nal: Prevent looping until the stack successfully connects to remote

* `NetworkStack::connect()`:
  * Add timeout for connection attempt
  * Now returns the socket at TCP ESTABLISHED or CLOSED states, or after connection timeout
* Split `NetworkStack::update()` into `update()` (for controlling the clock) and `poll()` (for polling the smoltcp EthernetInterface)
* Also remove option `auto_time_update`; the main application is responsible for what values `embedded_time::clock::Clock::try_now()` should return

src/nal.rs

@@ -1,5 +1,5 @@
 use core::cell::RefCell;
-use core::convert::TryFrom;
+use core::convert::TryInto;
 use heapless::{consts, Vec};
 use embedded_nal as nal;
 use nal::nb;
@@ -40,7 +40,8 @@ where
     unused_handles: RefCell<Vec<net::socket::SocketHandle, consts::U16>>,
     time_ms: RefCell<u32>,
     last_update_instant: RefCell<Option<time::Instant<IntClock>>>,
-    clock: IntClock
+    clock: IntClock,
+    connection_timeout_ms: u32,
 }
 
 impl<'a, SPI, NSS, IntClock> NetworkStack<'a, SPI, NSS, IntClock>
@@ -49,7 +50,12 @@ where
     NSS: OutputPin,
     IntClock: time::Clock<T = u32>,
 {
-    pub fn new(interface: NetworkInterface<SPI, NSS>, sockets: net::socket::SocketSet<'a>, clock: IntClock) -> Self {
+    pub fn new(
+        interface: NetworkInterface<SPI, NSS>,
+        sockets: net::socket::SocketSet<'a>,
+        clock: IntClock,
+        connection_timeout_ms: u32,
+    ) -> Self {
         let mut unused_handles: Vec<net::socket::SocketHandle, consts::U16> = Vec::new();
         for socket in sockets.iter() {
             unused_handles.push(socket.handle()).unwrap();
@@ -62,13 +68,13 @@ where
             time_ms: RefCell::new(0),
             last_update_instant: RefCell::new(None),
             clock,
+            connection_timeout_ms,
         }
     }
 
-    // Include auto_time_update to allow Instant::now() to not be called
-    // Instant::now() is not safe to call in `init()` context
-    pub fn update(&self, auto_time_update: bool) -> Result<bool, NetworkError> {
-        if auto_time_update {
+    // Initiate or advance the timer, and return the duration in ms as u32.
+    fn update(&self) -> Result<u32, NetworkError> {
+        let mut duration_ms: u32 = 0;
         // Check if it is the first time the stack has updated the time itself
         let now = match *self.last_update_instant.borrow() {
             // If it is the first time, do not advance time
@@ -78,18 +84,39 @@ where
             Some(instant) => {
                 // Calculate elapsed time
                 let now = self.clock.try_now().map_err(|_| NetworkError::TimeFault)?;
-                    let duration = now.checked_duration_since(&instant).ok_or(NetworkError::TimeFault)?;
-                    let duration_ms = time::duration::Milliseconds::<u32>::try_from(duration).map_err(|_| NetworkError::TimeFault)?;
+                let mut duration = now.checked_duration_since(&instant);
+                // Normally, the wrapping clock should produce a valid duration.
+                // However, if `now` is earlier than `instant` (e.g. because the main 
+                // application cannot get a valid epoch time during initialisation, 
+                // we should still produce a duration that is just 1ms.
+                if duration.is_none() {
+                    self.time_ms.replace(0);
+                    duration = Some(Milliseconds(1_u32)
+                        .to_generic::<u32>(IntClock::SCALING_FACTOR)
+                        .map_err(|_| NetworkError::TimeFault)?);
+                }
+                let duration_ms_time: Milliseconds<u32> = duration.unwrap().try_into()
+                    .map_err(|_| NetworkError::TimeFault)?;
+                duration_ms = *duration_ms_time.integer();
                 // Adjust duration into ms (note: decimal point truncated)
-                    self.advance_time(*duration_ms.integer());
+                self.advance_time(duration_ms);
                 now
             }
         };
         self.last_update_instant.replace(Some(now));
+        Ok(duration_ms)
     }
+
+    fn advance_time(&self, duration_ms: u32) {
+        let time = self.time_ms.borrow().wrapping_add(duration_ms);
+        self.time_ms.replace(time);
+    }
+
+    // Poll on the smoltcp interface
+    fn poll(&self) -> Result<bool, NetworkError> {
         match self.network_interface.borrow_mut().poll(
             &mut self.sockets.borrow_mut(),
-            net::time::Instant::from_millis(*self.time_ms.borrow() as i64),
+            net::time::Instant::from_millis(*self.time_ms.borrow() as u32),
         ) {
             Ok(changed) => Ok(!changed),
             Err(_e) => {
@@ -98,11 +125,6 @@ where
         }
     }
 
-    pub fn advance_time(&self, duration: u32) {
-        let time = self.time_ms.try_borrow().unwrap().wrapping_add(duration);
-        self.time_ms.replace(time);
-    }
-
     fn get_ephemeral_port(&self) -> u16 {
         // Get the next ephemeral port
         let current_port = self.next_port.borrow().clone();
@@ -132,20 +154,27 @@ where
         }
     }
 
-    // Ideally connect is only to be performed in `init()` of `main.rs`
-    // Calling `Instant::now()` of `rtic::cyccnt` would face correctness issue during `init()`
     fn connect(
         &self,
         socket: Self::TcpSocket,
         remote: nal::SocketAddr,
     ) -> Result<Self::TcpSocket, Self::Error> {
-        let address = {
+        {
+            // If the socket has already been connected, ignore the connection
+            // request silently.
             let mut sockets = self.sockets.borrow_mut();
             let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(socket);
-            // If we're already in the process of connecting, ignore the request silently.
-            if internal_socket.is_open() {
-                return Ok(socket);
+            if internal_socket.state() == net::socket::TcpState::Established {
+                return Ok(socket)
             }
+        }
+
+        {
+            let mut sockets = self.sockets.borrow_mut();
+            let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(socket);
+            // abort() instead of close() prevents TcpSocket::connect() from
+            // raising an error
+            internal_socket.abort();
             match remote.ip() {
                 nal::IpAddr::V4(addr) => {
                     let address =
@@ -154,45 +183,56 @@ where
                         .connect((address, remote.port()), self.get_ephemeral_port())
                         .map_err(|_| NetworkError::ConnectionFailure)?;
                     net::wire::IpAddress::Ipv4(address)
-                }
+                },
                 nal::IpAddr::V6(addr) => {
-                    let address = net::wire::Ipv6Address::from_parts(&addr.segments()[..]);
-                    internal_socket.connect((address, remote.port()), self.get_ephemeral_port())
+                    let address =
+                        net::wire::Ipv6Address::from_parts(&addr.segments()[..]);
+                    internal_socket
+                        .connect((address, remote.port()), self.get_ephemeral_port())
                         .map_err(|_| NetworkError::ConnectionFailure)?;
                     net::wire::IpAddress::Ipv6(address)
                 }
             }
         };
-        // Blocking connect
+
+        // Loop to wait until the socket is staying established or closed,
+        // or the connection attempt has timed out.
+        let mut timeout_ms: u32 = 0;
         loop {
-            match self.is_connected(&socket) {
-                Ok(true) => break,
-                _ => {
+            {
                 let mut sockets = self.sockets.borrow_mut();
                 let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(socket);
-                    // If the connect got ACK->RST, it will end up in Closed TCP state
-                    // Perform reconnection in this case
+                // TCP state at ESTABLISHED means there is connection, so
+                // simply return the socket.
+                if internal_socket.state() == net::socket::TcpState::Established {
+                    return Ok(socket)
+                }
+                // TCP state at CLOSED implies that the remote rejected connection;
+                // In this case, abort the connection, and then return the socket
+                // for re-connection in the future.
                 if internal_socket.state() == net::socket::TcpState::Closed {
-                        internal_socket.close();
-                        internal_socket
-                            .connect((address, remote.port()), self.get_ephemeral_port())
-                            .map_err(|_| NetworkError::ConnectionFailure)?;
+                    internal_socket.abort();
+                    // TODO: Return Err(), but would require changes in quartiq/minimq
+                    return Ok(socket)
                 }
             }
-            }
-            // Avoid using Instant::now() and Advance time manually
-            self.update(false)?;
-            {
-                self.advance_time(1);
+            // Any TCP states other than CLOSED and ESTABLISHED are considered
+            // "transient", so this function should keep waiting and let smoltcp poll
+            // (e.g. for handling echo reqeust/reply) at the same time.
+            timeout_ms += self.update()?;
+            self.poll()?;
+            // Time out, and return the socket for re-connection in the future.
+            if timeout_ms > self.connection_timeout_ms {
+                // TODO: Return Err(), but would require changes in quartiq/minimq
+                return Ok(socket)
             }
         }
-        Ok(socket)
     }
 
     fn is_connected(&self, socket: &Self::TcpSocket) -> Result<bool, Self::Error> {
         let mut sockets = self.sockets.borrow_mut();
-        let socket: &mut net::socket::TcpSocket = &mut *sockets.get(*socket);
-        Ok(socket.may_send() && socket.may_recv())
+        let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(*socket);
+        Ok(internal_socket.state() == net::socket::TcpState::Established)
     }
 
     fn write(&self, socket: &mut Self::TcpSocket, buffer: &[u8]) -> nb::Result<usize, Self::Error> {
@@ -208,7 +248,8 @@ where
                 Ok(num_bytes) => {
                     // In case the buffer is filled up, push bytes into ethernet driver
                     if num_bytes != non_queued_bytes.len() {
-                        self.update(true)?;
+                        self.update()?;
+                        self.poll()?;
                     }
                     // Process the unwritten bytes again, if any
                     non_queued_bytes = &non_queued_bytes[num_bytes..]
@@ -225,7 +266,8 @@ where
         buffer: &mut [u8],
     ) -> nb::Result<usize, Self::Error> {
         // Enqueue received bytes into the TCP socket buffer
-        self.update(true)?;
+        self.update()?;
+        self.poll()?;
         let mut sockets = self.sockets.borrow_mut();
         let socket: &mut net::socket::TcpSocket = &mut *sockets.get(*socket);
         let result = socket.recv_slice(buffer);