Ping Doesn't Work As Execpted, Return ERROR CODE == EAGAIN

Description

Ping command does't work properly, for example ping 8.8.8.8. I am sure that 8.8.8.8 is reachable. Console output:

redox login: user
Welcome to Redox OS!

user:~# ping 8.8.8.8
 : io error : Try again (os error 11)
user:~# ping www.google.com                                                                              
 : io error : Try again (os error 11)  

Environment info

• git rev-parse HEAD: 34d1ec9c2e9f7904b57547ca16d4c3145c109880
• rustc -V: rustc 1.61.0-nightly (58f11791a 2022-03-17)
• uname -a: Linux ccs-PC 5.15.0-56-generic #62~20.04.1-Ubuntu SMP Tue Nov 22 21:24:20 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Steps to reproduce

• Log in (make FILESYSTEM_SIZE=512 qemu kvm=no vga=no)
• Open terminal
• Input ping X.X.X.X

Extra

When event_queue.trigger_all is called, the on_echo_event callback is triggered. However, the io read function returns EAGAIN because of nothing to read in ping_fd's buffer during this period.

// netstack/source/src/smolnetd/scheme/icmp.rs

    fn write_buf(
        &mut self,
        file: &mut SocketFile<Self::DataT>,
        buf: &[u8],
    ) -> SyscallResult<Option<usize>> {
        if self.can_send() {
            match file.data.socket_type {
                IcmpSocketType::Echo => {
                    if buf.len() < mem::size_of::<u16>() {
                        return Err(SyscallError::new(syscall::EINVAL));
                    }
                    let (seq_buf, payload) = buf.split_at(mem::size_of::<u16>());
                    let seq_no = NetworkEndian::read_u16(seq_buf);
                    let icmp_repr = Icmpv4Repr::EchoRequest {
                        ident: file.data.ident,
                        seq_no,
                        data: payload,
                    };

                    let icmp_payload = self.send(icmp_repr.buffer_len(), file.data.ip)
                        .map_err(|_| syscall::Error::new(syscall::EINVAL))?;
                    let mut icmp_packet = Icmpv4Packet::new_unchecked(icmp_payload);
                    //TODO: replace Default with actual caps
                    icmp_repr.emit(&mut icmp_packet, &Default::default());
                    Ok(Some(buf.len()))
                }
                IcmpSocketType::Udp => {
                    Err(SyscallError::new(syscall::EINVAL))
                }
            }
        } else if file.flags & syscall::O_NONBLOCK == syscall::O_NONBLOCK {
            Err(SyscallError::new(syscall::EAGAIN))
        } else {
            Ok(None) // internally scheduled to re-read
        }
    }

I try to figure it out by triggering time event only, and it seems to work:

diff --git a/src/ping/main.rs b/src/ping/main.rs
index 2c94104..3bbda3a 100644
--- a/src/ping/main.rs
+++ b/src/ping/main.rs
@@ -340,11 +340,11 @@ fn run() -> Result<()> {
              move |_| ping_.borrow_mut().on_echo_event())?;

     let ping_ = ping.clone();
-    event_queue
+    let time_queue_id = event_queue
         .add(time_fd as RawFd,
              move |_| ping_.borrow_mut().on_time_event())?;

-    event_queue.trigger_all(event::Event {
+    event_queue.trigger(time_queue_id, event::Event {
         fd: 0,
         flags: syscall::EventFlags::empty(),
     })?;