Handle default body types for SIP event packages in res_pjsip_pubsub

Prior to this change, we would reject SUBSCRIBE requests that had no Accept
headers. Now event package handlers that handle the default type for the
event package indicate that they do so. Therefore, if we have a handler that
can handle the default type, we can allow SUBSCRIBEs for the handler's event
package that have no Accept headers.

(closes issue ASTERISK-22067)
reported by Mark Michelson

Review: https://reviewboard.asterisk.org/r/2774


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@397441 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/res_pjsip_pubsub.h

@@ -228,7 +228,21 @@ struct ast_sip_subscription_handler {
 	const char *event_name;
 	/*! The types of body this handler accepts */
 	const char *accept[AST_SIP_MAX_ACCEPT];
-
+	/*!
+	 * \brief Indicates if this handler can be used as a default handler for an event type.
+	 *
+	 * Typically, a SUBSCRIBE request will contain one or more Accept headers that tell
+	 * what format they expect the body of NOTIFY requests to use. However, every event
+	 * package is required to define a default body format type to be used if a SUBSCRIBE
+	 * request for the event contains no Accept header.
+	 *
+	 * If this value is non-zero, then this handler provides the default body format for
+	 * the event package and can handle SUBSCRIBES with no Accept headers present.
+	 * If this value is zero, then this handler provides an alternative body format
+	 * from the default for the event package and cannot handle SUBSCRIBEs with no
+	 * Accept header.
+	 */
+	unsigned int handles_default_accept;
 	/*!
 	 * \brief Called when a subscription is to be destroyed
 	 *

res/res_pjsip_exten_state.c

@@ -515,6 +515,8 @@ static void subscription_terminated(struct ast_sip_subscription *sub,
 	send_notify(exten_state_sub, NULL, PJSIP_EVSUB_STATE_TERMINATED);
 }
 
+#define DEFAULT_PRESENCE_BODY "application/pidf+xml"
+
 /*!
  * \internal
  * \brief Create and register a subscription handler.
@@ -534,6 +536,9 @@ static struct ast_sip_subscription_handler *create_and_register_handler(
 
 	handler->event_name = event_name;
 	handler->accept[0] = accept;
+	if (!strcmp(accept, DEFAULT_PRESENCE_BODY)) {
+		handler->handles_default_accept = 1;
+	}
 
 	handler->subscription_shutdown = subscription_shutdown;
 	handler->new_subscribe = new_subscribe;

res/res_pjsip_mwi.c

@@ -64,6 +64,7 @@ static int mwi_refresh_subscription(struct ast_sip_subscription *sub);
 static struct ast_sip_subscription_handler mwi_handler = {
 	.event_name = "message-summary",
 	.accept = { "application/simple-message-summary", },
+	.handles_default_accept = 1,
 	.subscription_shutdown = mwi_subscription_shutdown,
 	.new_subscribe = mwi_new_subscribe,
 	.resubscribe = mwi_resubscribe,

res/res_pjsip_pubsub.c

@@ -585,6 +585,12 @@ static struct ast_sip_subscription_handler *find_sub_handler(const char *event,
 			continue;
 		}
 		ast_debug(3, "Event name match: %s = %s\n", event, iter->event_name);
+		if (!num_accept && iter->handles_default_accept) {
+			/* The SUBSCRIBE contained no Accept headers, and this subscription handler
+			 * provides the default body type, so it's a match!
+			 */
+			break;
+		}
 		for (i = 0; i < num_accept; ++i) {
 			for (j = 0; j < num_accept; ++j) {
 				if (ast_strlen_zero(iter->accept[i])) {
@@ -620,7 +626,7 @@ static pj_bool_t pubsub_on_rx_subscribe_request(pjsip_rx_data *rdata)
 	struct ast_sip_subscription_handler *handler;
 	RAII_VAR(struct ast_sip_endpoint *, endpoint, NULL, ao2_cleanup);
 	struct ast_sip_subscription *sub;
-	int i;
+	size_t num_accept_headers;
 
 	endpoint = ast_pjsip_rdata_get_endpoint(rdata);
 	ast_assert(endpoint != NULL);
@@ -646,20 +652,21 @@ static pj_bool_t pubsub_on_rx_subscribe_request(pjsip_rx_data *rdata)
 		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 489, NULL, NULL, NULL);
 		return PJ_TRUE;
 	}
+	ast_copy_pj_str(event, &event_header->event_type, sizeof(event));
 
 	accept_header = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_ACCEPT, rdata->msg_info.msg->hdr.next);
-	if (!accept_header) {
-		ast_log(LOG_WARNING, "Incoming SUBSCRIBE request with no Accept header\n");
-		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 400, NULL, NULL, NULL);
-		return PJ_TRUE;
+	if (accept_header) {
+		int i;
+
+		for (i = 0; i < accept_header->count; ++i) {
+			ast_copy_pj_str(accept[i], &accept_header->values[i], sizeof(accept[i]));
+		}
+		num_accept_headers = accept_header->count;
+	} else {
+		num_accept_headers = 0;
 	}
 
-	ast_copy_pj_str(event, &event_header->event_type, sizeof(event));
-	for (i = 0; i < accept_header->count; ++i) {
-		ast_copy_pj_str(accept[i], &accept_header->values[i], sizeof(accept[i]));
-	}
-
-	handler = find_sub_handler(event, accept, accept_header->count);
+	handler = find_sub_handler(event, accept, num_accept_headers);
 	if (!handler) {
 		ast_log(LOG_WARNING, "No registered subscribe handler for event %s\n", event);
 		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 489, NULL, NULL, NULL);