fix: cache participant attrs for BYE attributes_to_headers (#404)

pkg/sip/attrs_headers_test.go

@@ -0,0 +1,79 @@
+// Copyright 2026 LiveKit, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sip
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// Regression for livekit/sip#404: when the agent deletes the room before SIP
+// sends BYE, LocalParticipant is gone. attributes_to_headers must still map
+// from the last cached participant attributes.
+func TestFillHeadersUsesCachedAttrsWhenRoomNil(t *testing.T) {
+	call := &inboundCall{
+		attrsToHdr: map[string]string{
+			"sip.custom": "X-Custom-Header",
+		},
+	}
+	call.storeParticipantAttrs(map[string]string{
+		"sip.custom": "value-from-cache",
+		"other":      "ignored",
+	})
+	call.lkRoom = nil
+	cc := &sipInbound{call: call}
+
+	headers := cc.fillHeaders(nil)
+	require.Equal(t, map[string]string{"X-Custom-Header": "value-from-cache"}, headers)
+
+	// No mapping configured → leave headers untouched.
+	call.attrsToHdr = nil
+	require.Nil(t, cc.fillHeaders(nil))
+
+	// Mapping configured but cache empty → leave headers untouched.
+	call.attrsToHdr = map[string]string{"sip.custom": "X-Custom-Header"}
+	call.attrsMu.Lock()
+	call.cachedAttrs = nil
+	call.attrsMu.Unlock()
+	require.Nil(t, cc.fillHeaders(nil))
+}
+
+func TestOutboundSetAttrsToHeadersUsesCachedAttrsWhenRoomNil(t *testing.T) {
+	call := &outboundCall{
+		sipConf: sipOutboundConfig{
+			attrsToHeaders: map[string]string{
+				"sip.custom": "X-Custom-Header",
+			},
+		},
+	}
+	call.storeParticipantAttrs(map[string]string{
+		"sip.custom": "outbound-cache",
+	})
+	call.lkRoom = nil
+
+	headers := call.setAttrsToHeaders(nil)
+	require.Equal(t, map[string]string{"X-Custom-Header": "outbound-cache"}, headers)
+}
+
+func TestAttrsToHeaders(t *testing.T) {
+	attrs := map[string]string{"a": "1", "b": "2"}
+	mapping := map[string]string{"a": "X-A", "missing": "X-Missing"}
+	headers := AttrsToHeaders(attrs, mapping, map[string]string{"Keep": "yes"})
+	require.Equal(t, map[string]string{
+		"Keep": "yes",
+		"X-A":  "1",
+	}, headers)
+}

pkg/sip/inbound.go

@@ -684,6 +684,8 @@ type inboundCall struct {
 	callStart   time.Time
 	extraAttrs  map[string]string
 	attrsToHdr  map[string]string
+	attrsMu     sync.Mutex
+	cachedAttrs map[string]string // last-seen participant attrs for BYE/REFER after room teardown (#404)
 	ctx         context.Context
 	cancel      func()
 	closeReason atomic.Pointer[ReasonHeader]
@@ -1368,10 +1370,11 @@ func (c *inboundCall) close(ctx context.Context, end EndCall) {
 		defer log.Infow("Inbound call closed")
 	}
 
+	// Snapshot attrs before teardown. Prefer live room state, but keep the
+	// cache so attributes_to_headers still works when the agent deleted the
+	// room first (Room() is already nil). See livekit/sip#404.
+	c.snapshotParticipantAttrs()
 	// Send BYE _before_ closing media/room connection.
-	// This ensures participant attributes are still available for
-	// attributes_to_headers mapping in the setHeaders callback.
-	// See: https://github.com/livekit/sip/issues/404
 	c.cc.CloseWithStatus(ctx, result, end.Headers)
 	c.closeMedia()
 	if callDurFn := c.callDur; callDurFn != nil {
@@ -1514,6 +1517,7 @@ func (c *inboundCall) setStatus(v CallStatus) {
 	r.LocalParticipant.SetAttributes(map[string]string{
 		livekit.AttrSIPCallStatus: attr,
 	})
+	c.snapshotParticipantAttrs()
 }
 
 func (c *inboundCall) createLiveKitParticipant(ctx context.Context, rconf RoomConfig, status CallStatus) error {
@@ -1547,6 +1551,10 @@ func (c *inboundCall) createLiveKitParticipant(ctx context.Context, rconf RoomCo
 	if err != nil {
 		return err
 	}
+	// Seed attrs cache from the join config so BYE mapping works even if the
+	// room is torn down before we read LocalParticipant again (#404).
+	c.storeParticipantAttrs(partConf.Attributes)
+	c.snapshotParticipantAttrs()
 	if err := registerSignalingRPC(c.lkRoom, c.cc); err != nil {
 		return err
 	}
@@ -1788,11 +1796,44 @@ func (c *sipInbound) fillHeaders(headers map[string]string) map[string]string {
 	if c == nil || c.call == nil || len(c.call.attrsToHdr) == 0 {
 		return headers
 	}
-	r := c.call.lkRoom.Room()
-	if r == nil {
+	attrs := c.call.participantAttributes()
+	if len(attrs) == 0 {
 		return headers
 	}
-	return AttrsToHeaders(r.LocalParticipant.Attributes(), c.call.attrsToHdr, headers)
+	return AttrsToHeaders(attrs, c.call.attrsToHdr, headers)
+}
+
+// snapshotParticipantAttrs caches LocalParticipant attributes while the room
+// is still connected. Used so BYE/REFER can map attributes_to_headers after
+// the room has already been torn down (livekit/sip#404).
+func (c *inboundCall) snapshotParticipantAttrs() {
+	if c == nil || c.lkRoom == nil {
+		return
+	}
+	r := c.lkRoom.Room()
+	if r == nil || r.LocalParticipant == nil {
+		return
+	}
+	attrs := r.LocalParticipant.Attributes() // clones
+	c.attrsMu.Lock()
+	c.cachedAttrs = attrs
+	c.attrsMu.Unlock()
+}
+
+func (c *inboundCall) storeParticipantAttrs(attrs map[string]string) {
+	if c == nil || len(attrs) == 0 {
+		return
+	}
+	c.attrsMu.Lock()
+	c.cachedAttrs = maps.Clone(attrs)
+	c.attrsMu.Unlock()
+}
+
+func (c *inboundCall) participantAttributes() map[string]string {
+	c.snapshotParticipantAttrs()
+	c.attrsMu.Lock()
+	defer c.attrsMu.Unlock()
+	return maps.Clone(c.cachedAttrs)
 }
 
 func (c *sipInbound) Drop() {

pkg/sip/outbound.go

@@ -82,11 +82,13 @@ type outboundCall struct {
 	jitterBuf bool
 	projectID string
 
-	mu       sync.RWMutex
-	mon      *stats.CallMonitor
-	lkRoom   RoomInterface
-	lkRoomIn msdk.PCM16Writer // output to room; OPUS at 48k
-	sipConf  sipOutboundConfig
+	mu          sync.RWMutex
+	mon         *stats.CallMonitor
+	lkRoom      RoomInterface
+	lkRoomIn    msdk.PCM16Writer // output to room; OPUS at 48k
+	sipConf     sipOutboundConfig
+	attrsMu     sync.Mutex
+	cachedAttrs map[string]string // last-seen participant attrs for BYE after room teardown (#404)
 }
 
 func (c *Client) newCall(ctx context.Context, tid traceid.ID, conf *config.Config, log logger.Logger, id LocalTag, room RoomConfig, sipConf sipOutboundConfig, state *CallState, projectID string) (*outboundCall, error) {
@@ -171,11 +173,41 @@ func (c *outboundCall) setAttrsToHeaders(headers map[string]string) map[string]s
 	if len(c.sipConf.attrsToHeaders) == 0 {
 		return headers
 	}
-	r := c.lkRoom.Room()
-	if r == nil {
+	attrs := c.participantAttributes()
+	if len(attrs) == 0 {
 		return headers
 	}
-	return AttrsToHeaders(r.LocalParticipant.Attributes(), c.sipConf.attrsToHeaders, headers)
+	return AttrsToHeaders(attrs, c.sipConf.attrsToHeaders, headers)
+}
+
+func (c *outboundCall) snapshotParticipantAttrs() {
+	if c == nil || c.lkRoom == nil {
+		return
+	}
+	r := c.lkRoom.Room()
+	if r == nil || r.LocalParticipant == nil {
+		return
+	}
+	attrs := r.LocalParticipant.Attributes() // clones
+	c.attrsMu.Lock()
+	c.cachedAttrs = attrs
+	c.attrsMu.Unlock()
+}
+
+func (c *outboundCall) storeParticipantAttrs(attrs map[string]string) {
+	if c == nil || len(attrs) == 0 {
+		return
+	}
+	c.attrsMu.Lock()
+	c.cachedAttrs = maps.Clone(attrs)
+	c.attrsMu.Unlock()
+}
+
+func (c *outboundCall) participantAttributes() map[string]string {
+	c.snapshotParticipantAttrs()
+	c.attrsMu.Lock()
+	defer c.attrsMu.Unlock()
+	return maps.Clone(c.cachedAttrs)
 }
 
 func (c *outboundCall) ensureClosed(ctx context.Context) {
@@ -375,10 +407,10 @@ func (c *outboundCall) close(ctx context.Context, end EndCall) bool {
 			info.DisconnectReason = end.Reason
 		})
 
+		// Snapshot attrs before teardown so attributes_to_headers still works
+		// when the room was already deleted (livekit/sip#404).
+		c.snapshotParticipantAttrs()
 		// Send BYE _before_ closing media/room connection.
-		// This ensures participant attributes are still available for
-		// attributes_to_headers mapping in the setHeaders callback.
-		// See: https://github.com/livekit/sip/issues/404
 		c.stopSIP(ctx, end.Term, end.Headers)
 		if c.media != nil {
 			c.media.Close()
@@ -473,6 +505,8 @@ func (c *outboundCall) connectToRoom(ctx context.Context, lkNew RoomConfig, getR
 	}
 	c.lkRoom = r
 	c.lkRoomIn = local
+	c.storeParticipantAttrs(attrs)
+	c.snapshotParticipantAttrs()
 	if err := registerSignalingRPC(c.lkRoom, c.cc); err != nil {
 		return err
 	}
@@ -641,6 +675,7 @@ func (c *outboundCall) setStatus(v CallStatus) {
 	r.LocalParticipant.SetAttributes(map[string]string{
 		livekit.AttrSIPCallStatus: attr,
 	})
+	c.snapshotParticipantAttrs()
 }
 
 func (c *outboundCall) setExtraAttrs(hdrToAttr map[string]string, opts livekit.SIPHeaderOptions, cc Signaling, hdrs Headers) {
@@ -649,6 +684,7 @@ func (c *outboundCall) setExtraAttrs(hdrToAttr map[string]string, opts livekit.S
 		room := c.lkRoom.Room()
 		if room != nil {
 			room.LocalParticipant.SetAttributes(extra)
+			c.snapshotParticipantAttrs()
 		} else {
 			c.log.Warnw("could not set attributes on nil room", nil, "attrs", extra)
 		}