add vty_is_active()

For async callbacks it is useful to determine whether a given VTY pointer is still valid.

For example, in osmo-msc, a silent call can be triggered by VTY, which causes a
Paging. The paging_cb then writes to the VTY console that the silent call has
succeeded. Unless the telnet vty session has already ended, in which case
osmo-msc crashes; e.g. from an osmo_interact_vty.py command invocation. With
this function, osmo-msc can ask whether the vty pointer passed to the paging
callback is still active, and skip vty_out() if not.

Change-Id: I42cf2af47283dd42c101faae0fac293c3a68d599

0 files changed, 0 insertions, 0 deletions