Feature/sip refer (#18)

* support for sip refer to transfer an incoming call

* when sending REFER for call transfer, format Refer-To with carrier trunk if applicable

* better handling of e164 on Refer-To header

app.js

@@ -83,7 +83,18 @@ srf.locals = {...srf.locals,
     retrieveSet
   }
 };
-srf.locals.getFeatureServer = require('./lib/fs-tracking')(srf, logger);
+const {
+  wasOriginatedFromCarrier,
+  getApplicationForDidAndCarrier,
+  getOutboundGatewayForRefer
+} = require('./lib/db-utils')(srf, logger);
+srf.locals = {
+  ...srf.locals,
+  wasOriginatedFromCarrier,
+  getApplicationForDidAndCarrier,
+  getOutboundGatewayForRefer,
+  getFeatureServer: require('./lib/fs-tracking')(srf, logger)
+};
 const activeCallIds = srf.locals.activeCallIds;
 
 const {

lib/call-session.js

@@ -1,7 +1,7 @@
 const Emitter = require('events');
 const {makeRtpEngineOpts, SdpWantsSrtp, makeCallCountKey} = require('./utils');
 const {forwardInDialogRequests} = require('drachtio-fn-b2b-sugar');
-const {parseUri, SipError} = require('drachtio-srf');
+const {parseUri, stringifyUri, SipError} = require('drachtio-srf');
 const debug = require('debug')('jambonz:sbc-inbound');
 const MS_TEAMS_USER_AGENT = 'Microsoft.PSTNHub.SIPProxy';
 const MS_TEAMS_SIP_ENDPOINT = 'sip.pstnhub.microsoft.com';
@@ -469,11 +469,42 @@ Duration=${payload.duration} `
     try {
       const referTo = req.getParsedHeader('Refer-To');
       const uri = parseUri(referTo.uri);
-      this.logger.info({uri, referTo}, 'received REFER from feature server');
+      this.logger.info({uri, referTo, headers: req.headers}, 'received REFER from feature server');
       const arr = /context-(.*)/.exec(uri.user);
       if (!arr) {
-        this.logger.info(`invalid Refer-To header: ${referTo.uri}`);
-        return res.send(501);
+        /* call transfer requested */
+        const {gateway} = this.req.locals;
+        const referredBy = req.getParsedHeader('Referred-By');
+        if (!referredBy) return res.send(400);
+        const u = parseUri(referredBy.uri);
+
+        let selectedGateway = false;
+        let e164 = false;
+        if (gateway) {
+          /* host of Refer-to to an outbound gateway */
+          const gw = await this.srf.locals.getOutboundGatewayForRefer(gateway.voip_carrier_sid);
+          if (gw) {
+            selectedGateway = true;
+            e164 = gw.e164_leading_plus;
+            uri.host = gw.ipv4;
+            uri.port = gw.port;
+          }
+        }
+        if (!selectedGateway) {
+          uri.host = this.req.source_address;
+          uri.port = this.req.source_port;
+        }
+        if (e164 && !uri.user.startsWith('+')) {
+          uri.user = `+${uri.user}`;
+        }
+        const response = await this.uas.request({
+          method: 'REFER',
+          headers: {
+            'Refer-To': stringifyUri(uri),
+            'Referred-By': stringifyUri(u)
+          }
+        });
+        return res.send(response.status);
       }
       res.send(202);
 

lib/db-utils.js

@@ -35,6 +35,13 @@ SELECT * FROM phone_numbers
 WHERE number = ? 
 AND voip_carrier_sid = ?`;
 
+const sqlSelectOutboundGatewayForCarrier = `
+SELECT ipv4, port, e164_leading_plus  
+FROM sip_gateways sg, voip_carriers vc 
+WHERE sg.voip_carrier_sid = ? 
+AND sg.voip_carrier_sid = vc.voip_carrier_sid 
+AND outbound = 1`;
+
 const gatewayMatchesSourceAddress = (source_address, gw) => {
   if (32 === gw.netmask && gw.ipv4 === source_address) return true;
   if (gw.netmask < 32) {
@@ -48,6 +55,19 @@ module.exports = (srf, logger) => {
   const {pool}  = srf.locals.dbHelpers;
   const pp = pool.promise();
 
+  const getOutboundGatewayForRefer = async(voip_carrier_sid) => {
+    try {
+      const [r] = await pp.query(sqlSelectOutboundGatewayForCarrier, [voip_carrier_sid]);
+      if (0 === r.length) return null;
+
+      /* if multiple, prefer a DNS name */
+      const hasDns = r.find((row) => row.ipv4.match(/^[A-Za-z]/));
+      return hasDns || r[0];
+    } catch (err) {
+      logger.error({err}, 'getOutboundGatewayForRefer');
+    }
+  };
+
   const getApplicationForDidAndCarrier = async(req, voip_carrier_sid) => {
     const did = normalizeDID(req.calledNumber);
 
@@ -125,6 +145,7 @@ module.exports = (srf, logger) => {
 
   return {
     wasOriginatedFromCarrier,
-    getApplicationForDidAndCarrier
+    getApplicationForDidAndCarrier,
+    getOutboundGatewayForRefer
   };
 };

lib/middleware.js

@@ -68,8 +68,6 @@ module.exports = function(srf, logger) {
     blacklistUnknownRealms: true,
     emitter: new AuthOutcomeReporter(stats)
   });
-  const {wasOriginatedFromCarrier, getApplicationForDidAndCarrier} = require('./db-utils')(srf, logger);
-
 
   const initLocals = (req, res, next) => {
     req.locals = req.locals || {};
@@ -113,7 +111,7 @@ module.exports = function(srf, logger) {
 
   const identifyAccount = async(req, res, next) => {
     try {
-
+      const {wasOriginatedFromCarrier, getApplicationForDidAndCarrier} = req.srf.locals;
       const {fromCarrier, gateway, account_sid, application_sid, account} = await wasOriginatedFromCarrier(req);
       /**
        * calls come from 3 sources:
@@ -133,6 +131,7 @@ module.exports = function(srf, logger) {
         req.locals = {
           originator: 'trunk',
           carrier: gateway.name,
+          gateway,
           application_sid: sid || gateway.application_sid,
           account_sid,
           account,

package.json

@@ -39,7 +39,7 @@
     "cidr-matcher": "^2.1.1",
     "debug": "^4.3.1",
     "drachtio-fn-b2b-sugar": "0.0.12",
-    "drachtio-srf": "^4.4.55",
+    "drachtio-srf": "^4.4.59",
     "pino": "^6.8.0",
     "rtpengine-client": "^0.2.0"
   },