Failing example with LWN's "Namespaces in operation, part 4: more on PID namespaces"

Question

The final example from this article fails to work as intended. This is the code:

• simple_init.c
• ns_child_exec.c
• orphan.c
• ns_run.c

My environment is Fedora 24, and this is the output I should receive:

• # ./ns_child_exec -p ./simple_init -v
      init: my PID is 1
  init$
      init: SIGCHLD handler: PID 3 terminated
  

• # ps -C sleep -C simple_init
    PID TTY          TIME CMD
   9147 pts/8    00:00:00 simple_init
  # ./ns_run -f -n /proc/9147/ns/pid ./orphan
  Parent (PID=2) created child with PID 3
  Parent (PID=2; PPID=0) terminating
  # 
  Child  (PID=3) now an orphan (parent PID=1)
  Child  (PID=3) terminating
  

However, this is the output I receive:

• # sudo ./ns_child_exec -p ./simple_init -v
      init: my PID is 1
  init$ 
  

• # sudo ps -C sleep -C simple_init
    PID TTY          TIME CMD
   2665 pts/2    00:00:00 simple_init
  # sudo ./ns_run -f -n /proc/2665/ns/pid ./orphan
  Parent (PID=2) created child with PID 3
  Parent (PID=2; PPID=0) terminating
  # sudo ./ns_run -f -n /proc/2665/ns/pid ./orphan
  Parent (PID=4) created child with PID 5
  Parent (PID=4; PPID=0) terminating
  # sudo ./ns_run -f -n /proc/2665/ns/pid ./orphan
  Parent (PID=6) created child with PID 7
  Parent (PID=6; PPID=0) terminating
  # sudo ./ns_run -f -n /proc/2665/ns/pid ./orphan
  Parent (PID=8) created child with PID 9
  Parent (PID=8; PPID=0) terminating
  

It's as if orphan's child does nothing, and is never re-parented. However, running orphan via simple_init's shell (without ns_run) works as expected.