freeswitch capture sip error and propagate the same error (#1489)

* fix: propagate SIP 488 error to SBC on endpoint allocation failure

When FreeSWITCH returns a SIP 488 'Not Acceptable Here' error during
endpoint allocation (e.g., codec incompatibility), this error was not
being propagated back to the SBC/client. Instead, the call would wait
indefinitely for websocket commands or return a generic 603 response.

Implementation:
- In _evalEndpointPrecondition(), detect SipError by checking
  err.type === 'SipError' or err.name === 'SipError'
- Extract the SIP status code (e.g., 488), reason, and the Reason
  header from the error response (e.g., Q.850;cause=88;text=INCOMPATIBLE_DESTINATION)
- Send the SIP error response immediately to the SBC with:
  - X-Reason header: endpoint allocation failure details
  - Reason header: original Q.850 cause from FreeSWITCH
- Notify call status change as Failed with proper SIP status
- Release the call immediately instead of waiting for commands

Also added fallback handling in InboundCallSession._onTasksDone() to
propagate the stored error if immediate send was not possible.

* wip

* Simplify SipError check to only use err.name

lib/session/call-session.js

@@ -2500,6 +2500,36 @@ Duration=${duration} `
       }
       else {
         this.logger.error(err, `Error attempting to allocate endpoint for for task ${task.name}`);
+        // Check for SipError type (e.g., 488 codec incompatibility)
+        const isSipError = err.name === 'SipError';
+        if (isSipError && err.status) {
+          // Extract Reason header from SIP response if available (e.g., Q.850;cause=88;text="INCOMPATIBLE_DESTINATION")
+          const sipReasonHeader = err.res?.msg?.headers?.reason;
+          this._endpointAllocationError = {
+            status: err.status,
+            reason: err.reason || 'Endpoint Allocation Failed',
+            sipReasonHeader
+          };
+          this.logger.info({endpointAllocationError: this._endpointAllocationError},
+            'Captured SipError for propagation to SBC');
+
+          // Send SIP error response immediately for inbound calls
+          if (this.res && !this.res.finalResponseSent) {
+            this.logger.info(`Sending ${err.status} response to SBC due to SipError`);
+            this.res.send(err.status, {
+              headers: {
+                'X-Reason': `endpoint allocation failure: ${err.reason || 'Endpoint Allocation Failed'}`,
+                ...(sipReasonHeader && {'Reason': sipReasonHeader})
+              }
+            });
+            this._notifyCallStatusChange({
+              callStatus: CallStatus.Failed,
+              sipStatus: err.status,
+              sipReason: err.reason || 'Endpoint Allocation Failed'
+            });
+            this._callReleased();
+          }
+        }
         throw new Error(`${BADPRECONDITIONS}: unable to allocate endpoint`);
       }
     }

lib/session/inbound-call-session.js

@@ -60,6 +60,19 @@ class InboundCallSession extends CallSession {
           }
         });
       }
+      else if (this._endpointAllocationError) {
+        // Propagate SIP error from endpoint allocation failure back to the client
+        const {status, reason, sipReasonHeader} = this._endpointAllocationError;
+        this.rootSpan.setAttributes({'call.termination': `endpoint allocation SIP error ${status}`});
+        this.logger.info({endpointAllocationError: this._endpointAllocationError},
+          `InboundCallSession:_onTasksDone generating ${status} due to endpoint allocation failure`);
+        this.res.send(status, {
+          headers: {
+            'X-Reason': `endpoint allocation failure: ${reason}`,
+            ...(sipReasonHeader && {'Reason': sipReasonHeader})
+          }
+        });
+      }
       else {
         this.rootSpan.setAttributes({'call.termination': 'tasks completed without answering call'});
         this.logger.info('InboundCallSession:_onTasksDone auto-generating non-success response to invite');