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::poll;
   5 use nix::libc::pollfd;
   6 use nix::libc::POLLIN;
   7 use nix::libc::RTMGRP_IPV4_IFADDR;
   8 use nix::libc::RTMGRP_IPV6_IFADDR;
   9 use nix::libc::RTMGRP_LINK;
  10 use nix::sys::socket::bind;
  11 use nix::sys::socket::recv;
  12 use nix::sys::socket::socket;
  13 use nix::sys::socket::AddressFamily;
  14 use nix::sys::socket::MsgFlags;
  15 use nix::sys::socket::NetlinkAddr;
  16 use nix::sys::socket::SockFlag;
  17 use nix::sys::socket::SockProtocol;
  18 use nix::sys::socket::SockType;
  19 use nix::unistd::pipe;
  20
  21 use crate::Error;
  22 use crate::List;
  23 use crate::Update;
  24
  25 pub(crate) struct WatchHandle {
  26     // Dropping will close the fd which will be detected by poll
  27     _pipefd: OwnedFd,
  28 }
  29
  30 pub(crate) fn watch_interfaces<F: FnMut(Update) + Send + 'static>(
  31     callback: F,
  32 ) -> Result<WatchHandle, Error> {
  33     let pipefd = start_watcher_thread(callback)?;
  34     Ok(WatchHandle { _pipefd: pipefd })
  35 }
  36
  37 fn start_watcher_thread<F: FnMut(Update) + Send + 'static>(
  38     mut callback: F,
  39 ) -> Result<OwnedFd, Error> {
  40     let sockfd = socket(
  41         AddressFamily::Netlink,
  42         SockType::Raw,
  43         SockFlag::empty(),
  44         Some(SockProtocol::NetlinkRoute),
  45     )
  46     .map_err(|_| Error::Internal)?; // TODO: proper errors
  47     let sa_nl = NetlinkAddr::new(
  48         0,
  49         (RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR) as u32,
  50     );
  51     bind(sockfd.as_raw_fd(), &sa_nl).map_err(|_| Error::Internal)?; // TODO: proper errors
  52     let (pipe_rd, pipe_wr) = pipe().map_err(|_| Error::Internal)?;
  53
  54     let mut prev_list = List::default();
  55     let mut handle_update = move |new_list: List| {
  56         if new_list == prev_list {
  57             return;
  58         }
  59         let update = Update {
  60             interfaces: new_list.0.clone(),
  61             diff: new_list.diff_from(&prev_list),
  62         };
  63         (callback)(update);
  64         prev_list = new_list;
  65     };
  66
  67     // Now that netlink socket is open, provide an initial update.
  68     // By having this outside the thread we can return an error synchronously if it
  69     // looks like we're going to have trouble listing interfaces.
  70     handle_update(crate::list::list_interfaces()?);
  71
  72     std::thread::spawn(move || {
  73         let mut buf = [0u8; 4096];
  74
  75         loop {
  76             let mut fds = [
  77                 pollfd {
  78                     fd: sockfd.as_raw_fd(),
  79                     events: POLLIN,
  80                     revents: 0,
  81                 },
  82                 pollfd {
  83                     fd: pipe_rd.as_raw_fd(),
  84                     events: POLLIN,
  85                     revents: 0,
  86                 },
  87             ];
  88             unsafe {
  89                 poll(&mut fds as *mut _, 2, -1);
  90             }
  91             if fds[0].revents != 0 {
  92                 // netlink socket had something happen
  93                 if recv(sockfd.as_raw_fd(), &mut buf, MsgFlags::empty()).is_ok() {
  94                     let Ok(new_list) = crate::list::list_interfaces() else {
  95                         continue;
  96                     };
  97                     handle_update(new_list);
  98                 }
  99             }
 100             if fds[1].revents != 0 {
 101                 // pipe had something happen
 102                 break;
 103             }
 104         }
 105     });
 106
 107     Ok(pipe_wr)
 108 }