docs/formatbackup.rst | 3 ++- src/qemu/libvirtd_qemu.aug | 2 ++ src/qemu/qemu.conf.in | 9 ++++++++ src/qemu/qemu_backup.c | 33 +++++++++++++++++++++--------- src/qemu/qemu_conf.c | 25 ++++++++++++++++++++++ src/qemu/qemu_conf.h | 6 ++++++ src/qemu/qemu_domain.h | 1 + src/qemu/qemu_driver.c | 6 ++++++ src/qemu/test_libvirtd_qemu.aug.in | 2 ++ 9 files changed, 76 insertions(+), 11 deletions(-)
Previously, users had to manually specify a TCP port when starting
a pull-mode backup with an NBD server. A TODO comment in
qemuBackupPrepare() noted this limitation and pointed toward using
virPortAllocator, as done for migration, VNC, and SPICE ports.
Add backup_port_min and backup_port_max configuration options to
qemu.conf, defaulting to 10809-10872 (10809 is the IANA-assigned
NBD port; range of 64 matches the migration port pattern).
When a pull-mode backup is started without specifying a TCP port,
a port is now acquired automatically from the configured range via
virPortAllocatorAcquire(). The port is released when the backup
ends or if startup fails.
Signed-off-by: Lucas Amaral <lucaaamaral@gmail.com>
---
Build-tested and passed full test suite on CentOS Stream 9
(298 OK, 0 failures).
Runtime-validated against an actual patched virtqemud instance
running inside a privileged container (CentOS Stream 9, QEMU 10.1.0)
with a live aarch64/virt guest.
Config parsing validation:
- Default config (no backup_port_* set): daemon starts OK
- Custom range (backup_port_min=20000, backup_port_max=20010):
daemon starts OK
- Invalid (min > max): daemon correctly refuses to start
- Invalid (min = 0): daemon correctly refuses to start
- Invalid (max > 65535): daemon correctly refuses to start
Port auto-allocation (live VM backup):
- Pull-mode backup WITHOUT port specified:
backup-begin succeeds, backup-dumpxml shows auto-allocated
port='10809' from default range.
Previously this would fail with:
"<domainbackup> must specify TCP port for now"
- Pull-mode backup WITH explicit port=10809:
backup-begin succeeds, backup-dumpxml shows port='10809'.
Behavior unchanged from before the patch.
Port conflict and exhaustion (range set to 10809-10810, 3 VMs):
- Auto-allocate on vm1 (got 10809), then manual port=10809
on vm2: QEMU correctly rejects with "Address already in use"
- Auto-allocate vm1=10809, vm2=10810 (range full), vm3 attempt:
"Unable to find an unused port in range 'backup' (10809-10810)"
- After aborting vm1 backup (releasing 10809), vm3 retries and
gets 10809: port release and reuse works correctly
docs/formatbackup.rst | 3 ++-
src/qemu/libvirtd_qemu.aug | 2 ++
src/qemu/qemu.conf.in | 9 ++++++++
src/qemu/qemu_backup.c | 33 +++++++++++++++++++++---------
src/qemu/qemu_conf.c | 25 ++++++++++++++++++++++
src/qemu/qemu_conf.h | 6 ++++++
src/qemu/qemu_domain.h | 1 +
src/qemu/qemu_driver.c | 6 ++++++
src/qemu/test_libvirtd_qemu.aug.in | 2 ++
9 files changed, 76 insertions(+), 11 deletions(-)
diff --git a/docs/formatbackup.rst b/docs/formatbackup.rst
index df6392e3bd..24857eaf72 100644
--- a/docs/formatbackup.rst
+++ b/docs/formatbackup.rst
@@ -42,7 +42,8 @@ were supplied). The following child elements and attributes are supported:
```protocol`` element of a disk <formatdomain.html#hard-drives-floppy-disks-cdroms>`__ attached
via NBD in the domain (such as transport, socket, name, port, or tls),
necessary to set up an NBD server that exposes the content of each disk at
- the time the backup is started.
+ the time the backup is started. For TCP transport, if ``port`` is omitted, a
+ port is allocated automatically from the range configured in ``/etc/libvirt/qemu.conf``.
In addition to the above the NBD server used for backups allows using
``transport='fd' fdgroup='NAME'`` where ``NAME`` is the name used with
diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
index 0286582169..eb790d48be 100644
--- a/src/qemu/libvirtd_qemu.aug
+++ b/src/qemu/libvirtd_qemu.aug
@@ -146,6 +146,8 @@ module Libvirtd_qemu =
| int_entry "migration_port_min"
| int_entry "migration_port_max"
| str_entry "migration_host"
+ | int_entry "backup_port_min"
+ | int_entry "backup_port_max"
let log_entry = bool_entry "log_timestamp"
diff --git a/src/qemu/qemu.conf.in b/src/qemu/qemu.conf.in
index 2d1c67034d..5eacd70022 100644
--- a/src/qemu/qemu.conf.in
+++ b/src/qemu/qemu.conf.in
@@ -969,6 +969,15 @@
#migration_port_max = 49215
+# Port range used for automatic allocation of NBD backup server ports.
+# When a pull-mode backup is started without specifying a TCP port, a
+# port from this range will be assigned automatically. The NBD standard
+# port is 10809.
+#
+#backup_port_min = 10809
+#backup_port_max = 10872
+
+
# Timestamp QEMU's log messages (if QEMU supports it)
#
# Defaults to 1.
diff --git a/src/qemu/qemu_backup.c b/src/qemu/qemu_backup.c
index 44514d08fc..12ef64b14e 100644
--- a/src/qemu/qemu_backup.c
+++ b/src/qemu/qemu_backup.c
@@ -32,6 +32,7 @@
#include "storage_source.h"
#include "storage_source_conf.h"
#include "virerror.h"
+#include "virportallocator.h"
#include "virlog.h"
#include "virbuffer.h"
#include "backup_conf.h"
@@ -71,16 +72,7 @@ qemuBackupPrepare(virDomainBackupDef *def)
switch (def->server->transport) {
case VIR_STORAGE_NET_HOST_TRANS_TCP:
- /* TODO: Update qemu.conf to provide a port range,
- * probably starting at 10809, for obtaining automatic
- * port via virPortAllocatorAcquire, as well as store
- * somewhere if we need to call virPortAllocatorRelease
- * during BackupEnd. Until then, user must provide port */
- if (!def->server->port) {
- virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
- _("<domainbackup> must specify TCP port for now"));
- return -1;
- }
+ /* port is auto-allocated if not set */
break;
case VIR_STORAGE_NET_HOST_TRANS_UNIX:
@@ -841,6 +833,16 @@ qemuBackupBegin(virDomainObj *vm,
if (qemuBackupPrepare(def) < 0)
goto endjob;
+ if (pull && def->server &&
+ def->server->transport == VIR_STORAGE_NET_HOST_TRANS_TCP &&
+ !def->server->port) {
+ unsigned short port = 0;
+ if (virPortAllocatorAcquire(priv->driver->backupPorts, &port) < 0)
+ goto endjob;
+ def->server->port = port;
+ priv->backupNBDPort = port;
+ }
+
if (qemuBackupBeginPrepareTLS(vm, cfg, def, &tlsProps, &tlsSecretProps) < 0)
goto endjob;
@@ -969,6 +971,11 @@ qemuBackupBegin(virDomainObj *vm,
qemuDomainObjExitMonitor(vm);
}
+ if (ret < 0 && priv->backupNBDPort) {
+ virPortAllocatorRelease(priv->backupNBDPort);
+ priv->backupNBDPort = 0;
+ }
+
if (ret < 0 && !job_started && priv->backup)
def = g_steal_pointer(&priv->backup);
@@ -1026,6 +1033,12 @@ qemuBackupNotifyBlockjobEndStopNBD(virDomainObj *vm,
qemuDomainObjExitMonitor(vm);
backup->nbdStopped = true;
+
+ if (priv->backupNBDPort) {
+ virPortAllocatorRelease(priv->backupNBDPort);
+ priv->backupNBDPort = 0;
+ backup->server->port = 0;
+ }
}
diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index de6e51177a..99e6a29148 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -74,6 +74,9 @@ VIR_LOG_INIT("qemu.qemu_conf");
#define QEMU_MIGRATION_PORT_MIN 49152
#define QEMU_MIGRATION_PORT_MAX 49215
+#define QEMU_BACKUP_PORT_MIN 10809
+#define QEMU_BACKUP_PORT_MAX 10872
+
VIR_ENUM_IMPL(virQEMUSchedCore,
QEMU_SCHED_CORE_LAST,
"none",
@@ -265,6 +268,9 @@ virQEMUDriverConfig *virQEMUDriverConfigNew(bool privileged,
cfg->migrationPortMin = QEMU_MIGRATION_PORT_MIN;
cfg->migrationPortMax = QEMU_MIGRATION_PORT_MAX;
+ cfg->backupPortMin = QEMU_BACKUP_PORT_MIN;
+ cfg->backupPortMax = QEMU_BACKUP_PORT_MAX;
+
/* For privileged driver, try and find hugetlbfs mounts automatically.
* Non-privileged driver requires admin to create a dir for the
* user, chown it, and then let user configure it manually. */
@@ -985,6 +991,25 @@ virQEMUDriverConfigLoadNetworkEntry(virQEMUDriverConfig *cfg,
return -1;
}
+ if (virConfGetValueUInt(conf, "backup_port_min", &cfg->backupPortMin) < 0)
+ return -1;
+ if (cfg->backupPortMin <= 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("%1$s: backup_port_min: port must be greater than 0"),
+ filename);
+ return -1;
+ }
+
+ if (virConfGetValueUInt(conf, "backup_port_max", &cfg->backupPortMax) < 0)
+ return -1;
+ if (cfg->backupPortMax > 65535 ||
+ cfg->backupPortMax < cfg->backupPortMin) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("%1$s: backup_port_max: port must be between the minimal port %2$d and 65535"),
+ filename, cfg->backupPortMin);
+ return -1;
+ }
+
if (virConfGetValueString(conf, "migration_host", &cfg->migrateHost) < 0)
return -1;
virStringStripIPv6Brackets(cfg->migrateHost);
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index c284e108a1..2e68f1de14 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -240,6 +240,9 @@ struct _virQEMUDriverConfig {
unsigned int migrationPortMin;
unsigned int migrationPortMax;
+ unsigned int backupPortMin;
+ unsigned int backupPortMax;
+
bool logTimestamp;
bool stdioLogD;
@@ -338,6 +341,9 @@ struct _virQEMUDriver {
/* Immutable pointer, immutable object */
virPortAllocatorRange *migrationPorts;
+ /* Immutable pointer, immutable object */
+ virPortAllocatorRange *backupPorts;
+
/* Immutable pointer, lockless APIs */
virSysinfoDef *hostsysinfo;
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index 5755d2adb0..1153d8c6e0 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -147,6 +147,7 @@ struct _qemuDomainObjPrivate {
char *origname;
int nbdPort; /* Port used for migration with NBD */
unsigned short migrationPort;
+ unsigned short backupNBDPort;
int preMigrationState;
unsigned long long preMigrationMemlock; /* Original RLIMIT_MEMLOCK in case
it was changed for the current
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index c5eedeedfa..a8034b4f26 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -714,6 +714,12 @@ qemuStateInitialize(bool privileged,
cfg->migrationPortMax)) == NULL)
goto error;
+ if ((qemu_driver->backupPorts =
+ virPortAllocatorRangeNew(_("backup"),
+ cfg->backupPortMin,
+ cfg->backupPortMax)) == NULL)
+ goto error;
+
if (qemuSecurityInit(qemu_driver) < 0)
goto error;
diff --git a/src/qemu/test_libvirtd_qemu.aug.in b/src/qemu/test_libvirtd_qemu.aug.in
index 82cfec3b4b..2582c6a09c 100644
--- a/src/qemu/test_libvirtd_qemu.aug.in
+++ b/src/qemu/test_libvirtd_qemu.aug.in
@@ -110,6 +110,8 @@ module Test_libvirtd_qemu =
{ "migration_host" = "host.example.com" }
{ "migration_port_min" = "49152" }
{ "migration_port_max" = "49215" }
+{ "backup_port_min" = "10809" }
+{ "backup_port_max" = "10872" }
{ "log_timestamp" = "0" }
{ "nvram"
{ "1" = "/usr/share/OVMF/OVMF_CODE.fd:/usr/share/OVMF/OVMF_VARS.fd" }
--
2.52.0© 2016 - 2026 Red Hat, Inc.