hmp: add NBD server commands

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hmp-commands.hx

@@ -1310,6 +1310,51 @@ Remove all matches from the access control list, and set the default
 policy back to @code{deny}.
 ETEXI
 
+    {
+        .name       = "nbd_server_start",
+        .args_type  = "all:-a,writable:-w,uri:s",
+        .params     = "nbd_server_start [-a] [-w] host:port",
+        .help       = "serve block devices on the given host and port",
+        .mhandler.cmd = hmp_nbd_server_start,
+    },
+STEXI
+@item nbd_server_start @var{host}:@var{port}
+@findex nbd_server_start
+Start an NBD server on the given host and/or port.  If the @option{-a}
+option is included, all of the virtual machine's block devices that
+have an inserted media on them are automatically exported; in this case,
+the @option{-w} option makes the devices writable too.
+ETEXI
+
+    {
+        .name       = "nbd_server_add",
+        .args_type  = "writable:-w,device:B",
+        .params     = "nbd_server_add [-w] device",
+        .help       = "export a block device via NBD",
+        .mhandler.cmd = hmp_nbd_server_add,
+    },
+STEXI
+@item nbd_server_add @var{device}
+@findex nbd_server_add
+Export a block device through QEMU's NBD server, which must be started
+beforehand with @command{nbd_server_start}.  The @option{-w} option makes the
+exported device writable too.
+ETEXI
+
+    {
+        .name       = "nbd_server_stop",
+        .args_type  = "",
+        .params     = "nbd_server_stop",
+        .help       = "stop serving block devices using the NBD protocol",
+        .mhandler.cmd = hmp_nbd_server_stop,
+    },
+STEXI
+@item nbd_server_stop
+@findex nbd_server_stop
+Stop the QEMU embedded NBD server.
+ETEXI
+
+
 #if defined(TARGET_I386)
 
     {

hmp.c

@@ -18,6 +18,7 @@
 #include "qemu-option.h"
 #include "qemu-timer.h"
 #include "qmp-commands.h"
+#include "qemu_socket.h"
 #include "monitor.h"
 #include "console.h"
 
@@ -1259,3 +1260,78 @@ void hmp_screen_dump(Monitor *mon, const QDict *qdict)
     qmp_screendump(filename, &err);
     hmp_handle_error(mon, &err);
 }
+
+void hmp_nbd_server_start(Monitor *mon, const QDict *qdict)
+{
+    const char *uri = qdict_get_str(qdict, "uri");
+    int writable = qdict_get_try_bool(qdict, "writable", 0);
+    int all = qdict_get_try_bool(qdict, "all", 0);
+    Error *local_err = NULL;
+    BlockInfoList *block_list, *info;
+    SocketAddress *addr;
+
+    if (writable && !all) {
+        error_setg(&local_err, "-w only valid together with -a");
+        goto exit;
+    }
+
+    /* First check if the address is valid and start the server.  */
+    addr = socket_parse(uri, &local_err);
+    if (local_err != NULL) {
+        goto exit;
+    }
+
+    qmp_nbd_server_start(addr, &local_err);
+    qapi_free_SocketAddress(addr);
+    if (local_err != NULL) {
+        goto exit;
+    }
+
+    if (!all) {
+        return;
+    }
+
+    /* Then try adding all block devices.  If one fails, close all and
+     * exit.
+     */
+    block_list = qmp_query_block(NULL);
+
+    for (info = block_list; info; info = info->next) {
+        if (!info->value->has_inserted) {
+            continue;
+        }
+
+        qmp_nbd_server_add(info->value->device, true, writable, &local_err);
+
+        if (local_err != NULL) {
+            qmp_nbd_server_stop(NULL);
+            break;
+        }
+    }
+
+    qapi_free_BlockInfoList(block_list);
+
+exit:
+    hmp_handle_error(mon, &local_err);
+}
+
+void hmp_nbd_server_add(Monitor *mon, const QDict *qdict)
+{
+    const char *device = qdict_get_str(qdict, "device");
+    int writable = qdict_get_try_bool(qdict, "writable", 0);
+    Error *local_err = NULL;
+
+    qmp_nbd_server_add(device, true, writable, &local_err);
+
+    if (local_err != NULL) {
+        hmp_handle_error(mon, &local_err);
+    }
+}
+
+void hmp_nbd_server_stop(Monitor *mon, const QDict *qdict)
+{
+    Error *errp = NULL;
+
+    qmp_nbd_server_stop(&errp);
+    hmp_handle_error(mon, &errp);
+}

hmp.h

@@ -77,5 +77,8 @@ void hmp_getfd(Monitor *mon, const QDict *qdict);
 void hmp_closefd(Monitor *mon, const QDict *qdict);
 void hmp_send_key(Monitor *mon, const QDict *qdict);
 void hmp_screen_dump(Monitor *mon, const QDict *qdict);
+void hmp_nbd_server_start(Monitor *mon, const QDict *qdict);
+void hmp_nbd_server_add(Monitor *mon, const QDict *qdict);
+void hmp_nbd_server_stop(Monitor *mon, const QDict *qdict);
 
 #endif