_SYNC_TYPE_CORE_NEXT_HINT are affected.

Found by code inspection while working on TLS 1.3 hardware offload
support.

Fixes: 84c61fe1a75b ("tls: rx: do not use the standard strparser")
Signed-off-by: Rishikesh Jethwani <rjethwani@purestorage.com>
---
 net/tls/tls_device.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index fbfe6ec3df04..a6c4d0cc54c7 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -839,6 +839,7 @@ static void tls_device_core_ctrl_rx_resync(struct tls_context *tls_ctx,
 					   struct tls_offload_context_rx *ctx,
 					   struct sock *sk, struct sk_buff *skb)
 {
+	struct tls_sw_context_rx *sw_ctx = tls_sw_ctx_rx(tls_ctx);
 	struct strp_msg *rxm;
 
 	/* device will request resyncs by itself based on stream scan */
@@ -877,8 +878,9 @@ static void tls_device_core_ctrl_rx_resync(struct tls_context *tls_ctx,
 		memcpy(rcd_sn, tls_ctx->rx.rec_seq, prot->rec_seq_size);
 		tls_bigint_increment(rcd_sn, prot->rec_seq_size);
 
-		tls_device_resync_rx(tls_ctx, sk, tcp_sk(sk)->copied_seq,
-				     rcd_sn);
+		tls_device_resync_rx(tls_ctx, sk,
+				     tls_strp_msg_seq(sw_ctx) +
+				     rxm->full_len, rcd_sn);
 	}
 }
 
-- 
2.50.1