Title: reply_thr_get() / ip
ip's reply_thr_get() is very similar to udp's reply_thr_get().
reply_thr_get() calls (indirectly) a function from a higher layer (e.g., sr_get_userdata()), udp_ip_arrived(). If sr_get_userdata() is called, it reports to a user process whether a previous operation requested by the user process was successful. reply, reply_thr_get()'s second parameter, indicates whether the previous operation was successful.
After sending the message to the user process, sr_get_userdata() processes the messages in the write or ioctl queue.