res_pjsip_mwi: Allow subscribe to vm access extension as an alias

Background:

If your extension is 1000 and the voicemail access extension is 1571 and you
dial 1571, usually a dialplan rule calls voicemailmain with your extension and
you are placed directly in your mailbox.  Therefore most admins program the
voicemail (or other speed dial) button on their phones to the access extension.
Some phones (Snom at least) use whatever is programmed there to also subscribe
for MWI and so can't dial one number and subscribe to another.  This works fine
in chan_sip because chan_sip completely ignores the user portion of the
SUBSCRIBE message request URI.  If it can match the peer, is subscribes to the
peer's mailbox.  The user could be set to anything or nothing and you'd still
get subscribed to your mailbox.

Issue:

chan_pjsip actually uses the user portion of the URI to find an aor and its
mailboxes.  Therefore a subscribe to 1571 results in a 404.  Sure, you can
create an aor for 1571 but you certainly can't add your entire voicemail
system's mailboxes to it and everyone would get notified of every MWI.

Solution:

When an MWI subscribe comes in and an aor can't be found that matches the
resource directly, check the resource against the endpoint's aors.  If an aor
is found that has a voicemail_extension that matches the resource, use it.

ASTERISK-25865
Reported-by: Ross Beer

Change-Id: I770ea185f751f1ada888fafb4b452115f1c06e9e

res/res_pjsip_mwi.c

@@ -431,6 +431,45 @@ static int send_unsolicited_mwi_notify_to_contact(void *obj, void *arg, int flag
 	return 0;
 }
 
+static struct ast_sip_aor *find_aor_for_resource(struct ast_sip_endpoint *endpoint, const char *resource)
+{
+	struct ast_sip_aor *aor;
+	char *aor_name;
+	char *aors_copy;
+
+	/* Direct match */
+	if ((aor = ast_sip_location_retrieve_aor(resource))) {
+		return aor;
+	}
+
+	if (!endpoint) {
+		return NULL;
+	}
+
+	/*
+	 * This may be a subscribe to the voicemail_extension.  If so,
+	 * look for an aor belonging to this endpoint that has a matching
+	 * voicemail_extension.
+	 */
+	aors_copy = ast_strdupa(endpoint->aors);
+	while ((aor_name = ast_strip(strsep(&aors_copy, ",")))) {
+		struct ast_sip_aor *check_aor = ast_sip_location_retrieve_aor(aor_name);
+
+		if (!check_aor) {
+			continue;
+		}
+
+		if (!strcasecmp(check_aor->voicemail_extension, resource)) {
+			ast_debug(1, "Found an aor (%s) that matches voicemail_extension %s\n", aor_name, resource);
+			return check_aor;
+		}
+
+		ao2_ref(check_aor, -1);
+	}
+
+	return NULL;
+}
+
 static void send_unsolicited_mwi_notify(struct mwi_subscription *sub,
 		struct ast_sip_message_accumulator *counter)
 {
@@ -490,11 +529,13 @@ static void send_mwi_notify(struct mwi_subscription *sub)
 		.body_type = AST_SIP_MESSAGE_ACCUMULATOR,
 		.body_data = &counter,
 	};
+	const char *resource = ast_sip_subscription_get_resource_name(sub->sip_sub);
 
 	ao2_callback(sub->stasis_subs, OBJ_NODATA, get_message_count, &counter);
 
 	if (sub->is_solicited) {
-		struct ast_sip_aor *aor = ast_sip_location_retrieve_aor(ast_sip_subscription_get_resource_name(sub->sip_sub));
+		struct ast_sip_endpoint *endpoint = ast_sip_subscription_get_endpoint(sub->sip_sub);
+		struct ast_sip_aor *aor = find_aor_for_resource(endpoint, resource);
 		pjsip_dialog *dlg = ast_sip_subscription_get_dialog(sub->sip_sub);
 		pjsip_sip_uri *sip_uri = ast_sip_subscription_get_sip_uri(sub->sip_sub);
 
@@ -503,6 +544,7 @@ static void send_mwi_notify(struct mwi_subscription *sub)
 		}
 
 		ao2_cleanup(aor);
+		ao2_cleanup(endpoint);
 		ast_sip_subscription_notify(sub->sip_sub, &data, 0);
 
 		return;
@@ -707,14 +749,9 @@ static struct mwi_subscription *mwi_subscribe_single(
 	struct ast_sip_aor *aor;
 	struct mwi_subscription *sub;
 
-	aor = ast_sip_location_retrieve_aor(name);
+	aor = find_aor_for_resource(endpoint, name);
 	if (!aor) {
-		/*! I suppose it's possible for the AOR to disappear on us
-		 * between accepting the subscription and sending the first
-		 * NOTIFY...
-		 */
-		ast_log(LOG_WARNING, "Unable to locate aor %s. MWI subscription failed.\n",
-			name);
+		ast_log(LOG_WARNING, "Unable to locate aor %s. MWI subscription failed.\n", name);
 		return NULL;
 	}
 
@@ -753,10 +790,9 @@ static int mwi_new_subscribe(struct ast_sip_endpoint *endpoint,
 		return 200;
 	}
 
-	aor = ast_sip_location_retrieve_aor(resource);
+	aor = find_aor_for_resource(endpoint, resource);
 	if (!aor) {
-		ast_debug(1, "Unable to locate aor %s. MWI subscription failed.\n",
-			resource);
+		ast_debug(1, "Unable to locate aor %s. MWI subscription failed.\n", resource);
 		return 404;
 	}
 
@@ -809,6 +845,7 @@ static void *mwi_get_notify_data(struct ast_sip_subscription *sub)
 	struct mwi_subscription *mwi_sub;
 	struct ast_datastore *mwi_datastore;
 	struct ast_sip_aor *aor;
+	struct ast_sip_endpoint *endpoint = ast_sip_subscription_get_endpoint(sub);
 
 	mwi_datastore = ast_sip_subscription_get_datastore(sub, MWI_DATASTORE);
 	if (!mwi_datastore) {
@@ -822,7 +859,7 @@ static void *mwi_get_notify_data(struct ast_sip_subscription *sub)
 		return NULL;
 	}
 
-	if ((aor = ast_sip_location_retrieve_aor(ast_sip_subscription_get_resource_name(sub)))) {
+	if ((aor = find_aor_for_resource(endpoint, ast_sip_subscription_get_resource_name(sub)))) {
 		pjsip_dialog *dlg = ast_sip_subscription_get_dialog(sub);
 		pjsip_sip_uri *sip_uri = ast_sip_subscription_get_sip_uri(sub);
 
@@ -831,6 +868,7 @@ static void *mwi_get_notify_data(struct ast_sip_subscription *sub)
 		}
 		ao2_ref(aor, -1);
 	}
+	ao2_cleanup(endpoint);
 
 	ao2_callback(mwi_sub->stasis_subs, OBJ_NODATA, get_message_count, counter);
 	ao2_cleanup(mwi_datastore);