How to use Linux Network Namespaces for per processes routing?

 1371         if (atomic_read(&p->real_cred->user->processes) >=
 1372                         task_rlimit(p, RLIMIT_NPROC)) {

1504    if ((current->flags & PF_NPROC_EXCEEDED) &&
1505        atomic_read(&current_user()->processes) > rlimit(RLIMIT_NPROC)) {
1506        retval = -EAGAIN;
1507        goto out_ret;

 atomic_t processes;    /* How many processes does this user have? */

1655 bad_fork_cleanup_count:
1656    atomic_dec(&p->cred->user->processes);

313 /*
314 * Copy credentials for the new process created by fork()
315 *
316 * We share if we can, but under some circumstances we have to generate a new
317 * set.
318 *
319 * The new process gets the current process's subjective credentials as its
320 * objective and subjective credentials
321 */
322 int copy_creds(struct task_struct *p, unsigned long clone_flags)

339         atomic_inc(&p->cred->user->processes);

372 atomic_inc(&new->user->processes);

   RLIMIT_NPROC
          The maximum number of processes (or, more precisely on Linux,
          threads) that can be created for the real user ID of the
          calling process.  Upon encountering this limit, fork(2) fails
          with the error EAGAIN.

#!/bin/bash

sudo ip netns exec controlnet sudo -u myuser bash -s <<'EOF'
startServer() {
  local endTime startTime retval
  while :; do
    startTime=$SECONDS
    ./hlds_run -game cstrike -pidfile ogp_game_startup.pid +map de_dust +ip 1.2.3.4 +port 27015 +maxplayers 14; retval=$?
    endTime=$SECONDS
    if (( (endTime - startTime) > 15 )); then
      echo "Server crashed with exit code $retval.  Respawning..." >&2
    else
      echo "Server exited with status $retval after less than 15 seconds" >&2
      echo "  not attempting to respawn" >&2
      return "$retval"
    fi
  sleep 3
  done
}

cd /home/ || exit
startServer
EOF