Mac build support

[matejsp]

Unable to build on mac Monterey 12.2.1. Any chance to get around this?

➜  virtiofsd git:(main) cargo build --release
   Compiling vhost v0.3.0
   Compiling futures-executor v0.3.19
   Compiling structopt v0.3.26
error[E0432]: unresolved import `vmm_sys_util::eventfd`
  --> /Users/myuser/.cargo/registry/src/g.yxqyang.asia-1ecc6299db9ec823/vhost-0.3.0/src/backend.rs:16:19
   |
16 | use vmm_sys_util::eventfd::EventFd;
   |                   ^^^^^^^ could not find `eventfd` in `vmm_sys_util`

error[E0432]: unresolved import `vmm_sys_util::sock_ctrl_msg`
  --> /Users/myuser/.cargo/registry/src/g.yxqyang.asia-1ecc6299db9ec823/vhost-0.3.0/src/vhost_user/connection.rs:18:19
   |
18 | use vmm_sys_util::sock_ctrl_msg::ScmSocket;
   |                   ^^^^^^^^^^^^^ could not find `sock_ctrl_msg` in `vmm_sys_util`

   Compiling futures v0.3.19
error[E0599]: no method named `send_with_fds` found for struct `UnixStream` in the current scope
   --> /Users/myuser/.cargo/registry/src/g.yxqyang.asia-1ecc6299db9ec823/vhost-0.3.0/src/vhost_user/connection.rs:142:19
    |
142 |         self.sock.send_with_fds(iovs, rfds).map_err(Into::into)
    |                   ^^^^^^^^^^^^^ method not found in `UnixStream`

error[E0599]: no method named `recv_with_fds` found for struct `UnixStream` in the current scope
   --> /Users/myuser/.cargo/registry/src/g.yxqyang.asia-1ecc6299db9ec823/vhost-0.3.0/src/vhost_user/connection.rs:317:45
    |
317 |         let (bytes, _) = unsafe { self.sock.recv_with_fds(&mut iovs, &mut [])? };
    |                                             ^^^^^^^^^^^^^ method not found in `UnixStream`

error[E0599]: no method named `recv_with_fds` found for struct `UnixStream` in the current scope
   --> /Users/myuser/.cargo/registry/src/g.yxqyang.asia-1ecc6299db9ec823/vhost-0.3.0/src/vhost_user/connection.rs:349:38
    |
349 |         let (bytes, fds) = self.sock.recv_with_fds(iovs, &mut fd_array)?;
    |                                      ^^^^^^^^^^^^^ method not found in `UnixStream`

Some errors have detailed explanations: E0432, E0599.
For more information about an error, try `rustc --explain E0432`.
error: could not compile `vhost` due to 5 previous errors
warning: build failed, waiting for other jobs to finish...
error: build failed

[jiangliu]

We need to find macos counterparts for send fd with UDS and eventfd:)

[slp]

Funny, right now I'm working on implementing macOS support on vmm-sys-util (which will enable vhost and vhost-user-backend to work on it too). Sending ancillary data (i.e. for sending fds) is supported on macOS, so it's just a matter of including the traits. As for eventfd and epoll, I'm emulating the first with pipefd and the second with kqueue. They aren't semantically identical, but they're close enough to allow daemons consuming vhost-user-backend to work properly.

[jiangliu]

The vmm_sys_util::sock_ctrl_msg related issues are solved by enhancing the vmm_sys_util, but the EventFd is problematic.

[jiangliu]

Funny, right now I'm working on implementing macOS support on vmm-sys-util (which will enable vhost and vhost-user-backend to work on it too). Sending ancillary data (i.e. for sending fds) is supported on macOS, so it's just a matter of including the traits. As for eventfd and epoll, I'm emulating the first with pipefd and the second with kqueue. They aren't semantically identical, but they're close enough to allow daemons consuming vhost-user-backend to work properly.

I have done a quick poc for sock_ctrl_msg:)

[stefano-garzarella]

@slp @jiangliu any plan on working on this?

If you have some PoC to share, maybe this could become a good first issue for some Mac user.