xs_internal.c

/*
 * xs_internal.c: access to Xen Store
 *
 * Copyright (C) 2006 Red Hat, Inc.
 *
 * See COPYING.LIB for the License of this software
 *
 * Daniel Veillard <veillard@redhat.com>
 */

#include <config.h>

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <stdint.h>

#include <xen/dom0_ops.h>
#include <xen/version.h>
#include <xen/xen.h>

#include <xs.h>

#include "internal.h"
#include "driver.h"
#include "xen_unified.h"
#include "xs_internal.h"
#include "xen_internal.h" /* for xenHypervisorCheckID */

#ifdef __linux__
#define XEN_HYPERVISOR_SOCKET "/proc/xen/privcmd"
#elif define(__sun__)
#define XEN_HYPERVISOR_SOCKET "/dev/xen/privcmd"
#else
#error "unsupported platform"
#endif

#ifndef PROXY
static char *xenStoreDomainGetOSType(virDomainPtr domain);

struct xenUnifiedDriver xenStoreDriver = {
    xenStoreOpen, /* open */
    xenStoreClose, /* close */
    NULL, /* version */
    NULL, /* hostname */
    NULL, /* URI */
    NULL, /* nodeGetInfo */
    NULL, /* getCapabilities */
    xenStoreListDomains, /* listDomains */
    NULL, /* numOfDomains */
    NULL, /* domainCreateLinux */
    NULL, /* domainSuspend */
    NULL, /* domainResume */
    xenStoreDomainShutdown, /* domainShutdown */
    xenStoreDomainReboot, /* domainReboot */
    NULL, /* domainDestroy */
    xenStoreDomainGetOSType, /* domainGetOSType */
    xenStoreDomainGetMaxMemory, /* domainGetMaxMemory */
    NULL, /* domainSetMaxMemory */
    xenStoreDomainSetMemory, /* domainSetMemory */
    xenStoreGetDomainInfo, /* domainGetInfo */
    NULL, /* domainSave */
    NULL, /* domainRestore */
    NULL, /* domainCoreDump */
    NULL, /* domainSetVcpus */
    NULL, /* domainPinVcpu */
    NULL, /* domainGetVcpus */
    NULL, /* domainGetMaxVcpus */
    NULL, /* listDefinedDomains */
    NULL, /* numOfDefinedDomains */
    NULL, /* domainCreate */
    NULL, /* domainDefineXML */
    NULL, /* domainUndefine */
    NULL, /* domainAttachDevice */
    NULL, /* domainDetachDevice */
    NULL, /* domainGetAutostart */
    NULL, /* domainSetAutostart */
    NULL, /* domainGetSchedulerType */
    NULL, /* domainGetSchedulerParameters */
    NULL, /* domainSetSchedulerParameters */
};

#endif /* ! PROXY */

/**
 * virXenStoreError:
 * @conn: the connection if available
 * @error: the error number
 * @info: extra information string
 *
 * Handle an error at the xend store interface
 */
static void
virXenStoreError(virConnectPtr conn, virErrorNumber error, const char *info)
{
    const char *errmsg;

    if (error == VIR_ERR_OK)
        return;

    errmsg = __virErrorMsg(error, info);
    __virRaiseError(conn, NULL, NULL, VIR_FROM_XENSTORE, error, VIR_ERR_ERROR,
                    errmsg, info, NULL, 0, 0, errmsg, info);
}

/************************************************************************
 *									*
 *		Helper internal APIs					*
 *									*
 ************************************************************************/
#ifndef PROXY
/**
 * virConnectDoStoreList:
 * @conn: pointer to the hypervisor connection
 * @path: the absolute path of the directory in the store to list
 * @nb: OUT pointer to the number of items found
 *
 * Internal API querying the Xenstore for a list
 *
 * Returns a string which must be freed by the caller or NULL in case of error
 */
static char **
virConnectDoStoreList(virConnectPtr conn, const char *path,
                      unsigned int *nb)
{
    xenUnifiedPrivatePtr priv;

    if (conn == NULL)
        return NULL;

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL || path == NULL || nb == NULL)
        return (NULL);

    return xs_directory (priv->xshandle, 0, path, nb);
}
#endif /* ! PROXY */

/**
 * virDomainDoStoreQuery:
 * @conn: pointer to the hypervisor connection
 * @domid: id of the domain
 * @path: the relative path of the data in the store to retrieve
 *
 * Internal API querying the Xenstore for a string value.
 *
 * Returns a string which must be freed by the caller or NULL in case of error
 */
static char *
virDomainDoStoreQuery(virConnectPtr conn, int domid, const char *path)
{
    char s[256];
    unsigned int len = 0;
    xenUnifiedPrivatePtr priv;

    if (!conn)
        return NULL;

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return (NULL);

    snprintf(s, 255, "/local/domain/%d/%s", domid, path);
    s[255] = 0;

    return xs_read(priv->xshandle, 0, &s[0], &len);
}

#ifndef PROXY
/**
 * virDomainDoStoreWrite:
 * @domain: a domain object
 * @path: the relative path of the data in the store to retrieve
 *
 * Internal API setting up a string value in the Xenstore
 * Requires write access to the XenStore
 *
 * Returns 0 in case of success, -1 in case of failure
 */
static int
virDomainDoStoreWrite(virDomainPtr domain, const char *path,
                      const char *value)
{
    char s[256];
    xenUnifiedPrivatePtr priv;
    int ret = -1;

    if (!VIR_IS_CONNECTED_DOMAIN(domain))
        return (-1);

    priv = (xenUnifiedPrivatePtr) domain->conn->privateData;
    if (priv->xshandle == NULL)
        return (-1);
    if (domain->conn->flags & VIR_CONNECT_RO)
        return (-1);

    snprintf(s, 255, "/local/domain/%d/%s", domain->id, path);
    s[255] = 0;

    if (xs_write(priv->xshandle, 0, &s[0], value, strlen(value)))
        ret = 0;

    return (ret);
}

/**
 * virDomainGetVM:
 * @domain: a domain object
 *
 * Internal API extracting a xenstore vm path.
 *
 * Returns the new string or NULL in case of error
 */
static char *
virDomainGetVM(virDomainPtr domain)
{
    char *vm;
    char query[200];
    unsigned int len;
    xenUnifiedPrivatePtr priv;

    if (!VIR_IS_CONNECTED_DOMAIN(domain))
        return (NULL);

    priv = (xenUnifiedPrivatePtr) domain->conn->privateData;
    if (priv->xshandle == NULL)
        return (NULL);

    snprintf(query, 199, "/local/domain/%d/vm", virDomainGetID(domain));
    query[199] = 0;

    vm = xs_read(priv->xshandle, 0, &query[0], &len);

    return (vm);
}

/**
 * virDomainGetVMInfo:
 * @domain: a domain object
 * @vm: the xenstore vm path
 * @name: the value's path
 *
 * Internal API extracting one information the device used
 * by the domain from xensttore
 *
 * Returns the new string or NULL in case of error
 */
static char *
virDomainGetVMInfo(virDomainPtr domain, const char *vm, const char *name)
{
    char s[256];
    char *ret = NULL;
    unsigned int len = 0;
    xenUnifiedPrivatePtr priv;

    if (!VIR_IS_CONNECTED_DOMAIN(domain))
        return (NULL);

    priv = (xenUnifiedPrivatePtr) domain->conn->privateData;
    if (priv->xshandle == NULL)
        return (NULL);

    snprintf(s, 255, "%s/%s", vm, name);
    s[255] = 0;

    ret = xs_read(priv->xshandle, 0, &s[0], &len);

    return (ret);
}

#endif /* ! PROXY */

/************************************************************************
 *									*
 *		Canonical internal APIs					*
 *									*
 ************************************************************************/
/**
 * xenStoreOpen:
 * @conn: pointer to the connection block
 * @name: URL for the target, NULL for local
 * @flags: combination of virDrvOpenFlag(s)
 *
 * Connects to the Xen hypervisor.
 *
 * Returns 0 or -1 in case of error.
 */
int
xenStoreOpen(virConnectPtr conn,
             xmlURIPtr uri ATTRIBUTE_UNUSED,
             virConnectAuthPtr auth ATTRIBUTE_UNUSED,
             int flags ATTRIBUTE_UNUSED)
{
    xenUnifiedPrivatePtr priv = (xenUnifiedPrivatePtr) conn->privateData;

#ifdef PROXY
    priv->xshandle = xs_daemon_open_readonly();
#else
    if (flags & VIR_CONNECT_RO)
        priv->xshandle = xs_daemon_open_readonly();
    else
        priv->xshandle = xs_daemon_open();
#endif /* ! PROXY */

    if (priv->xshandle == NULL) {
        /*
         * not being able to connect via the socket as a normal user
         * is rather normal, this should fallback to the proxy (or
         * remote) mechanism.
         */
        if (getuid() == 0) {
            virXenStoreError(NULL, VIR_ERR_NO_XEN,
                                 _("failed to connect to Xen Store"));
        }
        return (-1);
    }
    return (0);
}

/**
 * xenStoreClose:
 * @conn: pointer to the connection block
 *
 * Close the connection to the Xen hypervisor.
 *
 * Returns 0 in case of success or -1 in case of error.
 */
int
xenStoreClose(virConnectPtr conn)
{
    xenUnifiedPrivatePtr priv;

    if (conn == NULL) {
        virXenStoreError(conn, VIR_ERR_INVALID_ARG, __FUNCTION__);
        return(-1);
    }

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return(-1);

    xs_daemon_close(priv->xshandle);
    return (0);
}

#ifndef PROXY
/**
 * xenStoreGetDomainInfo:
 * @domain: pointer to the domain block
 * @info: the place where information should be stored
 *
 * Do an hypervisor call to get the related set of domain information.
 *
 * Returns 0 in case of success, -1 in case of error.
 */
int
xenStoreGetDomainInfo(virDomainPtr domain, virDomainInfoPtr info)
{
    char *tmp, **tmp2;
    unsigned int nb_vcpus;
    char request[200];
    xenUnifiedPrivatePtr priv;

    if (!VIR_IS_CONNECTED_DOMAIN(domain))
        return (-1);

    if ((domain == NULL) || (domain->conn == NULL) || (info == NULL)) {
        virXenStoreError(domain ? domain->conn : NULL, VIR_ERR_INVALID_ARG,
                         __FUNCTION__);
        return(-1);
    }

    priv = (xenUnifiedPrivatePtr) domain->conn->privateData;
    if (priv->xshandle == NULL)
        return(-1);

    if (domain->id == -1)
        return(-1);

    tmp = virDomainDoStoreQuery(domain->conn, domain->id, "running");
    if (tmp != NULL) {
        if (tmp[0] == '1')
            info->state = VIR_DOMAIN_RUNNING;
        free(tmp);
    } else {
        info->state = VIR_DOMAIN_NOSTATE;
    }
    tmp = virDomainDoStoreQuery(domain->conn, domain->id, "memory/target");
    if (tmp != NULL) {
        info->memory = atol(tmp);
        info->maxMem = atol(tmp);
        free(tmp);
    } else {
        info->memory = 0;
        info->maxMem = 0;
    }
#if 0
    /* doesn't seems to work */
    tmp = virDomainDoStoreQuery(domain->conn, domain->id, "cpu_time");
    if (tmp != NULL) {
        info->cpuTime = atol(tmp);
        free(tmp);
    } else {
        info->cpuTime = 0;
    }
#endif
    snprintf(request, 199, "/local/domain/%d/cpu", domain->id);
    request[199] = 0;
    tmp2 = virConnectDoStoreList(domain->conn, request, &nb_vcpus);
    if (tmp2 != NULL) {
        info->nrVirtCpu = nb_vcpus;
        free(tmp2);
    }
    return (0);
}

/**
 * xenStoreDomainSetMemory:
 * @domain: pointer to the domain block
 * @memory: the max memory size in kilobytes.
 *
 * Change the maximum amount of memory allowed in the xen store
 *
 * Returns 0 in case of success, -1 in case of error.
 */
int
xenStoreDomainSetMemory(virDomainPtr domain, unsigned long memory)
{
    int ret;
    char value[20];

    if ((domain == NULL) || (domain->conn == NULL) ||
        (memory < 1024 * MIN_XEN_GUEST_SIZE)) {
        virXenStoreError(domain ? domain->conn : NULL, VIR_ERR_INVALID_ARG,
                         __FUNCTION__);
        return(-1);
    }
    if (domain->id == -1)
        return(-1);
    if ((domain->id == 0) && (memory < (2 * MIN_XEN_GUEST_SIZE * 1024)))
        return(-1);
    snprintf(value, 19, "%lu", memory);
    value[19] = 0;
    ret = virDomainDoStoreWrite(domain, "memory/target", &value[0]);
    if (ret < 0)
        return (-1);
    return (0);
}

/**
 * xenStoreDomainGetMaxMemory:
 * @domain: pointer to the domain block
 *
 * Ask the xenstore for the maximum memory allowed for a domain
 *
 * Returns the memory size in kilobytes or 0 in case of error.
 */
unsigned long
xenStoreDomainGetMaxMemory(virDomainPtr domain)
{
    char *tmp;
    unsigned long ret = 0;

    if (!VIR_IS_CONNECTED_DOMAIN(domain))
        return (ret);
    if (domain->id == -1)
        return(-1);

    tmp = virDomainDoStoreQuery(domain->conn, domain->id, "memory/target");
    if (tmp != NULL) {
        ret = (unsigned long) atol(tmp);
        free(tmp);
    }
    return(ret);
}

/**
 * xenStoreNumOfDomains:
 * @conn: pointer to the hypervisor connection
 *
 * Provides the number of active domains.
 *
 * Returns the number of domain found or -1 in case of error
 */
int
xenStoreNumOfDomains(virConnectPtr conn)
{
    unsigned int num;
    char **idlist;
    int ret = -1;
    xenUnifiedPrivatePtr priv;

    if (conn == NULL) {
        virXenStoreError(conn, VIR_ERR_INVALID_ARG, __FUNCTION__);
        return -1;
    }

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL) {
        virXenStoreError(conn, VIR_ERR_INVALID_ARG, __FUNCTION__);
        return(-1);
    }
    idlist = xs_directory(priv->xshandle, 0, "/local/domain", &num);
    if (idlist) {
        free(idlist);
        ret = num;
    }
    return(ret);
}

/**
 * xenStoreListDomains:
 * @conn: pointer to the hypervisor connection
 * @ids: array to collect the list of IDs of active domains
 * @maxids: size of @ids
 *
 * Collect the list of active domains, and store their ID in @maxids
 *
 * Returns the number of domain found or -1 in case of error
 */
int
xenStoreListDomains(virConnectPtr conn, int *ids, int maxids)
{
    char **idlist = NULL, *endptr;
    unsigned int num, i;
    int ret;
    long id;
    xenUnifiedPrivatePtr priv;

    if ((conn == NULL) || (ids == NULL)) {
        virXenStoreError(conn, VIR_ERR_INVALID_ARG, __FUNCTION__);
        return(-1);
    }

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return(-1);

    idlist = xs_directory (priv->xshandle, 0, "/local/domain", &num);
    if (idlist == NULL)
        return(-1);

    for (ret = 0, i = 0; (i < num) && (ret < maxids); i++) {
        id = strtol(idlist[i], &endptr, 10);
        if ((endptr == idlist[i]) || (*endptr != 0)) {
            ret = -1;
            break;
        }
#if 0
        if (virConnectCheckStoreID(conn, (int) id) < 0)
            continue;
#endif
        ids[ret++] = (int) id;
    }
    free(idlist);
    return(ret);
}

/**
 * xenStoreLookupByName:
 * @conn: A xend instance
 * @name: The name of the domain
 *
 * Try to lookup a domain on the Xen Store based on its name.
 *
 * Returns a new domain object or NULL in case of failure
 */
virDomainPtr
xenStoreLookupByName(virConnectPtr conn, const char *name)
{
    virDomainPtr ret = NULL;
    unsigned int num, i, len;
    long id = -1;
    char **idlist = NULL, *endptr;
    char prop[200], *tmp;
    int found = 0;
    struct xend_domain *xenddomain = NULL;
    xenUnifiedPrivatePtr priv;

    if ((conn == NULL) || (name == NULL)) {
        virXenStoreError(conn, VIR_ERR_INVALID_ARG, __FUNCTION__);
        return(NULL);
    }

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return(NULL);

    idlist = xs_directory(priv->xshandle, 0, "/local/domain", &num);
    if (idlist == NULL)
        goto done;

    for (i = 0; i < num; i++) {
        id = strtol(idlist[i], &endptr, 10);
        if ((endptr == idlist[i]) || (*endptr != 0)) {
            goto done;
        }
#if 0
        if (virConnectCheckStoreID(conn, (int) id) < 0)
            continue;
#endif
        snprintf(prop, 199, "/local/domain/%s/name", idlist[i]);
        prop[199] = 0;
        tmp = xs_read(priv->xshandle, 0, prop, &len);
        if (tmp != NULL) {
            found = STREQ (name, tmp);
            free(tmp);
            if (found)
                break;
        }
    }
    if (!found)
        goto done;

    ret = virGetDomain(conn, name, NULL);
    if (ret == NULL)
        goto done;

    ret->id = id;

done:
        free(xenddomain);
        free(idlist);

    return(ret);
}

/**
 * xenStoreDomainShutdown:
 * @domain: pointer to the Domain block
 *
 * Shutdown the domain, the OS is requested to properly shutdown
 * and the domain may ignore it.  It will return immediately
 * after queuing the request.
 *
 * Returns 0 in case of success, -1 in case of error.
 */
int
xenStoreDomainShutdown(virDomainPtr domain)
{
    if ((domain == NULL) || (domain->conn == NULL)) {
        virXenStoreError((domain ? domain->conn : NULL), VIR_ERR_INVALID_ARG,
                         __FUNCTION__);
        return(-1);
    }
    if (domain->id == -1 || domain->id == 0)
        return(-1);
    /*
     * this is very hackish, the domU kernel probes for a special
     * node in the xenstore and launch the shutdown command if found.
     */
    return(virDomainDoStoreWrite(domain, "control/shutdown", "poweroff"));
}

/**
 * xenStoreDomainReboot:
 * @domain: pointer to the Domain block
 * @flags: extra flags for the reboot operation, not used yet
 *
 * Reboot the domain, the OS is requested to properly shutdown
 * and reboot but the domain may ignore it.  It will return immediately
 * after queuing the request.
 *
 * Returns 0 in case of success, -1 in case of error.
 */
int
xenStoreDomainReboot(virDomainPtr domain, unsigned int flags ATTRIBUTE_UNUSED)
{
    if ((domain == NULL) || (domain->conn == NULL)) {
        virXenStoreError((domain ? domain->conn : NULL), VIR_ERR_INVALID_ARG,
                         __FUNCTION__);
        return(-1);
    }
    if (domain->id == -1 || domain->id == 0)
        return(-1);
    /*
     * this is very hackish, the domU kernel probes for a special
     * node in the xenstore and launch the shutdown command if found.
     */
    return(virDomainDoStoreWrite(domain, "control/shutdown", "reboot"));
}

/*
 * xenStoreDomainGetOSType:
 * @domain: a domain object
 *
 * Get the type of domain operation system.
 *
 * Returns the new string or NULL in case of error, the string must be
 *         freed by the caller.
 */
static char *
xenStoreDomainGetOSType(virDomainPtr domain) {
    char *vm, *str = NULL;

    if ((domain == NULL) || (domain->conn == NULL)) {
        virXenStoreError((domain ? domain->conn : NULL), VIR_ERR_INVALID_ARG,
                         __FUNCTION__);
        return(NULL);
    }

    vm = virDomainGetVM(domain);
    if (vm) {
        str = virDomainGetVMInfo(domain, vm, "image/ostype");
        free(vm);
    }

    return (str);
}
#endif /* ! PROXY */

/**
 * xenStoreDomainGetVNCPort:
 * @conn: the hypervisor connection
 * @domid: id of the domain
 *
 * Return the port number on which the domain is listening for VNC
 * connections.
 *
 * Returns the port number, -1 in case of error
 */
int             xenStoreDomainGetVNCPort(virConnectPtr conn, int domid) {
    char *tmp;
    int ret = -1;

    tmp = virDomainDoStoreQuery(conn, domid, "console/vnc-port");
    if (tmp != NULL) {
        char *end;
        ret = strtol(tmp, &end, 10);
        if (ret == 0 && end == tmp)
            ret = -1;
        free(tmp);
    }
    return(ret);
}

/**
 * xenStoreDomainGetConsolePath:
 * @conn: the hypervisor connection
 * @domid: id of the domain
 *
 * Return the path to the psuedo TTY on which the guest domain's
 * serial console is attached.
 *
 * Returns the path to the serial console. It is the callers
 * responsibilty to free() the return string. Returns NULL
 * on error
 */
char *          xenStoreDomainGetConsolePath(virConnectPtr conn, int domid) {
  return virDomainDoStoreQuery(conn, domid, "console/tty");
}

#ifdef PROXY
/*
 * xenStoreDomainGetOSTypeID:
 * @conn: pointer to the connection.
 * @id: the domain id
 *
 * Get the type of domain operation system.
 *
 * Returns the new string or NULL in case of error, the string must be
 *         freed by the caller.
 */
char *
xenStoreDomainGetOSTypeID(virConnectPtr conn, int id) {
    char *vm, *str = NULL;
    char query[200];
    unsigned int len;
    xenUnifiedPrivatePtr priv;

    if (id < 0)
        return(NULL);

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return (NULL);

    snprintf(query, 199, "/local/domain/%d/vm", id);
    query[199] = 0;

    vm = xs_read(priv->xshandle, 0, &query[0], &len);

    if (vm) {
        snprintf(query, 199, "%s/image/ostype", vm);
        str = xs_read(priv->xshandle, 0, &query[0], &len);
        free(vm);
    }
    if (str == NULL)
        str = strdup("linux");


    return (str);
}
#endif /* PROXY */

/*
 * xenStoreDomainGetNetworkID:
 * @conn: pointer to the connection.
 * @id: the domain id
 * @mac: the mac address
 *
 * Get the reference (i.e. the string number) for the device on that domain
 * which uses the given mac address
 *
 * Returns the new string or NULL in case of error, the string must be
 *         freed by the caller.
 */
char *
xenStoreDomainGetNetworkID(virConnectPtr conn, int id, const char *mac) {
    char dir[80], path[128], **list = NULL, *val = NULL;
    unsigned int maclen, len, i, num;
    char *ret = NULL;
    xenUnifiedPrivatePtr priv;

    if (id < 0)
        return(NULL);

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return (NULL);
    if (mac == NULL)
        return (NULL);
    maclen = strlen(mac);
    if (maclen <= 0)
        return (NULL);

    snprintf(dir, sizeof(dir), "/local/domain/0/backend/vif/%d", id);
    list = xs_directory(priv->xshandle, 0, dir, &num);
    if (list == NULL)
        return(NULL);
    for (i = 0; i < num; i++) {
        snprintf(path, sizeof(path), "%s/%s/%s", dir, list[i], "mac");
        val = xs_read(priv->xshandle, 0, path, &len);
        if (val == NULL)
            break;
        if ((maclen != len) || memcmp(val, mac, len)) {
            free(val);
        } else {
            ret = strdup(list[i]);
            free(val);
            break;
        }
    }
    free(list);
    return(ret);
}

/*
 * xenStoreDomainGetDiskID:
 * @conn: pointer to the connection.
 * @id: the domain id
 * @dev: the virtual block device name
 *
 * Get the reference (i.e. the string number) for the device on that domain
 * which uses the given virtual block device name
 *
 * Returns the new string or NULL in case of error, the string must be
 *         freed by the caller.
 */
char *
xenStoreDomainGetDiskID(virConnectPtr conn, int id, const char *dev) {
    char dir[80], path[128], **list = NULL, *val = NULL;
    unsigned int devlen, len, i, num;
    char *ret = NULL;
    xenUnifiedPrivatePtr priv;

    if (id < 0)
        return(NULL);

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return (NULL);
    if (dev == NULL)
        return (NULL);
    devlen = strlen(dev);
    if (devlen <= 0)
        return (NULL);

    snprintf(dir, sizeof(dir), "/local/domain/0/backend/vbd/%d", id);
    list = xs_directory(priv->xshandle, 0, dir, &num);
    if (list != NULL) {
        for (i = 0; i < num; i++) {
            snprintf(path, sizeof(path), "%s/%s/%s", dir, list[i], "dev");
            val = xs_read(priv->xshandle, 0, path, &len);
            if (val == NULL)
                break;
            if ((devlen != len) || memcmp(val, dev, len)) {
                free (val);
            } else {
                ret = strdup(list[i]);
                free (val);
                free (list);
                return (ret);
            }
        }
        free (list);
    }
    snprintf(dir, sizeof(dir), "/local/domain/0/backend/tap/%d", id);
    list = xs_directory(priv->xshandle, 0, dir, &num);
    if (list != NULL) {
        for (i = 0; i < num; i++) {
            snprintf(path, sizeof(path), "%s/%s/%s", dir, list[i], "dev");
            val = xs_read(priv->xshandle, 0, path, &len);
            if (val == NULL)
                break;
            if ((devlen != len) || memcmp(val, dev, len)) {
                free (val);
            } else {
                ret = strdup(list[i]);
                free (val);
                free (list);
                return (ret);
            }
        }
        free (list);
    }
    return (NULL);
}

char *xenStoreDomainGetName(virConnectPtr conn,
                            int id) {
    char prop[200];
    xenUnifiedPrivatePtr priv;
    unsigned int len;

    priv = (xenUnifiedPrivatePtr) conn->privateData;
    if (priv->xshandle == NULL)
        return(NULL);

    snprintf(prop, 199, "/local/domain/%d/name", id);
    prop[199] = 0;
    return xs_read(priv->xshandle, 0, prop, &len);
}