Add initial implementation of Hold/Resume call

Author: Kaian

pkg/sip/inbound.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/frostbyte73/core"
 	"github.com/icholy/digest"
+	psdp "github.com/pion/sdp/v3"
 	"github.com/pkg/errors"
 
 	msdk "github.com/livekit/media-sdk"
@@ -1003,6 +1004,7 @@ func (c *inboundCall) runMediaConn(tid traceid.ID, offerData []byte, enc livekit
 	if err != nil {
 		return nil, err
 	}
+	c.cc.nextSDPVersion = answer.SDP.Origin.SessionVersion + 1
 	c.mon.SDPSize(len(answerData), false)
 	c.log().Debugw("SDP answer", "sdp", string(answerData))
 
@@ -1421,6 +1423,48 @@ func (c *inboundCall) transferCall(ctx context.Context, transferTo string, heade
 
 }
 
+func (c *inboundCall) holdCall(ctx context.Context) error {
+	c.log.Infow("holding inbound call")
+
+	// Disable media timeout during hold to prevent call termination
+	if c.media != nil {
+		c.media.EnableTimeout(false)
+		c.log.Infow("media timeout disabled for hold")
+	}
+
+	err := c.cc.holdCall(ctx)
+	if err != nil {
+		c.log.Infow("inbound call failed to hold", "error", err)
+		// Re-enable timeout if hold failed
+		if c.media != nil {
+			c.media.EnableTimeout(true)
+		}
+		return err
+	}
+
+	c.log.Infow("inbound call held")
+	return nil
+}
+
+func (c *inboundCall) unholdCall(ctx context.Context) error {
+	c.log.Infow("unholding inbound call")
+
+	err := c.cc.unholdCall(ctx)
+	if err != nil {
+		c.log.Infow("inbound call failed to unhold", "error", err)
+		return err
+	}
+
+	// Re-enable media timeout after unhold
+	if c.media != nil {
+		c.media.EnableTimeout(true)
+		c.log.Infow("media timeout re-enabled after unhold")
+	}
+
+	c.log.Infow("inbound call unheld")
+	return nil
+}
+
 func (s *Server) newInbound(log logger.Logger, contact URI, invite *sip.Request, inviteTx sip.ServerTransaction, getHeaders setHeadersFunc) *sipInbound {
 	c := &sipInbound{
 		log:      log,
@@ -1467,13 +1511,15 @@ type sipInbound struct {
 	referDone  chan error
 
 	mu              sync.RWMutex
+	sdpMu           sync.RWMutex
 	lastSDP         []byte
 	inviteOk        *sip.Response
 	nextRequestCSeq uint32
 	referCseq       uint32
 	ringing         chan struct{}
 	acked           core.Fuse
 	setHeaders      setHeadersFunc
+	nextSDPVersion  uint64
 }
 
 func (c *sipInbound) ValidateInvite() error {
@@ -1952,3 +1998,136 @@ func (c *sipInbound) CloseWithStatus(code sip.StatusCode, status string) {
 		c.drop()
 	}
 }
+
+func (c *sipInbound) setSDPMediaDirection(sdpData []byte, direction string) ([]byte, error) {
+	if len(sdpData) == 0 {
+		return sdpData, nil
+	}
+
+	// Parse SDP using the base Parse function (works for both offers and answers)
+	desc, err := sdp.Parse(sdpData)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse SDP: %w", err)
+	}
+
+	// Modify direction attributes in each media description
+	for _, mediaDesc := range desc.SDP.MediaDescriptions {
+		if mediaDesc == nil {
+			continue
+		}
+
+		// Find and remove existing direction attributes
+		newAttributes := slices.DeleteFunc(mediaDesc.Attributes, func(attr psdp.Attribute) bool {
+			switch attr.Key {
+			case "sendrecv", "sendonly", "recvonly", "inactive":
+				return true
+			default:
+				return false
+			}
+		})
+
+		// Add the new direction attribute
+		newAttributes = append(newAttributes, psdp.Attribute{
+			Key:   direction,
+			Value: "",
+		})
+
+		mediaDesc.Attributes = newAttributes
+	}
+
+	// Set session version to current value plus current unix timestamp
+	desc.SDP.Origin.SessionVersion = c.nextSDPVersion
+	c.nextSDPVersion += 1
+
+	// Marshal back to bytes
+	modifiedSDP, err := desc.SDP.Marshal()
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal modified SDP: %w", err)
+	}
+
+	return modifiedSDP, nil
+}
+
+func (c *sipInbound) createMediaUpdateRequest(direction string) (*sip.Request, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.sdpMu.Lock()
+	defer c.sdpMu.Unlock()
+
+	if c.invite == nil || c.inviteOk == nil {
+		return nil, psrpc.NewErrorf(psrpc.FailedPrecondition, "can't update media direction for non established call")
+	}
+
+	// Create INVITE with SDP modified for media update
+	req := sip.NewRequest(sip.INVITE, c.invite.Recipient)
+	c.setCSeq(req)
+
+	// Copy headers from original INVITE
+	req.AppendHeader(c.invite.From())
+	req.AppendHeader(c.invite.To())
+	req.AppendHeader(c.invite.CallID())
+	req.AppendHeader(c.contact)
+	req.AppendHeader(sip.NewHeader("Content-Type", "application/sdp"))
+	req.AppendHeader(sip.NewHeader("Allow", "INVITE, ACK, CANCEL, BYE, NOTIFY, REFER, MESSAGE, OPTIONS, INFO, SUBSCRIBE"))
+
+	// Modify SDP to set direction
+	sdpOffer := c.inviteOk.Body()
+	if len(sdpOffer) > 0 {
+		modifiedSDP, err := c.setSDPMediaDirection(sdpOffer, direction)
+		if err != nil {
+			return nil, err
+		}
+		req.SetBody(modifiedSDP)
+	}
+
+	c.swapSrcDst(req)
+	return req, nil
+}
+
+func (c *sipInbound) sendMediaUpdateRequest(ctx context.Context, direction string) error {
+	req, err := c.createMediaUpdateRequest(direction)
+	if err != nil {
+		return err
+	}
+
+	// Send the INVITE request
+	tx, err := c.Transaction(req)
+	if err != nil {
+		return err
+	}
+	defer tx.Terminate()
+
+	resp, err := sipResponse(ctx, tx, c.s.closing.Watch(), nil)
+	if err != nil {
+		return err
+	}
+
+	if resp.StatusCode != sip.StatusOK {
+		return &livekit.SIPStatus{
+			Code:   livekit.SIPStatusCode(resp.StatusCode),
+			Status: resp.Reason,
+		}
+	}
+
+	// Send ACK for the unhold INVITE
+	ack := sip.NewAckRequest(req, resp, nil)
+	if err := c.WriteRequest(ack); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (c *sipInbound) holdCall(ctx context.Context) error {
+	if err := c.sendMediaUpdateRequest(ctx, "sendonly"); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (c *sipInbound) unholdCall(ctx context.Context) error {
+	if err := c.sendMediaUpdateRequest(ctx, "sendrecv"); err != nil {
+		return err
+	}
+	return nil
+}