finding Replaces header Call-ID in dialog map

I am trying to figure the best way to find the Call-ID in the srf._dialogs map when I get an INVITE or REFER with a Replaces header. In an attended transfer scenario, the endpoint sets up a dialog with the transferTarget and then sends a REFER to the transferee with a Replaces header containing the Call-ID of the dialog with the transferTarget.

In this scenario, drachtio is acting as a B2BUA between all the endpoints (and media is just peer to peer for now), so I actually need to find the dialog of the other side of the call (UAS dialog if received on the UAC side, and vice versa).

I have a gist of a latter diagram and sip trace of a successful attended transfer through drachtio here.

I am wondering if there is a better way to find the dialog associated with the Call-ID in the replaces header than what I am doing below by looping through the map of dialogs:

// referParams has all the parsed elements of a refer header
findReplacesDialog(srf._dialogs, referParams.replacesCallId);

const findReplacesDialog = (dialogMap, replacesCallId) => {
  var replacesDialog;

  const dialogCallIds = Array.from(dialogMap.keys());
  debug('Dialog Keys');
  debug(dialogCallIds);
  dialogCallIds.every((dialog, i) => {
    const currentDialog = dialogMap.get(dialog);
    const previousDialog = dialogMap.get(dialogCallIds[i-1]);
    const nextDialog = dialogMap.get(dialogCallIds[i+1]);

    debug('replacesCallId');
    debug(replacesCallId);
    debug('currentDialog.sip.callId');
    debug(currentDialog.sip.callId);
    if (nextDialog) { debug('nextDialog.sip.callId'); debug(nextDialog.sip.callId); }
    if (previousDialog) { debug('previousDialog.sip.callId'); debug(previousDialog.sip.callId) }

    if (currentDialog.sip.callId == replacesCallId) {
      debug(`FOUND A MATCH!!!! ${dialog}`);
      // drachtio adds ';uas' when it's the UAS of the dialog
      if (dialog == `${replacesCallId};uas`) {
        debug('UAS dialog: setting repalcesDialog equal to previousDialog');
        replacesDialog = previousDialog;
        return false;
      } else {
        debug('UAC dialog: setting repalcesDialog equal to nextDialog');
        replacesDialog = nextDialog;
        return false;
      }
    }

    return true;
  });

  return replacesDialog;
};

[davehorton]

OK, just published drachtio-srf@4.4.7, which adds

findDialogById(stackDialogId), and
findDialogByCallIDAndFromTag(callId, tag)

Note: these functions require drachtio-server@v0.8.2-rc2 or above (currently the head of the ‘develop’ branch), which formats dialog ids as {Call-ID};from-tag={from-tag}.

additionally, if you have a reference to a dialog (uas or uac) that was created by Srf#createB2BUA then dialog.other will be a reference to the paired dialog.

So handling attended transfer should be a matter of:

• parsing the Refer-To header (I think I need to add a utility function somewhere to make that easier, probably in drachtio-sip), then
• calling findDialogByCallIDAndFromTag(callId, tag) to retrieve the dialog being replaced, then
• reinviting the paired dialog by calling Dialog#modify on dialog.other.

I’ll leave this issue open for now until you have time to test.

[byoungdale]

I was able to test. This worked great! Thank you so much