net/tls: add kernel-driven resync mechanism for TX

TLS offload drivers keep track of TCP seq numbers to make sure
the packets are fed into the HW in order.

When packets get dropped on the way through the stack, the driver
will get out of sync and have to use fallback encryption, but unless
TCP seq number is resynced it will never match the packets correctly
(or even worse - use incorrect record sequence number after TCP seq
wraps).

Existing drivers (mlx5) feed the entire record on every out-of-order
event, allowing FW/HW to always be in sync.

This patch adds an alternative, more akin to the RX resync.  When
driver sees a frame which is past its expected sequence number the
stream must have gotten out of order (if the sequence number is
smaller than expected its likely a retransmission which doesn't
require resync).  Driver will ask the stack to perform TX sync
before it submits the next full record, and fall back to software
crypto until stack has performed the sync.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 27 insertions, 0 deletions

diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index b35a3b902bfa..40076f423dcb 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -209,6 +209,29 @@ void tls_device_free_resources_tx(struct sock *sk)
 	tls_free_partial_record(sk, tls_ctx);
 }
 
+static void tls_device_resync_tx(struct sock *sk, struct tls_context *tls_ctx,
+				 u32 seq)
+{
+	struct net_device *netdev;
+	struct sk_buff *skb;
+	u8 *rcd_sn;
+
+	skb = tcp_write_queue_tail(sk);
+	if (skb)
+		TCP_SKB_CB(skb)->eor = 1;
+
+	rcd_sn = tls_ctx->tx.rec_seq;
+
+	down_read(&device_offload_lock);
+	netdev = tls_ctx->netdev;
+	if (netdev)
+		netdev->tlsdev_ops->tls_dev_resync(netdev, sk, seq, rcd_sn,
+						   TLS_OFFLOAD_CTX_DIR_TX);
+	up_read(&device_offload_lock);
+
+	clear_bit_unlock(TLS_TX_SYNC_SCHED, &tls_ctx->flags);
+}
+
 static void tls_append_frag(struct tls_record_info *record,
 			    struct page_frag *pfrag,
 			    int size)
@@ -264,6 +287,10 @@ static int tls_push_record(struct sock *sk,
 	list_add_tail(&record->list, &offload_ctx->records_list);
 	spin_unlock_irq(&offload_ctx->lock);
 	offload_ctx->open_record = NULL;
+
+	if (test_bit(TLS_TX_SYNC_SCHED, &ctx->flags))
+		tls_device_resync_tx(sk, ctx, tp->write_seq);
+
 	tls_advance_record_sn(sk, prot, &ctx->tx);
 
 	for (i = 0; i < record->num_frags; i++) {