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

   1 use std::os::fd::AsRawFd;
   2 use std::os::fd::OwnedFd;
   3 use std::sync::mpsc;
   4
   5 use nix::libc::poll;
   6 use nix::libc::pollfd;
   7 use nix::libc::POLLIN;
   8 use nix::sys::socket::bind;
   9 use nix::sys::socket::recv;
  10 use nix::sys::socket::socket;
  11 use nix::sys::socket::AddressFamily;
  12 use nix::sys::socket::MsgFlags;
  13 use nix::sys::socket::NetlinkAddr;
  14 use nix::sys::socket::SockFlag;
  15 use nix::sys::socket::SockProtocol;
  16 use nix::sys::socket::SockType;
  17 use nix::unistd::pipe;
  18
  19 use crate::Error;
  20 use crate::List;
  21 use crate::Update;
  22
  23 const RTMGRP_IPV4_IFADDR: u32 = 0x10;
  24 const RTMGRP_IPV6_IFADDR: u32 = 0x20;
  25 const RTMGRP_LINK: u32 = 0x01;
  26
  27 pub(crate) struct WatchHandle {
  28     // Close on drop, which will be detected by poll in background thread
  29     pipefd: Option<OwnedFd>,
  30
  31     // Detect when thread has completed
  32     complete: Option<mpsc::Receiver<()>>,
  33 }
  34
  35 impl Drop for WatchHandle {
  36     fn drop(&mut self) {
  37         drop(self.pipefd.take());
  38         let _ = self.complete.take().unwrap().recv();
  39     }
  40 }
  41
  42 pub(crate) fn watch_interfaces<F: FnMut(Update) + Send + 'static>(
  43     callback: F,
  44 ) -> Result<WatchHandle, Error> {
  45     let (pipefd, complete) = start_watcher_thread(callback)?;
  46     Ok(WatchHandle {
  47         pipefd: Some(pipefd),
  48         complete: Some(complete),
  49     })
  50 }
  51
  52 fn start_watcher_thread<F: FnMut(Update) + Send + 'static>(
  53     mut callback: F,
  54 ) -> Result<(OwnedFd, mpsc::Receiver<()>), Error> {
  55     let sockfd = socket(
  56         AddressFamily::Netlink,
  57         SockType::Raw,
  58         SockFlag::SOCK_NONBLOCK,
  59         Some(SockProtocol::NetlinkRoute),
  60     )
  61     .map_err(|e| Error::CreateSocket(e.to_string()))?;
  62     let sa_nl = NetlinkAddr::new(
  63         0,
  64         (RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR) as u32,
  65     );
  66     bind(sockfd.as_raw_fd(), &sa_nl).map_err(|e| Error::Bind(e.to_string()))?;
  67     let (pipe_rd, pipe_wr) = pipe().map_err(|e| Error::CreatePipe(e.to_string()))?;
  68
  69     let mut prev_list = List::default();
  70     let mut handle_update = move |new_list: List| {
  71         if new_list == prev_list {
  72             return;
  73         }
  74         let update = Update {
  75             interfaces: new_list.0.clone(),
  76             diff: new_list.diff_from(&prev_list),
  77         };
  78         (callback)(update);
  79         prev_list = new_list;
  80     };
  81
  82     // Now that netlink socket is open, provide an initial update.
  83     // By having this outside the thread we can return an error synchronously if it
  84     // looks like we're going to have trouble listing interfaces.
  85     handle_update(crate::list::list_interfaces()?);
  86
  87     let (complete_tx, complete_rx) = mpsc::channel();
  88
  89     std::thread::spawn(move || {
  90         let mut buf = [0u8; 4096];
  91
  92         loop {
  93             let mut fds = [
  94                 pollfd {
  95                     fd: sockfd.as_raw_fd(),
  96                     events: POLLIN,
  97                     revents: 0,
  98                 },
  99                 pollfd {
 100                     fd: pipe_rd.as_raw_fd(),
 101                     events: POLLIN,
 102                     revents: 0,
 103                 },
 104             ];
 105             unsafe {
 106                 poll(&mut fds as *mut _, 2, -1);
 107             }
 108             if fds[0].revents != 0 {
 109                 // netlink socket had something happen
 110                 if recv(sockfd.as_raw_fd(), &mut buf, MsgFlags::empty()).is_ok() {
 111                     let Ok(new_list) = crate::list::list_interfaces() else {
 112                         continue;
 113                     };
 114                     handle_update(new_list);
 115                 }
 116             }
 117             if fds[1].revents != 0 {
 118                 // pipe had something happen
 119                 break;
 120             }
 121         }
 122
 123         drop(complete_tx);
 124     });
 125
 126     Ok((pipe_wr, complete_rx))
 127 }