qemu: conf: add setup for automatic port allocation for pull-mode backup NBD servers

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).

Signed-off-by: Lucas Amaral <lucaaamaral@gmail.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

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"
 

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.

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",
@@ -268,6 +271,9 @@ 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. */
@@ -989,6 +995,25 @@ 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);

src/qemu/qemu_conf.h

@@ -241,6 +241,9 @@ struct _virQEMUDriverConfig {
     unsigned int migrationPortMin;
     unsigned int migrationPortMax;
 
+    unsigned int backupPortMin;
+    unsigned int backupPortMax;
+
     bool logTimestamp;
     bool stdioLogD;
 

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" }