From b41f69f10acfeb2ec4179b519e663cd4b7c960a7 Mon Sep 17 00:00:00 2001
From: Pavel Březina <pbrezina@redhat.com>
Date: Fri, 2 Aug 2013 23:01:57 +0200
Subject: ad srv: prefer servers that are in the same domain as client

https://fedorahosted.org/sssd/ticket/2001
---
 src/providers/ad/ad_srv.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/src/providers/ad/ad_srv.c b/src/providers/ad/ad_srv.c
index dfb15b30..01660c48 100644
--- a/src/providers/ad/ad_srv.c
+++ b/src/providers/ad/ad_srv.c
@@ -26,6 +26,7 @@
 
 #include "util/util.h"
 #include "util/sss_ldap.h"
+#include "util/slinklist.h"
 #include "resolv/async_resolv.h"
 #include "providers/dp_backend.h"
 #include "providers/fail_over.h"
@@ -548,6 +549,75 @@ static void ad_srv_plugin_dcs_done(struct tevent_req *subreq);
 static void ad_srv_plugin_site_done(struct tevent_req *subreq);
 static void ad_srv_plugin_servers_done(struct tevent_req *subreq);
 
+static errno_t ad_sort_servers(struct ares_srv_reply **list, void *pvt)
+{
+    struct ad_srv_plugin_state *state = NULL;
+    struct ares_srv_reply *final_list = NULL;
+    struct ares_srv_reply *inside_list = NULL;
+    struct ares_srv_reply *outside_list = NULL;
+    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) but obey their weight */
+
+    next = *list;
+    do {
+        cur = next;
+        next = cur->next;
+
+        /* split servers into two lists - inside and outside of the preferred
+         * domain */
+        if (is_host_in_domain(cur->host, domain)) {
+            SLIST_ADD_END(inside_list, cur, struct ares_srv_reply);
+        } else {
+            SLIST_ADD_END(outside_list, cur, struct ares_srv_reply);
+        }
+        cur->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 list into final list and start over with
+             * next priority */
+            SLIST_CONCATENATE(final_list, inside_list, struct ares_srv_reply);
+            SLIST_CONCATENATE(final_list, outside_list, struct ares_srv_reply);
+            inside_list = NULL;
+            outside_list = NULL;
+        }
+    } while (next != NULL);
+
+    *list = final_list;
+
+    ret = EOK;
+
+done:
+    return ret;
+}
+
 /* 1. Do a DNS lookup to find any DC in domain
  *    _ldap._tcp.domain.name
  * 2. Send a CLDAP ping to the found DC to get the desirable site
@@ -720,7 +790,7 @@ static void ad_srv_plugin_site_done(struct tevent_req *subreq)
                                       state->ctx->be_res->resolv,
                                       state->service, state->protocol,
                                       primary_domain, backup_domain,
-                                      NULL, NULL);
+                                      ad_sort_servers, state);
     if (subreq == NULL) {
         ret = ENOMEM;
         goto done;
-- 
cgit