On Mon, Feb 23, 2026 at 19:52:22 -0300, Lucas Amaral wrote:
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> ---
[...]
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(-)
Sorry for the delay in reviewing this patch. The code looks good, but normally we'd request splitting of the 'qemu.conf' related changes into a separate patch. In this case I'll do the split (obviously preserving authorship) before pushing so that you don't need to follow up with another version.
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; + }
This code belongs to BackupPrepare instead of the comment.
+ 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);
Pre existing problem (in other port ranges) that I'll fix in a follow-up. VIR_ERR_INTERNAL_ERROR is not appropriate error code for user mis-configuration.
+ return -1; + } + if (virConfGetValueString(conf, "migration_host", &cfg->migrateHost) < 0) return -1; virStringStripIPv6Brackets(cfg->migrateHost);
Reviewed-by: Peter Krempa <pkrempa@redhat.com>