xref: /openbmc/qemu/blockdev-nbd.c (revision 36f96c4b)
1 /*
2  * Serving QEMU block devices via NBD
3  *
4  * Copyright (c) 2012 Red Hat, Inc.
5  *
6  * Author: Paolo Bonzini <pbonzini@redhat.com>
7  *
8  * This work is licensed under the terms of the GNU GPL, version 2 or
9  * later.  See the COPYING file in the top-level directory.
10  */
11 
12 #include "sysemu/blockdev.h"
13 #include "sysemu/block-backend.h"
14 #include "hw/block/block.h"
15 #include "qapi/qmp/qerror.h"
16 #include "sysemu/sysemu.h"
17 #include "qmp-commands.h"
18 #include "trace.h"
19 #include "block/nbd.h"
20 #include "qemu/sockets.h"
21 
22 static int server_fd = -1;
23 
24 static void nbd_accept(void *opaque)
25 {
26     struct sockaddr_in addr;
27     socklen_t addr_len = sizeof(addr);
28 
29     int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
30     if (fd >= 0) {
31         nbd_client_new(NULL, fd, nbd_client_put);
32     }
33 }
34 
35 void qmp_nbd_server_start(SocketAddress *addr, Error **errp)
36 {
37     if (server_fd != -1) {
38         error_setg(errp, "NBD server already running");
39         return;
40     }
41 
42     server_fd = socket_listen(addr, errp);
43     if (server_fd != -1) {
44         qemu_set_fd_handler(server_fd, nbd_accept, NULL, NULL);
45     }
46 }
47 
48 /*
49  * Hook into the BlockBackend notifiers to close the export when the
50  * backend is closed.
51  */
52 typedef struct NBDCloseNotifier {
53     Notifier n;
54     NBDExport *exp;
55     QTAILQ_ENTRY(NBDCloseNotifier) next;
56 } NBDCloseNotifier;
57 
58 static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers =
59     QTAILQ_HEAD_INITIALIZER(close_notifiers);
60 
61 static void nbd_close_notifier(Notifier *n, void *data)
62 {
63     NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n);
64 
65     notifier_remove(&cn->n);
66     QTAILQ_REMOVE(&close_notifiers, cn, next);
67 
68     nbd_export_close(cn->exp);
69     nbd_export_put(cn->exp);
70     g_free(cn);
71 }
72 
73 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
74                         Error **errp)
75 {
76     BlockBackend *blk;
77     NBDExport *exp;
78     NBDCloseNotifier *n;
79 
80     if (server_fd == -1) {
81         error_setg(errp, "NBD server not running");
82         return;
83     }
84 
85     if (nbd_export_find(device)) {
86         error_setg(errp, "NBD server already exporting device '%s'", device);
87         return;
88     }
89 
90     blk = blk_by_name(device);
91     if (!blk) {
92         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
93                   "Device '%s' not found", device);
94         return;
95     }
96     if (!blk_is_inserted(blk)) {
97         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
98         return;
99     }
100 
101     if (!has_writable) {
102         writable = false;
103     }
104     if (blk_is_read_only(blk)) {
105         writable = false;
106     }
107 
108     exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL,
109                          errp);
110     if (!exp) {
111         return;
112     }
113 
114     nbd_export_set_name(exp, device);
115 
116     n = g_new0(NBDCloseNotifier, 1);
117     n->n.notify = nbd_close_notifier;
118     n->exp = exp;
119     blk_add_close_notifier(blk, &n->n);
120     QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
121 }
122 
123 void qmp_nbd_server_stop(Error **errp)
124 {
125     while (!QTAILQ_EMPTY(&close_notifiers)) {
126         NBDCloseNotifier *cn = QTAILQ_FIRST(&close_notifiers);
127         nbd_close_notifier(&cn->n, nbd_export_get_blockdev(cn->exp));
128     }
129 
130     if (server_fd != -1) {
131         qemu_set_fd_handler(server_fd, NULL, NULL, NULL);
132         close(server_fd);
133         server_fd = -1;
134     }
135 }
136