[Qemu-block] [PATCH v7 4/9] block/nbd: add cmdline and qapi parameter reconnect-delay

[Vladimir Sementsov-Ogievskiy]

Reconnect will be implemented in the following commit, so for now,
in semantics below, disconnect itself is a "serious error".

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
 qapi/block-core.json | 11 ++++++++++-
 block/nbd.c          | 16 +++++++++++++++-
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 61124431d8..17faf723e0 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3858,13 +3858,22 @@
 #                  traditional "base:allocation" block status (see
 #                  NBD_OPT_LIST_META_CONTEXT in the NBD protocol) (since 3.0)
 #
+# @reconnect-delay: On an unexpected disconnect, the nbd client tries to
+#                   connect again until succeeding or encountering a serious
+#                   error.  During the first @reconnect-delay seconds, all
+#                   requests are paused and will be rerun on a successful
+#                   reconnect. After that time, any delayed requests and all
+#                   future requests before a successful reconnect will
+#                   immediately fail. Default 0 (Since 4.1)
+#
 # Since: 2.9
 ##
 { 'struct': 'BlockdevOptionsNbd',
   'data': { 'server': 'SocketAddress',
             '*export': 'str',
             '*tls-creds': 'str',
-            '*x-dirty-bitmap': 'str' } }
+            '*x-dirty-bitmap': 'str',
+            '*reconnect-delay': 'uint32' } }
 
 ##
 # @BlockdevOptionsRaw:
diff --git a/block/nbd.c b/block/nbd.c
index 9e505c895a..df9b0a2c8a 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1276,6 +1276,7 @@ static int nbd_client_init(BlockDriverState *bs,
                            QCryptoTLSCreds *tlscreds,
                            const char *hostname,
                            const char *x_dirty_bitmap,
+                           uint32_t reconnect_delay,
                            Error **errp)
 {
     int ret;
@@ -1601,6 +1602,17 @@ static QemuOptsList nbd_runtime_opts = {
             .help = "experimental: expose named dirty bitmap in place of "
                     "block status",
         },
+        {
+            .name = "reconnect-delay",
+            .type = QEMU_OPT_NUMBER,
+            .help = "On an unexpected disconnect, the nbd client tries to "
+                    "connect again until succeeding or encountering a serious "
+                    "error.  During the first @reconnect-delay seconds, all "
+                    "requests are paused and will be rerun on a successful "
+                    "reconnect. After that time, any delayed requests and all "
+                    "future requests before a successful reconnect will "
+                    "immediately fail. Default 0",
+        },
         { /* end of list */ }
     },
 };
@@ -1652,7 +1664,9 @@ static int nbd_open(BlockDriverState *bs, QDict *options, 
int flags,
 
     /* NBD handshake */
     ret = nbd_client_init(bs, s->saddr, s->export, tlscreds, hostname,
-                          qemu_opt_get(opts, "x-dirty-bitmap"), errp);
+                          qemu_opt_get(opts, "x-dirty-bitmap"),
+                          qemu_opt_get_number(opts, "reconnect-delay", 0),
+                          errp);
 
  error:
     if (tlscreds) {
-- 
2.18.0