fix: align IMS calls with MMTel dialog requirements (#48)

* fix: align IMS calls with MMTel routing

* fix: originate calls with associated public identity

* fix: use carrier-specific IMS dial URIs

* fix: acknowledge rejected INVITE transactions

* docs: record sanitized IMS call validation

* Delete docs/IMS_CALL_INTEROPERABILITY.md

* Update README.md

---------

Co-authored-by: Meng Meng <[email protected]>

internal/vowifi/carrier_compat.go

@@ -33,6 +33,11 @@ type CarrierProfile struct {
 	IMSRegisterProfile string
 	IMSIPSecEncryption string
 	SMSCenter          string
+	PANICountry        string
+	PANINode           string
+	IMSDialURIScheme   string
+	IMSUserEqPhone     bool
+	IMSVoiceCodecs     []string
 }
 
 type carrierProfileDocument struct {
@@ -75,11 +80,16 @@ type carrierProfileIKE struct {
 }
 
 type carrierProfileIMS struct {
-	Transport       string `json:"transport"`
-	IdentityProfile string `json:"identity_profile"`
-	RegisterProfile string `json:"register_profile"`
-	IPSecEncryption string `json:"ipsec_encryption"`
-	SMSCenter       string `json:"sms_center"`
+	Transport       string   `json:"transport"`
+	IdentityProfile string   `json:"identity_profile"`
+	RegisterProfile string   `json:"register_profile"`
+	IPSecEncryption string   `json:"ipsec_encryption"`
+	SMSCenter       string   `json:"sms_center"`
+	PANICountry     string   `json:"pani_country"`
+	PANINode        string   `json:"pani_node"`
+	DialURIScheme   string   `json:"dial_uri_scheme"`
+	UserEqPhone     *bool    `json:"user_eq_phone"`
+	VoiceCodecs     []string `json:"voice_codecs"`
 }
 
 //go:embed carrier_profiles.json
@@ -140,6 +150,20 @@ func validCarrierProfileRule(rule carrierProfileRule) bool {
 		encryption != "aes-cbc" && encryption != "null" {
 		return false
 	}
+	if country := strings.ToUpper(strings.TrimSpace(rule.IMS.PANICountry)); country != "" &&
+		(len(country) != 2 || country[0] < 'A' || country[0] > 'Z' || country[1] < 'A' || country[1] > 'Z') {
+		return false
+	}
+	if scheme := strings.ToLower(strings.TrimSpace(rule.IMS.DialURIScheme)); scheme != "" && scheme != "tel" && scheme != "sip" {
+		return false
+	}
+	for _, codec := range rule.IMS.VoiceCodecs {
+		switch strings.ToUpper(strings.TrimSpace(codec)) {
+		case "PCMA", "PCMU", "AMR", "AMR-WB":
+		default:
+			return false
+		}
+	}
 	return true
 }
 
@@ -155,6 +179,8 @@ func ResolveCarrierProfile(identity SIMIdentity) CarrierProfile {
 		IMSIdentityProfile: IMSProfileStandard,
 		IMSRegisterProfile: IMSProfileStandard,
 		IMSIPSecEncryption: "aes-cbc",
+		IMSDialURIScheme:   "tel",
+		IMSVoiceCodecs:     []string{"PCMA", "PCMU"},
 	}
 	bestScore := -1
 	for _, rule := range builtinCarrierProfiles {
@@ -256,9 +282,37 @@ func applyCarrierProfileRule(base CarrierProfile, rule carrierProfileRule, sourc
 		base.IMSIPSecEncryption = value
 	}
 	base.SMSCenter = strings.TrimSpace(rule.IMS.SMSCenter)
+	base.PANICountry = strings.ToUpper(strings.TrimSpace(rule.IMS.PANICountry))
+	base.PANINode = strings.TrimSpace(rule.IMS.PANINode)
+	if value := strings.ToLower(strings.TrimSpace(rule.IMS.DialURIScheme)); value != "" {
+		base.IMSDialURIScheme = value
+	}
+	if rule.IMS.UserEqPhone != nil {
+		base.IMSUserEqPhone = *rule.IMS.UserEqPhone
+	}
+	if len(rule.IMS.VoiceCodecs) > 0 {
+		base.IMSVoiceCodecs = normalizeVoiceCodecs(rule.IMS.VoiceCodecs)
+	}
 	return base
 }
 
+func normalizeVoiceCodecs(values []string) []string {
+	result := make([]string, 0, len(values))
+	seen := make(map[string]struct{}, len(values))
+	for _, value := range values {
+		value = strings.ToUpper(strings.TrimSpace(value))
+		if value == "" {
+			continue
+		}
+		if _, duplicate := seen[value]; duplicate {
+			continue
+		}
+		seen[value] = struct{}{}
+		result = append(result, value)
+	}
+	return result
+}
+
 func canonicalPLMN(mcc, mnc string) string {
 	mcc = strings.TrimSpace(mcc)
 	mnc = strings.TrimSpace(mnc)

internal/vowifi/carrier_profiles.json

@@ -18,7 +18,13 @@
         "imsi_prefixes": ["23433"],
         "iccid_prefixes": ["894430"]
       },
-      "route": { "mcc": "234", "mnc": "30" }
+      "route": { "mcc": "234", "mnc": "30" },
+      "ims": {
+        "pani_country": "GB",
+        "pani_node": "000000000000",
+        "dial_uri_scheme": "sip",
+        "voice_codecs": ["PCMA", "PCMU"]
+      }
     },
     {
       "id": "att-us",
@@ -58,7 +64,8 @@
       "match": { "home_plmns": ["23410"] },
       "ims": {
         "transport": "udp",
-        "sms_center": "+447802000332"
+        "sms_center": "+447802000332",
+        "user_eq_phone": true
       }
     },
     {

internal/vowifi/ims/call_runtime.go

@@ -20,21 +20,30 @@ var (
 
 const terminalCallRetention = 30 * time.Second
 
+const (
+	mmtelServiceURN = "urn:urn-7:3gpp-service.ims.icsi.mmtel"
+	mmtelFeatureTag = "urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel"
+)
+
 type imsCall struct {
-	public     vowifi.Call
-	callID     string
-	target     string
-	from       string
-	to         string
-	branch     string
-	cseq       uint32
-	invite     *sipRequest
-	respond    func([]byte) error
-	responses  chan *sipResponse
-	remoteTag  string
-	routes     []string
-	terminated bool
-	media      *rtpMedia
+	public         vowifi.Call
+	callID         string
+	target         string
+	from           string
+	to             string
+	branch         string
+	cseq           uint32
+	inviteTarget   string
+	invite         *sipRequest
+	respond        func([]byte) error
+	responses      chan *sipResponse
+	remoteTag      string
+	routes         []string
+	terminated     bool
+	media          *rtpMedia
+	pracked        map[string]bool
+	sessionExpires int
+	sessionCancel  context.CancelFunc
 }
 
 func (session *Session) Calls() []vowifi.Call {
@@ -67,12 +76,14 @@ func (session *Session) DialCall(ctx context.Context, number string) (vowifi.Cal
 		return vowifi.Call{}, err
 	}
 	callID := callToken + "@" + addressHost(session.conn.LocalAddr())
-	target := "tel:" + number
+	carrierProfile := vowifi.ResolveCarrierProfile(session.request.Identity)
+	target := callTargetURI(number, session.identity.domain, carrierProfile)
 	session.mu.Lock()
 	cseq := session.cseq
 	session.cseq++
 	routes := append([]string(nil), session.evidence.ServiceRoute...)
 	securityHeaders := runtimeSecurityHeaders(session.securityActive, session.securityAgreement.verifyValue)
+	fromIdentity, preferredIdentity, identitySource := session.callOriginatingIdentitiesLocked(carrierProfile)
 	session.mu.Unlock()
 	media, err := newRTPMedia(session.localMediaIP())
 	if err != nil {
@@ -80,7 +91,7 @@ func (session *Session) DialCall(ctx context.Context, number string) (vowifi.Cal
 	}
 	body := media.offerSDP(session.localMediaIP())
 	transportUpper := strings.ToUpper(session.transport)
-	from := "<" + session.identity.public + ">;tag=" + session.fromTag
+	from := "<" + fromIdentity + ">;tag=" + session.fromTag
 	to := "<" + target + ">"
 	lines := []string{
 		"INVITE " + target + " SIP/2.0",
@@ -100,10 +111,17 @@ func (session *Session) DialCall(ctx context.Context, number string) (vowifi.Cal
 		"To: "+to,
 		"Call-ID: "+callID,
 		fmt.Sprintf("CSeq: %d INVITE", cseq),
-		"Contact: <sip:"+session.identity.user+"@"+session.contactAddress()+";transport="+session.transport+">",
-		"P-Preferred-Identity: <"+session.identity.public+">",
-		"Allow: INVITE, ACK, CANCEL, BYE, OPTIONS, MESSAGE",
-		"Supported: timer",
+		session.dialogContactHeader(),
+		"P-Preferred-Identity: <"+preferredIdentity+">",
+		"P-Preferred-Service: "+mmtelServiceURN,
+		`Accept-Contact: *;+g.3gpp.icsi-ref="`+mmtelFeatureTag+`"`,
+		"P-Access-Network-Info: "+session.pAccessNetworkInfo(),
+		"User-Agent: "+session.callUserAgent(),
+		"Allow: INVITE, ACK, CANCEL, BYE, OPTIONS, MESSAGE, PRACK, UPDATE, INFO",
+		"Supported: 100rel, timer, replaces",
+		"Session-Expires: 1800;refresher=uac",
+		"Min-SE: 90",
+		"Accept: application/sdp",
 		"Content-Type: application/sdp",
 		"Content-Length: "+strconv.Itoa(len(body)), "", "",
 	)
@@ -120,12 +138,19 @@ func (session *Session) DialCall(ctx context.Context, number string) (vowifi.Cal
 	session.transactionsMu.Unlock()
 	call := &imsCall{
 		public: vowifi.Call{ID: callID, Number: number, Direction: "outgoing", State: "dialing", StartedAt: time.Now().UTC()},
-		callID: callID, target: target, from: from, to: to, branch: branch, cseq: cseq, responses: responses,
-		routes: routes, media: media,
+		callID: callID, target: target, inviteTarget: target, from: from, to: to, branch: branch, cseq: cseq, responses: responses,
+		routes: routes, media: media, pracked: make(map[string]bool),
 	}
 	session.callMu.Lock()
 	session.calls[callID] = call
 	session.callMu.Unlock()
+	if session.provider != nil && session.provider.config.Logger != nil {
+		session.provider.config.Logger.Info("IMS call started",
+			"direction", "outgoing",
+			"identity_source", identitySource,
+			"target_scheme", strings.ToLower(strings.TrimSuffix(strings.SplitN(target, ":", 2)[0], ":")),
+		)
+	}
 	session.writeMu.Lock()
 	_, err = session.conn.Write(request)
 	session.writeMu.Unlock()
@@ -166,24 +191,26 @@ func (session *Session) watchOutgoingCall(call *imsCall, key sipTransactionKey)
 			if response == nil {
 				continue
 			}
+			diagnostic := callResponseDiagnostic(response)
+			session.logCallResponse(response, diagnostic)
 			if response.StatusCode < 200 {
-				session.setCallDiagnostic(call.callID, response.StatusCode, response.Reason)
-				if response.StatusCode >= 180 {
+				session.setCallDiagnostic(call.callID, response.StatusCode, diagnostic)
+				session.updateCallDialogFromResponse(call, response)
+				if len(response.Body) > 0 {
+					if mediaErr := call.media.configureRemote(response.Body); mediaErr == nil {
+						session.setCallMediaReady(call.callID)
+						session.setCallState(call.callID, "early_media")
+					}
+				} else if response.StatusCode >= 180 {
 					session.setCallState(call.callID, "ringing")
 				}
+				if reliableProvisional(response) {
+					go session.sendPRACK(call, response)
+				}
 				continue
 			}
 			if response.StatusCode >= 200 && response.StatusCode < 300 {
-				session.callMu.Lock()
-				call.to = response.value("To")
-				call.remoteTag = headerParameter(call.to, "tag")
-				if contact := headerURI(response.value("Contact")); contact != "" {
-					call.target = contact
-				}
-				if recordRoutes := response.values("Record-Route"); len(recordRoutes) > 0 {
-					call.routes = reverseStrings(recordRoutes)
-				}
-				session.callMu.Unlock()
+				session.updateCallDialogFromResponse(call, response)
 				mediaErr := call.media.configureRemote(response.Body)
 				_ = session.sendACK(call)
 				if mediaErr != nil {
@@ -197,13 +224,23 @@ func (session *Session) watchOutgoingCall(call *imsCall, key sipTransactionKey)
 				}
 				session.setCallMediaReady(call.callID)
 				session.setCallState(call.callID, "active")
-			} else if session.callWasTerminated(call.callID) {
-				// CANCEL normally causes the pending INVITE transaction to finish
-				// with 487 Request Terminated.  It is the expected response to our
-				// local hang-up, not a new network rejection.
-				session.finishCall(call.callID, "ended", response.StatusCode, response.Reason)
+				session.startSessionTimer(call, response.value("Session-Expires"))
 			} else {
-				session.finishCall(call.callID, "failed", response.StatusCode, response.Reason)
+				if ackErr := session.sendRejectedInviteACK(call, response); ackErr != nil && session.provider != nil && session.provider.config.Logger != nil {
+					session.provider.config.Logger.Warn("IMS rejected INVITE ACK failed",
+						"carrier_profile", vowifi.ResolveCarrierProfile(session.request.Identity).ID,
+						"sip_status", response.StatusCode,
+						"error", safeSIPDiagnostic(ackErr.Error()),
+					)
+				}
+				if session.callWasTerminated(call.callID) {
+					// CANCEL normally causes the pending INVITE transaction to finish
+					// with 487 Request Terminated.  It is the expected response to our
+					// local hang-up, not a new network rejection.
+					session.finishCall(call.callID, "ended", response.StatusCode, diagnostic)
+				} else {
+					session.finishCall(call.callID, "failed", response.StatusCode, diagnostic)
+				}
 			}
 			return
 		}
@@ -223,7 +260,13 @@ func (session *Session) AnswerCall(_ context.Context, id string) (vowifi.Call, e
 	}
 	request, respond := call.invite, call.respond
 	session.callMu.Unlock()
-	response, err := buildSIPResponseWithBody(request, 200, session.fromTag, call.media.answerSDP(session.localMediaIP()))
+	response, err := buildSIPResponseWithBody(
+		request,
+		200,
+		session.fromTag,
+		call.media.answerSDP(session.localMediaIP()),
+		session.dialogContactHeader(),
+	)
 	if err != nil {
 		return vowifi.Call{}, err
 	}
@@ -231,6 +274,7 @@ func (session *Session) AnswerCall(_ context.Context, id string) (vowifi.Call, e
 		return vowifi.Call{}, err
 	}
 	session.setCallState(id, "active")
+	session.startSessionTimer(call, request.value("Session-Expires"))
 	if call.media.ready() {
 		session.setCallMediaReady(id)
 	}
@@ -264,7 +308,7 @@ func (session *Session) HangupCall(ctx context.Context, id string) error {
 		return nil
 	}
 	method := "BYE"
-	if direction == "outgoing" && (state == "dialing" || state == "ringing") {
+	if direction == "outgoing" && (state == "dialing" || state == "ringing" || state == "early_media") {
 		method = "CANCEL"
 	}
 	err := session.sendDialogRequest(ctx, call, method)
@@ -288,6 +332,12 @@ func (session *Session) handleCallRequest(request *sipRequest, respond func([]by
 		if callID == "" {
 			return true
 		}
+		session.callMu.Lock()
+		existing := session.calls[callID]
+		session.callMu.Unlock()
+		if existing != nil && existing.public.State == "active" {
+			return session.handleDialogOffer(request, respond, existing)
+		}
 		number := identityNumber(request.value("From"))
 		target := headerURI(request.value("Contact"))
 		if target == "" {
@@ -311,8 +361,9 @@ func (session *Session) handleCallRequest(request *sipRequest, respond func([]by
 		}
 		call := &imsCall{
 			public: vowifi.Call{ID: callID, Number: number, Direction: "incoming", State: "ringing", StartedAt: time.Now().UTC()},
-			callID: callID, target: target, from: request.value("To") + ";tag=" + session.fromTag,
+			callID: callID, target: target, inviteTarget: request.URI, from: request.value("To") + ";tag=" + session.fromTag,
 			to: request.value("From"), invite: request, respond: respond, routes: request.values("Record-Route"), media: media,
+			pracked: make(map[string]bool),
 		}
 		session.callMu.Lock()
 		session.calls[callID] = call
@@ -322,6 +373,21 @@ func (session *Session) handleCallRequest(request *sipRequest, respond func([]by
 			_ = respond(response)
 		}
 		return true
+	case "PRACK":
+		response, err := buildSIPResponseWithBody(request, 200, session.fromTag, nil)
+		if err == nil {
+			_ = respond(response)
+		}
+		return true
+	case "UPDATE":
+		callID := strings.TrimSpace(request.value("Call-ID"))
+		session.callMu.Lock()
+		call := session.calls[callID]
+		session.callMu.Unlock()
+		if call == nil {
+			return false
+		}
+		return session.handleDialogOffer(request, respond, call)
 	case "ACK":
 		callID := strings.TrimSpace(request.value("Call-ID"))
 		session.callMu.Lock()
@@ -366,9 +432,199 @@ func (session *Session) sendACK(call *imsCall) error {
 	return err
 }
 
+// sendRejectedInviteACK acknowledges a non-2xx final response using the
+// original INVITE transaction branch and request URI. Unlike a 2xx ACK this is
+// part of the INVITE transaction; sending a dialog-style ACK with a new branch
+// leaves the P-CSCF retransmitting the rejection and leaking transaction state.
+func (session *Session) sendRejectedInviteACK(call *imsCall, response *sipResponse) error {
+	if call == nil || response == nil || response.StatusCode < 300 {
+		return nil
+	}
+	if session == nil || session.conn == nil {
+		return errors.New("ims: SIP connection unavailable for rejected INVITE ACK")
+	}
+	target := call.inviteTarget
+	if target == "" {
+		target = call.target
+	}
+	to := strings.TrimSpace(response.value("To"))
+	if to == "" {
+		to = call.to
+	}
+	lines := []string{
+		"ACK " + target + " SIP/2.0",
+		fmt.Sprintf("Via: SIP/2.0/%s %s;branch=z9hG4bK%s;rport", strings.ToUpper(session.transport), session.conn.LocalAddr().String(), call.branch),
+		"Max-Forwards: 70",
+	}
+	session.mu.Lock()
+	securityHeaders := runtimeSecurityHeaders(session.securityActive, session.securityAgreement.verifyValue)
+	session.mu.Unlock()
+	lines = append(lines, securityHeaders...)
+	for _, route := range call.routes {
+		lines = append(lines, "Route: "+route)
+	}
+	lines = append(lines,
+		"From: "+call.from,
+		"To: "+to,
+		"Call-ID: "+call.callID,
+		fmt.Sprintf("CSeq: %d ACK", call.cseq),
+		"P-Access-Network-Info: "+session.pAccessNetworkInfo(),
+		"User-Agent: "+session.callUserAgent(),
+		"Content-Length: 0", "", "",
+	)
+	session.writeMu.Lock()
+	_, err := session.conn.Write([]byte(strings.Join(lines, "\r\n")))
+	session.writeMu.Unlock()
+	return err
+}
+
+func reliableProvisional(response *sipResponse) bool {
+	if response == nil || strings.TrimSpace(response.value("RSeq")) == "" {
+		return false
+	}
+	for _, token := range strings.Split(strings.ToLower(response.value("Require")), ",") {
+		if strings.TrimSpace(token) == "100rel" {
+			return true
+		}
+	}
+	return false
+}
+
+func (session *Session) updateCallDialogFromResponse(call *imsCall, response *sipResponse) {
+	if call == nil || response == nil {
+		return
+	}
+	session.callMu.Lock()
+	defer session.callMu.Unlock()
+	call.to = response.value("To")
+	call.remoteTag = headerParameter(call.to, "tag")
+	if contact := headerURI(response.value("Contact")); contact != "" {
+		call.target = contact
+	}
+	if recordRoutes := response.values("Record-Route"); len(recordRoutes) > 0 {
+		call.routes = reverseStrings(recordRoutes)
+	}
+}
+
+func (session *Session) sendPRACK(call *imsCall, response *sipResponse) {
+	rseq := strings.TrimSpace(response.value("RSeq"))
+	inviteCSeq := strings.TrimSpace(response.value("CSeq"))
+	if rseq == "" || inviteCSeq == "" {
+		return
+	}
+	key := rseq + "|" + inviteCSeq
+	session.callMu.Lock()
+	if call.pracked == nil {
+		call.pracked = make(map[string]bool)
+	}
+	if call.pracked[key] || call.public.EndedAt != nil {
+		session.callMu.Unlock()
+		return
+	}
+	call.pracked[key] = true
+	target, to, from := call.target, call.to, call.from
+	routes := append([]string(nil), call.routes...)
+	session.callMu.Unlock()
+
+	session.mu.Lock()
+	cseq := session.cseq
+	session.cseq++
+	session.mu.Unlock()
+	branch, _ := randomHex(12)
+	lines := []string{
+		"PRACK " + target + " SIP/2.0",
+		fmt.Sprintf("Via: SIP/2.0/%s %s;branch=z9hG4bK%s;rport", strings.ToUpper(session.transport), session.conn.LocalAddr().String(), branch),
+		"Max-Forwards: 70",
+	}
+	session.mu.Lock()
+	securityHeaders := runtimeSecurityHeaders(session.securityActive, session.securityAgreement.verifyValue)
+	session.mu.Unlock()
+	lines = append(lines, securityHeaders...)
+	for _, route := range routes {
+		lines = append(lines, "Route: "+route)
+	}
+	lines = append(lines,
+		"From: "+from, "To: "+to, "Call-ID: "+call.callID,
+		fmt.Sprintf("CSeq: %d PRACK", cseq), "RAck: "+rseq+" "+inviteCSeq,
+		"P-Access-Network-Info: "+session.pAccessNetworkInfo(),
+		"User-Agent: "+session.callUserAgent(),
+		"Content-Length: 0", "", "",
+	)
+	ctx, cancel := context.WithTimeout(session.refreshContext, 10*time.Second)
+	defer cancel()
+	result, err := session.exchangeRuntime(ctx, []byte(strings.Join(lines, "\r\n")), sipTransactionKey{callID: call.callID, cseq: cseq, method: "PRACK"})
+	if err != nil || result.StatusCode < 200 || result.StatusCode >= 300 {
+		reason := "reliable provisional response could not be acknowledged"
+		if err != nil {
+			reason = err.Error()
+		}
+		session.finishCall(call.callID, "failed", 0, reason)
+	}
+}
+
+func (session *Session) handleDialogOffer(request *sipRequest, respond func([]byte) error, call *imsCall) bool {
+	var body []byte
+	if len(request.Body) > 0 {
+		if err := call.media.configureRemote(request.Body); err != nil {
+			if response, buildErr := buildSIPResponseWithBody(request, 488, session.fromTag, nil); buildErr == nil {
+				_ = respond(response)
+			}
+			return true
+		}
+		body = call.media.answerSDP(session.localMediaIP())
+		session.setCallMediaReady(call.callID)
+	}
+	extraHeaders := []string(nil)
+	if request.Method == "INVITE" {
+		extraHeaders = append(extraHeaders, session.dialogContactHeader())
+	}
+	response, err := buildSIPResponseWithBody(request, 200, session.fromTag, body, extraHeaders...)
+	if err == nil {
+		_ = respond(response)
+		session.startSessionTimer(call, request.value("Session-Expires"))
+	}
+	return true
+}
+
+func (session *Session) startSessionTimer(call *imsCall, header string) {
+	value := strings.TrimSpace(strings.Split(header, ";")[0])
+	seconds, err := strconv.Atoi(value)
+	if err != nil || seconds < 90 || seconds > 86400 || call == nil {
+		return
+	}
+	ctx, cancel := context.WithCancel(session.refreshContext)
+	session.callMu.Lock()
+	if call.sessionCancel != nil {
+		call.sessionCancel()
+	}
+	call.sessionExpires = seconds
+	call.sessionCancel = cancel
+	session.callMu.Unlock()
+	go func() {
+		interval := time.Duration(seconds) * time.Second / 2
+		timer := time.NewTimer(interval)
+		defer timer.Stop()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-timer.C:
+				refreshContext, cancelRefresh := context.WithTimeout(ctx, 15*time.Second)
+				refreshErr := session.sendDialogRequest(refreshContext, call, "UPDATE")
+				cancelRefresh()
+				if refreshErr != nil {
+					session.finishCall(call.callID, "failed", 0, "SIP session refresh failed")
+					return
+				}
+				timer.Reset(interval)
+			}
+		}
+	}()
+}
+
 func (session *Session) sendDialogRequest(ctx context.Context, call *imsCall, method string) error {
 	cseq := call.cseq
-	if method == "BYE" {
+	if method == "BYE" || method == "UPDATE" {
 		session.mu.Lock()
 		cseq = session.cseq
 		session.cseq++
@@ -396,15 +652,23 @@ func (session *Session) buildDialogRequest(call *imsCall, method string, cseq ui
 	if method == "CANCEL" {
 		branch = call.branch
 	}
+	target := call.target
+	if method == "CANCEL" && call.inviteTarget != "" {
+		target = call.inviteTarget
+	}
 	to := call.to
 	if to == "" {
 		to = "<" + call.target + ">"
 	}
 	lines := []string{
-		method + " " + call.target + " SIP/2.0",
+		method + " " + target + " SIP/2.0",
 		fmt.Sprintf("Via: SIP/2.0/%s %s;branch=z9hG4bK%s;rport", strings.ToUpper(session.transport), session.conn.LocalAddr().String(), branch),
 		"Max-Forwards: 70",
 	}
+	session.mu.Lock()
+	securityHeaders := runtimeSecurityHeaders(session.securityActive, session.securityAgreement.verifyValue)
+	session.mu.Unlock()
+	lines = append(lines, securityHeaders...)
 	for _, route := range call.routes {
 		lines = append(lines, "Route: "+route)
 	}
@@ -413,8 +677,19 @@ func (session *Session) buildDialogRequest(call *imsCall, method string, cseq ui
 		"To: "+to,
 		"Call-ID: "+call.callID,
 		fmt.Sprintf("CSeq: %d %s", cseq, method),
-		"Content-Length: 0", "", "",
+		"Supported: 100rel, timer",
+		"User-Agent: "+session.callUserAgent(),
 	)
+	if method != "CANCEL" {
+		lines = append(lines, "P-Access-Network-Info: "+session.pAccessNetworkInfo())
+	}
+	if method == "UPDATE" {
+		lines = append(lines, session.dialogContactHeader())
+	}
+	lines = append(lines, "Content-Length: 0", "", "")
+	if method == "UPDATE" && call.sessionExpires > 0 {
+		lines = append(lines[:len(lines)-3], fmt.Sprintf("Session-Expires: %d;refresher=uac", call.sessionExpires), "Content-Length: 0", "", "")
+	}
 	return []byte(strings.Join(lines, "\r\n"))
 }
 
@@ -426,7 +701,7 @@ func (session *Session) localMediaIP() net.IP {
 	return addressIP(localAddress)
 }
 
-func buildSIPResponseWithBody(request *sipRequest, status int, tag string, body []byte) ([]byte, error) {
+func buildSIPResponseWithBody(request *sipRequest, status int, tag string, body []byte, extraHeaders ...string) ([]byte, error) {
 	reasons := map[int]string{180: "Ringing", 200: "OK", 486: "Busy Here", 487: "Request Terminated", 488: "Not Acceptable Here"}
 	reason := reasons[status]
 	if reason == "" {
@@ -446,6 +721,14 @@ func buildSIPResponseWithBody(request *sipRequest, status int, tag string, body
 		lines = append(lines, "Via: "+value)
 	}
 	lines = append(lines, "From: "+from, "To: "+to, "Call-ID: "+callID, "CSeq: "+cseq)
+	for _, header := range extraHeaders {
+		if strings.TrimSpace(header) != "" {
+			lines = append(lines, header)
+		}
+	}
+	if value := strings.TrimSpace(request.value("Session-Expires")); value != "" && status >= 200 && status < 300 && (request.Method == "INVITE" || request.Method == "UPDATE") {
+		lines = append(lines, "Supported: timer", "Session-Expires: "+value)
+	}
 	if len(body) > 0 {
 		lines = append(lines, "Content-Type: application/sdp")
 	}
@@ -453,10 +736,110 @@ func buildSIPResponseWithBody(request *sipRequest, status int, tag string, body
 	return append([]byte(strings.Join(lines, "\r\n")), body...), nil
 }
 
+func (session *Session) dialogContactHeader() string {
+	if session == nil || session.conn == nil || strings.TrimSpace(session.identity.user) == "" {
+		return ""
+	}
+	contact := "Contact: <sip:" + session.identity.user + "@" + session.contactAddress() + ";transport=" + session.transport + ">"
+	if strings.TrimSpace(session.instanceID) != "" {
+		contact += `;+sip.instance="<` + session.instanceID + `>"`
+	}
+	return contact + `;audio;+g.3gpp.icsi-ref="` + mmtelFeatureTag + `"`
+}
+
+func callTargetURI(number, domain string, profile vowifi.CarrierProfile) string {
+	domain = strings.TrimSpace(domain)
+	if profile.IMSDialURIScheme == "sip" {
+		target := "sip:" + number + "@" + domain
+		if profile.IMSUserEqPhone {
+			target += ";user=phone"
+		}
+		return target
+	}
+	if strings.HasPrefix(number, "+") {
+		return "tel:" + number
+	}
+	return "tel:" + number + ";phone-context=" + domain
+}
+
+// callOriginatingIdentitiesLocked selects only a number that IMS explicitly
+// associated with this registration. 3GPP originating sessions use that
+// public identity in both From and P-Preferred-Identity; some TAS deployments
+// accept an IMSI IMPU at the P-CSCF and then terminate the session immediately.
+// The fallback deliberately remains the registered IMPU and never derives a
+// telephone number from IMSI digits.
+func (session *Session) callOriginatingIdentitiesLocked(profile vowifi.CarrierProfile) (from, preferred, source string) {
+	if number, numberSource, ok := vowifi.ExtractAssociatedMSISDN(session.evidence); ok {
+		from = "sip:" + number + "@" + session.identity.domain
+		if profile.IMSUserEqPhone {
+			from += ";user=phone"
+		}
+		return from, "tel:" + number, numberSource
+	}
+	return session.identity.public, session.identity.public, "registered_impu"
+}
+
+func (session *Session) pAccessNetworkInfo() string {
+	profile := vowifi.ResolveCarrierProfile(session.request.Identity)
+	node := strings.TrimSpace(profile.PANINode)
+	if node == "" {
+		node = "000000000000"
+	}
+	value := "IEEE-802.11;i-wlan-node-id=" + node
+	if country := strings.ToUpper(strings.TrimSpace(profile.PANICountry)); country != "" {
+		value += ";country=" + country
+	}
+	return value + ";network-provided"
+}
+
+func (session *Session) callUserAgent() string {
+	if session != nil && session.provider != nil {
+		if value := strings.TrimSpace(session.provider.config.UserAgent); value != "" {
+			return value
+		}
+	}
+	return "vocat/1"
+}
+
+func callResponseDiagnostic(response *sipResponse) string {
+	if response == nil {
+		return ""
+	}
+	parts := make([]string, 0, 3)
+	if reason := safeSIPDiagnostic(response.Reason); reason != "" {
+		parts = append(parts, reason)
+	}
+	for _, name := range []string{"Reason", "Warning"} {
+		for _, value := range response.values(name) {
+			if value = safeSIPDiagnostic(value); value != "" {
+				parts = append(parts, name+": "+value)
+			}
+		}
+	}
+	return safeSIPDiagnostic(strings.Join(parts, "; "))
+}
+
+func (session *Session) logCallResponse(response *sipResponse, diagnostic string) {
+	if session == nil || session.provider == nil || session.provider.config.Logger == nil || response == nil {
+		return
+	}
+	session.provider.config.Logger.Info("IMS call response",
+		"carrier_profile", vowifi.ResolveCarrierProfile(session.request.Identity).ID,
+		"sip_status", response.StatusCode,
+		"diagnostic", diagnostic,
+		"content_type", safeSIPDiagnostic(response.value("Content-Type")),
+		"body_bytes", len(response.Body),
+	)
+}
+
 func (session *Session) setCallState(id, state string) {
 	session.callMu.Lock()
 	if call := session.calls[id]; call != nil {
 		call.public.State = state
+		if state == "active" && call.public.AnsweredAt == nil {
+			now := time.Now().UTC()
+			call.public.AnsweredAt = &now
+		}
 		if state != "ended" && state != "failed" {
 			call.public.EndedAt = nil
 		}
@@ -509,6 +892,10 @@ func (session *Session) finishCall(id, state string, code int, reason string) {
 			call.public.Reason = reason
 		}
 		call.public.EndedAt = &now
+		if call.sessionCancel != nil {
+			call.sessionCancel()
+			call.sessionCancel = nil
+		}
 	}
 	session.callMu.Unlock()
 	if media != nil {

internal/vowifi/ims/call_runtime_test.go

@@ -2,6 +2,8 @@ package ims
 
 import (
 	"context"
+	"io"
+	"net"
 	"strings"
 	"testing"
 	"time"
@@ -10,7 +12,13 @@ import (
 )
 
 func TestIncomingCallCanRingAndAnswerWithMediaOffer(t *testing.T) {
-	session := &Session{fromTag: "local-tag", calls: make(map[string]*imsCall)}
+	client, peer := net.Pipe()
+	defer client.Close()
+	defer peer.Close()
+	session := &Session{
+		fromTag: "local-tag", calls: make(map[string]*imsCall), conn: client,
+		identity: identitySet{user: "subscriber"}, transport: "udp",
+	}
 	packet, err := parseSIPPacket([]byte(strings.Join([]string{
 		"INVITE sip:[email protected] SIP/2.0",
 		"Via: SIP/2.0/UDP 192.0.2.10:5060;branch=z9hG4bK-incoming",
@@ -42,6 +50,9 @@ func TestIncomingCallCanRingAndAnswerWithMediaOffer(t *testing.T) {
 	if answered.State != "active" || len(responses) != 2 || !strings.Contains(string(responses[1]), "a=sendrecv") {
 		t.Fatalf("answered = %#v, response = %q", answered, responses[1])
 	}
+	if !strings.Contains(string(responses[1]), "Contact: <sip:subscriber@pipe;transport=udp>") {
+		t.Fatalf("answer omitted dialog Contact: %q", responses[1])
+	}
 }
 
 func TestIncomingCallCanBeRejected(t *testing.T) {
@@ -116,3 +127,155 @@ func TestValidCallNumber(t *testing.T) {
 		t.Fatal("call number validation mismatch")
 	}
 }
+
+func TestOutgoingLocalNumberUsesIMSPhoneContextAndMMTelHeaders(t *testing.T) {
+	client, peer := net.Pipe()
+	defer peer.Close()
+	refreshContext, cancelRefresh := context.WithCancel(context.Background())
+	defer cancelRefresh()
+	session := &Session{
+		provider: &Provider{config: Config{
+			UserAgent:    "VoCat Test",
+			SecurityMode: SecurityDisabled,
+		}},
+		request: vowifi.IMSRequest{Identity: vowifi.SIMIdentity{
+			HomeMCC: "234", HomeMNC: "33", IMSI: "234330000000001", ICCID: "8944300000000000000",
+		}},
+		identity: identitySet{
+			domain: "ims.mnc033.mcc234.3gppnetwork.org",
+			public: "sip:[email protected]",
+			user:   "234330000000001",
+		},
+		endpoint:       pcscfEndpoint{host: "pcscf.test", port: 5060},
+		transport:      "tcp",
+		conn:           client,
+		fromTag:        "local-tag",
+		instanceID:     "urn:uuid:00000000-0000-4000-8000-000000000001",
+		cseq:           1,
+		transactions:   make(map[sipTransactionKey]chan *sipResponse),
+		calls:          make(map[string]*imsCall),
+		refreshContext: refreshContext,
+		evidence: vowifi.IMSEvidence{
+			PAssociatedURI: []string{"<tel:+447700900123>"},
+			ServiceRoute:   []string{"<sip:route.ims.test;lr>"},
+		},
+	}
+	wireResult := make(chan string, 1)
+	go func() {
+		packet, _ := io.ReadAll(peer)
+		wireResult <- string(packet)
+	}()
+
+	call, err := session.DialCall(context.Background(), "888")
+	if err != nil {
+		t.Fatal(err)
+	}
+	session.finishCall(call.ID, "ended", 0, "test complete")
+	cancelRefresh()
+	_ = client.Close()
+	wire := <-wireResult
+
+	for _, expected := range []string{
+		"INVITE sip:[email protected] SIP/2.0\r\n",
+		"To: <sip:[email protected]>\r\n",
+		"From: <sip:[email protected]>;tag=local-tag\r\n",
+		"P-Preferred-Identity: <tel:+447700900123>\r\n",
+		"P-Preferred-Service: " + mmtelServiceURN + "\r\n",
+		`Accept-Contact: *;+g.3gpp.icsi-ref="` + mmtelFeatureTag + `"` + "\r\n",
+		"P-Access-Network-Info: IEEE-802.11;i-wlan-node-id=000000000000;country=GB;network-provided\r\n",
+		"User-Agent: VoCat Test\r\n",
+		"Accept: application/sdp\r\n",
+	} {
+		if !strings.Contains(wire, expected) {
+			t.Fatalf("INVITE omitted %q:\n%s", expected, wire)
+		}
+	}
+}
+
+func TestCallOriginatingIdentitiesFallBackToRegisteredIMPU(t *testing.T) {
+	session := &Session{
+		identity: identitySet{
+			domain: "ims.mnc033.mcc234.3gppnetwork.org",
+			public: "sip:[email protected]",
+		},
+	}
+	from, preferred, source := session.callOriginatingIdentitiesLocked(vowifi.CarrierProfile{})
+	if from != session.identity.public || preferred != session.identity.public || source != "registered_impu" {
+		t.Fatalf("fallback identities = (%q, %q, %q)", from, preferred, source)
+	}
+}
+
+func TestCallTargetURIUsesPhoneContextOnlyForLocalNumbers(t *testing.T) {
+	domain := "ims.mnc033.mcc234.3gppnetwork.org"
+	if got := callTargetURI("888", domain, vowifi.CarrierProfile{IMSDialURIScheme: "tel"}); got != "tel:888;phone-context="+domain {
+		t.Fatalf("local target = %q", got)
+	}
+	if got := callTargetURI("+447700900123", domain, vowifi.CarrierProfile{IMSDialURIScheme: "tel"}); got != "tel:+447700900123" {
+		t.Fatalf("global target = %q", got)
+	}
+	if got := callTargetURI("888", domain, vowifi.CarrierProfile{IMSDialURIScheme: "sip"}); got != "sip:888@"+domain {
+		t.Fatalf("SIP target = %q", got)
+	}
+	if got := callTargetURI("888", domain, vowifi.CarrierProfile{IMSDialURIScheme: "sip", IMSUserEqPhone: true}); got != "sip:888@"+domain+";user=phone" {
+		t.Fatalf("SIP user=phone target = %q", got)
+	}
+}
+
+func TestCallResponseDiagnosticIncludesNetworkReason(t *testing.T) {
+	response := &sipResponse{
+		StatusCode: 487,
+		Reason:     "Request Terminated",
+		Headers: map[string][]string{
+			"reason": {`Q.850;cause=31;text="Normal, unspecified"`},
+		},
+	}
+	want := `Request Terminated; Reason: Q.850;cause=31;text="Normal, unspecified"`
+	if got := callResponseDiagnostic(response); got != want {
+		t.Fatalf("diagnostic = %q, want %q", got, want)
+	}
+}
+
+func TestRejectedInviteACKUsesOriginalTransaction(t *testing.T) {
+	client, peer := net.Pipe()
+	defer client.Close()
+	defer peer.Close()
+	session := &Session{
+		provider:  &Provider{config: Config{UserAgent: "VoCat Test"}},
+		request:   vowifi.IMSRequest{Identity: vowifi.SIMIdentity{HomeMCC: "234", HomeMNC: "33"}},
+		identity:  identitySet{domain: "ims.mnc033.mcc234.3gppnetwork.org"},
+		transport: "tcp",
+		conn:      client,
+	}
+	call := &imsCall{
+		callID:       "call-1",
+		inviteTarget: "sip:[email protected]",
+		from:         "<sip:[email protected]>;tag=local",
+		to:           "<sip:[email protected]>",
+		branch:       "original-branch",
+		cseq:         41,
+		routes:       []string{"<sip:pcscf.test;lr>"},
+	}
+	response := &sipResponse{StatusCode: 487, Headers: map[string][]string{
+		"to": {"<sip:[email protected]>;tag=tas"},
+	}}
+	ackResult := make(chan string, 1)
+	go func() {
+		buffer := make([]byte, 4096)
+		count, _ := peer.Read(buffer)
+		ackResult <- string(buffer[:count])
+	}()
+	if err := session.sendRejectedInviteACK(call, response); err != nil {
+		t.Fatal(err)
+	}
+	ack := <-ackResult
+	for _, expected := range []string{
+		"ACK sip:[email protected] SIP/2.0\r\n",
+		"branch=z9hG4bKoriginal-branch;rport",
+		"To: <sip:[email protected]>;tag=tas\r\n",
+		"CSeq: 41 ACK\r\n",
+	} {
+		if !strings.Contains(ack, expected) {
+			t.Fatalf("rejected INVITE ACK omitted %q:\n%s", expected, ack)
+		}
+	}
+}

internal/vowifi/ims/security.go

@@ -783,7 +783,7 @@ func zeroBytes(value []byte) {
 }
 
 func (session *Session) securityOffered() bool {
-	return session.provider.config.SecurityMode != SecurityDisabled && !session.securityDeclined
+	return session.provider != nil && session.provider.config.SecurityMode != SecurityDisabled && !session.securityDeclined
 }
 
 func (session *Session) securityFromResponse(response *sipResponse) (securityAgreement, bool, error) {

internal/vowifi/types.go

@@ -405,6 +405,7 @@ type Call struct {
 	Direction  string     `json:"direction"`
 	State      string     `json:"state"`
 	StartedAt  time.Time  `json:"started_at"`
+	AnsweredAt *time.Time `json:"answered_at,omitempty"`
 	SIPCode    int        `json:"sip_code,omitempty"`
 	Reason     string     `json:"reason,omitempty"`
 	MediaReady bool       `json:"media_ready,omitempty"`