drbd: drbd_send_ack_dp must not rely on header information

drbd commit 17c854fea474a5eb3cfa12e4fb019e46debbc4ec
drbd: receiving of big packets, for payloads between 64kByte and 4GByte
introduced a new on-the-wire packet header format.  We must no longer
assume either format, but use the result of whatever drbd_recv_header
has decoded.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_int.h

@@ -1230,7 +1230,7 @@ extern int drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
 extern int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
 			struct p_block_req *rp);
 extern int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
-			struct p_data *dp);
+			struct p_data *dp, int data_size);
 extern int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
 			    sector_t sector, int blksize, u64 block_id);
 extern int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,

drivers/block/drbd/drbd_main.c

@@ -2193,13 +2193,14 @@ static int _drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
 	return ok;
 }
 
+/* dp->sector and dp->block_id already/still in network byte order,
+ * data_size is payload size according to dp->head,
+ * and may need to be corrected for digest size. */
 int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
-		     struct p_data *dp)
+		     struct p_data *dp, int data_size)
 {
-	const int header_size = sizeof(struct p_data)
-			      - sizeof(struct p_header80);
-	int data_size  = ((struct p_header80 *)dp)->length - header_size;
-
+	data_size -= (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+		crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
 	return _drbd_send_ack(mdev, cmd, dp->sector, cpu_to_be32(data_size),
 			      dp->block_id);
 }

drivers/block/drbd/drbd_receiver.c

@@ -1630,7 +1630,7 @@ static int receive_RSDataReply(struct drbd_conf *mdev, enum drbd_packets cmd, un
 
 		ok = drbd_drain_block(mdev, data_size);
 
-		drbd_send_ack_dp(mdev, P_NEG_ACK, p);
+		drbd_send_ack_dp(mdev, P_NEG_ACK, p, data_size);
 	}
 
 	atomic_add(data_size >> 9, &mdev->rs_sect_in);
@@ -1787,7 +1787,7 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
 			mdev->peer_seq++;
 		spin_unlock(&mdev->peer_seq_lock);
 
-		drbd_send_ack_dp(mdev, P_NEG_ACK, p);
+		drbd_send_ack_dp(mdev, P_NEG_ACK, p, data_size);
 		atomic_inc(&mdev->current_epoch->epoch_size);
 		return drbd_drain_block(mdev, data_size);
 	}