pid.rs

use log::info;
use nix::{
    sched::{unshare, CloneFlags},
    sys::stat::stat,
    unistd::{getpid, getppid, gettid},
};
pub type StratisResult<T> = Result<T, StratisError>;

#[derive(Debug)]
pub enum StratisError {
    Msg(String),
    Nix(nix::Error),
}

impl From<nix::Error> for StratisError {
    fn from(err: nix::Error) -> StratisError {
        StratisError::Nix(err)
    }
}

/// Path to the root mount namespace
const INIT_MNT_NS_PATH: &str = "/proc/1/ns/mnt";

fn main() {
    env_logger::init();

    let main_pid = getpid();
    let ppid = getppid();
    let tid = gettid();

    info!("main pid: {}", main_pid);
    info!("ppid: {}", ppid);
    info!("tid: {}", tid);

    unshare_namespace().unwrap();
}

/// Check if the stratisd mount namespace for this thread is in the root namespace.
fn is_in_root_namespace() -> StratisResult<bool> {
    let tid = gettid();

    let pid_one_stat = stat(INIT_MNT_NS_PATH)?;
    let self_stat = stat(format!("/proc/self/task/{}/ns/mnt", tid).as_str())?;
    info!("pid_one_stat.st_ino: {}", pid_one_stat.st_ino);
    info!("self_stat.st_ino: {}", self_stat.st_ino);

    info!("pid_one_stat.st_dev: {}", pid_one_stat.st_dev);
    info!("self_stat.st_dev: {}", self_stat.st_dev);

    Ok(pid_one_stat.st_ino == self_stat.st_ino && pid_one_stat.st_dev == self_stat.st_dev)
}

fn unshare_namespace() -> StratisResult<()> {
    if is_in_root_namespace()? {
        info!("unshare");
        unshare(CloneFlags::CLONE_NEWNS)?;
        assert!(!is_in_root_namespace()?);
    }
    info!("success");
    Ok(())
}