code.octet-stream.net Git - netwatcher/blob - src/watch_linux.rs

   1 use std::os::fd::AsRawFd;
   2 use std::os::fd::OwnedFd;
   3
   4 use nix::libc::RTMGRP_IPV4_IFADDR;
   5 use nix::libc::RTMGRP_IPV6_IFADDR;
   6 use nix::libc::RTMGRP_LINK;
   7 use nix::sys::socket::bind;
   8 use nix::sys::socket::recv;
   9 use nix::sys::socket::socket;
  10 use nix::sys::socket::AddressFamily;
  11 use nix::sys::socket::MsgFlags;
  12 use nix::sys::socket::NetlinkAddr;
  13 use nix::sys::socket::SockFlag;
  14 use nix::sys::socket::SockProtocol;
  15 use nix::sys::socket::SockType;
  16
  17 use crate::Error;
  18 use crate::List;
  19 use crate::Update;
  20
  21 pub(crate) struct WatchHandle {
  22     // PROBLEM: close() doesn't cancel recv() for a netlink socket
  23     // SOLUTION: open a pipe() and use poll() inside the thread to watch for cancellation too
  24     sockfd: OwnedFd,
  25 }
  26
  27 pub(crate) fn watch_interfaces<F: FnMut(Update) + Send + 'static>(
  28     callback: F,
  29 ) -> Result<WatchHandle, Error> {
  30     let sockfd = start_watcher_thread(callback)?;
  31     Ok(WatchHandle { sockfd })
  32 }
  33
  34 fn start_watcher_thread<F: FnMut(Update) + Send + 'static>(mut callback: F) -> Result<OwnedFd, Error> {
  35     let sockfd = socket(AddressFamily::Netlink, SockType::Raw, SockFlag::empty(), Some(SockProtocol::NetlinkRoute))
  36         .map_err(|_| Error::Internal)?; // TODO: proper errors
  37     let sa_nl = NetlinkAddr::new(0, (RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR) as u32);
  38     bind(sockfd.as_raw_fd(), &sa_nl).map_err(|_| Error::Internal)?; // TODO: proper errors
  39     let fd = sockfd.as_raw_fd();
  40     println!("netlink socket on fd {}", fd);
  41
  42     std::thread::spawn(move || {
  43         println!("watch thread running");
  44         let mut prev_list = List::default();
  45         let mut buf = [0u8; 4096];
  46         let mut handle_update = move |new_list: List| {
  47             if new_list == prev_list {
  48                 return;
  49             }
  50             let update = Update {
  51                 interfaces: new_list.0.clone(),
  52                 diff: new_list.diff_from(&prev_list),
  53             };
  54             (callback)(update);
  55             prev_list = new_list;
  56         };
  57
  58         if let Ok(initial) = crate::list::list_interfaces() {
  59             handle_update(initial);
  60         };
  61
  62         while let Ok(n) = recv(fd, &mut buf, MsgFlags::empty()) {
  63             println!("something on the netlink socket: {} bytes", n);
  64             let Ok(new_list) = crate::list::list_interfaces() else {
  65                 continue;
  66             };
  67             handle_update(new_list);
  68         }
  69         println!("netlink recv thread terminating");
  70     });
  71
  72     Ok(sockfd)
  73 }