xref: /openbmc/qemu/blockdev-nbd.c (revision 154fd4d1) 
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 "qemu/osdep.h"
13 #include "sysemu/blockdev.h"
14 #include "sysemu/block-backend.h"
15 #include "hw/block/block.h"
16 #include "qapi/error.h"
17 #include "qapi/clone-visitor.h"
18 #include "qapi/qapi-visit-block-export.h"
19 #include "qapi/qapi-commands-block-export.h"
20 #include "block/nbd.h"
21 #include "io/channel-socket.h"
22 #include "io/net-listener.h"
23 
24 typedef struct NBDConn {
25     QIOChannelSocket *cioc;
26     QLIST_ENTRY(NBDConn) next;
27 } NBDConn;
28 
29 typedef struct NBDServerData {
30     QIONetListener *listener;
31     QCryptoTLSCreds *tlscreds;
32     char *tlsauthz;
33     uint32_t max_connections;
34     uint32_t connections;
35     QLIST_HEAD(, NBDConn) conns;
36 } NBDServerData;
37 
38 static NBDServerData *nbd_server;
39 static int qemu_nbd_connections = -1; /* Non-negative if this is qemu-nbd */
40 
41 static void nbd_update_server_watch(NBDServerData *s);
42 
43 void nbd_server_is_qemu_nbd(int max_connections)
44 {
45     qemu_nbd_connections = max_connections;
46 }
47 
48 bool nbd_server_is_running(void)
49 {
50     return nbd_server || qemu_nbd_connections >= 0;
51 }
52 
53 int nbd_server_max_connections(void)
54 {
55     return nbd_server ? nbd_server->max_connections : qemu_nbd_connections;
56 }
57 
58 static void nbd_blockdev_client_closed(NBDClient *client, bool ignored)
59 {
60     NBDConn *conn = nbd_client_owner(client);
61 
62     assert(qemu_in_main_thread() && nbd_server);
63 
64     object_unref(OBJECT(conn->cioc));
65     QLIST_REMOVE(conn, next);
66     g_free(conn);
67 
68     nbd_client_put(client);
69     assert(nbd_server->connections > 0);
70     nbd_server->connections--;
71     nbd_update_server_watch(nbd_server);
72 }
73 
74 static void nbd_accept(QIONetListener *listener, QIOChannelSocket *cioc,
75                        gpointer opaque)
76 {
77     NBDConn *conn = g_new0(NBDConn, 1);
78 
79     assert(qemu_in_main_thread() && nbd_server);
80     nbd_server->connections++;
81     object_ref(OBJECT(cioc));
82     conn->cioc = cioc;
83     QLIST_INSERT_HEAD(&nbd_server->conns, conn, next);
84     nbd_update_server_watch(nbd_server);
85 
86     qio_channel_set_name(QIO_CHANNEL(cioc), "nbd-server");
87     /* TODO - expose handshake timeout as QMP option */
88     nbd_client_new(cioc, NBD_DEFAULT_HANDSHAKE_MAX_SECS,
89                    nbd_server->tlscreds, nbd_server->tlsauthz,
90                    nbd_blockdev_client_closed, conn);
91 }
92 
93 static void nbd_update_server_watch(NBDServerData *s)
94 {
95     if (s->listener) {
96         if (!s->max_connections || s->connections < s->max_connections) {
97             qio_net_listener_set_client_func(s->listener, nbd_accept, NULL,
98                                              NULL);
99         } else {
100             qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL);
101         }
102     }
103 }
104 
105 static void nbd_server_free(NBDServerData *server)
106 {
107     NBDConn *conn, *tmp;
108 
109     if (!server) {
110         return;
111     }
112 
113     /*
114      * Forcefully close the listener socket, and any clients that have
115      * not yet disconnected on their own.
116      */
117     qio_net_listener_disconnect(server->listener);
118     object_unref(OBJECT(server->listener));
119     server->listener = NULL;
120     QLIST_FOREACH_SAFE(conn, &server->conns, next, tmp) {
121         qio_channel_shutdown(QIO_CHANNEL(conn->cioc), QIO_CHANNEL_SHUTDOWN_BOTH,
122                              NULL);
123     }
124 
125     AIO_WAIT_WHILE_UNLOCKED(NULL, server->connections > 0);
126 
127     if (server->tlscreds) {
128         object_unref(OBJECT(server->tlscreds));
129     }
130     g_free(server->tlsauthz);
131 
132     g_free(server);
133 }
134 
135 static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
136 {
137     Object *obj;
138     QCryptoTLSCreds *creds;
139 
140     obj = object_resolve_path_component(
141         object_get_objects_root(), id);
142     if (!obj) {
143         error_setg(errp, "No TLS credentials with id '%s'",
144                    id);
145         return NULL;
146     }
147     creds = (QCryptoTLSCreds *)
148         object_dynamic_cast(obj, TYPE_QCRYPTO_TLS_CREDS);
149     if (!creds) {
150         error_setg(errp, "Object with id '%s' is not TLS credentials",
151                    id);
152         return NULL;
153     }
154 
155     if (!qcrypto_tls_creds_check_endpoint(creds,
156                                           QCRYPTO_TLS_CREDS_ENDPOINT_SERVER,
157                                           errp)) {
158         return NULL;
159     }
160     object_ref(obj);
161     return creds;
162 }
163 
164 
165 void nbd_server_start(SocketAddress *addr, const char *tls_creds,
166                       const char *tls_authz, uint32_t max_connections,
167                       Error **errp)
168 {
169     if (nbd_server) {
170         error_setg(errp, "NBD server already running");
171         return;
172     }
173 
174     nbd_server = g_new0(NBDServerData, 1);
175     nbd_server->max_connections = max_connections;
176     nbd_server->listener = qio_net_listener_new();
177 
178     qio_net_listener_set_name(nbd_server->listener,
179                               "nbd-listener");
180 
181     /*
182      * Because this server is persistent, a backlog of SOMAXCONN is
183      * better than trying to size it to max_connections.
184      */
185     if (qio_net_listener_open_sync(nbd_server->listener, addr, SOMAXCONN,
186                                    errp) < 0) {
187         goto error;
188     }
189 
190     if (tls_creds) {
191         nbd_server->tlscreds = nbd_get_tls_creds(tls_creds, errp);
192         if (!nbd_server->tlscreds) {
193             goto error;
194         }
195     }
196 
197     nbd_server->tlsauthz = g_strdup(tls_authz);
198 
199     nbd_update_server_watch(nbd_server);
200 
201     return;
202 
203  error:
204     nbd_server_free(nbd_server);
205     nbd_server = NULL;
206 }
207 
208 void nbd_server_start_options(NbdServerOptions *arg, Error **errp)
209 {
210     if (!arg->has_max_connections) {
211         arg->max_connections = NBD_DEFAULT_MAX_CONNECTIONS;
212     }
213 
214     nbd_server_start(arg->addr, arg->tls_creds, arg->tls_authz,
215                      arg->max_connections, errp);
216 }
217 
218 void qmp_nbd_server_start(SocketAddressLegacy *addr,
219                           const char *tls_creds,
220                           const char *tls_authz,
221                           bool has_max_connections, uint32_t max_connections,
222                           Error **errp)
223 {
224     SocketAddress *addr_flat = socket_address_flatten(addr);
225 
226     if (!has_max_connections) {
227         max_connections = NBD_DEFAULT_MAX_CONNECTIONS;
228     }
229 
230     nbd_server_start(addr_flat, tls_creds, tls_authz, max_connections, errp);
231     qapi_free_SocketAddress(addr_flat);
232 }
233 
234 void qmp_nbd_server_add(NbdServerAddOptions *arg, Error **errp)
235 {
236     BlockExport *export;
237     BlockDriverState *bs;
238     BlockBackend *on_eject_blk;
239     BlockExportOptions *export_opts;
240 
241     bs = bdrv_lookup_bs(arg->device, arg->device, errp);
242     if (!bs) {
243         return;
244     }
245 
246     /*
247      * block-export-add would default to the node-name, but we may have to use
248      * the device name as a default here for compatibility.
249      */
250     if (!arg->name) {
251         arg->name = g_strdup(arg->device);
252     }
253 
254     export_opts = g_new(BlockExportOptions, 1);
255     *export_opts = (BlockExportOptions) {
256         .type                   = BLOCK_EXPORT_TYPE_NBD,
257         .id                     = g_strdup(arg->name),
258         .node_name              = g_strdup(bdrv_get_node_name(bs)),
259         .has_writable           = arg->has_writable,
260         .writable               = arg->writable,
261     };
262     QAPI_CLONE_MEMBERS(BlockExportOptionsNbdBase, &export_opts->u.nbd,
263                        qapi_NbdServerAddOptions_base(arg));
264     if (arg->bitmap) {
265         BlockDirtyBitmapOrStr *el = g_new(BlockDirtyBitmapOrStr, 1);
266 
267         *el = (BlockDirtyBitmapOrStr) {
268             .type = QTYPE_QSTRING,
269             .u.local = g_strdup(arg->bitmap),
270         };
271         export_opts->u.nbd.has_bitmaps = true;
272         QAPI_LIST_PREPEND(export_opts->u.nbd.bitmaps, el);
273     }
274 
275     /*
276      * nbd-server-add doesn't complain when a read-only device should be
277      * exported as writable, but simply downgrades it. This is an error with
278      * block-export-add.
279      */
280     if (bdrv_is_read_only(bs)) {
281         export_opts->has_writable = true;
282         export_opts->writable = false;
283     }
284 
285     export = blk_exp_add(export_opts, errp);
286     if (!export) {
287         goto fail;
288     }
289 
290     /*
291      * nbd-server-add removes the export when the named BlockBackend used for
292      * @device goes away.
293      */
294     on_eject_blk = blk_by_name(arg->device);
295     if (on_eject_blk) {
296         nbd_export_set_on_eject_blk(export, on_eject_blk);
297     }
298 
299 fail:
300     qapi_free_BlockExportOptions(export_opts);
301 }
302 
303 void qmp_nbd_server_remove(const char *name,
304                            bool has_mode, BlockExportRemoveMode mode,
305                            Error **errp)
306 {
307     BlockExport *exp;
308 
309     exp = blk_exp_find(name);
310     if (exp && exp->drv->type != BLOCK_EXPORT_TYPE_NBD) {
311         error_setg(errp, "Block export '%s' is not an NBD export", name);
312         return;
313     }
314 
315     qmp_block_export_del(name, has_mode, mode, errp);
316 }
317 
318 void qmp_nbd_server_stop(Error **errp)
319 {
320     if (!nbd_server) {
321         error_setg(errp, "NBD server not running");
322         return;
323     }
324 
325     blk_exp_close_all_type(BLOCK_EXPORT_TYPE_NBD);
326 
327     nbd_server_free(nbd_server);
328     nbd_server = NULL;
329 }
330