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 "monitor/monitor.h" 16 #include "qapi/qmp/qerror.h" 17 #include "sysemu/sysemu.h" 18 #include "qmp-commands.h" 19 #include "trace.h" 20 #include "block/nbd.h" 21 #include "qemu/sockets.h" 22 23 static int server_fd = -1; 24 25 static void nbd_accept(void *opaque) 26 { 27 struct sockaddr_in addr; 28 socklen_t addr_len = sizeof(addr); 29 30 int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len); 31 if (fd >= 0 && !nbd_client_new(NULL, fd, nbd_client_put)) { 32 shutdown(fd, 2); 33 close(fd); 34 } 35 } 36 37 void qmp_nbd_server_start(SocketAddress *addr, Error **errp) 38 { 39 if (server_fd != -1) { 40 error_setg(errp, "NBD server already running"); 41 return; 42 } 43 44 server_fd = socket_listen(addr, errp); 45 if (server_fd != -1) { 46 qemu_set_fd_handler(server_fd, nbd_accept, NULL, NULL); 47 } 48 } 49 50 /* 51 * Hook into the BlockBackend notifiers to close the export when the 52 * backend is closed. 53 */ 54 typedef struct NBDCloseNotifier { 55 Notifier n; 56 NBDExport *exp; 57 QTAILQ_ENTRY(NBDCloseNotifier) next; 58 } NBDCloseNotifier; 59 60 static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers = 61 QTAILQ_HEAD_INITIALIZER(close_notifiers); 62 63 static void nbd_close_notifier(Notifier *n, void *data) 64 { 65 NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n); 66 67 notifier_remove(&cn->n); 68 QTAILQ_REMOVE(&close_notifiers, cn, next); 69 70 nbd_export_close(cn->exp); 71 nbd_export_put(cn->exp); 72 g_free(cn); 73 } 74 75 void qmp_nbd_server_add(const char *device, bool has_writable, bool writable, 76 Error **errp) 77 { 78 BlockBackend *blk; 79 NBDExport *exp; 80 NBDCloseNotifier *n; 81 82 if (server_fd == -1) { 83 error_setg(errp, "NBD server not running"); 84 return; 85 } 86 87 if (nbd_export_find(device)) { 88 error_setg(errp, "NBD server already exporting device '%s'", device); 89 return; 90 } 91 92 blk = blk_by_name(device); 93 if (!blk) { 94 error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND, 95 "Device '%s' not found", device); 96 return; 97 } 98 if (!blk_is_inserted(blk)) { 99 error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device); 100 return; 101 } 102 103 if (!has_writable) { 104 writable = false; 105 } 106 if (blk_is_read_only(blk)) { 107 writable = false; 108 } 109 110 exp = nbd_export_new(blk, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY, NULL, 111 errp); 112 if (!exp) { 113 return; 114 } 115 116 nbd_export_set_name(exp, device); 117 118 n = g_new0(NBDCloseNotifier, 1); 119 n->n.notify = nbd_close_notifier; 120 n->exp = exp; 121 blk_add_close_notifier(blk, &n->n); 122 QTAILQ_INSERT_TAIL(&close_notifiers, n, next); 123 } 124 125 void qmp_nbd_server_stop(Error **errp) 126 { 127 while (!QTAILQ_EMPTY(&close_notifiers)) { 128 NBDCloseNotifier *cn = QTAILQ_FIRST(&close_notifiers); 129 nbd_close_notifier(&cn->n, nbd_export_get_blockdev(cn->exp)); 130 } 131 132 if (server_fd != -1) { 133 qemu_set_fd_handler(server_fd, NULL, NULL, NULL); 134 close(server_fd); 135 server_fd = -1; 136 } 137 } 138