tls: Fix recvmsg() to be able to peek across multiple records

This fixes recvmsg() to be able to peek across multiple tls records.
Without this patch, the tls's selftests test case
'recv_peek_large_buf_mult_recs' fails. Each tls receive context now
maintains a 'rx_list' to retain incoming skb carrying tls records. If a
tls record needs to be retained e.g. for peek case or for the case when
the buffer passed to recvmsg() has a length smaller than decrypted
record length, then it is added to 'rx_list'. Additionally, records are
added in 'rx_list' if the crypto operation runs in async mode. The
records are dequeued from 'rx_list' after the decrypted data is consumed
by copying into the buffer passed to recvmsg(). In case, the MSG_PEEK
flag is used in recvmsg(), then records are not consumed or removed
from the 'rx_list'.

Signed-off-by: Vakul Garg <vakul.garg@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tls.h

@@ -145,12 +145,13 @@ struct tls_sw_context_tx {
 struct tls_sw_context_rx {
 	struct crypto_aead *aead_recv;
 	struct crypto_wait async_wait;
-
 	struct strparser strp;
+	struct sk_buff_head rx_list;	/* list of decrypted 'data' records */
 	void (*saved_data_ready)(struct sock *sk);
 
 	struct sk_buff *recv_pkt;
 	u8 control;
+	int async_capable;
 	bool decrypted;
 	atomic_t decrypt_pending;
 	bool async_notify;