net: tls: Set async_capable for tls zerocopy only if we see EINPROGRESS

Currently we don't zerocopy if the crypto framework async bit is set.
However some crypto algorithms (such as x86 AESNI) support async,
but in the context of sendmsg, will never run asynchronously.  Instead,
check for actual EINPROGRESS return code before assuming algorithm is
async.
Signed-off-by: Dave Watson <davejwatson@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tls.h

@@ -142,6 +142,7 @@ struct tls_sw_context_tx {
 	struct list_head tx_list;
 	atomic_t encrypt_pending;
 	int async_notify;
+	int async_capable;
 
 #define BIT_TX_SCHEDULED	0
 	unsigned long tx_bitmask;

net/tls/tls_sw.c

@@ -718,6 +718,7 @@ static int tls_push_record(struct sock *sk, int flags,
 				tls_merge_open_record(sk, rec, tmp, orig_end);
 			}
 		}
+		ctx->async_capable = 1;
 		return rc;
 	} else if (split) {
 		msg_pl = &tmp->msg_plaintext;
@@ -859,8 +860,7 @@ int tls_sw_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
 	long timeo = sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT);
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
 	struct tls_sw_context_tx *ctx = tls_sw_ctx_tx(tls_ctx);
-	struct crypto_tfm *tfm = crypto_aead_tfm(ctx->aead_send);
-	bool async_capable = tfm->__crt_alg->cra_flags & CRYPTO_ALG_ASYNC;
+	bool async_capable = ctx->async_capable;
 	unsigned char record_type = TLS_RECORD_TYPE_DATA;
 	bool is_kvec = iov_iter_is_kvec(&msg->msg_iter);
 	bool eor = !(msg->msg_flags & MSG_MORE);