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feat(fake-tcp) add tcp keep-alive support to client

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Andrea
2022-12-16 22:11:46 +08:00
parent 7c98012a67
commit 25a1cf9aab
2 changed files with 130 additions and 22 deletions
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47
fake-tcp/src/lib.rs
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@@ -178,6 +178,34 @@ impl Socket {
}
}
/// Sends a keep-alive (zero length) datagram to the other end.
///
/// This method takes `&self`, and it can be called safely by multiple threads
/// at the same time.
///
/// A return of `None` means the Tun socket returned an error
/// and this socket must be closed.
pub async fn send_keepalive(&self) -> Option<()> {
match self.state {
State::Established => {
let ack = self.ack.load(Ordering::Relaxed);
self.last_ack.store(ack, Ordering::Relaxed);
let buf = build_tcp_packet(
self.local_addr,
self.remote_addr,
// the current sequence number is one byte less than the next expected sequence number
self.seq.load(Ordering::Relaxed) - 1,
ack,
tcp::TcpFlags::ACK,
None,
);
self.tun.send(&buf).await.ok().and(Some(()))
}
_ => unreachable!(),
}
}
/// Attempt to receive a datagram from the other end.
///
/// This method takes `&self`, and it can be called safely by multiple threads
@@ -198,11 +226,22 @@ impl Socket {
let payload = tcp_packet.payload();
let new_ack = tcp_packet.get_sequence().wrapping_add(payload.len() as u32);
let last_ask = self.last_ack.load(Ordering::Relaxed);
self.ack.store(new_ack, Ordering::Relaxed);
let need_ack = if payload.len() == 0 {
let current_head = self.ack.load(Ordering::Relaxed);
// If it's a keep alive packet
let kp = tcp_packet.get_sequence() == current_head - 1;
if kp {
trace!("{} Keepalive packet received!", self);
}
kp
} else {
let new_ack = tcp_packet.get_sequence().wrapping_add(payload.len() as u32);
let last_ask = self.last_ack.load(Ordering::Relaxed);
self.ack.store(new_ack, Ordering::Relaxed);
new_ack.overflowing_sub(last_ask).0 > MAX_UNACKED_LEN
};
if new_ack.overflowing_sub(last_ask).0 > MAX_UNACKED_LEN {
if need_ack {
let buf = self.build_tcp_packet(tcp::TcpFlags::ACK, None);
if let Err(e) = self.tun.try_send(&buf) {
// This should not really happen as we have not sent anything for