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