migration: add support for migrateURI configuration

For now, we set the migration URI via command line '--migrate_uri' or
construct the URI by looking up the dest host's hostname which could be
solved by DNS automatically.

But in cases the dest host have two or more NICs to reach, we may need to
send the migration data over a specific NIC which is different from the
automatically resolved one for some reason like performance, security, etc.
Thus we must explicitly specify the migrateuri in command line everytime,
but it is too troublesome if there are many such hosts (and don't forget
virt-manager).

This patch adds a configuration file option on dest host to save the
default value set which can be specified to a migration hostname or
one of this host's addresses used for transferring data, thus user doesn't
have to specify it in command line everytime.

Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

src/qemu/libvirtd_qemu.aug

@@ -84,6 +84,7 @@ module Libvirtd_qemu =
    let network_entry = str_entry "migration_address"
                  | int_entry "migration_port_min"
                  | int_entry "migration_port_max"
+                 | str_entry "migration_host"
 
    let log_entry = bool_entry "log_timestamp"
 

src/qemu/qemu.conf

@@ -450,12 +450,19 @@
 #seccomp_sandbox = 1
 
 
-
 # Override the listen address for all incoming migrations. Defaults to
 # 0.0.0.0, or :: if both host and qemu are capable of IPv6.
 #migration_address = "127.0.0.1"
 
 
+# The default hostname or IP address which will be used by a migration
+# source for transferring migration data to this host.  The migration
+# source has to be able to resolve this hostname and connect to it so
+# setting "localhost" will not work.  By default, the host's configured
+# hostname is used.
+#migration_host = "host.example.com"
+
+
 # Override the port range used for incoming migrations.
 #
 # Minimum must be greater than 0, however when QEMU is not running as root,

src/qemu/qemu_conf.c

@@ -576,6 +576,7 @@ int virQEMUDriverConfigLoadFile(virQEMUDriverConfigPtr cfg,
 
     GET_VALUE_LONG("seccomp_sandbox", cfg->seccompSandbox);
 
+    GET_VALUE_STR("migration_host", cfg->migrateHost);
     GET_VALUE_STR("migration_address", cfg->migrationAddress);
 
     GET_VALUE_BOOL("log_timestamp", cfg->logTimestamp);

src/qemu/qemu_conf.h

@@ -163,6 +163,7 @@ struct _virQEMUDriverConfig {
 
     int seccompSandbox;
 
+    char *migrateHost;
     /* The default for -incoming */
     char *migrationAddress;
     int migrationPortMin;

src/qemu/qemu_migration.c

@@ -2640,6 +2640,8 @@ qemuMigrationPrepareDirect(virQEMUDriverPtr driver,
     int ret = -1;
     virURIPtr uri = NULL;
     bool well_formed_uri = true;
+    virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
+    const char *migrateHost = cfg->migrateHost;
 
     VIR_DEBUG("driver=%p, dconn=%p, cookiein=%s, cookieinlen=%d, "
               "cookieout=%p, cookieoutlen=%p, uri_in=%s, uri_out=%p, "
@@ -2653,8 +2655,9 @@ qemuMigrationPrepareDirect(virQEMUDriverPtr driver,
     /* The URI passed in may be NULL or a string "tcp://somehostname:port".
      *
      * If the URI passed in is NULL then we allocate a port number
-     * from our pool of port numbers and return a URI of
-     * "tcp://ourhostname:port".
+     * from our pool of port numbers, and if the migrateHost is configured,
+     * we return a URI of "tcp://migrateHost:port", otherwise return a URI
+     * of "tcp://ourhostname:port".
      *
      * If the URI passed in is not NULL then we try to parse out the
      * port number and use that (note that the hostname is assumed
@@ -2664,8 +2667,17 @@ qemuMigrationPrepareDirect(virQEMUDriverPtr driver,
         if (virPortAllocatorAcquire(driver->migrationPorts, &port) < 0)
             goto cleanup;
 
-        if ((hostname = virGetHostname()) == NULL)
-            goto cleanup;
+        if (migrateHost != NULL) {
+            if (virSocketAddrIsNumeric(migrateHost) &&
+                virSocketAddrParse(NULL, migrateHost, AF_UNSPEC) < 0)
+                goto cleanup;
+
+           if (VIR_STRDUP(hostname, migrateHost) < 0)
+                goto cleanup;
+        } else {
+            if ((hostname = virGetHostname()) == NULL)
+                goto cleanup;
+        }
 
         if (STRPREFIX(hostname, "localhost")) {
             virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -2747,6 +2759,7 @@ qemuMigrationPrepareDirect(virQEMUDriverPtr driver,
  cleanup:
     virURIFree(uri);
     VIR_FREE(hostname);
+    virObjectUnref(cfg);
     if (ret != 0) {
         VIR_FREE(*uri_out);
         if (autoPort)

src/qemu/test_libvirtd_qemu.aug.in

@@ -70,6 +70,7 @@ module Test_libvirtd_qemu =
 { "keepalive_count" = "5" }
 { "seccomp_sandbox" = "1" }
 { "migration_address" = "127.0.0.1" }
+{ "migration_host" = "host.example.com" }
 { "migration_port_min" = "49152" }
 { "migration_port_max" = "49215" }
 { "log_timestamp" = "0" }