[SSSD] [PATCHES] ad srv: prefer servers that are in the same domain as client
Pavel Březina
pbrezina at redhat.com
Fri Aug 23 17:36:22 UTC 2013
On 08/23/2013 05:44 PM, Jakub Hrozek wrote:
> On Thu, Aug 08, 2013 at 01:24:17PM +0200, Pavel Březina wrote:
>> On 08/08/2013 03:32 AM, Simo Sorce wrote:
>>> On Wed, 2013-08-07 at 13:56 +0200, Lukas Slebodnik wrote:
>>> [..]
>>> nitpicking some more given Lucas nacked.
>>>
>>>>> +static errno_t ad_sort_servers(struct ares_srv_reply **list, void *pvt)
>>>>> +{
>>>>> + struct ad_srv_plugin_state *state = NULL;
>>>>> + struct ares_srv_reply dummy[3] = {{NULL, NULL, 0, 0, 0}};
>>>
>>> I think this can be done by simply writing:
>>>
>>> struct ares_srv_reply dummy[3] = { 0 };
>>>
>>>>> + struct ares_srv_reply *head = &dummy[0];
>>>>> + struct ares_srv_reply *tail = &dummy[0];
>>>>> + struct ares_srv_reply *in_head = &dummy[1];
>>>>> + struct ares_srv_reply *in_tail = &dummy[1];
>>>>> + struct ares_srv_reply *out_head = &dummy[2];
>>>>> + struct ares_srv_reply *out_tail = &dummy[2];
>>>>> + struct ares_srv_reply *cur = NULL;
>>>>> + struct ares_srv_reply *next = NULL;
>>>>> + const char *domain = NULL;
>>>>> + errno_t ret;
>>>>> +
>>>>> + if (list == NULL) {
>>>>> + ret = EINVAL;
>>>>> + goto done;
>>>>> + }
>>>>> +
>>>>> + if (*list == NULL || (*list)->next == NULL) {
>>>>> + ret = EOK;
>>>>> + goto done;
>>>>> + }
>>>>> +
>>>>> + state = talloc_get_type(pvt, struct ad_srv_plugin_state);
>>>>> + domain = state->discovery_domain;
>>>>> +
>>>>> + /* first sort by rfc2782 */
>>>>> + ret = resolv_sort_srv_reply(list);
>>>>> + if (ret != EOK) {
>>>>> + DEBUG(SSSDBG_CRIT_FAILURE, ("resolv_sort_srv_reply() failed "
>>>>> + "[%d]: %s\n", ret, strerror(ret)));
>>>>> + goto done;
>>>>> + }
>>>>> +
>>>>> + /* when several servers share priority, prefer the one that is located
>>>>> + * in the same domain as client (e.g. child domain instead of forest
>>>>> + * root) */
>>>>> +
>>>>> + next = *list;
>>>>> + do {
>>>>> + cur = next;
>>>>> + next = cur->next;
>>>>> +
>>>>> + if (is_host_in_domain(cur->host, domain)) {
>>>>> + in_tail->next = cur;
>>>>> + in_tail = in_tail->next;
>>>>> + in_tail->next = NULL;
>>>>> + } else {
>>>>> + out_tail->next = cur;
>>>>> + out_tail = out_tail->next;
>>>>> + out_tail->next = NULL;
>>>>> + }
>>>>> +
>>>>> + if (next == NULL || cur->priority != next->priority) {
>>>>> + /* priority has changed or we have reached the end of the srv list,
>>>>> + * we will merge the lists */
>>>>> + APPEND_ARES_LIST(tail, in_head, in_tail);
>>>>> + APPEND_ARES_LIST(tail, out_head, out_tail);
>>>>> + }
>>>>> + } while (next != NULL);
>>>>> +
>>>>> + *list = head->next;
>>>>> +
>>>>> + ret = EOK;
>>>>> +
>>>>> +done:
>>>>> + return ret;
>>>>> +}
>>>>
>>>> I am sorry, but this linked list sorting is not very readable.
>>>> There is a lot of "struct ares_srv_reply" pointers:
>>>> head, tail, in_head, in_tail, out_head, out_tail, cur, next
>>>> I tried to visualize this sorting with pencil and paper, but
>>>> it was a real mess.
>>>>
>>>> I would prefer to:
>>>> either: use similar approach like in reply_priority_sort
>>>> from file src/resolv/async_resolv.c (merger-sort)
>>>> or: don't change this function, but unit test should be written for this
>>>> function
>>>
>>> Why not simply make this a doubly linked list and use the functions in
>>> src/util/dlinklist.h ?
>>
>> I'm working with struct ares_srv_reply that comes from ares api.
>>
>>> Or if you really have to use single linked, maybe add a slinklist.h file
>>> in util/ that does things as much as possible like dlinklist.h so that
>>> we use the same style.
>>
>> Done.
>>
>>
>>
>
> I was wondering if we make the ordering plugin a property of the SRV
> lookup plugin and set it either using fo_set_srv_lookup_plugin() or with
> a new function? In general, I think that the sorting would be only used
> by the same provider as the lookup plugin, so it would be nice if we
> could avoid new parameters for a generic function and keep the API
> clean.
Hmm, then I guess I can move the whole functionality into the plugin
itself. Instead of sorting ares result in fo_discover_srv*, we can sort
fo_server_info in the AD plugin. It will require some changes I wanted
to avoid, but its doable.
Does this sound right?
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