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-rw-r--r--docs/interop/nbd.txt1
-rw-r--r--nbd/server.c21
2 files changed, 22 insertions, 0 deletions
diff --git a/docs/interop/nbd.txt b/docs/interop/nbd.txt
index f5ca25174a..9aae5e1f29 100644
--- a/docs/interop/nbd.txt
+++ b/docs/interop/nbd.txt
@@ -69,3 +69,4 @@ NBD_CMD_BLOCK_STATUS for "qemu:dirty-bitmap:", NBD_CMD_CACHE
 NBD_CMD_FLAG_FAST_ZERO
 * 5.2: NBD_CMD_BLOCK_STATUS for "qemu:allocation-depth"
 * 7.1: NBD_FLAG_CAN_MULTI_CONN for shareable writable exports
+* 8.2: NBD_OPT_EXTENDED_HEADERS
diff --git a/nbd/server.c b/nbd/server.c
index 183efe27bf..d3eed6535b 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -482,6 +482,10 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
         [10 .. 133]   reserved     (0) [unless no_zeroes]
      */
     trace_nbd_negotiate_handle_export_name();
+    if (client->mode >= NBD_MODE_EXTENDED) {
+        error_setg(errp, "Extended headers already negotiated");
+        return -EINVAL;
+    }
     if (client->optlen > NBD_MAX_STRING_SIZE) {
         error_setg(errp, "Bad length received");
         return -EINVAL;
@@ -1264,6 +1268,10 @@ static int nbd_negotiate_options(NBDClient *client, Error **errp)
             case NBD_OPT_STRUCTURED_REPLY:
                 if (length) {
                     ret = nbd_reject_length(client, false, errp);
+                } else if (client->mode >= NBD_MODE_EXTENDED) {
+                    ret = nbd_negotiate_send_rep_err(
+                        client, NBD_REP_ERR_EXT_HEADER_REQD, errp,
+                        "extended headers already negotiated");
                 } else if (client->mode >= NBD_MODE_STRUCTURED) {
                     ret = nbd_negotiate_send_rep_err(
                         client, NBD_REP_ERR_INVALID, errp,
@@ -1280,6 +1288,19 @@ static int nbd_negotiate_options(NBDClient *client, Error **errp)
                                                  errp);
                 break;
 
+            case NBD_OPT_EXTENDED_HEADERS:
+                if (length) {
+                    ret = nbd_reject_length(client, false, errp);
+                } else if (client->mode >= NBD_MODE_EXTENDED) {
+                    ret = nbd_negotiate_send_rep_err(
+                        client, NBD_REP_ERR_INVALID, errp,
+                        "extended headers already negotiated");
+                } else {
+                    ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
+                    client->mode = NBD_MODE_EXTENDED;
+                }
+                break;
+
             default:
                 ret = nbd_opt_drop(client, NBD_REP_ERR_UNSUP, errp,
                                    "Unsupported option %" PRIu32 " (%s)",