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::nlmsghdr;
   5 use nix::libc::RTMGRP_IPV4_IFADDR;
   6 use nix::libc::RTMGRP_IPV6_IFADDR;
   7 use nix::libc::RTMGRP_LINK;
   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
  18 use crate::Error;
  19 use crate::Update;
  20
  21 pub(crate) struct WatchHandle {
  22     // PROBLEM: close() doesn't cancel recv() for a netlink socket
  23     sockfd: OwnedFd,
  24 }
  25
  26 pub(crate) fn watch_interfaces<F: FnMut(Update) + 'static>(
  27     callback: F,
  28 ) -> Result<WatchHandle, Error> {
  29     let sockfd = start_watcher_thread(callback)?;
  30     Ok(WatchHandle { sockfd })
  31 }
  32
  33 fn start_watcher_thread<F: FnMut(Update) + 'static>(callback: F) -> Result<OwnedFd, Error> {
  34     let sockfd = socket(AddressFamily::Netlink, SockType::Raw, SockFlag::empty(), Some(SockProtocol::NetlinkRoute))
  35         .map_err(|_| Error::Internal)?; // TODO: proper errors
  36     let sa_nl = NetlinkAddr::new(0, (RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR) as u32);
  37     bind(sockfd.as_raw_fd(), &sa_nl).map_err(|_| Error::Internal)?; // TODO: proper errors
  38     let fd = sockfd.as_raw_fd();
  39     println!("netlink socket on fd {}", fd);
  40
  41     std::thread::spawn(move || {
  42         println!("watch thread running");
  43         let mut buf = [0u8; 4096];
  44         // recvmsg?
  45         while let Ok(n) = recv(fd, &mut buf, MsgFlags::empty()) {
  46             println!("something on the netlink socket: {} bytes", n);
  47             let nlmsg_ptr = &buf as *const _ as *const nlmsghdr;
  48             let nlmsg = unsafe { &*nlmsg_ptr };
  49             // Right conventionally there's some trick here involving macros NLMSG_OK
  50             // I can presumably do this using NetlinkGeneric too
  51             // It's unclear whether this is worse or not - need to know what those macros do
  52         }
  53         println!("netlink recv thread terminating");
  54     });
  55
  56     Ok(sockfd)
  57 }