net/tls: avoid spurious decryption error with HW resync

When device loses sync mid way through a record - kernel
has to re-encrypt the part of the record which the device
already decrypted to be able to decrypt and authenticate
the record in its entirety.

The re-encryption piggy backs on the decryption routine,
but obviously because the partially decrypted record can't
be authenticated crypto API returns an error which is then
ignored by tls_device_reencrypt().

Commit 5c5ec668 ("net/tls: add TlsDecryptError stat")
added a statistic to count decryption errors, this statistic
can't be incremented when we see the expected re-encryption
error. Move the inc to the caller.
Reported-and-tested-by: NDavid Beckett <david.beckett@netronome.com>
Fixes: 5c5ec668 ("net/tls: add TlsDecryptError stat")
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: NSimon Horman <simon.horman@netronome.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/tls/tls_sw.c

@@ -256,8 +256,6 @@ static int tls_do_decryption(struct sock *sk,
 			return ret;
 
 		ret = crypto_wait_req(ret, &ctx->async_wait);
-	} else if (ret == -EBADMSG) {
-		TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSDECRYPTERROR);
 	}
 
 	if (async)
@@ -1515,7 +1513,9 @@ static int decrypt_skb_update(struct sock *sk, struct sk_buff *skb,
 				if (err == -EINPROGRESS)
 					tls_advance_record_sn(sk, prot,
 							      &tls_ctx->rx);
-
+				else if (err == -EBADMSG)
+					TLS_INC_STATS(sock_net(sk),
+						      LINUX_MIB_TLSDECRYPTERROR);
 				return err;
 			}
 		} else {