libxl: support migration stream V2 in migration

Similar to "support Xen migration stream V2 in save/restore",
add support for indicating the migration stream version in
the migration code. To accomplish this, add a minimal migration
cookie in the libxl driver that is passed between source and
destination hosts. Initially, the cookie is only used in
the Begin and Prepare phases of migration to communicate the
version of the migration stream produced by the source.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>

src/libxl/libxl_driver.c

@@ -5151,8 +5151,8 @@ static char *
 libxlDomainMigrateBegin3Params(virDomainPtr domain,
                                virTypedParameterPtr params,
                                int nparams,
-                               char **cookieout ATTRIBUTE_UNUSED,
+                               char **cookieout,
-                               int *cookieoutlen ATTRIBUTE_UNUSED,
+                               int *cookieoutlen,
                                unsigned int flags)
 {
     const char *xmlin = NULL;
@@ -5193,15 +5193,16 @@ libxlDomainMigrateBegin3Params(virDomainPtr domain,
         return NULL;
     }
 
-    return libxlDomainMigrationBegin(domain->conn, vm, xmlin);
+    return libxlDomainMigrationBegin(domain->conn, vm, xmlin,
+                                     cookieout, cookieoutlen);
 }
 
 static int
 libxlDomainMigratePrepare3Params(virConnectPtr dconn,
                                  virTypedParameterPtr params,
                                  int nparams,
-                                 const char *cookiein ATTRIBUTE_UNUSED,
+                                 const char *cookiein,
-                                 int cookieinlen ATTRIBUTE_UNUSED,
+                                 int cookieinlen,
                                  char **cookieout ATTRIBUTE_UNUSED,
                                  int *cookieoutlen ATTRIBUTE_UNUSED,
                                  char **uri_out,
@@ -5240,7 +5241,8 @@ libxlDomainMigratePrepare3Params(virConnectPtr dconn,
     if (virDomainMigratePrepare3ParamsEnsureACL(dconn, def) < 0)
         goto error;
 
-    if (libxlDomainMigrationPrepare(dconn, &def, uri_in, uri_out, flags) < 0)
+    if (libxlDomainMigrationPrepare(dconn, &def, uri_in, uri_out,
+                                    cookiein, cookieinlen, flags) < 0)
         goto error;
 
     return 0;

src/libxl/libxl_migration.c

@@ -48,6 +48,18 @@
 
 VIR_LOG_INIT("libxl.libxl_migration");
 
+typedef struct _libxlMigrationCookie libxlMigrationCookie;
+typedef libxlMigrationCookie *libxlMigrationCookiePtr;
+struct _libxlMigrationCookie {
+    /* Host properties */
+    char *srcHostname;
+    uint32_t xenMigStreamVer;
+
+    /* Guest properties */
+    unsigned char uuid[VIR_UUID_BUFLEN];
+    char *name;
+};
+
 typedef struct _libxlMigrationDstArgs {
     virObject parent;
 
@@ -55,6 +67,7 @@ typedef struct _libxlMigrationDstArgs {
     virConnectPtr conn;
     virDomainObjPtr vm;
     unsigned int flags;
+    libxlMigrationCookiePtr migcookie;
 
     /* for freeing listen sockets */
     virNetSocketPtr *socks;
@@ -63,11 +76,166 @@ typedef struct _libxlMigrationDstArgs {
 
 static virClassPtr libxlMigrationDstArgsClass;
 
+
+static void
+libxlMigrationCookieFree(libxlMigrationCookiePtr mig)
+{
+    if (!mig)
+        return;
+
+    VIR_FREE(mig->srcHostname);
+    VIR_FREE(mig->name);
+    VIR_FREE(mig);
+}
+
+static libxlMigrationCookiePtr
+libxlMigrationCookieNew(virDomainObjPtr dom)
+{
+    libxlMigrationCookiePtr mig = NULL;
+
+    if (VIR_ALLOC(mig) < 0)
+        goto error;
+
+    if (VIR_STRDUP(mig->name, dom->def->name) < 0)
+        goto error;
+
+    memcpy(mig->uuid, dom->def->uuid, VIR_UUID_BUFLEN);
+
+    if (!(mig->srcHostname = virGetHostname()))
+        goto error;
+
+    mig->xenMigStreamVer = LIBXL_SAVE_VERSION;
+
+    return mig;
+
+ error:
+    libxlMigrationCookieFree(mig);
+    return NULL;
+}
+
+
+static int
+libxlMigrationBakeCookie(libxlMigrationCookiePtr mig,
+                         char **cookieout,
+                         int *cookieoutlen)
+{
+    virBuffer buf = VIR_BUFFER_INITIALIZER;
+    char uuidstr[VIR_UUID_STRING_BUFLEN];
+
+    if (!cookieout || !cookieoutlen)
+        return 0;
+
+    *cookieoutlen = 0;
+    virUUIDFormat(mig->uuid, uuidstr);
+
+    virBufferAddLit(&buf, "<libxl-migration>\n");
+    virBufferAdjustIndent(&buf, 2);
+    virBufferEscapeString(&buf, "<name>%s</name>\n", mig->name);
+    virBufferAsprintf(&buf, "<uuid>%s</uuid>\n", uuidstr);
+    virBufferEscapeString(&buf, "<hostname>%s</hostname>\n", mig->srcHostname);
+    virBufferAsprintf(&buf, "<migration-stream-version>%u</migration-stream-version>\n", mig->xenMigStreamVer);
+    virBufferAdjustIndent(&buf, -2);
+    virBufferAddLit(&buf, "</libxl-migration>\n");
+
+    if (virBufferCheckError(&buf) < 0)
+        return -1;
+
+    *cookieout = virBufferContentAndReset(&buf);
+    *cookieoutlen = strlen(*cookieout) + 1;
+
+    VIR_DEBUG("cookielen=%d cookie=%s", *cookieoutlen, *cookieout);
+
+    return 0;
+}
+
+static int
+libxlMigrationEatCookie(const char *cookiein,
+                        int cookieinlen,
+                        libxlMigrationCookiePtr *migout)
+{
+    libxlMigrationCookiePtr mig = NULL;
+    xmlDocPtr doc = NULL;
+    xmlXPathContextPtr ctxt = NULL;
+    char *uuidstr = NULL;
+    int ret = -1;
+
+    /*
+     * Assume a legacy (V1) migration stream if request came from a
+     * source host without cookie support, and hence no way to
+     * specify a stream version.
+     */
+    if (!cookiein || !cookieinlen) {
+        if (VIR_ALLOC(mig) < 0)
+            return -1;
+
+        mig->xenMigStreamVer = 1;
+        *migout = mig;
+        return 0;
+    }
+
+    if (cookiein[cookieinlen-1] != '\0') {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Migration cookie was not NULL terminated"));
+        return -1;
+    }
+
+    VIR_DEBUG("cookielen=%d cookie='%s'", cookieinlen, NULLSTR(cookiein));
+
+    if (VIR_ALLOC(mig) < 0)
+        return -1;
+
+    if (!(doc = virXMLParseStringCtxt(cookiein,
+                                      _("(libxl_migration_cookie)"),
+                                      &ctxt)))
+        goto error;
+
+    /* Extract domain name */
+    if (!(mig->name = virXPathString("string(./name[1])", ctxt))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "%s", _("missing name element in migration data"));
+        goto error;
+    }
+
+    /* Extract domain uuid */
+    uuidstr = virXPathString("string(./uuid[1])", ctxt);
+    if (!uuidstr) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "%s", _("missing uuid element in migration data"));
+        goto error;
+    }
+    if (virUUIDParse(uuidstr, mig->uuid) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       "%s", _("malformed uuid element"));
+        goto error;
+    }
+
+    if (virXPathUInt("string(./migration-stream-version[1])",
+                     ctxt, &mig->xenMigStreamVer) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("missing Xen migration stream version"));
+        goto error;
+    }
+
+    *migout = mig;
+    ret = 0;
+    goto cleanup;
+
+ error:
+    libxlMigrationCookieFree(mig);
+
+ cleanup:
+    VIR_FREE(uuidstr);
+    xmlXPathFreeContext(ctxt);
+    xmlFreeDoc(doc);
+    return ret;
+}
+
 static void
 libxlMigrationDstArgsDispose(void *obj)
 {
     libxlMigrationDstArgs *args = obj;
 
+    libxlMigrationCookieFree(args->migcookie);
     VIR_FREE(args->socks);
 }
 
@@ -106,7 +274,8 @@ libxlDoMigrateReceive(void *opaque)
      * Always start the domain paused.  If needed, unpause in the
      * finish phase, after transfer of the domain is complete.
      */
-    ret = libxlDomainStartRestore(driver, vm, true, recvfd, LIBXL_SAVE_VERSION);
+    ret = libxlDomainStartRestore(driver, vm, true, recvfd,
+                                  args->migcookie->xenMigStreamVer);
 
     if (ret < 0 && !vm->persistent)
         remove_dom = true;
@@ -227,10 +396,13 @@ libxlDomainMigrationIsAllowed(virDomainDefPtr def)
 char *
 libxlDomainMigrationBegin(virConnectPtr conn,
                           virDomainObjPtr vm,
-                          const char *xmlin)
+                          const char *xmlin,
+                          char **cookieout,
+                          int *cookieoutlen)
 {
     libxlDriverPrivatePtr driver = conn->privateData;
     libxlDriverConfigPtr cfg = libxlDriverConfigGet(driver);
+    libxlMigrationCookiePtr mig;
     virDomainDefPtr tmpdef = NULL;
     virDomainDefPtr def;
     char *xml = NULL;
@@ -238,6 +410,12 @@ libxlDomainMigrationBegin(virConnectPtr conn,
     if (libxlDomainObjBeginJob(driver, vm, LIBXL_JOB_MODIFY) < 0)
         goto cleanup;
 
+    if (!(mig = libxlMigrationCookieNew(vm)))
+        goto endjob;
+
+    if (libxlMigrationBakeCookie(mig, cookieout, cookieoutlen) < 0)
+        goto endjob;
+
     if (xmlin) {
         if (!(tmpdef = virDomainDefParseString(xmlin, cfg->caps,
                                                driver->xmlopt,
@@ -308,9 +486,12 @@ libxlDomainMigrationPrepare(virConnectPtr dconn,
                             virDomainDefPtr *def,
                             const char *uri_in,
                             char **uri_out,
+                            const char *cookiein,
+                            int cookieinlen,
                             unsigned int flags)
 {
     libxlDriverPrivatePtr driver = dconn->privateData;
+    libxlMigrationCookiePtr mig = NULL;
     virDomainObjPtr vm = NULL;
     char *hostname = NULL;
     unsigned short port;
@@ -323,6 +504,16 @@ libxlDomainMigrationPrepare(virConnectPtr dconn,
     size_t i;
     int ret = -1;
 
+    if (libxlMigrationEatCookie(cookiein, cookieinlen, &mig) < 0)
+        goto error;
+
+    if (mig->xenMigStreamVer > LIBXL_SAVE_VERSION) {
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                       _("Xen migration stream version '%d' is not supported on this host"),
+                       mig->xenMigStreamVer);
+        goto error;
+    }
+
     if (!(vm = virDomainObjListAdd(driver->domains, *def,
                                    driver->xmlopt,
                                    VIR_DOMAIN_OBJ_LIST_ADD_LIVE |
@@ -409,6 +600,7 @@ libxlDomainMigrationPrepare(virConnectPtr dconn,
     args->flags = flags;
     args->socks = socks;
     args->nsocks = nsocks;
+    args->migcookie = mig;
 
     for (i = 0; i < nsocks; i++) {
         if (virNetSocketSetBlocking(socks[i], true) < 0)
@@ -479,11 +671,14 @@ libxlDoMigrateP2P(libxlDriverPrivatePtr driver,
     char *uri_out = NULL;
     char *dom_xml = NULL;
     unsigned long destflags;
+    char *cookieout = NULL;
+    int cookieoutlen;
     bool cancelled = true;
     virErrorPtr orig_err = NULL;
     int ret = -1;
 
-    dom_xml = libxlDomainMigrationBegin(sconn, vm, xmlin);
+    dom_xml = libxlDomainMigrationBegin(sconn, vm, xmlin,
+                                        &cookieout, &cookieoutlen);
     if (!dom_xml)
         goto cleanup;
 
@@ -509,7 +704,7 @@ libxlDoMigrateP2P(libxlDriverPrivatePtr driver,
     VIR_DEBUG("Prepare3");
     virObjectUnlock(vm);
     ret = dconn->driver->domainMigratePrepare3Params
-        (dconn, params, nparams, NULL, 0, NULL, NULL, &uri_out, destflags);
+        (dconn, params, nparams, cookieout, cookieoutlen, NULL, NULL, &uri_out, destflags);
     virObjectLock(vm);
 
     if (ret == -1)
@@ -580,6 +775,7 @@ libxlDoMigrateP2P(libxlDriverPrivatePtr driver,
         virFreeError(orig_err);
     }
 
+    VIR_FREE(cookieout);
     VIR_FREE(dom_xml);
     VIR_FREE(uri_out);
     virTypedParamsFree(params, nparams);

src/libxl/libxl_migration.h

@@ -42,7 +42,9 @@
 char *
 libxlDomainMigrationBegin(virConnectPtr conn,
                           virDomainObjPtr vm,
-                          const char *xmlin);
+                          const char *xmlin,
+                          char **cookieout,
+                          int *cookieoutlen);
 
 virDomainDefPtr
 libxlDomainMigrationPrepareDef(libxlDriverPrivatePtr driver,
@@ -54,6 +56,8 @@ libxlDomainMigrationPrepare(virConnectPtr dconn,
                             virDomainDefPtr *def,
                             const char *uri_in,
                             char **uri_out,
+                            const char *cookiein,
+                            int cookieinlen,
                             unsigned int flags);
 
 int