fix: return distinct error when not able to allocate interface index

pkg/cmd/daemoncmd/connmgr.go

@@ -44,6 +44,8 @@ import (
 var (
  // ErrNoPortsAvailable is returned when no ports are available.
  ErrNoPortsAvailable = status.Errorf(codes.FailedPrecondition, "no ports available")
+ // ErrNoIndexAvailable is returned when no utun index is available.
+ ErrNoIndexAvailable = status.Errorf(codes.FailedPrecondition, "no utun index available")
  // ErrNotConnected is returned when the node is not connected to the mesh.
  ErrNotConnected = status.Errorf(codes.FailedPrecondition, "not connected to the specified network")
  // ErrAlreadyConnected is returned when the node is already connected to the mesh.
@@ -336,7 +338,7 @@ func (m *ConnManager) assignUTUNIndex(connID string) (uint16, error) {
  }
  index++
  if index > maxIndex {
- return 0, ErrNoPortsAvailable
+ return 0, ErrNoIndexAvailable
  }
  }
 }