renet/renet
renet
/
renet
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Implement TCP keep-alive.

This commit is contained in:
whitequark 2017-09-16 10:54:59 +00:00
parent be0dcb145c
commit fe80bca19d
2 changed files with 184 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
README.md
View File

@ -59,6 +59,7 @@ The TCP protocol is supported over IPv4. Server and client sockets are supported
* Multiple packets will be transmitted without waiting for an acknowledgement.
* Lost packets will be retransmitted with exponential backoff, starting at
a fixed delay of 100 ms.
* Sending keep-alive packets is supported, with a configurable interval.
* After arriving at the TIME-WAIT state, sockets will close after a fixed delay of 10 s.
* TCP urgent pointer is **not** supported; any urgent octets will be received alongside
data octets.
@ -71,7 +72,6 @@ The TCP protocol is supported over IPv4. Server and client sockets are supported
* Timestamping (used in round-trip time measurement and protection against wrapped sequences)
is **not** supported.
* Fast open is **not** supported when smoltcp initiates connection.
* Keepalive is **not** supported.
## Installation

216
src/socket/tcp.rs
View File

@ -48,7 +48,9 @@ impl fmt::Display for State {
#[derive(Debug, Clone, Copy, PartialEq)]
enum Timer {
Idle,
Idle {
keep_alive_at: Option<u64>,
},
Retransmit {
expires_at: u64,
delay: u64
@ -61,7 +63,23 @@ enum Timer {
const RETRANSMIT_DELAY: u64 = 100;
const CLOSE_DELAY: u64 = 10_000;
impl Default for Timer {
fn default() -> Timer {
Timer::Idle { keep_alive_at: None }
}
}
impl Timer {
fn should_keep_alive(&self, timestamp: u64) -> bool {
match *self {
Timer::Idle { keep_alive_at: Some(keep_alive_at) }
if timestamp >= keep_alive_at => {
true
}
_ => false
}
}
fn should_retransmit(&self, timestamp: u64) -> Option<u64> {
match *self {
Timer::Retransmit { expires_at, delay }
@ -84,19 +102,40 @@ impl Timer {
fn poll_at(&self) -> Option<u64> {
match *self {
Timer::Idle => None,
Timer::Idle { keep_alive_at } => keep_alive_at,
Timer::Retransmit { expires_at, .. } => Some(expires_at),
Timer::Close { expires_at, .. } => Some(expires_at),
Timer::Close { expires_at } => Some(expires_at),
}
}
fn reset(&mut self) {
*self = Timer::Idle
fn set_for_idle(&mut self, timestamp: u64, interval: Option<u64>) {
*self = Timer::Idle {
keep_alive_at: interval.map(|interval| timestamp + interval)
}
}
fn set_keep_alive(&mut self) {
match *self {
Timer::Idle { ref mut keep_alive_at }
if keep_alive_at.is_none() => {
*keep_alive_at = Some(0)
}
_ => ()
}
}
fn rewind_keep_alive(&mut self, timestamp: u64, interval: Option<u64>) {
match self {
&mut Timer::Idle { ref mut keep_alive_at } => {
*keep_alive_at = interval.map(|interval| timestamp + interval)
}
_ => ()
}
}
fn set_for_retransmit(&mut self, timestamp: u64) {
match *self {
Timer::Idle => {
Timer::Idle { .. } => {
*self = Timer::Retransmit {
expires_at: timestamp + RETRANSMIT_DELAY,
delay: RETRANSMIT_DELAY,
@ -134,6 +173,8 @@ pub struct TcpSocket<'a> {
timer: Timer,
rx_buffer: SocketBuffer<'a>,
tx_buffer: SocketBuffer<'a>,
/// Interval at which keep-alive packets will be sent.
keep_alive: Option<u64>,
/// Address passed to listen(). Listen address is set when listen() is called and
/// used every time the socket is reset back to the LISTEN state.
listen_address: IpAddress,
@ -183,9 +224,10 @@ impl<'a> TcpSocket<'a> {
Socket::Tcp(TcpSocket {
debug_id: 0,
state: State::Closed,
timer: Timer::Idle,
timer: Timer::default(),
tx_buffer: tx_buffer.into(),
rx_buffer: rx_buffer.into(),
keep_alive: None,
listen_address: IpAddress::default(),
local_endpoint: IpEndpoint::default(),
remote_endpoint: IpEndpoint::default(),
@ -213,6 +255,34 @@ impl<'a> TcpSocket<'a> {
self.debug_id = id
}
/// Return the keep-alive interval.
///
/// See also the [set_keep_alive](#method.set_keep_alive) method.
pub fn keep_alive(&self) -> Option<u64> {
self.keep_alive
}
/// Set the keep-alive interval.
///
/// An idle socket with a set keep-alive interval will transmit a "challenge ACK" packet
/// every time it receives no communication during that interval. As a result, three things
/// may happen:
///
/// * The remote endpoint is fine and answers with an ACK packet.
/// * The remote endpoint has rebooted and answers with an RST packet.
/// * The remote endpoint has crashed and does not answer.
///
/// The keep-alive functionality together with the timeout functionality allows to react
/// to these error conditions.
pub fn set_keep_alive(&mut self, interval: Option<u64>) {
self.keep_alive = interval;
if self.keep_alive.is_some() {
// If the connection is idle and we've just set the option, it would not take effect
// until the next packet, unless we wind up the timer explicitly.
self.timer.set_keep_alive();
}
}
/// Return the local endpoint.
#[inline]
pub fn local_endpoint(&self) -> IpEndpoint {
@ -233,6 +303,8 @@ impl<'a> TcpSocket<'a> {
fn reset(&mut self) {
self.state = State::Closed;
self.timer = Timer::default();
self.keep_alive = None;
self.listen_address = IpAddress::default();
self.local_endpoint = IpEndpoint::default();
self.remote_endpoint = IpEndpoint::default();
@ -243,7 +315,6 @@ impl<'a> TcpSocket<'a> {
self.remote_last_win = 0;
self.remote_win_len = 0;
self.remote_mss = DEFAULT_MSS;
self.timer.reset();
self.tx_buffer.clear();
self.rx_buffer.clear();
}
@ -328,14 +399,10 @@ impl<'a> TcpSocket<'a> {
self.set_state(State::Closed),
// In the SYN-RECEIVED, ESTABLISHED and CLOSE-WAIT states the transmit half
// of the connection is open, and needs to be explicitly closed with a FIN.
State::SynReceived | State::Established => {
self.timer.reset();
self.set_state(State::FinWait1);
}
State::CloseWait => {
self.timer.reset();
self.set_state(State::LastAck);
}
State::SynReceived | State::Established =>
self.set_state(State::FinWait1),
State::CloseWait =>
self.set_state(State::LastAck),
// In the FIN-WAIT-1, FIN-WAIT-2, CLOSING, LAST-ACK, TIME-WAIT and CLOSED states,
// the transmit half of the connection is already closed, and no further
// action is needed.
@ -481,7 +548,6 @@ impl<'a> TcpSocket<'a> {
net_trace!("[{}]{}:{}: tx buffer: enqueueing {} octets (now {})",
self.debug_id, self.local_endpoint, self.remote_endpoint,
buffer.len(), _old_length + buffer.len());
self.timer.reset();
}
Ok(buffer)
}
@ -495,14 +561,13 @@ impl<'a> TcpSocket<'a> {
pub fn send_slice(&mut self, data: &[u8]) -> Result<usize> {
if !self.may_send() { return Err(Error::Illegal) }
let old_length = self.tx_buffer.len();
let _old_length = self.tx_buffer.len();
let enqueued = self.tx_buffer.enqueue_slice(data);
if enqueued != 0 {
#[cfg(any(test, feature = "verbose"))]
net_trace!("[{}]{}:{}: tx buffer: enqueueing {} octets (now {})",
self.debug_id, self.local_endpoint, self.remote_endpoint,
enqueued, old_length + enqueued);
self.timer.reset();
enqueued, _old_length + enqueued);
}
Ok(enqueued)
}
@ -884,13 +949,13 @@ impl<'a> TcpSocket<'a> {
self.remote_mss = max_seg_size as usize
}
self.set_state(State::SynReceived);
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// ACK packets in the SYN-RECEIVED state change it to ESTABLISHED.
(State::SynReceived, TcpControl::None) => {
self.set_state(State::Established);
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// FIN packets in the SYN-RECEIVED state change it to CLOSE-WAIT.
@ -899,7 +964,7 @@ impl<'a> TcpSocket<'a> {
(State::SynReceived, TcpControl::Fin) => {
self.remote_seq_no += 1;
self.set_state(State::CloseWait);
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// SYN|ACK packets in the SYN-SENT state change it to ESTABLISHED.
@ -913,19 +978,19 @@ impl<'a> TcpSocket<'a> {
self.remote_mss = max_seg_size as usize;
}
self.set_state(State::Established);
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// ACK packets in ESTABLISHED state reset the retransmit timer.
(State::Established, TcpControl::None) => {
self.timer.reset()
self.timer.set_for_idle(timestamp, self.keep_alive);
},
// FIN packets in ESTABLISHED state indicate the remote side has closed.
(State::Established, TcpControl::Fin) => {
self.remote_seq_no += 1;
self.set_state(State::CloseWait);
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// ACK packets in FIN-WAIT-1 state change it to FIN-WAIT-2, if we've already
@ -934,7 +999,7 @@ impl<'a> TcpSocket<'a> {
if ack_of_fin {
self.set_state(State::FinWait2);
}
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// FIN packets in FIN-WAIT-1 state change it to CLOSING, or to TIME-WAIT
@ -946,7 +1011,7 @@ impl<'a> TcpSocket<'a> {
self.timer.set_for_close(timestamp);
} else {
self.set_state(State::Closing);
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
}
@ -963,13 +1028,13 @@ impl<'a> TcpSocket<'a> {
self.set_state(State::TimeWait);
self.timer.set_for_close(timestamp);
} else {
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
}
// ACK packets in CLOSE-WAIT state reset the retransmit timer.
(State::CloseWait, TcpControl::None) => {
self.timer.reset();
self.timer.set_for_idle(timestamp, self.keep_alive);
}
// ACK packets in LAST-ACK state change it to CLOSED.
@ -1121,6 +1186,8 @@ impl<'a> TcpSocket<'a> {
// If we have window length increase to advertise, do it.
} else if self.timer.should_retransmit(timestamp).is_some() {
// If we have packets to retransmit, do it.
} else if self.timer.should_keep_alive(timestamp) {
// If we need to transmit a keep-alive packet, do it.
} else if repr.control == TcpControl::Rst {
// If we need to abort the connection, do it.
} else {
@ -1147,6 +1214,17 @@ impl<'a> TcpSocket<'a> {
flags);
}
let is_keep_alive;
if self.timer.should_keep_alive(timestamp) {
net_trace!("[{}]{}:{}: sending a keep-alive",
self.debug_id, self.local_endpoint, self.remote_endpoint);
repr.seq_number = repr.seq_number - 1;
repr.payload = b"\x00"; // RFC 1122 says we should do this
is_keep_alive = true;
} else {
is_keep_alive = false;
}
// Remember the header length before enabling the MSS option, since that option
// only affects SYN packets.
let header_len = repr.header_len();
@ -1179,13 +1257,20 @@ impl<'a> TcpSocket<'a> {
emit((ip_repr, repr))?;
// We've sent something, whether useful data or a keep-alive packet, so rewind
// the keep-alive timer.
self.timer.rewind_keep_alive(timestamp, self.keep_alive);
// Leave the rest of the state intact if sending a keep-alive packet.
if is_keep_alive { return Ok(()) }
// We've sent a packet successfully, so we can update the internal state now.
self.remote_last_seq = repr.seq_number + repr.segment_len();
self.remote_last_ack = repr.ack_number;
self.remote_last_win = repr.window_len;
if !self.seq_to_transmit(repr.control) && repr.segment_len() > 0 {
// If we've transmitted all data could (and there was something at all,
// If we've transmitted all data we could (and there was something at all,
// data or flag, to transmit, not just an ACK), wind up the retransmit timer.
self.timer.set_for_retransmit(timestamp);
}
@ -1229,7 +1314,7 @@ mod test {
#[test]
fn test_timer_retransmit() {
let mut r = Timer::Idle;
let mut r = Timer::default();
assert_eq!(r.should_retransmit(1000), None);
r.set_for_retransmit(1000);
assert_eq!(r.should_retransmit(1000), None);
@ -1240,7 +1325,7 @@ mod test {
assert_eq!(r.should_retransmit(1150), None);
assert_eq!(r.should_retransmit(1200), None);
assert_eq!(r.should_retransmit(1301), Some(300));
r.reset();
r.set_for_idle(1301, None);
assert_eq!(r.should_retransmit(1350), None);
}
@ -2952,6 +3037,71 @@ mod test {
}]);
}
// =========================================================================================//
// Tests for keep-alive
// =========================================================================================//
#[test]
fn test_responds_to_keep_alive() {
let mut s = socket_established();
send!(s, TcpRepr {
seq_number: REMOTE_SEQ,
ack_number: Some(LOCAL_SEQ + 1),
..SEND_TEMPL
}, Ok(Some(TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1),
..RECV_TEMPL
})));
}
#[test]
fn test_sends_keep_alive() {
let mut s = socket_established();
s.set_keep_alive(Some(100));
// drain the forced keep-alive packet
assert_eq!(s.poll_at(), Some(0));
recv!(s, time 0, Ok(TcpRepr {
seq_number: LOCAL_SEQ,
ack_number: Some(REMOTE_SEQ + 1),
payload: &[0],
..RECV_TEMPL
}));
assert_eq!(s.poll_at(), Some(100));
recv!(s, time 95, Err(Error::Exhausted));
recv!(s, time 100, Ok(TcpRepr {
seq_number: LOCAL_SEQ,
ack_number: Some(REMOTE_SEQ + 1),
payload: &[0],
..RECV_TEMPL
}));
assert_eq!(s.poll_at(), Some(200));
recv!(s, time 195, Err(Error::Exhausted));
recv!(s, time 200, Ok(TcpRepr {
seq_number: LOCAL_SEQ,
ack_number: Some(REMOTE_SEQ + 1),
payload: &[0],
..RECV_TEMPL
}));
send!(s, time 250, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
..SEND_TEMPL
});
assert_eq!(s.poll_at(), Some(350));
recv!(s, time 345, Err(Error::Exhausted));
recv!(s, time 350, Ok(TcpRepr {
seq_number: LOCAL_SEQ,
ack_number: Some(REMOTE_SEQ + 1),
payload: &b"\x00"[..],
..RECV_TEMPL
}));
}
// =========================================================================================//
// Tests for packet filtering
// =========================================================================================//