Merge remote-tracking branch 'bonzini/nbd-next' into staging

* bonzini/nbd-next: (30 commits)
  qmp: add NBD server commands
  block: add close notifiers
  block: prepare code for adding block notifiers
  qemu-sockets: add socket_listen, socket_connect, socket_parse
  tests: do not include tools-obj-y Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
  qemu-sockets: return InetSocketAddress from inet_parse
  qapi: add socket address types
  build: add QAPI files to the tools
  vnc: drop QERR_VNC_SERVER_FAILED
  qemu-sockets: add error propagation to Unix socket functions
  qemu-sockets: add error propagation to inet_parse
  qemu-sockets: add error propagation to inet_dgram_opts
  qemu-sockets: add error propagation to inet_connect_addr
  qemu-sockets: include strerror or gai_strerror output in error messages
  vnc: add error propagation to vnc_display_open
  vnc: reorganize code for reverse mode
  vnc: introduce a single label for error returns
  vnc: avoid Yoda conditionals
  qemu-ga: ask and print error information from qemu-sockets
  nbd: ask and print error information from qemu-sockets
  ...

28 files changed, 763 insertions, 420 deletions

diff --git a/Makefile b/Makefile
index 88285a4..17e2d58 100644
--- a/Makefile
+++ b/Makefile
@@ -161,11 +161,10 @@ qemu-img.o: qemu-img-cmds.h
 
 tools-obj-y = $(oslib-obj-y) $(trace-obj-y) qemu-tool.o qemu-timer.o \
 	qemu-timer-common.o main-loop.o notify.o \
-	iohandler.o cutils.o iov.o async.o
+	iohandler.o cutils.o iov.o async.o error.o
 tools-obj-$(CONFIG_POSIX) += compatfd.o
 
-qemu-img$(EXESUF): qemu-img.o $(tools-obj-y) $(block-obj-y) $(qapi-obj-y) \
-                              qapi-visit.o qapi-types.o
+qemu-img$(EXESUF): qemu-img.o $(tools-obj-y) $(block-obj-y)
 qemu-nbd$(EXESUF): qemu-nbd.o $(tools-obj-y) $(block-obj-y)
 qemu-io$(EXESUF): qemu-io.o cmd.o $(tools-obj-y) $(block-obj-y)
 
diff --git a/Makefile.objs b/Makefile.objs
index 74b3542..9eca179 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -43,11 +43,12 @@ coroutine-obj-$(CONFIG_WIN32) += coroutine-win32.o
 
 block-obj-y = cutils.o iov.o cache-utils.o qemu-option.o module.o async.o
 block-obj-y += nbd.o block.o blockjob.o aio.o aes.o qemu-config.o
-block-obj-y += qemu-progress.o qemu-sockets.o uri.o
+block-obj-y += qemu-progress.o qemu-sockets.o uri.o notify.o
 block-obj-y += $(coroutine-obj-y) $(qobject-obj-y) $(version-obj-y)
 block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 block-obj-y += block/
+block-obj-y += $(qapi-obj-y) qapi-types.o qapi-visit.o
 
 ifeq ($(CONFIG_VIRTIO)$(CONFIG_VIRTFS)$(CONFIG_PCI),yyy)
 # Lots of the fsdev/9pcode is pulled in by vl.c via qemu_fsdev_add.
@@ -60,7 +61,7 @@ endif
 # suppress *all* target specific code in case of system emulation, i.e. a
 # single QEMU executable should support all CPUs and machines.
 
-common-obj-y = $(block-obj-y) blockdev.o block/
+common-obj-y = $(block-obj-y) blockdev.o blockdev-nbd.o block/
 common-obj-y += net.o net/
 common-obj-y += qom/
 common-obj-y += readline.o console.o cursor.o
@@ -93,7 +94,7 @@ common-obj-y += bt-host.o bt-vhci.o
 common-obj-y += dma-helpers.o
 common-obj-y += iov.o acl.o
 common-obj-$(CONFIG_POSIX) += compatfd.o
-common-obj-y += notify.o event_notifier.o
+common-obj-y += event_notifier.o
 common-obj-y += qemu-timer.o qemu-timer-common.o
 common-obj-y += qtest.o
 common-obj-y += vl.o
@@ -239,9 +240,9 @@ QEMU_CFLAGS+=$(GLIB_CFLAGS)
 
 nested-vars += \
 	qga-obj-y \
-	block-obj-y \
 	qom-obj-y \
 	qapi-obj-y \
+	block-obj-y \
 	user-obj-y \
 	common-obj-y \
 	extra-obj-y
diff --git a/block.c b/block.c
index e95f613..56426a9 100644
--- a/block.c
+++ b/block.c
@@ -30,6 +30,7 @@
 #include "module.h"
 #include "qjson.h"
 #include "sysemu.h"
+#include "notify.h"
 #include "qemu-coroutine.h"
 #include "qmp-commands.h"
 #include "qemu-timer.h"
@@ -312,9 +313,16 @@ BlockDriverState *bdrv_new(const char *device_name)
         QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
     }
     bdrv_iostatus_disable(bs);
+    notifier_list_init(&bs->close_notifiers);
+
     return bs;
 }
 
+void bdrv_add_close_notifier(BlockDriverState *bs, Notifier *notify)
+{
+    notifier_list_add(&bs->close_notifiers, notify);
+}
+
 BlockDriver *bdrv_find_format(const char *format_name)
 {
     BlockDriver *drv1;
@@ -1098,12 +1106,13 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
 void bdrv_close(BlockDriverState *bs)
 {
     bdrv_flush(bs);
-    if (bs->drv) {
-        if (bs->job) {
-            block_job_cancel_sync(bs->job);
-        }
-        bdrv_drain_all();
+    if (bs->job) {
+        block_job_cancel_sync(bs->job);
+    }
+    bdrv_drain_all();
+    notifier_list_notify(&bs->close_notifiers, bs);
 
+    if (bs->drv) {
         if (bs == bs_snapshots) {
             bs_snapshots = NULL;
         }
diff --git a/block.h b/block.h
index e2d89d7..aa608a8 100644
--- a/block.h
+++ b/block.h
@@ -144,6 +144,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
 void bdrv_reopen_commit(BDRVReopenState *reopen_state);
 void bdrv_reopen_abort(BDRVReopenState *reopen_state);
 void bdrv_close(BlockDriverState *bs);
+void bdrv_add_close_notifier(BlockDriverState *bs, Notifier *notify);
 int bdrv_attach_dev(BlockDriverState *bs, void *dev);
 void bdrv_attach_dev_nofail(BlockDriverState *bs, void *dev);
 void bdrv_detach_dev(BlockDriverState *bs, void *dev);
diff --git a/block_int.h b/block_int.h
index f4bae04..cedabbd 100644
--- a/block_int.h
+++ b/block_int.h
@@ -233,6 +233,8 @@ struct BlockDriverState {
     BlockDriverState *backing_hd;
     BlockDriverState *file;
 
+    NotifierList close_notifiers;
+
     /* number of in-flight copy-on-read requests */
     unsigned int copy_on_read_in_flight;
 
diff --git a/blockdev-nbd.c b/blockdev-nbd.c
new file mode 100644
index 0000000..8031813
--- /dev/null
+++ b/blockdev-nbd.c
@@ -0,0 +1,119 @@
+/*
+ * Serving QEMU block devices via NBD
+ *
+ * Copyright (c) 2012 Red Hat, Inc.
+ *
+ * Author: Paolo Bonzini <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * later.  See the COPYING file in the top-level directory.
+ */
+
+#include "blockdev.h"
+#include "hw/block-common.h"
+#include "monitor.h"
+#include "qerror.h"
+#include "sysemu.h"
+#include "qmp-commands.h"
+#include "trace.h"
+#include "nbd.h"
+#include "qemu_socket.h"
+
+static int server_fd = -1;
+
+static void nbd_accept(void *opaque)
+{
+    struct sockaddr_in addr;
+    socklen_t addr_len = sizeof(addr);
+
+    int fd = accept(server_fd, (struct sockaddr *)&addr, &addr_len);
+    if (fd >= 0) {
+        nbd_client_new(NULL, fd, nbd_client_put);
+    }
+}
+
+void qmp_nbd_server_start(SocketAddress *addr, Error **errp)
+{
+    if (server_fd != -1) {
+        error_setg(errp, "NBD server already running");
+        return;
+    }
+
+    server_fd = socket_listen(addr, errp);
+    if (server_fd != -1) {
+        qemu_set_fd_handler2(server_fd, NULL, nbd_accept, NULL, NULL);
+    }
+}
+
+/* Hook into the BlockDriverState notifiers to close the export when
+ * the file is closed.
+ */
+typedef struct NBDCloseNotifier {
+    Notifier n;
+    NBDExport *exp;
+    QTAILQ_ENTRY(NBDCloseNotifier) next;
+} NBDCloseNotifier;
+
+static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers =
+    QTAILQ_HEAD_INITIALIZER(close_notifiers);
+
+static void nbd_close_notifier(Notifier *n, void *data)
+{
+    NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n);
+
+    notifier_remove(&cn->n);
+    QTAILQ_REMOVE(&close_notifiers, cn, next);
+
+    nbd_export_close(cn->exp);
+    nbd_export_put(cn->exp);
+    g_free(cn);
+}
+
+static void nbd_server_put_ref(NBDExport *exp)
+{
+    BlockDriverState *bs = nbd_export_get_blockdev(exp);
+    drive_put_ref(drive_get_by_blockdev(bs));
+}
+
+void qmp_nbd_server_add(const char *device, bool has_writable, bool writable,
+                        Error **errp)
+{
+    BlockDriverState *bs;
+    NBDExport *exp;
+    NBDCloseNotifier *n;
+
+    if (nbd_export_find(device)) {
+        error_setg(errp, "NBD server already exporting device '%s'", device);
+        return;
+    }
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+
+    exp = nbd_export_new(bs, 0, -1, writable ? 0 : NBD_FLAG_READ_ONLY,
+                         nbd_server_put_ref);
+
+    nbd_export_set_name(exp, device);
+    drive_get_ref(drive_get_by_blockdev(bs));
+
+    n = g_malloc0(sizeof(NBDCloseNotifier));
+    n->n.notify = nbd_close_notifier;
+    n->exp = exp;
+    bdrv_add_close_notifier(bs, &n->n);
+    QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
+}
+
+void qmp_nbd_server_stop(Error **errp)
+{
+    while (!QTAILQ_EMPTY(&close_notifiers)) {
+        NBDCloseNotifier *cn = QTAILQ_FIRST(&close_notifiers);
+        nbd_close_notifier(&cn->n, nbd_export_get_blockdev(cn->exp));
+    }
+
+    qemu_set_fd_handler2(server_fd, NULL, NULL, NULL, NULL);
+    close(server_fd);
+    server_fd = -1;
+}
diff --git a/console.h b/console.h
index f990684..6099d8d 100644
--- a/console.h
+++ b/console.h
@@ -378,7 +378,7 @@ void cocoa_display_init(DisplayState *ds, int full_screen);
 /* vnc.c */
 void vnc_display_init(DisplayState *ds);
 void vnc_display_close(DisplayState *ds);
-int vnc_display_open(DisplayState *ds, const char *display);
+void vnc_display_open(DisplayState *ds, const char *display, Error **errp);
 void vnc_display_add_client(DisplayState *ds, int csock, int skipauth);
 int vnc_display_disable_login(DisplayState *ds);
 char *vnc_display_local_addr(DisplayState *ds);
diff --git a/error.c b/error.c
index 1f05fc4..128d88c 100644
--- a/error.c
+++ b/error.c
@@ -43,6 +43,34 @@ void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
     *errp = err;
 }
 
+void error_set_errno(Error **errp, int os_errno, ErrorClass err_class,
+                     const char *fmt, ...)
+{
+    Error *err;
+    char *msg1;
+    va_list ap;
+
+    if (errp == NULL) {
+        return;
+    }
+    assert(*errp == NULL);
+
+    err = g_malloc0(sizeof(*err));
+
+    va_start(ap, fmt);
+    msg1 = g_strdup_vprintf(fmt, ap);
+    if (os_errno != 0) {
+        err->msg = g_strdup_printf("%s: %s", msg1, strerror(os_errno));
+        g_free(msg1);
+    } else {
+        err->msg = msg1;
+    }
+    va_end(ap);
+    err->err_class = err_class;
+
+    *errp = err;
+}
+
 Error *error_copy(const Error *err)
 {
     Error *err_new;
diff --git a/error.h b/error.h
index da7fed3..4d52e73 100644
--- a/error.h
+++ b/error.h
@@ -30,10 +30,19 @@ typedef struct Error Error;
 void error_set(Error **err, ErrorClass err_class, const char *fmt, ...) GCC_FMT_ATTR(3, 4);
 
 /**
+ * Set an indirect pointer to an error given a ErrorClass value and a
+ * printf-style human message, followed by a strerror() string if
+ * @os_error is not zero.
+ */
+void error_set_errno(Error **err, int os_error, ErrorClass err_class, const char *fmt, ...) GCC_FMT_ATTR(4, 5);
+
+/**
  * Same as error_set(), but sets a generic error
  */
 #define error_setg(err, fmt, ...) \
     error_set(err, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__)
+#define error_setg_errno(err, os_error, fmt, ...) \
+    error_set_errno(err, os_error, ERROR_CLASS_GENERIC_ERROR, fmt, ## __VA_ARGS__)
 
 /**
  * Returns true if an indirect pointer to an error is pointing to a valid
diff --git a/migration-exec.c b/migration-exec.c
index 6c97db9..519af57 100644
--- a/migration-exec.c
+++ b/migration-exec.c
@@ -60,22 +60,18 @@ static int exec_close(MigrationState *s)
     return ret;
 }
 
-int exec_start_outgoing_migration(MigrationState *s, const char *command)
+void exec_start_outgoing_migration(MigrationState *s, const char *command, Error **errp)
 {
     FILE *f;
 
     f = popen(command, "w");
     if (f == NULL) {
-        DPRINTF("Unable to popen exec target\n");
-        goto err_after_popen;
+        error_setg_errno(errp, errno, "failed to popen the migration target");
+        return;
     }
 
     s->fd = fileno(f);
-    if (s->fd == -1) {
-        DPRINTF("Unable to retrieve file descriptor for popen'd handle\n");
-        goto err_after_open;
-    }
-
+    assert(s->fd != -1);
     socket_set_nonblock(s->fd);
 
     s->opaque = qemu_popen(f, "w");
@@ -85,12 +81,6 @@ int exec_start_outgoing_migration(MigrationState *s, const char *command)
     s->write = file_write;
 
     migrate_fd_connect(s);
-    return 0;
-
-err_after_open:
-    pclose(f);
-err_after_popen:
-    return -1;
 }
 
 static void exec_accept_incoming_migration(void *opaque)
@@ -102,19 +92,17 @@ static void exec_accept_incoming_migration(void *opaque)
     qemu_fclose(f);
 }
 
-int exec_start_incoming_migration(const char *command)
+void exec_start_incoming_migration(const char *command, Error **errp)
 {
     QEMUFile *f;
 
     DPRINTF("Attempting to start an incoming migration\n");
     f = qemu_popen_cmd(command, "r");
     if(f == NULL) {
-        DPRINTF("Unable to apply qemu wrapper to popen file\n");
-        return -errno;
+        error_setg_errno(errp, errno, "failed to popen the migration source");
+        return;
     }
 
     qemu_set_fd_handler2(qemu_stdio_fd(f), NULL,
 			 exec_accept_incoming_migration, NULL, f);
-
-    return 0;
 }
diff --git a/migration-fd.c b/migration-fd.c
index 7335167..ce6932d 100644
--- a/migration-fd.c
+++ b/migration-fd.c
@@ -73,30 +73,19 @@ static int fd_close(MigrationState *s)
     return 0;
 }
 
-int fd_start_outgoing_migration(MigrationState *s, const char *fdname)
+void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **errp)
 {
-    s->fd = monitor_get_fd(cur_mon, fdname, NULL);
+    s->fd = monitor_get_fd(cur_mon, fdname, errp);
     if (s->fd == -1) {
-        DPRINTF("fd_migration: invalid file descriptor identifier\n");
-        goto err_after_get_fd;
-    }
-
-    if (fcntl(s->fd, F_SETFL, O_NONBLOCK) == -1) {
-        DPRINTF("Unable to set nonblocking mode on file descriptor\n");
-        goto err_after_open;
+        return;
     }
 
+    fcntl(s->fd, F_SETFL, O_NONBLOCK);
     s->get_error = fd_errno;
     s->write = fd_write;
     s->close = fd_close;
 
     migrate_fd_connect(s);
-    return 0;
-
-err_after_open:
-    close(s->fd);
-err_after_get_fd:
-    return -1;
 }
 
 static void fd_accept_incoming_migration(void *opaque)
@@ -108,7 +97,7 @@ static void fd_accept_incoming_migration(void *opaque)
     qemu_fclose(f);
 }
 
-int fd_start_incoming_migration(const char *infd)
+void fd_start_incoming_migration(const char *infd, Error **errp)
 {
     int fd;
     QEMUFile *f;
@@ -118,11 +107,9 @@ int fd_start_incoming_migration(const char *infd)
     fd = strtol(infd, NULL, 0);
     f = qemu_fdopen(fd, "rb");
     if(f == NULL) {
-        DPRINTF("Unable to apply qemu wrapper to file descriptor\n");
-        return -errno;
+        error_setg_errno(errp, errno, "failed to open the source descriptor");
+        return;
     }
 
     qemu_set_fd_handler2(fd, NULL, fd_accept_incoming_migration, NULL, f);
-
-    return 0;
 }
diff --git a/migration-tcp.c b/migration-tcp.c
index a15c2b8..46f6ac5 100644
--- a/migration-tcp.c
+++ b/migration-tcp.c
@@ -68,21 +68,13 @@ static void tcp_wait_for_connect(int fd, void *opaque)
     }
 }
 
-int tcp_start_outgoing_migration(MigrationState *s, const char *host_port,
-                                 Error **errp)
+void tcp_start_outgoing_migration(MigrationState *s, const char *host_port, Error **errp)
 {
     s->get_error = socket_errno;
     s->write = socket_write;
     s->close = tcp_close;
 
-    s->fd = inet_nonblocking_connect(host_port, tcp_wait_for_connect, s,
-                                     errp);
-    if (error_is_set(errp)) {
-        migrate_fd_error(s);
-        return -1;
-    }
-
-    return 0;
+    s->fd = inet_nonblocking_connect(host_port, tcp_wait_for_connect, s, errp);
 }
 
 static void tcp_accept_incoming_migration(void *opaque)
@@ -119,18 +111,15 @@ out2:
     close(s);
 }
 
-int tcp_start_incoming_migration(const char *host_port, Error **errp)
+void tcp_start_incoming_migration(const char *host_port, Error **errp)
 {
     int s;
 
     s = inet_listen(host_port, NULL, 256, SOCK_STREAM, 0, errp);
-
     if (s < 0) {
-        return -1;
+        return;
     }
 
     qemu_set_fd_handler2(s, NULL, tcp_accept_incoming_migration, NULL,
                          (void *)(intptr_t)s);
-
-    return 0;
 }
diff --git a/migration-unix.c b/migration-unix.c
index 169de88..ed3db3a 100644
--- a/migration-unix.c
+++ b/migration-unix.c
@@ -53,69 +53,28 @@ static int unix_close(MigrationState *s)
     return r;
 }
 
-static void unix_wait_for_connect(void *opaque)
+static void unix_wait_for_connect(int fd, void *opaque)
 {
     MigrationState *s = opaque;
-    int val, ret;
-    socklen_t valsize = sizeof(val);
 
-    DPRINTF("connect completed\n");
-    do {
-        ret = getsockopt(s->fd, SOL_SOCKET, SO_ERROR, (void *) &val, &valsize);
-    } while (ret == -1 && errno == EINTR);
-
-    if (ret < 0) {
+    if (fd < 0) {
+        DPRINTF("migrate connect error\n");
+        s->fd = -1;
         migrate_fd_error(s);
-        return;
-    }
-
-    qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
-
-    if (val == 0)
+    } else {
+        DPRINTF("migrate connect success\n");
+        s->fd = fd;
         migrate_fd_connect(s);
-    else {
-        DPRINTF("error connecting %d\n", val);
-        migrate_fd_error(s);
     }
 }
 
-int unix_start_outgoing_migration(MigrationState *s, const char *path)
+void unix_start_outgoing_migration(MigrationState *s, const char *path, Error **errp)
 {
-    struct sockaddr_un addr;
-    int ret;
-
-    addr.sun_family = AF_UNIX;
-    snprintf(addr.sun_path, sizeof(addr.sun_path), "%s", path);
     s->get_error = unix_errno;
     s->write = unix_write;
     s->close = unix_close;
 
-    s->fd = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
-    if (s->fd == -1) {
-        DPRINTF("Unable to open socket");
-        return -errno;
-    }
-
-    socket_set_nonblock(s->fd);
-
-    do {
-        ret = connect(s->fd, (struct sockaddr *)&addr, sizeof(addr));
-        if (ret == -1) {
-            ret = -errno;
-        }
-        if (ret == -EINPROGRESS || ret == -EWOULDBLOCK) {
-	    qemu_set_fd_handler2(s->fd, NULL, NULL, unix_wait_for_connect, s);
-            return 0;
-        }
-    } while (ret == -EINTR);
-
-    if (ret < 0) {
-        DPRINTF("connect failed\n");
-        migrate_fd_error(s);
-        return ret;
-    }
-    migrate_fd_connect(s);
-    return 0;
+    s->fd = unix_nonblocking_connect(path, unix_wait_for_connect, s, errp);
 }
 
 static void unix_accept_incoming_migration(void *opaque)
@@ -152,43 +111,15 @@ out2:
     close(s);
 }
 
-int unix_start_incoming_migration(const char *path)
+void unix_start_incoming_migration(const char *path, Error **errp)
 {
-    struct sockaddr_un addr;
     int s;
-    int ret;
-
-    DPRINTF("Attempting to start an incoming migration\n");
-
-    s = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
-    if (s == -1) {
-        fprintf(stderr, "Could not open unix socket: %s\n", strerror(errno));
-        return -errno;
-    }
-
-    memset(&addr, 0, sizeof(addr));
-    addr.sun_family = AF_UNIX;
-    snprintf(addr.sun_path, sizeof(addr.sun_path), "%s", path);
 
-    unlink(addr.sun_path);
-    if (bind(s, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
-        ret = -errno;
-        fprintf(stderr, "bind(unix:%s): %s\n", addr.sun_path, strerror(errno));
-        goto err;
-    }
-    if (listen(s, 1) == -1) {
-        fprintf(stderr, "listen(unix:%s): %s\n", addr.sun_path,
-                strerror(errno));
-        ret = -errno;
-        goto err;
+    s = unix_listen(path, NULL, 0, errp);
+    if (s < 0) {
+        return;
     }
 
     qemu_set_fd_handler2(s, NULL, unix_accept_incoming_migration, NULL,
                          (void *)(intptr_t)s);
-
-    return 0;
-
-err:
-    close(s);
-    return ret;
 }
diff --git a/migration.c b/migration.c
index 62e0304..bd55a15 100644
--- a/migration.c
+++ b/migration.c
@@ -64,26 +64,23 @@ MigrationState *migrate_get_current(void)
     return &current_migration;
 }
 
-int qemu_start_incoming_migration(const char *uri, Error **errp)
+void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p;
-    int ret;
 
     if (strstart(uri, "tcp:", &p))
-        ret = tcp_start_incoming_migration(p, errp);
+        tcp_start_incoming_migration(p, errp);
 #if !defined(WIN32)
     else if (strstart(uri, "exec:", &p))
-        ret =  exec_start_incoming_migration(p);
+        exec_start_incoming_migration(p, errp);
     else if (strstart(uri, "unix:", &p))
-        ret = unix_start_incoming_migration(p);
+        unix_start_incoming_migration(p, errp);
     else if (strstart(uri, "fd:", &p))
-        ret = fd_start_incoming_migration(p);
+        fd_start_incoming_migration(p, errp);
 #endif
     else {
-        fprintf(stderr, "unknown migration protocol: %s\n", uri);
-        ret = -EPROTONOSUPPORT;
+        error_setg(errp, "unknown migration protocol: %s\n", uri);
     }
-    return ret;
 }
 
 void process_incoming_migration(QEMUFile *f)
@@ -483,10 +480,10 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
                  bool has_inc, bool inc, bool has_detach, bool detach,
                  Error **errp)
 {
+    Error *local_err = NULL;
     MigrationState *s = migrate_get_current();
     MigrationParams params;
     const char *p;
-    int ret;
 
     params.blk = blk;
     params.shared = inc;
@@ -508,26 +505,23 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
     s = migrate_init(&params);
 
     if (strstart(uri, "tcp:", &p)) {
-        ret = tcp_start_outgoing_migration(s, p, errp);
+        tcp_start_outgoing_migration(s, p, &local_err);
 #if !defined(WIN32)
     } else if (strstart(uri, "exec:", &p)) {
-        ret = exec_start_outgoing_migration(s, p);
+        exec_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "unix:", &p)) {
-        ret = unix_start_outgoing_migration(s, p);
+        unix_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "fd:", &p)) {
-        ret = fd_start_outgoing_migration(s, p);
+        fd_start_outgoing_migration(s, p, &local_err);
 #endif
     } else {
         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "uri", "a valid migration protocol");
         return;
     }
 
-    if (ret < 0) {
-        if (!error_is_set(errp)) {
-            DPRINTF("migration failed: %s\n", strerror(-ret));
-            /* FIXME: we should return meaningful errors */
-            error_set(errp, QERR_UNDEFINED_ERROR);
-        }
+    if (local_err) {
+        migrate_fd_error(s);
+        error_propagate(errp, local_err);
         return;
     }
 
diff --git a/migration.h b/migration.h
index 1c3e9b7..c3a23cc 100644
--- a/migration.h
+++ b/migration.h
@@ -49,7 +49,7 @@ struct MigrationState
 
 void process_incoming_migration(QEMUFile *f);
 
-int qemu_start_incoming_migration(const char *uri, Error **errp);
+void qemu_start_incoming_migration(const char *uri, Error **errp);
 
 uint64_t migrate_max_downtime(void);
 
@@ -57,22 +57,21 @@ void do_info_migrate_print(Monitor *mon, const QObject *data);
 
 void do_info_migrate(Monitor *mon, QObject **ret_data);
 
-int exec_start_incoming_migration(const char *host_port);
+void exec_start_incoming_migration(const char *host_port, Error **errp);
 
-int exec_start_outgoing_migration(MigrationState *s, const char *host_port);
+void exec_start_outgoing_migration(MigrationState *s, const char *host_port, Error **errp);
 
-int tcp_start_incoming_migration(const char *host_port, Error **errp);
+void tcp_start_incoming_migration(const char *host_port, Error **errp);
 
-int tcp_start_outgoing_migration(MigrationState *s, const char *host_port,
-                                 Error **errp);
+void tcp_start_outgoing_migration(MigrationState *s, const char *host_port, Error **errp);
 
-int unix_start_incoming_migration(const char *path);
+void unix_start_incoming_migration(const char *path, Error **errp);
 
-int unix_start_outgoing_migration(MigrationState *s, const char *path);
+void unix_start_outgoing_migration(MigrationState *s, const char *path, Error **errp);
 
-int fd_start_incoming_migration(const char *path);
+void fd_start_incoming_migration(const char *path, Error **errp);
 
-int fd_start_outgoing_migration(MigrationState *s, const char *fdname);
+void fd_start_outgoing_migration(MigrationState *s, const char *fdname, Error **errp);
 
 void migrate_fd_error(MigrationState *s);
 
diff --git a/nbd.c b/nbd.c
index 6f0db62..cec5a94 100644
--- a/nbd.c
+++ b/nbd.c
@@ -208,7 +208,14 @@ int tcp_socket_outgoing(const char *address, uint16_t port)
 
 int tcp_socket_outgoing_spec(const char *address_and_port)
 {
-    return inet_connect(address_and_port, NULL);
+    Error *local_err = NULL;
+    int fd = inet_connect(address_and_port, &local_err);
+
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 int tcp_socket_incoming(const char *address, uint16_t port)
@@ -220,22 +227,38 @@ int tcp_socket_incoming(const char *address, uint16_t port)
 
 int tcp_socket_incoming_spec(const char *address_and_port)
 {
-    char *ostr  = NULL;
-    int olen = 0;
-    return inet_listen(address_and_port, ostr, olen, SOCK_STREAM, 0, NULL);
+    Error *local_err = NULL;
+    int fd = inet_listen(address_and_port, NULL, 0, SOCK_STREAM, 0, &local_err);
+
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 int unix_socket_incoming(const char *path)
 {
-    char *ostr = NULL;
-    int olen = 0;
+    Error *local_err = NULL;
+    int fd = unix_listen(path, NULL, 0, &local_err);
 
-    return unix_listen(path, ostr, olen);
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 int unix_socket_outgoing(const char *path)
 {
-    return unix_connect(path);
+    Error *local_err = NULL;
+    int fd = unix_connect(path, &local_err);
+
+    if (local_err != NULL) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    return fd;
 }
 
 /* Basic flow for negotiation
diff --git a/qapi-schema.json b/qapi-schema.json
index c615ee2..6fd263e 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2519,6 +2519,59 @@
     'opts': 'NetClientOptions' } }
 
 ##
+# @InetSocketAddress
+#
+# Captures a socket address or address range in the Internet namespace.
+#
+# @host: host part of the address
+#
+# @port: port part of the address, or lowest port if @to is present
+#
+# @to: highest port to try
+#
+# @ipv4: whether to accept IPv4 addresses, default try both IPv4 and IPv6
+#        #optional
+#
+# @ipv6: whether to accept IPv6 addresses, default try both IPv4 and IPv6
+#        #optional
+#
+# Since 1.3
+##
+{ 'type': 'InetSocketAddress',
+  'data': {
+    'host': 'str',
+    'port': 'str',
+    '*to': 'uint16',
+    '*ipv4': 'bool',
+    '*ipv6': 'bool' } }
+
+##
+# @UnixSocketAddress
+#
+# Captures a socket address in the local ("Unix socket") namespace.
+#
+# @path: filesystem path to use
+#
+# Since 1.3
+##
+{ 'type': 'UnixSocketAddress',
+  'data': {
+    'path': 'str' } }
+
+##
+# @SocketAddress
+#
+# Captures the address of a socket, which could also be a named file descriptor
+#
+# Since 1.3
+##
+{ 'union': 'SocketAddress',
+  'data': {
+    'inet': 'InetSocketAddress',
+    'unix': 'UnixSocketAddress',
+    'fd': 'String' } }
+
+##
 # @getfd:
 #
 # Receive a file descriptor via SCM rights and assign it a name
@@ -2810,3 +2863,46 @@
 # Since: 0.14.0
 ##
 { 'command': 'screendump', 'data': {'filename': 'str'} }
+
+##
+# @nbd-server-start:
+#
+# Start an NBD server listening on the given host and port.  Block
+# devices can then be exported using @nbd-server-add.  The NBD
+# server will present them as named exports; for example, another
+# QEMU instance could refer to them as "nbd:HOST:PORT:exportname=NAME".
+#
+# @addr: Address on which to listen.
+#
+# Returns: error if the server is already running.
+#
+# Since: 1.3.0
+##
+{ 'command': 'nbd-server-start',
+  'data': { 'addr': 'SocketAddress' } }
+
+##
+# @nbd-server-add:
+#
+# Export a device to QEMU's embedded NBD server.
+#
+# @device: Block device to be exported
+#
+# @writable: Whether clients should be able to write to the device via the
+#     NBD connection (default false). #optional
+#
+# Returns: error if the device is already marked for export.
+#
+# Since: 1.3.0
+##
+{ 'command': 'nbd-server-add', 'data': {'device': 'str', '*writable': 'bool'} }
+
+##
+# @nbd-server-stop:
+#
+# Stop QEMU's embedded NBD server, and unregister all devices previously
+# added via @nbd-server-add.
+#
+# Since: 1.3.0
+##
+{ 'command': 'nbd-server-stop' }
diff --git a/qemu-char.c b/qemu-char.c
index b082bae..afe2bfb 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2097,14 +2097,14 @@ static CharDriverState *qemu_chr_open_udp(QemuOpts *opts)
 {
     CharDriverState *chr = NULL;
     NetCharDriver *s = NULL;
+    Error *local_err = NULL;
     int fd = -1;
 
     chr = g_malloc0(sizeof(CharDriverState));
     s = g_malloc0(sizeof(NetCharDriver));
 
-    fd = inet_dgram_opts(opts);
+    fd = inet_dgram_opts(opts, &local_err);
     if (fd < 0) {
-        fprintf(stderr, "inet_dgram_opts failed\n");
         goto return_err;
     }
 
@@ -2118,6 +2118,10 @@ static CharDriverState *qemu_chr_open_udp(QemuOpts *opts)
     return chr;
 
 return_err:
+    if (local_err) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
     g_free(chr);
     g_free(s);
     if (fd >= 0) {
@@ -2428,6 +2432,7 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
 {
     CharDriverState *chr = NULL;
     TCPCharDriver *s = NULL;
+    Error *local_err = NULL;
     int fd = -1;
     int is_listen;
     int is_waitconnect;
@@ -2448,15 +2453,15 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
 
     if (is_unix) {
         if (is_listen) {
-            fd = unix_listen_opts(opts);
+            fd = unix_listen_opts(opts, &local_err);
         } else {
-            fd = unix_connect_opts(opts);
+            fd = unix_connect_opts(opts, &local_err, NULL, NULL);
         }
     } else {
         if (is_listen) {
-            fd = inet_listen_opts(opts, 0, NULL);
+            fd = inet_listen_opts(opts, 0, &local_err);
         } else {
-            fd = inet_connect_opts(opts, NULL, NULL, NULL);
+            fd = inet_connect_opts(opts, &local_err, NULL, NULL);
         }
     }
     if (fd < 0) {
@@ -2517,8 +2522,13 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts *opts)
     return chr;
 
  fail:
-    if (fd >= 0)
+    if (local_err) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+    }
+    if (fd >= 0) {
         closesocket(fd);
+    }
     g_free(s);
     g_free(chr);
     return NULL;
diff --git a/qemu-sockets.c b/qemu-sockets.c
index 2b1ed2f..cfed9c5 100644
--- a/qemu-sockets.c
+++ b/qemu-sockets.c
@@ -22,6 +22,7 @@
 #include <errno.h>
 #include <unistd.h>
 
+#include "monitor.h"
 #include "qemu_socket.h"
 #include "qemu-common.h" /* for qemu_isdigit */
 #include "main-loop.h"
@@ -120,8 +121,7 @@ int inet_listen_opts(QemuOpts *opts, int port_offset, Error **errp)
 
     if ((qemu_opt_get(opts, "host") == NULL) ||
         (qemu_opt_get(opts, "port") == NULL)) {
-        fprintf(stderr, "%s: host and/or port not specified\n", __FUNCTION__);
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        error_setg(errp, "host and/or port not specified");
         return -1;
     }
     pstrcpy(port, sizeof(port), qemu_opt_get(opts, "port"));
@@ -138,9 +138,8 @@ int inet_listen_opts(QemuOpts *opts, int port_offset, Error **errp)
         snprintf(port, sizeof(port), "%d", atoi(port) + port_offset);
     rc = getaddrinfo(strlen(addr) ? addr : NULL, port, &ai, &res);
     if (rc != 0) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        error_setg(errp, "address resolution failed for %s:%s: %s", addr, port,
+                   gai_strerror(rc));
         return -1;
     }
 
@@ -151,10 +150,8 @@ int inet_listen_opts(QemuOpts *opts, int port_offset, Error **errp)
 		        NI_NUMERICHOST | NI_NUMERICSERV);
         slisten = qemu_socket(e->ai_family, e->ai_socktype, e->ai_protocol);
         if (slisten < 0) {
-            fprintf(stderr,"%s: socket(%s): %s\n", __FUNCTION__,
-                    inet_strfamily(e->ai_family), strerror(errno));
             if (!e->ai_next) {
-                error_set(errp, QERR_SOCKET_CREATE_FAILED);
+                error_set_errno(errp, errno, QERR_SOCKET_CREATE_FAILED);
             }
             continue;
         }
@@ -176,24 +173,19 @@ int inet_listen_opts(QemuOpts *opts, int port_offset, Error **errp)
                 goto listen;
             }
             if (p == port_max) {
-                fprintf(stderr,"%s: bind(%s,%s,%d): %s\n", __FUNCTION__,
-                        inet_strfamily(e->ai_family), uaddr, inet_getport(e),
-                        strerror(errno));
                 if (!e->ai_next) {
-                    error_set(errp, QERR_SOCKET_BIND_FAILED);
+                    error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED);
                 }
             }
         }
         closesocket(slisten);
     }
-    fprintf(stderr, "%s: FAILED\n", __FUNCTION__);
     freeaddrinfo(res);
     return -1;
 
 listen:
     if (listen(slisten,1) != 0) {
-        error_set(errp, QERR_SOCKET_LISTEN_FAILED);
-        perror("listen");
+        error_set_errno(errp, errno, QERR_SOCKET_LISTEN_FAILED);
         closesocket(slisten);
         freeaddrinfo(res);
         return -1;
@@ -225,7 +217,7 @@ typedef struct ConnectState {
 } ConnectState;
 
 static int inet_connect_addr(struct addrinfo *addr, bool *in_progress,
-                             ConnectState *connect_state);
+                             ConnectState *connect_state, Error **errp);
 
 static void wait_for_connect(void *opaque)
 {
@@ -252,16 +244,19 @@ static void wait_for_connect(void *opaque)
     }
 
     /* try to connect to the next address on the list */
-    while (s->current_addr->ai_next != NULL && s->fd < 0) {
-        s->current_addr = s->current_addr->ai_next;
-        s->fd = inet_connect_addr(s->current_addr, &in_progress, s);
-        /* connect in progress */
-        if (in_progress) {
-            return;
+    if (s->current_addr) {
+        while (s->current_addr->ai_next != NULL && s->fd < 0) {
+            s->current_addr = s->current_addr->ai_next;
+            s->fd = inet_connect_addr(s->current_addr, &in_progress, s, NULL);
+            /* connect in progress */
+            if (in_progress) {
+                return;
+            }
         }
+
+        freeaddrinfo(s->addr_list);
     }
 
-    freeaddrinfo(s->addr_list);
     if (s->callback) {
         s->callback(s->fd, s->opaque);
     }
@@ -269,7 +264,7 @@ static void wait_for_connect(void *opaque)
 }
 
 static int inet_connect_addr(struct addrinfo *addr, bool *in_progress,
-                             ConnectState *connect_state)
+                             ConnectState *connect_state, Error **errp)
 {
     int sock, rc;
 
@@ -277,8 +272,7 @@ static int inet_connect_addr(struct addrinfo *addr, bool *in_progress,
 
     sock = qemu_socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
     if (sock < 0) {
-        fprintf(stderr, "%s: socket(%s): %s\n", __func__,
-                inet_strfamily(addr->ai_family), strerror(errno));
+        error_set_errno(errp, errno, QERR_SOCKET_CREATE_FAILED);
         return -1;
     }
     qemu_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
@@ -299,6 +293,7 @@ static int inet_connect_addr(struct addrinfo *addr, bool *in_progress,
                              connect_state);
         *in_progress = true;
     } else if (rc < 0) {
+        error_set_errno(errp, errno, QERR_SOCKET_CONNECT_FAILED);
         closesocket(sock);
         return -1;
     }
@@ -321,9 +316,7 @@ static struct addrinfo *inet_parse_connect_opts(QemuOpts *opts, Error **errp)
     addr = qemu_opt_get(opts, "host");
     port = qemu_opt_get(opts, "port");
     if (addr == NULL || port == NULL) {
-        fprintf(stderr,
-                "inet_parse_connect_opts: host and/or port not specified\n");
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        error_setg(errp, "host and/or port not specified");
         return NULL;
     }
 
@@ -337,9 +330,8 @@ static struct addrinfo *inet_parse_connect_opts(QemuOpts *opts, Error **errp)
     /* lookup */
     rc = getaddrinfo(addr, port, &ai, &res);
     if (rc != 0) {
-        fprintf(stderr, "getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        error_setg(errp, "address resolution failed for %s:%s: %s", addr, port,
+                   gai_strerror(rc));
         return NULL;
     }
     return res;
@@ -384,7 +376,7 @@ int inet_connect_opts(QemuOpts *opts, Error **errp,
         if (connect_state != NULL) {
             connect_state->current_addr = e;
         }
-        sock = inet_connect_addr(e, &in_progress, connect_state);
+        sock = inet_connect_addr(e, &in_progress, connect_state, errp);
         if (in_progress) {
             return sock;
         } else if (sock >= 0) {
@@ -395,21 +387,16 @@ int inet_connect_opts(QemuOpts *opts, Error **errp,
             break;
         }
     }
-    if (sock < 0) {
-        error_set(errp, QERR_SOCKET_CONNECT_FAILED);
-    }
     g_free(connect_state);
     freeaddrinfo(res);
     return sock;
 }
 
-int inet_dgram_opts(QemuOpts *opts)
+int inet_dgram_opts(QemuOpts *opts, Error **errp)
 {
     struct addrinfo ai, *peer = NULL, *local = NULL;
     const char *addr;
     const char *port;
-    char uaddr[INET6_ADDRSTRLEN+1];
-    char uport[33];
     int sock = -1, rc;
 
     /* lookup peer addr */
@@ -424,7 +411,7 @@ int inet_dgram_opts(QemuOpts *opts)
         addr = "localhost";
     }
     if (port == NULL || strlen(port) == 0) {
-        fprintf(stderr, "inet_dgram: port not specified\n");
+        error_setg(errp, "remote port not specified");
         return -1;
     }
 
@@ -434,8 +421,8 @@ int inet_dgram_opts(QemuOpts *opts)
         ai.ai_family = PF_INET6;
 
     if (0 != (rc = getaddrinfo(addr, port, &ai, &peer))) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
+        error_setg(errp, "address resolution failed for %s:%s: %s", addr, port,
+                   gai_strerror(rc));
 	return -1;
     }
 
@@ -454,44 +441,28 @@ int inet_dgram_opts(QemuOpts *opts)
         port = "0";
 
     if (0 != (rc = getaddrinfo(addr, port, &ai, &local))) {
-        fprintf(stderr,"getaddrinfo(%s,%s): %s\n", addr, port,
-                gai_strerror(rc));
+        error_setg(errp, "address resolution failed for %s:%s: %s", addr, port,
+                   gai_strerror(rc));
         goto err;
     }
 
     /* create socket */
     sock = qemu_socket(peer->ai_family, peer->ai_socktype, peer->ai_protocol);
     if (sock < 0) {
-        fprintf(stderr,"%s: socket(%s): %s\n", __FUNCTION__,
-                inet_strfamily(peer->ai_family), strerror(errno));
+        error_set_errno(errp, errno, QERR_SOCKET_CREATE_FAILED);
         goto err;
     }
     setsockopt(sock,SOL_SOCKET,SO_REUSEADDR,(void*)&on,sizeof(on));
 
     /* bind socket */
-    if (getnameinfo((struct sockaddr*)local->ai_addr,local->ai_addrlen,
-                    uaddr,INET6_ADDRSTRLEN,uport,32,
-                    NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
-        fprintf(stderr, "%s: getnameinfo: oops\n", __FUNCTION__);
-        goto err;
-    }
     if (bind(sock, local->ai_addr, local->ai_addrlen) < 0) {
-        fprintf(stderr,"%s: bind(%s,%s,%d): OK\n", __FUNCTION__,
-                inet_strfamily(local->ai_family), uaddr, inet_getport(local));
+        error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED);
         goto err;
     }
 
     /* connect to peer */
-    if (getnameinfo((struct sockaddr*)peer->ai_addr, peer->ai_addrlen,
-                    uaddr, INET6_ADDRSTRLEN, uport, 32,
-                    NI_NUMERICHOST | NI_NUMERICSERV) != 0) {
-        fprintf(stderr, "%s: getnameinfo: oops\n", __FUNCTION__);
-        goto err;
-    }
     if (connect(sock,peer->ai_addr,peer->ai_addrlen) < 0) {
-        fprintf(stderr, "%s: connect(%s,%s,%s,%s): %s\n", __FUNCTION__,
-                inet_strfamily(peer->ai_family),
-                peer->ai_canonname, uaddr, uport, strerror(errno));
+        error_set_errno(errp, errno, QERR_SOCKET_CONNECT_FAILED);
         goto err;
     }
 
@@ -510,59 +481,91 @@ err:
 }
 
 /* compatibility wrapper */
-static int inet_parse(QemuOpts *opts, const char *str)
+static InetSocketAddress *inet_parse(const char *str, Error **errp)
 {
+    InetSocketAddress *addr;
     const char *optstr, *h;
-    char addr[64];
+    char host[64];
     char port[33];
+    int to;
     int pos;
 
+    addr = g_new0(InetSocketAddress, 1);
+
     /* parse address */
     if (str[0] == ':') {
         /* no host given */
-        addr[0] = '\0';
-        if (1 != sscanf(str,":%32[^,]%n",port,&pos)) {
-            fprintf(stderr, "%s: portonly parse error (%s)\n",
-                    __FUNCTION__, str);
-            return -1;
+        host[0] = '\0';
+        if (1 != sscanf(str, ":%32[^,]%n", port, &pos)) {
+            error_setg(errp, "error parsing port in address '%s'", str);
+            goto fail;
         }
     } else if (str[0] == '[') {
         /* IPv6 addr */
-        if (2 != sscanf(str,"[%64[^]]]:%32[^,]%n",addr,port,&pos)) {
-            fprintf(stderr, "%s: ipv6 parse error (%s)\n",
-                    __FUNCTION__, str);
-            return -1;
+        if (2 != sscanf(str, "[%64[^]]]:%32[^,]%n", host, port, &pos)) {
+            error_setg(errp, "error parsing IPv6 address '%s'", str);
+            goto fail;
         }
-        qemu_opt_set(opts, "ipv6", "on");
+        addr->ipv6 = addr->has_ipv6 = true;
     } else if (qemu_isdigit(str[0])) {
         /* IPv4 addr */
-        if (2 != sscanf(str,"%64[0-9.]:%32[^,]%n",addr,port,&pos)) {
-            fprintf(stderr, "%s: ipv4 parse error (%s)\n",
-                    __FUNCTION__, str);
-            return -1;
+        if (2 != sscanf(str, "%64[0-9.]:%32[^,]%n", host, port, &pos)) {
+            error_setg(errp, "error parsing IPv4 address '%s'", str);
+            goto fail;
         }
-        qemu_opt_set(opts, "ipv4", "on");
+        addr->ipv4 = addr->has_ipv4 = true;
     } else {
         /* hostname */
-        if (2 != sscanf(str,"%64[^:]:%32[^,]%n",addr,port,&pos)) {
-            fprintf(stderr, "%s: hostname parse error (%s)\n",
-                    __FUNCTION__, str);
-            return -1;
+        if (2 != sscanf(str, "%64[^:]:%32[^,]%n", host, port, &pos)) {
+            error_setg(errp, "error parsing address '%s'", str);
+            goto fail;
         }
     }
-    qemu_opt_set(opts, "host", addr);
-    qemu_opt_set(opts, "port", port);
+
+    addr->host = g_strdup(host);
+    addr->port = g_strdup(port);
 
     /* parse options */
     optstr = str + pos;
     h = strstr(optstr, ",to=");
-    if (h)
-        qemu_opt_set(opts, "to", h+4);
-    if (strstr(optstr, ",ipv4"))
-        qemu_opt_set(opts, "ipv4", "on");
-    if (strstr(optstr, ",ipv6"))
-        qemu_opt_set(opts, "ipv6", "on");
-    return 0;
+    if (h) {
+        if (1 != sscanf(str, "%d%n", &to, &pos) ||
+            (str[pos] != '\0' && str[pos] != ',')) {
+            error_setg(errp, "error parsing to= argument");
+            goto fail;
+        }
+        addr->has_to = true;
+        addr->to = to;
+    }
+    if (strstr(optstr, ",ipv4")) {
+        addr->ipv4 = addr->has_ipv4 = true;
+    }
+    if (strstr(optstr, ",ipv6")) {
+        addr->ipv6 = addr->has_ipv6 = true;
+    }
+    return addr;
+
+fail:
+    qapi_free_InetSocketAddress(addr);
+    return NULL;
+}
+
+static void inet_addr_to_opts(QemuOpts *opts, InetSocketAddress *addr)
+{
+    bool ipv4 = addr->ipv4 || !addr->has_ipv4;
+    bool ipv6 = addr->ipv6 || !addr->has_ipv6;
+
+    if (!ipv4 || !ipv6) {
+        qemu_opt_set_bool(opts, "ipv4", ipv4);
+        qemu_opt_set_bool(opts, "ipv6", ipv6);
+    }
+    if (addr->has_to) {
+        char to[20];
+        snprintf(to, sizeof(to), "%d", addr->to);
+        qemu_opt_set(opts, "to", to);
+    }
+    qemu_opt_set(opts, "host", addr->host);
+    qemu_opt_set(opts, "port", addr->port);
 }
 
 int inet_listen(const char *str, char *ostr, int olen,
@@ -571,9 +574,13 @@ int inet_listen(const char *str, char *ostr, int olen,
     QemuOpts *opts;
     char *optstr;
     int sock = -1;
+    InetSocketAddress *addr;
 
-    opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
-    if (inet_parse(opts, str) == 0) {
+    addr = inet_parse(str, errp);
+    if (addr != NULL) {
+        opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
+        inet_addr_to_opts(opts, addr);
+        qapi_free_InetSocketAddress(addr);
         sock = inet_listen_opts(opts, port_offset, errp);
         if (sock != -1 && ostr) {
             optstr = strchr(str, ',');
@@ -589,10 +596,8 @@ int inet_listen(const char *str, char *ostr, int olen,
                          optstr ? optstr : "");
             }
         }
-    } else {
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        qemu_opts_del(opts);
     }
-    qemu_opts_del(opts);
     return sock;
 }
 
@@ -608,14 +613,16 @@ int inet_connect(const char *str, Error **errp)
 {
     QemuOpts *opts;
     int sock = -1;
+    InetSocketAddress *addr;
 
-    opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
-    if (inet_parse(opts, str) == 0) {
+    addr = inet_parse(str, errp);
+    if (addr != NULL) {
+        opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
+        inet_addr_to_opts(opts, addr);
+        qapi_free_InetSocketAddress(addr);
         sock = inet_connect_opts(opts, errp, NULL, NULL);
-    } else {
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        qemu_opts_del(opts);
     }
-    qemu_opts_del(opts);
     return sock;
 }
 
@@ -638,22 +645,24 @@ int inet_nonblocking_connect(const char *str,
 {
     QemuOpts *opts;
     int sock = -1;
+    InetSocketAddress *addr;
 
     g_assert(callback != NULL);
 
-    opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
-    if (inet_parse(opts, str) == 0) {
+    addr = inet_parse(str, errp);
+    if (addr != NULL) {
+        opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
+        inet_addr_to_opts(opts, addr);
+        qapi_free_InetSocketAddress(addr);
         sock = inet_connect_opts(opts, errp, callback, opaque);
-    } else {
-        error_set(errp, QERR_SOCKET_CREATE_FAILED);
+        qemu_opts_del(opts);
     }
-    qemu_opts_del(opts);
     return sock;
 }
 
 #ifndef _WIN32
 
-int unix_listen_opts(QemuOpts *opts)
+int unix_listen_opts(QemuOpts *opts, Error **errp)
 {
     struct sockaddr_un un;
     const char *path = qemu_opt_get(opts, "path");
@@ -661,7 +670,7 @@ int unix_listen_opts(QemuOpts *opts)
 
     sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
     if (sock < 0) {
-        perror("socket(unix)");
+        error_set_errno(errp, errno, QERR_SOCKET_CREATE_FAILED);
         return -1;
     }
 
@@ -686,11 +695,11 @@ int unix_listen_opts(QemuOpts *opts)
 
     unlink(un.sun_path);
     if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
-        fprintf(stderr, "bind(unix:%s): %s\n", un.sun_path, strerror(errno));
+        error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED);
         goto err;
     }
     if (listen(sock, 1) < 0) {
-        fprintf(stderr, "listen(unix:%s): %s\n", un.sun_path, strerror(errno));
+        error_set_errno(errp, errno, QERR_SOCKET_LISTEN_FAILED);
         goto err;
     }
 
@@ -701,37 +710,85 @@ err:
     return -1;
 }
 
-int unix_connect_opts(QemuOpts *opts)
+int unix_connect_opts(QemuOpts *opts, Error **errp,
+                      NonBlockingConnectHandler *callback, void *opaque)
 {
     struct sockaddr_un un;
     const char *path = qemu_opt_get(opts, "path");
-    int sock;
+    ConnectState *connect_state = NULL;
+    int sock, rc;
 
     if (NULL == path) {
-        fprintf(stderr, "unix connect: no path specified\n");
+        error_setg(errp, "unix connect: no path specified\n");
         return -1;
     }
 
     sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0);
     if (sock < 0) {
-        perror("socket(unix)");
+        error_set_errno(errp, errno, QERR_SOCKET_CREATE_FAILED);
         return -1;
     }
+    if (callback != NULL) {
+        connect_state = g_malloc0(sizeof(*connect_state));
+        connect_state->callback = callback;
+        connect_state->opaque = opaque;
+        socket_set_nonblock(sock);
+    }
 
     memset(&un, 0, sizeof(un));
     un.sun_family = AF_UNIX;
     snprintf(un.sun_path, sizeof(un.sun_path), "%s", path);
-    if (connect(sock, (struct sockaddr*) &un, sizeof(un)) < 0) {
-        fprintf(stderr, "connect(unix:%s): %s\n", path, strerror(errno));
+
+    /* connect to peer */
+    do {
+        rc = 0;
+        if (connect(sock, (struct sockaddr *) &un, sizeof(un)) < 0) {
+            rc = -socket_error();
+        }
+    } while (rc == -EINTR);
+
+    if (connect_state != NULL && QEMU_SOCKET_RC_INPROGRESS(rc)) {
+        connect_state->fd = sock;
+        qemu_set_fd_handler2(sock, NULL, NULL, wait_for_connect,
+                             connect_state);
+        return sock;
+    } else if (rc >= 0) {
+        /* non blocking socket immediate success, call callback */
+        if (callback != NULL) {
+            callback(sock, opaque);
+        }
+    }
+
+    if (rc < 0) {
+        error_set_errno(errp, -rc, QERR_SOCKET_CONNECT_FAILED);
         close(sock);
-	return -1;
+        sock = -1;
     }
 
+    g_free(connect_state);
     return sock;
 }
 
+#else
+
+int unix_listen_opts(QemuOpts *opts, Error **errp)
+{
+    error_setg(errp, "unix sockets are not available on windows");
+    errno = ENOTSUP;
+    return -1;
+}
+
+int unix_connect_opts(QemuOpts *opts, Error **errp,
+                      NonBlockingConnectHandler *callback, void *opaque)
+{
+    error_setg(errp, "unix sockets are not available on windows");
+    errno = ENOTSUP;
+    return -1;
+}
+#endif
+
 /* compatibility wrapper */
-int unix_listen(const char *str, char *ostr, int olen)
+int unix_listen(const char *str, char *ostr, int olen, Error **errp)
 {
     QemuOpts *opts;
     char *path, *optstr;
@@ -752,7 +809,7 @@ int unix_listen(const char *str, char *ostr, int olen)
         qemu_opt_set(opts, "path", str);
     }
 
-    sock = unix_listen_opts(opts);
+    sock = unix_listen_opts(opts, errp);
 
     if (sock != -1 && ostr)
         snprintf(ostr, olen, "%s%s", qemu_opt_get(opts, "path"), optstr ? optstr : "");
@@ -760,49 +817,132 @@ int unix_listen(const char *str, char *ostr, int olen)
     return sock;
 }
 
-int unix_connect(const char *path)
+int unix_connect(const char *path, Error **errp)
 {
     QemuOpts *opts;
     int sock;
 
     opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
     qemu_opt_set(opts, "path", path);
-    sock = unix_connect_opts(opts);
+    sock = unix_connect_opts(opts, errp, NULL, NULL);
     qemu_opts_del(opts);
     return sock;
 }
 
-#else
 
-int unix_listen_opts(QemuOpts *opts)
+int unix_nonblocking_connect(const char *path,
+                             NonBlockingConnectHandler *callback,
+                             void *opaque, Error **errp)
 {
-    fprintf(stderr, "unix sockets are not available on windows\n");
-    errno = ENOTSUP;
-    return -1;
+    QemuOpts *opts;
+    int sock = -1;
+
+    g_assert(callback != NULL);
+
+    opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
+    qemu_opt_set(opts, "path", path);
+    sock = unix_connect_opts(opts, errp, callback, opaque);
+    qemu_opts_del(opts);
+    return sock;
 }
 
-int unix_connect_opts(QemuOpts *opts)
+SocketAddress *socket_parse(const char *str, Error **errp)
 {
-    fprintf(stderr, "unix sockets are not available on windows\n");
-    errno = ENOTSUP;
-    return -1;
+    SocketAddress *addr = NULL;
+
+    addr = g_new(SocketAddress, 1);
+    if (strstart(str, "unix:", NULL)) {
+        if (str[5] == '\0') {
+            error_setg(errp, "invalid Unix socket address\n");
+            goto fail;
+        } else {
+            addr->kind = SOCKET_ADDRESS_KIND_UNIX;
+            addr->q_unix = g_new(UnixSocketAddress, 1);
+            addr->q_unix->path = g_strdup(str + 5);
+        }
+    } else if (strstart(str, "fd:", NULL)) {
+        if (str[3] == '\0') {
+            error_setg(errp, "invalid file descriptor address\n");
+            goto fail;
+        } else {
+            addr->kind = SOCKET_ADDRESS_KIND_FD;
+            addr->fd = g_new(String, 1);
+            addr->fd->str = g_strdup(str + 3);
+        }
+    } else {
+        addr->kind = SOCKET_ADDRESS_KIND_INET;
+        addr->inet = g_new(InetSocketAddress, 1);
+        addr->inet = inet_parse(str, errp);
+        if (addr->inet == NULL) {
+            goto fail;
+        }
+    }
+    return addr;
+
+fail:
+    qapi_free_SocketAddress(addr);
+    return NULL;
 }
 
-int unix_listen(const char *path, char *ostr, int olen)
+int socket_connect(SocketAddress *addr, Error **errp,
+                   NonBlockingConnectHandler *callback, void *opaque)
 {
-    fprintf(stderr, "unix sockets are not available on windows\n");
-    errno = ENOTSUP;
-    return -1;
+    QemuOpts *opts;
+    int fd;
+
+    opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
+    switch (addr->kind) {
+    case SOCKET_ADDRESS_KIND_INET:
+        inet_addr_to_opts(opts, addr->inet);
+        fd = inet_connect_opts(opts, errp, callback, opaque);
+        break;
+
+    case SOCKET_ADDRESS_KIND_UNIX:
+        qemu_opt_set(opts, "path", addr->q_unix->path);
+        fd = unix_connect_opts(opts, errp, callback, opaque);
+        break;
+
+    case SOCKET_ADDRESS_KIND_FD:
+        fd = monitor_get_fd(cur_mon, addr->fd->str, errp);
+        if (callback) {
+            callback(fd, opaque);
+        }
+        break;
+
+    default:
+        abort();
+    }
+    qemu_opts_del(opts);
+    return fd;
 }
 
-int unix_connect(const char *path)
+int socket_listen(SocketAddress *addr, Error **errp)
 {
-    fprintf(stderr, "unix sockets are not available on windows\n");
-    errno = ENOTSUP;
-    return -1;
-}
+    QemuOpts *opts;
+    int fd;
 
-#endif
+    opts = qemu_opts_create(&dummy_opts, NULL, 0, NULL);
+    switch (addr->kind) {
+    case SOCKET_ADDRESS_KIND_INET:
+        inet_addr_to_opts(opts, addr->inet);
+        fd = inet_listen_opts(opts, 0, errp);
+        break;
+
+    case SOCKET_ADDRESS_KIND_UNIX:
+        qemu_opt_set(opts, "path", addr->q_unix->path);
+        fd = unix_listen_opts(opts, errp);
+        break;
+
+    case SOCKET_ADDRESS_KIND_FD:
+        fd = monitor_get_fd(cur_mon, addr->fd->str, errp);
+        break;
+
+    default:
+        abort();
+    }
+    qemu_opts_del(opts);
+    return fd;
+}
 
 #ifdef _WIN32
 static void socket_cleanup(void)
diff --git a/qemu-tool.c b/qemu-tool.c
index f2f9813..da4c05a 100644
--- a/qemu-tool.c
+++ b/qemu-tool.c
@@ -38,6 +38,12 @@ const char *qemu_get_vm_name(void)
 
 Monitor *cur_mon;
 
+int monitor_get_fd(Monitor *mon, const char *name, Error **errp)
+{
+    error_setg(errp, "only QEMU supports file descriptor passing");
+    return -1;
+}
+
 void vm_stop(RunState state)
 {
     abort();
diff --git a/qemu_socket.h b/qemu_socket.h
index 3e8aee9..02490ad 100644
--- a/qemu_socket.h
+++ b/qemu_socket.h
@@ -53,13 +53,22 @@ int inet_nonblocking_connect(const char *str,
                              NonBlockingConnectHandler *callback,
                              void *opaque, Error **errp);
 
-int inet_dgram_opts(QemuOpts *opts);
+int inet_dgram_opts(QemuOpts *opts, Error **errp);
 const char *inet_strfamily(int family);
 
-int unix_listen_opts(QemuOpts *opts);
-int unix_listen(const char *path, char *ostr, int olen);
-int unix_connect_opts(QemuOpts *opts);
-int unix_connect(const char *path);
+int unix_listen_opts(QemuOpts *opts, Error **errp);
+int unix_listen(const char *path, char *ostr, int olen, Error **errp);
+int unix_connect_opts(QemuOpts *opts, Error **errp,
+                      NonBlockingConnectHandler *callback, void *opaque);
+int unix_connect(const char *path, Error **errp);
+int unix_nonblocking_connect(const char *str,
+                             NonBlockingConnectHandler *callback,
+                             void *opaque, Error **errp);
+
+SocketAddress *socket_parse(const char *str, Error **errp);
+int socket_connect(SocketAddress *addr, Error **errp,
+                   NonBlockingConnectHandler *callback, void *opaque);
+int socket_listen(SocketAddress *addr, Error **errp);
 
 /* Old, ipv4 only bits.  Don't use for new code. */
 int parse_host_port(struct sockaddr_in *saddr, const char *str);
diff --git a/qerror.h b/qerror.h
index c91708c..f23b978 100644
--- a/qerror.h
+++ b/qerror.h
@@ -237,9 +237,6 @@ void assert_no_error(Error *err);
 #define QERR_VIRTFS_FEATURE_BLOCKS_MIGRATION \
     ERROR_CLASS_GENERIC_ERROR, "Migration is disabled when VirtFS export path '%s' is mounted in the guest using mount_tag '%s'"
 
-#define QERR_VNC_SERVER_FAILED \
-    ERROR_CLASS_GENERIC_ERROR, "Could not start VNC server on %s"
-
 #define QERR_SOCKET_CONNECT_FAILED \
     ERROR_CLASS_GENERIC_ERROR, "Failed to connect to socket"
 
diff --git a/qga/channel-posix.c b/qga/channel-posix.c
index 57eea06..d152827 100644
--- a/qga/channel-posix.c
+++ b/qga/channel-posix.c
@@ -181,9 +181,11 @@ static gboolean ga_channel_open(GAChannel *c, const gchar *path, GAChannelMethod
         break;
     }
     case GA_CHANNEL_UNIX_LISTEN: {
-        int fd = unix_listen(path, NULL, strlen(path));
-        if (fd == -1) {
-            g_critical("error opening path: %s", strerror(errno));
+        Error *local_err = NULL;
+        int fd = unix_listen(path, NULL, strlen(path), &local_err);
+        if (local_err != NULL) {
+            g_critical("%s", error_get_pretty(local_err));
+            error_free(local_err);
             return false;
         }
         ga_channel_listen_add(c, fd, true);
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 5ba8c48..ebe9a78 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2552,6 +2552,22 @@ EQMP
     },
 
     {
+        .name       = "nbd-server-start",
+        .args_type  = "addr:q",
+        .mhandler.cmd_new = qmp_marshal_input_nbd_server_start,
+    },
+    {
+        .name       = "nbd-server-add",
+        .args_type  = "device:B,writable:b?",
+        .mhandler.cmd_new = qmp_marshal_input_nbd_server_add,
+    },
+    {
+        .name       = "nbd-server-stop",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_nbd_server_stop,
+    },
+
+    {
         .name       = "change-vnc-password",
         .args_type  = "password:s",
         .mhandler.cmd_new = qmp_marshal_input_change_vnc_password,
diff --git a/qmp.c b/qmp.c
index 36c54c5..31bc3bf 100644
--- a/qmp.c
+++ b/qmp.c
@@ -349,11 +349,9 @@ void qmp_change_vnc_password(const char *password, Error **errp)
     }
 }
 
-static void qmp_change_vnc_listen(const char *target, Error **err)
+static void qmp_change_vnc_listen(const char *target, Error **errp)
 {
-    if (vnc_display_open(NULL, target) < 0) {
-        error_set(err, QERR_VNC_SERVER_FAILED, target);
-    }
+    vnc_display_open(NULL, target, errp);
 }
 
 static void qmp_change_vnc(const char *target, bool has_arg, const char *arg,
diff --git a/tests/Makefile b/tests/Makefile
index 26a67ce..86c9b79 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -42,11 +42,11 @@ test-qapi-obj-y += module.o
 
 $(test-obj-y): QEMU_INCLUDES += -Itests
 
-tests/check-qint$(EXESUF): tests/check-qint.o qint.o $(tools-obj-y)
-tests/check-qstring$(EXESUF): tests/check-qstring.o qstring.o $(tools-obj-y)
-tests/check-qdict$(EXESUF): tests/check-qdict.o qdict.o qfloat.o qint.o qstring.o qbool.o qlist.o $(tools-obj-y)
-tests/check-qlist$(EXESUF): tests/check-qlist.o qlist.o qint.o $(tools-obj-y)
-tests/check-qfloat$(EXESUF): tests/check-qfloat.o qfloat.o $(tools-obj-y)
+tests/check-qint$(EXESUF): tests/check-qint.o qint.o
+tests/check-qstring$(EXESUF): tests/check-qstring.o qstring.o
+tests/check-qdict$(EXESUF): tests/check-qdict.o qdict.o qfloat.o qint.o qstring.o qbool.o qlist.o
+tests/check-qlist$(EXESUF): tests/check-qlist.o qlist.o qint.o
+tests/check-qfloat$(EXESUF): tests/check-qfloat.o qfloat.o
 tests/check-qjson$(EXESUF): tests/check-qjson.o $(qobject-obj-y) $(tools-obj-y)
 tests/test-coroutine$(EXESUF): tests/test-coroutine.o $(coroutine-obj-y) $(tools-obj-y)
 tests/test-iov$(EXESUF): tests/test-iov.o iov.o
diff --git a/ui/vnc.c b/ui/vnc.c
index 66ae930..d0ffcc5 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2850,7 +2850,7 @@ char *vnc_display_local_addr(DisplayState *ds)
     return vnc_socket_local_addr("%s:%s", vs->lsock);
 }
 
-int vnc_display_open(DisplayState *ds, const char *display)
+void vnc_display_open(DisplayState *ds, const char *display, Error **errp)
 {
     VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;
     const char *options;
@@ -2868,14 +2868,15 @@ int vnc_display_open(DisplayState *ds, const char *display)
 #endif
     int lock_key_sync = 1;
 
-    if (!vnc_display)
-        return -1;
+    if (!vnc_display) {
+        error_setg(errp, "VNC display not active");
+        return;
+    }
     vnc_display_close(ds);
     if (strcmp(display, "none") == 0)
-        return 0;
+        return;
 
-    if (!(vs->display = strdup(display)))
-        return -1;
+    vs->display = g_strdup(display);
     vs->share_policy = VNC_SHARE_POLICY_ALLOW_EXCLUSIVE;
 
     options = display;
@@ -2883,13 +2884,11 @@ int vnc_display_open(DisplayState *ds, const char *display)
         options++;
         if (strncmp(options, "password", 8) == 0) {
             if (fips_get_state()) {
-                fprintf(stderr,
-                        "VNC password auth disabled due to FIPS mode, "
-                        "consider using the VeNCrypt or SASL authentication "
-                        "methods as an alternative\n");
-                g_free(vs->display);
-                vs->display = NULL;
-                return -1;
+                error_setg(errp,
+                           "VNC password auth disabled due to FIPS mode, "
+                           "consider using the VeNCrypt or SASL authentication "
+                           "methods as an alternative");
+                goto fail;
             }
             password = 1; /* Require password auth */
         } else if (strncmp(options, "reverse", 7) == 0) {
@@ -2919,18 +2918,14 @@ int vnc_display_open(DisplayState *ds, const char *display)
 
                 VNC_DEBUG("Trying certificate path '%s'\n", path);
                 if (vnc_tls_set_x509_creds_dir(vs, path) < 0) {
-                    fprintf(stderr, "Failed to find x509 certificates/keys in %s\n", path);
+                    error_setg(errp, "Failed to find x509 certificates/keys in %s", path);
                     g_free(path);
-                    g_free(vs->display);
-                    vs->display = NULL;
-                    return -1;
+                    goto fail;
                 }
                 g_free(path);
             } else {
-                fprintf(stderr, "No certificate path provided\n");
-                g_free(vs->display);
-                vs->display = NULL;
-                return -1;
+                error_setg(errp, "No certificate path provided");
+                goto fail;
             }
 #endif
 #if defined(CONFIG_VNC_TLS) || defined(CONFIG_VNC_SASL)
@@ -2949,10 +2944,8 @@ int vnc_display_open(DisplayState *ds, const char *display)
             } else if (strncmp(options+6, "force-shared", 12) == 0) {
                 vs->share_policy = VNC_SHARE_POLICY_FORCE_SHARED;
             } else {
-                fprintf(stderr, "unknown vnc share= option\n");
-                g_free(vs->display);
-                vs->display = NULL;
-                return -1;
+                error_setg(errp, "unknown vnc share= option");
+                goto fail;
             }
         }
     }
@@ -3053,52 +3046,50 @@ int vnc_display_open(DisplayState *ds, const char *display)
 
 #ifdef CONFIG_VNC_SASL
     if ((saslErr = sasl_server_init(NULL, "qemu")) != SASL_OK) {
-        fprintf(stderr, "Failed to initialize SASL auth %s",
-                sasl_errstring(saslErr, NULL, NULL));
-        g_free(vs->display);
-        vs->display = NULL;
-        return -1;
+        error_setg(errp, "Failed to initialize SASL auth: %s",
+                   sasl_errstring(saslErr, NULL, NULL));
+        goto fail;
     }
 #endif
     vs->lock_key_sync = lock_key_sync;
 
     if (reverse) {
         /* connect to viewer */
-        if (strncmp(display, "unix:", 5) == 0)
-            vs->lsock = unix_connect(display+5);
-        else
-            vs->lsock = inet_connect(display, NULL);
-        if (-1 == vs->lsock) {
-            g_free(vs->display);
-            vs->display = NULL;
-            return -1;
+        int csock;
+        vs->lsock = -1;
+        if (strncmp(display, "unix:", 5) == 0) {
+            csock = unix_connect(display+5, errp);
         } else {
-            int csock = vs->lsock;
-            vs->lsock = -1;
-            vnc_connect(vs, csock, 0);
+            csock = inet_connect(display, errp);
         }
-        return 0;
-
+        if (csock < 0) {
+            goto fail;
+        }
+        vnc_connect(vs, csock, 0);
     } else {
         /* listen for connects */
         char *dpy;
         dpy = g_malloc(256);
         if (strncmp(display, "unix:", 5) == 0) {
             pstrcpy(dpy, 256, "unix:");
-            vs->lsock = unix_listen(display+5, dpy+5, 256-5);
+            vs->lsock = unix_listen(display+5, dpy+5, 256-5, errp);
         } else {
             vs->lsock = inet_listen(display, dpy, 256,
-                                    SOCK_STREAM, 5900, NULL);
+                                    SOCK_STREAM, 5900, errp);
         }
-        if (-1 == vs->lsock) {
+        if (vs->lsock < 0) {
             g_free(dpy);
-            return -1;
-        } else {
-            g_free(vs->display);
-            vs->display = dpy;
+            goto fail;
         }
+        g_free(vs->display);
+        vs->display = dpy;
+        qemu_set_fd_handler2(vs->lsock, NULL, vnc_listen_read, NULL, vs);
     }
-    return qemu_set_fd_handler2(vs->lsock, NULL, vnc_listen_read, NULL, vs);
+    return;
+
+fail:
+    g_free(vs->display);
+    vs->display = NULL;
 }
 
 void vnc_display_add_client(DisplayState *ds, int csock, int skipauth)
diff --git a/vl.c b/vl.c
index ee3c43a..9f99ef4 100644
--- a/vl.c
+++ b/vl.c
@@ -3711,10 +3711,13 @@ int main(int argc, char **argv, char **envp)
 #ifdef CONFIG_VNC
     /* init remote displays */
     if (vnc_display) {
+        Error *local_err = NULL;
         vnc_display_init(ds);
-        if (vnc_display_open(ds, vnc_display) < 0) {
-            fprintf(stderr, "Failed to start VNC server on `%s'\n",
-                    vnc_display);
+        vnc_display_open(ds, vnc_display, &local_err);
+        if (local_err != NULL) {
+            fprintf(stderr, "Failed to start VNC server on `%s': %s\n",
+                    vnc_display, error_get_pretty(local_err));
+            error_free(local_err);
             exit(1);
         }
 
@@ -3766,16 +3769,12 @@ int main(int argc, char **argv, char **envp)
     }
 
     if (incoming) {
-        Error *errp = NULL;
-        int ret = qemu_start_incoming_migration(incoming, &errp);
-        if (ret < 0) {
-            if (error_is_set(&errp)) {
-                fprintf(stderr, "Migrate: %s\n", error_get_pretty(errp));
-                error_free(errp);
-            }
-            fprintf(stderr, "Migration failed. Exit code %s(%d), exiting.\n",
-                    incoming, ret);
-            exit(ret);
+        Error *local_err = NULL;
+        qemu_start_incoming_migration(incoming, &local_err);
+        if (local_err) {
+            fprintf(stderr, "-incoming %s: %s\n", incoming, error_get_pretty(local_err));
+            error_free(local_err);
+            exit(1);
         }
     } else if (autostart) {
         vm_start();