pjsip_message_filter.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2014-2016, Digium, Inc.
 *
 * Joshua Colp <[email protected]>
 *
 * 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.
 */

#include "asterisk.h"

#include <pjsip.h>
#include <pjsip_ua.h>

#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_session.h"
#include "include/res_pjsip_private.h"
#include "asterisk/module.h"

#define MOD_DATA_RESTRICTIONS "restrictions"

static pj_status_t filter_on_tx_message(pjsip_tx_data *tdata);
static pj_bool_t filter_on_rx_message(pjsip_rx_data *rdata);

/*! \brief Outgoing message modification restrictions */
struct filter_message_restrictions {
 /*! \brief Disallow modification of the From domain */
 unsigned int disallow_from_domain_modification;
};

static pjsip_module filter_module_transport = {
 .name = { "Message Filtering Transport", 27 },
 .id = -1,
 .priority = PJSIP_MOD_PRIORITY_TRANSPORT_LAYER,
 .on_rx_request = filter_on_rx_message,
};

static pjsip_module filter_module_tsx = {
 .name = { "Message Filtering TSX", 21 },
 .id = -1,
 .priority = PJSIP_MOD_PRIORITY_TSX_LAYER - 1,
 .on_tx_request = filter_on_tx_message,
 .on_tx_response = filter_on_tx_message,
};

/*! \brief Helper function to get (or allocate if not already present) restrictions on a message */
static struct filter_message_restrictions *get_restrictions(pjsip_tx_data *tdata)
{
 struct filter_message_restrictions *restrictions;

 restrictions = ast_sip_mod_data_get(tdata->mod_data, filter_module_tsx.id, MOD_DATA_RESTRICTIONS);
 if (restrictions) {
 return restrictions;
 }

 restrictions = PJ_POOL_ALLOC_T(tdata->pool, struct filter_message_restrictions);
 ast_sip_mod_data_set(tdata->pool, tdata->mod_data, filter_module_tsx.id, MOD_DATA_RESTRICTIONS, restrictions);

 return restrictions;
}

/*! \brief Callback invoked on non-session outgoing messages */
static void filter_outgoing_message(struct ast_sip_endpoint *endpoint, struct ast_sip_contact *contact, struct pjsip_tx_data *tdata)
{
 struct filter_message_restrictions *restrictions = get_restrictions(tdata);

 restrictions->disallow_from_domain_modification = !ast_strlen_zero(endpoint->fromdomain);
}

/*! \brief PJSIP Supplement for tagging messages with restrictions */
static struct ast_sip_supplement filter_supplement = {
 .priority = AST_SIP_SUPPLEMENT_PRIORITY_FIRST,
 .outgoing_request = filter_outgoing_message,
 .outgoing_response = filter_outgoing_message,
};

/*! \brief Callback invoked on session outgoing messages */
static void filter_session_outgoing_message(struct ast_sip_session *session, struct pjsip_tx_data *tdata)
{
 struct filter_message_restrictions *restrictions = get_restrictions(tdata);

 restrictions->disallow_from_domain_modification = !ast_strlen_zero(session->endpoint->fromdomain);
}

/*! \brief PJSIP Session Supplement for tagging messages with restrictions */
static struct ast_sip_session_supplement filter_session_supplement = {
 .priority = 1,
 .outgoing_request = filter_session_outgoing_message,
 .outgoing_response = filter_session_outgoing_message,
};

/*! \brief Helper function which returns a UDP transport bound to the given address and port */
static pjsip_transport *get_udp_transport(pj_str_t *address, int port)
{
 struct ao2_container *transport_states = ast_sip_get_transport_states();
 struct ast_sip_transport_state *transport_state;
 struct ao2_iterator iter;
 pjsip_transport *sip_transport = NULL;

 if (!transport_states) {
 return NULL;
 }

 for (iter = ao2_iterator_init(transport_states, 0); (transport_state = ao2_iterator_next(&iter)); ao2_ref(transport_state, -1)) {
 if (!transport_state->flow &&
 transport_state->type == AST_TRANSPORT_UDP &&
 !pj_strcmp(&transport_state->transport->local_name.host, address) &&
 transport_state->transport->local_name.port == port) {
 sip_transport = transport_state->transport;
 ao2_ref(transport_state, -1);
 break;
 }
 }
 ao2_iterator_destroy(&iter);

 ao2_ref(transport_states, -1);

 return sip_transport;
}

/*! \brief Helper function which determines if a transport is bound to any */
static int is_bound_any(pjsip_transport *transport)
{
 pj_uint32_t loop6[4] = {0, 0, 0, 0};

 if ((transport->local_addr.addr.sa_family == pj_AF_INET() &&
 transport->local_addr.ipv4.sin_addr.s_addr == PJ_INADDR_ANY) ||
 (transport->local_addr.addr.sa_family == pj_AF_INET6() &&
 !pj_memcmp(&transport->local_addr.ipv6.sin6_addr, loop6, sizeof(loop6)))) {
 return 1;
 }

 return 0;
}

/*! \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,
 ast_sip_get_host_ip_string(pj_AF_INET()))) ||
 (!pj_strcmp2(&sdp->conn->addr_type, "IP6") && !pj_strcmp2(&sdp->conn->addr,
 ast_sip_get_host_ip_string(pj_AF_INET6())))) {
 return 1;
 }

 return 0;
}

#define is_sip_uri(uri) \
 (PJSIP_URI_SCHEME_IS_SIP(uri) || PJSIP_URI_SCHEME_IS_SIPS(uri))

static void print_sanitize_debug(char *msg, pjsip_uri_context_e context, pjsip_sip_uri *uri)
{
#ifdef AST_DEVMODE
 char hdrbuf[512];
 int hdrbuf_len;

 hdrbuf_len = pjsip_uri_print(context, uri, hdrbuf, 512);
 hdrbuf[hdrbuf_len] = '\0';
 ast_debug(2, "%s: %s\n", msg, hdrbuf);
#endif
}

/* If in DEVMODE, prevent inlining to assist in debugging */
#ifdef AST_DEVMODE
#define FUNC_ATTRS __attribute__ ((noinline))
#else
#define FUNC_ATTRS
#endif

static void FUNC_ATTRS sanitize_tdata(pjsip_tx_data *tdata)
{
 static const pj_str_t x_name = { AST_SIP_X_AST_TXP, AST_SIP_X_AST_TXP_LEN };
 pjsip_param *x_transport;
 pjsip_sip_uri *uri;
 pjsip_hdr *hdr;

 if (tdata->msg->type == PJSIP_REQUEST_MSG) {
 if (is_sip_uri(tdata->msg->line.req.uri)) {
 uri = pjsip_uri_get_uri(tdata->msg->line.req.uri);
 print_sanitize_debug("Sanitizing Request", PJSIP_URI_IN_REQ_URI, uri);
 while ((x_transport = pjsip_param_find(&uri->other_param, &x_name))) {
 pj_list_erase(x_transport);
 }
 }
 }

 for (hdr = tdata->msg->hdr.next; hdr != &tdata->msg->hdr; hdr = hdr->next) {
 if (hdr->type == PJSIP_H_TO || hdr->type == PJSIP_H_FROM) {
 if (is_sip_uri(((pjsip_fromto_hdr *) hdr)->uri)) {
 uri = pjsip_uri_get_uri(((pjsip_fromto_hdr *) hdr)->uri);
 print_sanitize_debug("Sanitizing From/To header", PJSIP_URI_IN_FROMTO_HDR, uri);
 while ((x_transport = pjsip_param_find(&uri->other_param, &x_name))) {
 pj_list_erase(x_transport);
 }
 }
 } else if (hdr->type == PJSIP_H_CONTACT) {
 if (!((pjsip_contact_hdr *) hdr)->star && is_sip_uri(((pjsip_contact_hdr *) hdr)->uri)) {
 uri = pjsip_uri_get_uri(((pjsip_contact_hdr *) hdr)->uri);
 print_sanitize_debug("Sanitizing Contact header", PJSIP_URI_IN_CONTACT_HDR, uri);
 while ((x_transport = pjsip_param_find(&uri->other_param, &x_name))) {
 pj_list_erase(x_transport);
 }
 }
 }
 }

 pjsip_tx_data_invalidate_msg(tdata);
}

static pj_status_t filter_on_tx_message(pjsip_tx_data *tdata)
{
 struct filter_message_restrictions *restrictions =
 ast_sip_mod_data_get(tdata->mod_data, filter_module_transport.id, MOD_DATA_RESTRICTIONS);
 pjsip_tpmgr_fla2_param prm;
 pjsip_cseq_hdr *cseq;
 pjsip_via_hdr *via;
 pjsip_fromto_hdr *from;
 pjsip_tpselector sel;

 sanitize_tdata(tdata);

 /* 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 ((tdata->tp_info.transport->key.type != PJSIP_TRANSPORT_UDP) &&
 (tdata->tp_info.transport->key.type != PJSIP_TRANSPORT_UDP6)) {
 sel.type = PJSIP_TPSELECTOR_LISTENER;
 sel.u.listener = tdata->tp_info.transport->factory;
 prm.tp_sel = &sel;
 }

 /* 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;
 }

 /* For UDP we can have multiple transports so the port needs to be maintained */
 if (tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP ||
 tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP6) {
 prm.ret_port = tdata->tp_info.transport->local_name.port;
 }

 /* If the IP source differs from the existing transport see if we need to update it */
 if (pj_strcmp(&prm.ret_addr, &tdata->tp_info.transport->local_name.host)) {

 /* If the transport it is going out on is different reflect it in the message */
 if (tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP ||
 tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP6) {
 pjsip_transport *transport;

 transport = get_udp_transport(&prm.ret_addr, prm.ret_port);

 if (transport) {
 tdata->tp_info.transport = transport;
 }
 }

 /* If the chosen transport is not bound to any we can't use the source address as it won't get back to us */
 if (!is_bound_any(tdata->tp_info.transport)) {
 pj_strassign(&prm.ret_addr, &tdata->tp_info.transport->local_name.host);
 }
 } else {
 /* The transport chosen will deliver this but ensure it is updated with the right information */
 pj_strassign(&prm.ret_addr, &tdata->tp_info.transport->local_name.host);
 }

 /* If the message needs to be updated with new address do so */
 if (tdata->msg->type == PJSIP_REQUEST_MSG || !(cseq = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_CSEQ, NULL)) ||
 pj_strcmp2(&cseq->method.name, "REGISTER")) {
 pjsip_contact_hdr *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))
 && !(tdata->msg->type == PJSIP_RESPONSE_MSG && tdata->msg->line.status.code / 100 == 3)) {
 pjsip_sip_uri *uri = pjsip_uri_get_uri(contact->uri);

 /* prm.ret_addr is allocated from the tdata pool OR the transport so it is perfectly fine to just do an assignment like this */
 pj_strassign(&uri->host, &prm.ret_addr);
 uri->port = prm.ret_port;
 ast_debug(5, "Re-wrote Contact URI host/port to %.*s:%d (this may be re-written again later)\n",
 (int)pj_strlen(&uri->host), pj_strbuf(&uri->host), uri->port);

 if (tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP ||
 tdata->tp_info.transport->key.type == PJSIP_TRANSPORT_UDP6) {
 uri->transport_param.slen = 0;
 } else {
 pj_strdup2(tdata->pool, &uri->transport_param, pjsip_transport_get_type_name(tdata->tp_info.transport->key.type));
 }

 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);
 }

 if (tdata->msg->type == PJSIP_REQUEST_MSG && (from = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_FROM, NULL)) &&
 (restrictions && !restrictions->disallow_from_domain_modification)) {
 pjsip_name_addr *id_name_addr = (pjsip_name_addr *)from->uri;
 pjsip_sip_uri *uri = pjsip_uri_get_uri(id_name_addr);
 pj_sockaddr ip;

 if (pj_strcmp2(&uri->host, "localhost") && pj_sockaddr_parse(pj_AF_UNSPEC(), 0, &uri->host, &ip) == PJ_SUCCESS) {
 pj_strassign(&uri->host, &prm.ret_addr);
 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;
 static const pj_str_t STR_IP4 = { "IP4", 3 };
 static const pj_str_t STR_IP6 = { "IP6", 3 };
 pj_str_t STR_IP;
 int stream;

 STR_IP = tdata->tp_info.transport->key.type & PJSIP_TRANSPORT_IPV6 ? STR_IP6 : STR_IP4;

 pj_strassign(&sdp->origin.addr, &prm.ret_addr);
 sdp->origin.addr_type = STR_IP;
 pj_strassign(&sdp->conn->addr, &prm.ret_addr);
 sdp->conn->addr_type = STR_IP;

 for (stream = 0; stream < sdp->media_count; ++stream) {
 if (sdp->media[stream]->conn) {
 pj_strassign(&sdp->media[stream]->conn->addr, &prm.ret_addr);
 sdp->media[stream]->conn->addr_type = STR_IP;
 }
 }

 pjsip_tx_data_invalidate_msg(tdata);
 }

 return PJ_SUCCESS;
}

enum uri_type {
 URI_TYPE_REQUEST = -1,
 URI_TYPE_TO = PJSIP_H_TO,
 URI_TYPE_FROM = PJSIP_H_FROM,
 URI_TYPE_CONTACT = PJSIP_H_CONTACT,
};

static void print_uri_debug(enum uri_type ut, pjsip_rx_data *rdata, pjsip_hdr *hdr)
{
#ifdef AST_DEVMODE
 pjsip_uri *local_uri = NULL;
 char hdrbuf[512];
 int hdrbuf_len;
 char *request_uri;
 pjsip_uri_context_e context = PJSIP_URI_IN_OTHER;
 char header_name[32];

 switch (ut) {
 case(URI_TYPE_REQUEST):
 context = PJSIP_URI_IN_REQ_URI;
 strcpy(header_name, "Request"); /* Safe */
 local_uri = rdata->msg_info.msg->line.req.uri;
 break;
 case(PJSIP_H_FROM):
 strcpy(header_name, "From"); /* Safe */
 context = PJSIP_URI_IN_FROMTO_HDR;
 local_uri = pjsip_uri_get_uri(((pjsip_from_hdr *)hdr)->uri);
 break;
 case(PJSIP_H_TO):
 strcpy(header_name, "To"); /* Safe */
 context = PJSIP_URI_IN_FROMTO_HDR;
 local_uri = pjsip_uri_get_uri(((pjsip_to_hdr *)hdr)->uri);
 break;
 case(PJSIP_H_CONTACT):
 strcpy(header_name, "Contact"); /* Safe */
 context = PJSIP_URI_IN_CONTACT_HDR;
 local_uri = pjsip_uri_get_uri(((pjsip_contact_hdr *)hdr)->uri);
 break;
 }

 hdrbuf_len = pjsip_uri_print(PJSIP_URI_IN_REQ_URI, rdata->msg_info.msg->line.req.uri, hdrbuf, 512);
 hdrbuf[hdrbuf_len] = '\0';
 request_uri = ast_strdupa(hdrbuf);
 hdrbuf_len = pjsip_uri_print(context, local_uri, hdrbuf, 512);
 hdrbuf[hdrbuf_len] = '\0';

 ast_debug(2, "There was a non sip(s) URI scheme in %s URI '%s' for request '%*.*s %s'\n",
 header_name, hdrbuf,
 (int)rdata->msg_info.msg->line.req.method.name.slen,
 (int)rdata->msg_info.msg->line.req.method.name.slen,
 rdata->msg_info.msg->line.req.method.name.ptr, request_uri);
#endif
}

/*!
 * /internal
 *
 * We want to make sure that any incoming requests don't already
 * have x-ast-* parameters in any URIs or we may get confused
 * if symmetric transport (x-ast-txp) or rewrite_contact (x-ast-orig-host)
 * is used later on.
 */
static void remove_x_ast_params(pjsip_uri *header_uri){
 pjsip_sip_uri *uri;
 pjsip_param *param;

 if (!header_uri) {
 return;
 }

 uri = pjsip_uri_get_uri(header_uri);
 if (!uri) {
 return;
 }

 param = uri->other_param.next;

 while (param != &uri->other_param) {
 /* We need to save off 'next' because pj_list_erase will remove it */
 pjsip_param *next = param->next;

 if (pj_strncmp2(&param->name, "x-ast-", 6) == 0) {
 pj_list_erase(param);
 }
 param = next;
 }
}

static pj_bool_t on_rx_process_uris(pjsip_rx_data *rdata)
{
 pjsip_contact_hdr *contact = NULL;

 if (rdata->msg_info.msg->type != PJSIP_REQUEST_MSG) {
 return PJ_FALSE;
 }

 if (!is_sip_uri(rdata->msg_info.msg->line.req.uri)) {
 print_uri_debug(URI_TYPE_REQUEST, rdata, NULL);
 pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata,
 PJSIP_SC_UNSUPPORTED_URI_SCHEME, NULL, NULL, NULL);
 return PJ_TRUE;
 }
 remove_x_ast_params(rdata->msg_info.msg->line.req.uri);

 if (!is_sip_uri(rdata->msg_info.from->uri)) {
 print_uri_debug(URI_TYPE_FROM, rdata, (pjsip_hdr *)rdata->msg_info.from);
 pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata,
 PJSIP_SC_UNSUPPORTED_URI_SCHEME, NULL, NULL, NULL);
 return PJ_TRUE;
 }
 remove_x_ast_params(rdata->msg_info.from->uri);

 if (!is_sip_uri(rdata->msg_info.to->uri)) {
 print_uri_debug(URI_TYPE_TO, rdata, (pjsip_hdr *)rdata->msg_info.to);
 pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata,
 PJSIP_SC_UNSUPPORTED_URI_SCHEME, NULL, NULL, NULL);
 return PJ_TRUE;
 }
 remove_x_ast_params(rdata->msg_info.to->uri);

 contact = (pjsip_contact_hdr *) pjsip_msg_find_hdr(
 rdata->msg_info.msg, PJSIP_H_CONTACT, NULL);

 if (!contact && pjsip_method_creates_dialog(&rdata->msg_info.msg->line.req.method)) {
 /* A contact header is required for dialog creating methods */
 static const pj_str_t missing_contact = { "Missing Contact header", 22 };
 pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 400,
 &missing_contact, NULL, NULL);
 return PJ_TRUE;
 }

 while (contact) {
 if (!contact->star && !is_sip_uri(contact->uri)) {
 print_uri_debug(URI_TYPE_CONTACT, rdata, (pjsip_hdr *)contact);
 pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata,
 PJSIP_SC_UNSUPPORTED_URI_SCHEME, NULL, NULL, NULL);
 return PJ_TRUE;
 }
 remove_x_ast_params(contact->uri);

 contact = (pjsip_contact_hdr *) pjsip_msg_find_hdr(
 rdata->msg_info.msg, PJSIP_H_CONTACT, contact->next);
 }

 return PJ_FALSE;
}

static pj_bool_t on_rx_process_symmetric_transport(pjsip_rx_data *rdata)
{
 pjsip_contact_hdr *contact;
 pjsip_sip_uri *uri;
 const char *transport_id;
 struct ast_sip_transport *transport;
 pjsip_param *x_transport;

 if (rdata->msg_info.msg->type != PJSIP_REQUEST_MSG) {
 return PJ_FALSE;
 }

 contact = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_CONTACT, NULL);
 if (!(contact && contact->uri
 && ast_begins_with(rdata->tp_info.transport->info, AST_SIP_X_AST_TXP ":"))) {
 return PJ_FALSE;
 }

 uri = pjsip_uri_get_uri(contact->uri);

 transport_id = rdata->tp_info.transport->info + AST_SIP_X_AST_TXP_LEN + 1;
 transport = ast_sorcery_retrieve_by_id(ast_sip_get_sorcery(), "transport", transport_id);

 if (!(transport && transport->symmetric_transport)) {
 ao2_cleanup(transport);
 return PJ_FALSE;
 }
 ao2_cleanup(transport);

 x_transport = PJ_POOL_ALLOC_T(rdata->tp_info.pool, pjsip_param);
 x_transport->name = pj_strdup3(rdata->tp_info.pool, AST_SIP_X_AST_TXP);
 x_transport->value = pj_strdup3(rdata->tp_info.pool, transport_id);

 pj_list_insert_before(&uri->other_param, x_transport);

 ast_debug(1, "Set transport '%s' on %.*s from %.*s:%d\n", transport_id,
 (int)rdata->msg_info.msg->line.req.method.name.slen,
 rdata->msg_info.msg->line.req.method.name.ptr,
 (int)uri->host.slen, uri->host.ptr, uri->port);

 return PJ_FALSE;
}

static pj_bool_t filter_on_rx_message(pjsip_rx_data *rdata)
{
 pj_bool_t rc;

 rc = on_rx_process_uris(rdata);
 if (rc == PJ_TRUE) {
 return rc;
 }

 rc = on_rx_process_symmetric_transport(rdata);
 if (rc == PJ_TRUE) {
 return rc;
 }

 return PJ_FALSE;
}

void ast_res_pjsip_cleanup_message_filter(void)
{
 ast_sip_unregister_service(&filter_module_tsx);
 ast_sip_unregister_service(&filter_module_transport);
 ast_sip_unregister_supplement(&filter_supplement);
 ast_sip_session_unregister_supplement(&filter_session_supplement);
}

int ast_res_pjsip_init_message_filter(void)
{
 ast_sip_session_register_supplement(&filter_session_supplement);
 ast_sip_register_supplement(&filter_supplement);

 if (ast_sip_register_service(&filter_module_transport)) {
 ast_log(LOG_ERROR, "Could not register message filter module for incoming and outgoing requests\n");
 ast_res_pjsip_cleanup_message_filter();
 return -1;
 }

 if (ast_sip_register_service(&filter_module_tsx)) {
 ast_log(LOG_ERROR, "Could not register message filter module for incoming and outgoing requests\n");
 ast_res_pjsip_cleanup_message_filter();
 return -1;
 }

 return 0;
}