res_pjsip: Make message_filter and session multipart aware

Neither pjsip_message_filter's filter_on_tx_message() nor
res_pjsip_session's session_outgoing_nat_hook() were multipart
aware and just assumed that an SDP would be the only thing in
a message body.  Both were changed to use the new
pjsip_get_sdp_info() function which searches for an sdp in
both single- and multi- part message bodies.

ASTERISK-29813

Change-Id: I8f5b8cfdc27f1d4bd3e7491ea9090951a4525c56

res/res_pjsip/pjsip_message_filter.c

@@ -231,6 +231,8 @@ static pj_status_t filter_on_tx_message(pjsip_tx_data *tdata)
 	pjsip_via_hdr *via;
 	pjsip_fromto_hdr *from;
 	pjsip_tpselector sel;
+	pjsip_sdp_info *sdp_info;
+	pjmedia_sdp_session *sdp;
 
 	sanitize_tdata(tdata);
 
@@ -326,10 +328,23 @@ static pj_status_t filter_on_tx_message(pjsip_tx_data *tdata)
 		}
 	}
 
-	/* Update the SDP if it is present */
-	if (tdata->msg->body && ast_sip_is_content_type(&tdata->msg->body->content_type, "application", "sdp") &&
-		multihomed_rewrite_sdp(tdata->msg->body->data)) {
-		struct pjmedia_sdp_session *sdp = tdata->msg->body->data;
+	/* If there's no body in the tdata we can just return here. */
+	if (!tdata->msg->body) {
+		return PJ_SUCCESS;
+	}
+
+	/*
+	 * pjsip_get_sdp_info will search for an SDP even if it's in
+	 * a multipart message body.
+	 */
+	sdp_info = pjsip_get_sdp_info(tdata->pool, tdata->msg->body, NULL, &pjsip_media_type_application_sdp);
+	if (sdp_info->sdp_err != PJ_SUCCESS || !sdp_info->sdp) {
+		return PJ_SUCCESS;
+	}
+
+	sdp = sdp_info->sdp;
+
+	if (multihomed_rewrite_sdp(sdp)) {
 		static const pj_str_t STR_IP4 = { "IP4", 3 };
 		static const pj_str_t STR_IP6 = { "IP6", 3 };
 		pj_str_t STR_IP;

res/res_pjsip_session.c

@@ -5480,19 +5480,25 @@ static void session_outgoing_nat_hook(pjsip_tx_data *tdata, struct ast_sip_trans
 	RAII_VAR(struct ast_sip_transport_state *, transport_state, ast_sip_get_transport_state(ast_sorcery_object_get_id(transport)), ao2_cleanup);
 	struct ast_sip_nat_hook *hook = ast_sip_mod_data_get(
 		tdata->mod_data, session_module.id, MOD_DATA_NAT_HOOK);
-	struct pjmedia_sdp_session *sdp;
+	pjsip_sdp_info *sdp_info;
+	pjmedia_sdp_session *sdp;
 	pjsip_dialog *dlg = pjsip_tdata_get_dlg(tdata);
 	RAII_VAR(struct ast_sip_session *, session, dlg ? ast_sip_dialog_get_session(dlg) : NULL, ao2_cleanup);
 	int stream;
 
-	/* SDP produced by us directly will never be multipart */
-	if (!transport_state || hook || !tdata->msg->body ||
-		!ast_sip_are_media_types_equal(&tdata->msg->body->content_type, &pjsip_media_type_application_sdp) ||
-		ast_strlen_zero(transport->external_media_address)) {
+	/*
+	 * If there's no transport_state or body, or the hook
+	 * has already been run, just return.
+	 */
+	if (ast_strlen_zero(transport->external_media_address) || !transport_state || hook || !tdata->msg->body) {
 		return;
 	}
 
-	sdp = tdata->msg->body->data;
+	sdp_info = pjsip_get_sdp_info(tdata->pool, tdata->msg->body, NULL, &pjsip_media_type_application_sdp);
+	if (sdp_info->sdp_err != PJ_SUCCESS || !sdp_info->sdp) {
+		return;
+	}
+	sdp = sdp_info->sdp;
 
 	if (sdp->conn) {
 		char host[NI_MAXHOST];