char *
tapback_device_read(const vbd_t * const device, xs_transaction_t xst,
const char * const path)
{
ASSERT(device);
ASSERT(path);
return tapback_xs_read(device->backend->xs, xst, "%s/%s/%s",
device->backend->path, device->name, path);
}
char *
tapback_device_read_otherend(vbd_t * const device, xs_transaction_t xst,
const char * const path)
{
ASSERT(device);
ASSERT(path);
ASSERT(device->frontend_path);
return tapback_xs_read(device->backend->xs, xst, "%s/%s",
device->frontend_path, path);
}
int
tapback_xs_exists(struct xs_handle * const xs, xs_transaction_t xst,
char *path, const int *len)
{
int err = 0;
char *s = NULL;
bool exists = false;
char c = '\0';
ASSERT(xs);
ASSERT(path);
if (len) {
c = path[*len];
path[*len] = '\0';
}
s = tapback_xs_read(xs, xst, "%s", path);
if (s)
exists = true;
else {
err = errno;
ASSERT(err != 0);
if (err == ENOENT) {
err = 0;
exists = false;
}
}
free(s);
if (len)
path[*len] = c;
if (!err) {
if (exists) {
return 1;
} else {
return 0;
}
} else {
return -err;
}
}
int
tapback_backend_handle_otherend_watch(backend_t *backend,
const char * const path)
{
vbd_t *device = NULL;
int err = 0, state = 0;
char *s = NULL, *end = NULL, *_path = NULL;
ASSERT(backend);
ASSERT(path);
/*
* Find the device that has the same front-end state path.
*
* There should definitely be such a device in our list, otherwise this
* function would not have executed at all, since we would not be waiting
* on that XenStore path. The XenStore path we wait for is:
* /local/domain/<domid>/device/vbd/<devname>/state. In order to watch this
* path, it means that we have received a device create request, so the
* device will be there.
*
* TODO Instead of this linear search we could do better (hash table etc).
*/
tapback_backend_find_device(backend, device,
device->frontend_state_path &&
!strcmp(device->frontend_state_path, path));
if (!device) {
WARN(NULL, "path \'%s\' does not correspond to a known device\n",
path);
return ENODEV;
}
/*
* Read the new front-end's state.
*/
s = tapback_xs_read(device->backend->xs, XBT_NULL, "%s",
device->frontend_state_path);
if (!s) {
err = errno;
/*
* If the front-end XenBus node is missing, the XenBus device has been
* removed: remove the XenBus back-end node.
*/
if (err == ENOENT) {
err = asprintf(&_path, "%s/%s/%d/%d", XENSTORE_BACKEND,
device->backend->name, device->domid, device->devid);
if (err == -1) {
err = errno;
WARN(device, "failed to asprintf for %d/%d: %s\n",
strerror(err));
goto out;
}
err = 0;
if (!xs_rm(device->backend->xs, XBT_NULL, _path)) {
if (errno != ENOENT) {
err = errno;
WARN(device, "failed to remove %s: %s\n", path,
strerror(err));
}
}
}
} else {
state = strtol(s, &end, 0);
if (*end != 0 || end == s) {
WARN(device, "invalid XenBus state '%s'\n", s);
err = EINVAL;
} else
err = frontend_changed(device, state);
}
out:
free(s);
free(_path);
return err;
}