res_pjsip_multihomed: Add module which places the correct address within messages.

Due to how messages are handled within PJSIP it is not until a message is actually
sent that the destination is reliably known. This means that the addresses placed
within the message may not be of the interface the message is being sent out on.

This module determines what interface a message is being sent on and updates the
message to contain the correct address if applicable.

This module was tested by myself in a virtualized environment with multiple interfaces
and also by Kinsey Moore in the following configuration:

Networks:
* 10.24.16.0/21
** hard phone
** default gateway
* 10.24.64.0/21
** softphone with pjsip-based stack

Transport details:
bind address: 0.0.0.0
protocol: UDP

All endpoints were tested with explicitly configured transports and unconfigured transports.

This was tested with inbound and outbound calls, both of which were experiencing detrimental
effects from incorrect IP addresses in SIP messages. These effects were only experienced by the
soft phone on the 10.24.64.0 network since the messages to the hard phone on the 10.24.16.0
network had the correct IP address.

(closes issue ASTERISK-23020)
Reported by: xrobau

Review: https://reviewboard.asterisk.org/r/3102/
........

Merged revisions 410451 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@410452 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 187 insertions, 0 deletions

diff --git a/res/res_pjsip_multihomed.c b/res/res_pjsip_multihomed.c
new file mode 100644
index 000000000..c959fa777
--- /dev/null
+++ b/res/res_pjsip_multihomed.c
@@ -0,0 +1,187 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2014, Digium, Inc.
+ *
+ * Joshua Colp <jcolp@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*** MODULEINFO
+	<depend>pjproject</depend>
+	<depend>res_pjsip</depend>
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+
+#include <pjsip.h>
+#include <pjsip_ua.h>
+
+#include "asterisk/res_pjsip.h"
+#include "asterisk/module.h"
+
+/*! \brief Local host address for IPv4 */
+static char host_ipv4[PJ_INET_ADDRSTRLEN + 2];
+
+/*! \brief Local host address for IPv6 */
+static char host_ipv6[PJ_INET6_ADDRSTRLEN + 2];
+
+/*! \brief Helper function which returns a UDP transport bound to the given address and port */
+static pjsip_transport *multihomed_get_udp_transport(pj_str_t *address, int port)
+{
+	struct ao2_container *transports = ast_sorcery_retrieve_by_fields(ast_sip_get_sorcery(), "transport",
+		AST_RETRIEVE_FLAG_MULTIPLE | AST_RETRIEVE_FLAG_ALL, NULL);
+	struct ast_sip_transport *transport;
+	struct ao2_iterator iter;
+	pjsip_transport *sip_transport = NULL;
+
+	if (!transports) {
+		return NULL;
+	}
+
+	for (iter = ao2_iterator_init(transports, 0); (transport = ao2_iterator_next(&iter)); ao2_ref(transport, -1)) {
+		if ((transport->type != AST_TRANSPORT_UDP) ||
+			(pj_strcmp(&transport->state->transport->local_name.host, address)) ||
+			(transport->state->transport->local_name.port != port)) {
+			continue;
+		}
+
+		sip_transport = transport->state->transport;
+		ao2_ref(transport, -1);
+		break;
+	}
+	ao2_iterator_destroy(&iter);
+
+	ao2_ref(transports, -1);
+
+	return sip_transport;
+}
+
+/*! \brief Helper function which determines if the address within SDP should be rewritten */
+static int multihomed_rewrite_sdp(struct pjmedia_sdp_session *sdp)
+{
+	if (!sdp->conn) {
+		return 0;
+	}
+
+	/* If the host address is used in the SDP replace it with the address of what this is going out on */
+	if ((!pj_strcmp2(&sdp->conn->addr_type, "IP4") && !pj_strcmp2(&sdp->conn->addr, host_ipv4)) ||
+		(!pj_strcmp2(&sdp->conn->addr_type, "IP6") && !pj_strcmp2(&sdp->conn->addr, host_ipv6))) {
+		return 1;
+	}
+
+	return 0;
+}
+
+static pj_status_t multihomed_on_tx_message(pjsip_tx_data *tdata)
+{
+	pjsip_tpmgr_fla2_param prm;
+	pjsip_transport *transport;
+	pjsip_contact_hdr *contact;
+	pjsip_via_hdr *via;
+
+	/* Use the destination information to determine what local interface this message will go out on */
+	pjsip_tpmgr_fla2_param_default(&prm);
+	prm.tp_type = tdata->tp_info.transport->key.type;
+	pj_strset2(&prm.dst_host, tdata->tp_info.dst_name);
+	prm.local_if = PJ_TRUE;
+
+	/* If we can't get the local address use best effort and let it pass */
+	if (pjsip_tpmgr_find_local_addr2(pjsip_endpt_get_tpmgr(ast_sip_get_pjsip_endpoint()), tdata->pool, &prm) != PJ_SUCCESS) {
+		return PJ_SUCCESS;
+	}
+
+	/* If the transport it is going out on is different reflect it in the message */
+	transport = multihomed_get_udp_transport(&prm.ret_addr, prm.ret_port);
+	if (transport && (tdata->tp_info.transport != transport)) {
+		tdata->tp_info.transport = transport;
+	}
+
+	/* If the message needs to be updated with new address do so */
+	contact = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_CONTACT, NULL);
+	if (contact && (PJSIP_URI_SCHEME_IS_SIP(contact->uri) || PJSIP_URI_SCHEME_IS_SIPS(contact->uri))) {
+		pjsip_sip_uri *uri = pjsip_uri_get_uri(contact->uri);
+
+		/* prm.ret_addr is allocated from the tdata pool so it is perfectly fine to just do an assignment like this */
+		pj_strassign(&uri->host, &prm.ret_addr);
+		uri->port = prm.ret_port;
+
+		pjsip_tx_data_invalidate_msg(tdata);
+	}
+
+	if (tdata->msg->type == PJSIP_REQUEST_MSG && (via = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_VIA, NULL))) {
+		pj_strassign(&via->sent_by.host, &prm.ret_addr);
+		via->sent_by.port = prm.ret_port;
+
+		pjsip_tx_data_invalidate_msg(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;
+		int stream;
+
+		pj_strassign(&sdp->conn->addr, &prm.ret_addr);
+
+		for (stream = 0; stream < sdp->media_count; ++stream) {
+			if (sdp->media[stream]->conn) {
+				pj_strassign(&sdp->media[stream]->conn->addr, &prm.ret_addr);
+			}
+		}
+
+		pjsip_tx_data_invalidate_msg(tdata);
+	}
+
+	return PJ_SUCCESS;
+}
+
+static pjsip_module multihomed_module = {
+	.name = { "Multihomed Routing", 18 },
+	.id = -1,
+	.priority = PJSIP_MOD_PRIORITY_TSX_LAYER - 1,
+	.on_tx_request = multihomed_on_tx_message,
+	.on_tx_response = multihomed_on_tx_message,
+};
+
+static int unload_module(void)
+{
+	ast_sip_unregister_service(&multihomed_module);
+	return 0;
+}
+
+static int load_module(void)
+{
+	pj_sockaddr addr;
+
+	if (!pj_gethostip(pj_AF_INET(), &addr)) {
+		pj_sockaddr_print(&addr, host_ipv4, sizeof(host_ipv4), 2);
+	}
+
+	if (!pj_gethostip(pj_AF_INET6(), &addr)) {
+		pj_sockaddr_print(&addr, host_ipv6, sizeof(host_ipv6), 2);
+	}
+
+	if (ast_sip_register_service(&multihomed_module)) {
+		ast_log(LOG_ERROR, "Could not register multihomed module for incoming and outgoing requests\n");
+		return AST_MODULE_LOAD_FAILURE;
+	}
+
+	return AST_MODULE_LOAD_SUCCESS;
+}
+
+AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP Multihomed Routing Support",
+		.load = load_module,
+		.unload = unload_module,
+		.load_pri = AST_MODPRI_APP_DEPEND,
+	       );