diff --git a/lib/nbd-protocol.h b/lib/nbd-protocol.h
index e5d6404b..7247d775 100644
--- a/lib/nbd-protocol.h
+++ b/lib/nbd-protocol.h
@@ -1,5 +1,5 @@
 /* nbdkit
- * Copyright (C) 2013-2020 Red Hat Inc.
+ * Copyright (C) 2013-2021 Red Hat Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ -124,6 +124,7 @@ struct nbd_fixed_new_option_reply {
 #define NBD_OPT_STRUCTURED_REPLY   8
 #define NBD_OPT_LIST_META_CONTEXT  9
 #define NBD_OPT_SET_META_CONTEXT   10
+#define NBD_OPT_EXTENDED_HEADERS   11

 #define NBD_REP_ERR(val) (0x80000000 | (val))
 #define NBD_REP_IS_ERR(val) (!!((val) & 0x80000000))
@@ -188,6 +189,13 @@ struct nbd_block_descriptor {
   uint32_t status_flags;        /* block type (hole etc) */
 } NBD_ATTRIBUTE_PACKED;

+/* NBD_REPLY_TYPE_BLOCK_STATUS_EXT block descriptor. */
+struct nbd_block_descriptor_ext {
+  uint64_t length;              /* length of block */
+  uint32_t status_flags;        /* block type (hole etc) */
+  uint32_t pad;                 /* must be zero */
+} NBD_ATTRIBUTE_PACKED;
+
 /* Request (client -> server). */
 struct nbd_request {
   uint32_t magic;               /* NBD_REQUEST_MAGIC. */
@@ -197,6 +205,14 @@ struct nbd_request {
   uint64_t offset;              /* Request offset. */
   uint32_t count;               /* Request length. */
 } NBD_ATTRIBUTE_PACKED;
+struct nbd_request_ext {
+  uint32_t magic;               /* NBD_REQUEST_EXT_MAGIC. */
+  uint16_t flags;               /* Request flags. */
+  uint16_t type;                /* Request type. */
+  uint64_t handle;              /* Opaque handle. */
+  uint64_t offset;              /* Request offset. */
+  uint64_t count;               /* Request length. */
+} NBD_ATTRIBUTE_PACKED;

 /* Simple reply (server -> client). */
 struct nbd_simple_reply {
@@ -204,6 +220,13 @@ struct nbd_simple_reply {
   uint32_t error;               /* NBD_SUCCESS or one of NBD_E*. */
   uint64_t handle;              /* Opaque handle. */
 } NBD_ATTRIBUTE_PACKED;
+struct nbd_simple_reply_ext {
+  uint32_t magic;               /* NBD_SIMPLE_REPLY_EXT_MAGIC. */
+  uint32_t error;               /* NBD_SUCCESS or one of NBD_E*. */
+  uint64_t handle;              /* Opaque handle. */
+  uint64_t pad1;                /* Must be 0. */
+  uint64_t pad2;                /* Must be 0. */
+} NBD_ATTRIBUTE_PACKED;

 /* Structured reply (server -> client). */
 struct nbd_structured_reply {
@@ -213,6 +236,14 @@ struct nbd_structured_reply {
   uint64_t handle;              /* Opaque handle. */
   uint32_t length;              /* Length of payload which follows. */
 } NBD_ATTRIBUTE_PACKED;
+struct nbd_structured_reply_ext {
+  uint32_t magic;               /* NBD_STRUCTURED_REPLY_EXT_MAGIC. */
+  uint16_t flags;               /* NBD_REPLY_FLAG_* */
+  uint16_t type;                /* NBD_REPLY_TYPE_* */
+  uint64_t handle;              /* Opaque handle. */
+  uint64_t length;              /* Length of payload which follows. */
+  uint64_t pad;                 /* Must be 0. */
+} NBD_ATTRIBUTE_PACKED;

 struct nbd_structured_reply_offset_data {
   uint64_t offset;              /* offset */
@@ -224,15 +255,23 @@ struct nbd_structured_reply_offset_hole {
   uint32_t length;              /* Length of hole. */
 } NBD_ATTRIBUTE_PACKED;

+struct nbd_structured_reply_offset_hole_ext {
+  uint64_t offset;
+  uint64_t length;              /* Length of hole. */
+} NBD_ATTRIBUTE_PACKED;
+
 struct nbd_structured_reply_error {
   uint32_t error;               /* NBD_E* error number */
   uint16_t len;                 /* Length of human readable error. */
   /* Followed by human readable error string, and possibly more structure. */
 } NBD_ATTRIBUTE_PACKED;

-#define NBD_REQUEST_MAGIC           0x25609513
-#define NBD_SIMPLE_REPLY_MAGIC      0x67446698
-#define NBD_STRUCTURED_REPLY_MAGIC  0x668e33ef
+#define NBD_REQUEST_MAGIC               0x25609513
+#define NBD_REQUEST_EXT_MAGIC           0x21e41c71
+#define NBD_SIMPLE_REPLY_MAGIC          0x67446698
+#define NBD_SIMPLE_REPLY_EXT_MAGIC      0x60d12fd6
+#define NBD_STRUCTURED_REPLY_MAGIC      0x668e33ef
+#define NBD_STRUCTURED_REPLY_EXT_MAGIC  0x6e8a278c

 /* Structured reply flags. */
 #define NBD_REPLY_FLAG_DONE         (1<<0)
@@ -241,12 +280,14 @@ struct nbd_structured_reply_error {
 #define NBD_REPLY_TYPE_IS_ERR(val) (!!((val) & (1<<15)))

 /* Structured reply types. */
-#define NBD_REPLY_TYPE_NONE         0
-#define NBD_REPLY_TYPE_OFFSET_DATA  1
-#define NBD_REPLY_TYPE_OFFSET_HOLE  2
-#define NBD_REPLY_TYPE_BLOCK_STATUS 5
-#define NBD_REPLY_TYPE_ERROR        NBD_REPLY_TYPE_ERR (1)
-#define NBD_REPLY_TYPE_ERROR_OFFSET NBD_REPLY_TYPE_ERR (2)
+#define NBD_REPLY_TYPE_NONE             0
+#define NBD_REPLY_TYPE_OFFSET_DATA      1
+#define NBD_REPLY_TYPE_OFFSET_HOLE      2
+#define NBD_REPLY_TYPE_OFFSET_HOLE_EXT  3
+#define NBD_REPLY_TYPE_BLOCK_STATUS     5
+#define NBD_REPLY_TYPE_BLOCK_STATUS_EXT 6
+#define NBD_REPLY_TYPE_ERROR            NBD_REPLY_TYPE_ERR (1)
+#define NBD_REPLY_TYPE_ERROR_OFFSET     NBD_REPLY_TYPE_ERR (2)

 /* NBD commands. */
 #define NBD_CMD_READ              0
