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Implement TCP data reception.

v0.7.x
whitequark 2016-12-25 11:09:50 +00:00
parent bdfb99ea16
commit 0ae27678a0
3 changed files with 186 additions and 77 deletions
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2
README.md
View File

@ -47,7 +47,7 @@ The TCP protocol is supported over IPv4.
* TCP header checksum is supported.
* TCP options are **not** supported.
* TCP SYN packets with a payload are **not** supported.
* Reassembly of out-of-order segments is **not** supported.
Installation
------------

217
src/socket/tcp.rs
View File

@ -25,27 +25,19 @@ impl<'a> SocketBuffer<'a> {
}
}
/// Return the maximum amount of octets that can be enqueued in the buffer.
pub fn capacity(&self) -> usize {
fn capacity(&self) -> usize {
self.storage.len()
}
/// Return the amount of octets already enqueued in the buffer.
pub fn len(&self) -> usize {
fn len(&self) -> usize {
self.length
}
/// Return the amount of octets that remain to be enqueued in the buffer.
pub fn window(&self) -> usize {
fn window(&self) -> usize {
self.capacity() - self.len()
}
/// Enqueue a slice of octets up to the given size into the buffer, and return a pointer
/// to the slice.
///
/// The returned slice may be shorter than requested, as short as an empty slice,
/// if there is not enough contiguous free space in the buffer.
pub fn enqueue(&mut self, mut size: usize) -> &mut [u8] {
fn clamp_writer(&self, mut size: usize) -> (usize, usize) {
let write_at = (self.read_at + self.length) % self.storage.len();
// We can't enqueue more than there is free space.
let free = self.storage.len() - self.length;
@ -54,23 +46,52 @@ impl<'a> SocketBuffer<'a> {
let until_end = self.storage.len() - write_at;
if size > until_end { size = until_end }
(write_at, size)
}
fn enqueue(&mut self, size: usize) -> &mut [u8] {
let (write_at, size) = self.clamp_writer(size);
self.length += size;
&mut self.storage[write_at..write_at + size]
}
/// Dequeue a slice of octets up to the given size from the buffer, and return a pointer
/// to the slice.
///
/// The returned slice may be shorter than requested, as short as an empty slice,
/// if there is not enough contiguous filled space in the buffer.
pub fn dequeue(&mut self, mut size: usize) -> &[u8] {
fn enqueue_slice(&mut self, data: &[u8]) {
let data = {
let mut dest = self.enqueue(data.len());
let (data, rest) = data.split_at(dest.len());
dest.copy_from_slice(data);
rest
};
// Retry, in case we had a wraparound.
let mut dest = self.enqueue(data.len());
let (data, _) = data.split_at(dest.len());
dest.copy_from_slice(data);
}
fn clamp_reader(&self, mut size: usize) -> (usize, usize) {
let read_at = self.read_at;
// We can't dequeue more than was queued.
if size > self.length { size = self.length }
// We can't contiguously dequeue past the end of the storage.
let until_end = self.storage.len() - self.read_at;
let until_end = self.storage.len() - read_at;
if size > until_end { size = until_end }
(read_at, size)
}
fn peek(&self, size: usize) -> &[u8] {
let (read_at, size) = self.clamp_reader(size);
&self.storage[read_at..read_at + size]
}
fn advance(&mut self, size: usize) {
let (read_at, size) = self.clamp_reader(size);
self.read_at = (read_at + size) % self.storage.len();
self.length -= size;
}
fn dequeue(&mut self, size: usize) -> &[u8] {
let (read_at, size) = self.clamp_reader(size);
self.read_at = (self.read_at + size) % self.storage.len();
self.length -= size;
&self.storage[read_at..read_at + size]
@ -145,6 +166,7 @@ pub struct TcpSocket<'a> {
remote_endpoint: IpEndpoint,
local_seq_no: i32,
remote_seq_no: i32,
remote_win_len: usize,
retransmit: Retransmit,
rx_buffer: SocketBuffer<'a>,
tx_buffer: SocketBuffer<'a>
@ -166,6 +188,7 @@ impl<'a> TcpSocket<'a> {
remote_endpoint: IpEndpoint::default(),
local_seq_no: 0,
remote_seq_no: 0,
remote_win_len: 0,
retransmit: Retransmit::new(),
tx_buffer: tx_buffer.into(),
rx_buffer: rx_buffer.into()
@ -235,27 +258,30 @@ impl<'a> TcpSocket<'a> {
if !self.remote_endpoint.addr.is_unspecified() &&
self.remote_endpoint.addr != *src_addr { return Err(Error::Rejected) }
// Reject packets addressed to a closed socket.
if self.state == State::Closed {
net_trace!("tcp:{}:{}:{}: packet sent to a closed socket",
self.local_endpoint, src_addr, repr.src_port);
return Err(Error::Malformed)
}
// Reject unacceptable acknowledgements.
match (self.state, repr) {
// Reject packets addressed to a closed socket.
(State::Closed, TcpRepr { src_port, .. }) => {
net_trace!("tcp:{}:{}:{}: packet sent to a closed socket",
self.local_endpoint, src_addr, src_port);
return Err(Error::Malformed)
}
// Don't care about ACKs when performing the handshake.
(State::Listen, _) => (),
(State::SynSent, _) => (),
// Every packet after the initial SYN must be an acknowledgement.
(_, TcpRepr { ack_number: None, .. }) => {
net_trace!("tcp:{}:{}: expecting an ACK packet",
net_trace!("tcp:{}:{}: expecting an ACK",
self.local_endpoint, self.remote_endpoint);
return Err(Error::Malformed)
}
// Reject unacceptable acknowledgements.
// Every acknowledgement must be for transmitted but unacknowledged data.
(state, TcpRepr { ack_number: Some(ack_number), .. }) => {
let unacknowledged =
if state != State::SynReceived { self.rx_buffer.len() as i32 } else { 1 };
if !(ack_number - self.local_seq_no > 0 &&
let control_len =
if state == State::SynReceived { 1 } else { 0 };
let unacknowledged = self.tx_buffer.len() as i32 + control_len;
if !(ack_number - self.local_seq_no >= 0 &&
ack_number - (self.local_seq_no + unacknowledged) <= 0) {
net_trace!("tcp:{}:{}: unacceptable ACK ({} not in {}..{})",
self.local_endpoint, self.remote_endpoint,
@ -265,43 +291,80 @@ impl<'a> TcpSocket<'a> {
}
}
// Handle the incoming packet.
// Reject segments not occupying a valid portion of the receive window.
// For now, do not try to reassemble out-of-order segments.
if self.state != State::Listen {
let next_remote_seq = self.remote_seq_no + self.rx_buffer.len() as i32 +
repr.control.len();
if repr.seq_number - next_remote_seq > 0 {
net_trace!("tcp:{}:{}: unacceptable SEQ ({} not in {}..)",
self.local_endpoint, self.remote_endpoint,
repr.seq_number, next_remote_seq);
return Err(Error::Malformed)
} else if repr.seq_number - next_remote_seq != 0 {
net_trace!("tcp:{}:{}: duplicate SEQ ({} in ..{})",
self.local_endpoint, self.remote_endpoint,
repr.seq_number, next_remote_seq);
return Ok(())
}
}
// Validate and update the state.
let old_state = self.state;
match (self.state, repr) {
(State::Listen, TcpRepr {
src_port, dst_port, control: TcpControl::Syn, seq_number, ack_number: None,
payload, ..
src_port, dst_port, control: TcpControl::Syn, seq_number, ack_number: None, ..
}) => {
// FIXME: don't do this, just enqueue the payload
if payload.len() > 0 {
net_trace!("tcp:{}:{}: SYN with payload rejected",
IpEndpoint::new(*dst_addr, dst_port),
IpEndpoint::new(*src_addr, src_port));
return Err(Error::Malformed)
}
self.local_endpoint = IpEndpoint::new(*dst_addr, dst_port);
self.remote_endpoint = IpEndpoint::new(*src_addr, src_port);
self.remote_seq_no = seq_number + 1;
self.local_seq_no = -seq_number; // FIXME: use something more secure
self.remote_seq_no = seq_number + 1;
self.set_state(State::SynReceived);
self.retransmit.reset();
Ok(())
self.retransmit.reset()
}
(State::SynReceived, TcpRepr {
control: TcpControl::None, ack_number: Some(ack_number), ..
}) => {
self.local_seq_no = ack_number;
(State::SynReceived, TcpRepr { control: TcpControl::None, .. }) => {
self.set_state(State::Established);
// FIXME: queue data from ACK
self.retransmit.reset();
Ok(())
self.retransmit.reset()
}
_ => Err(Error::Malformed)
(State::Established, TcpRepr { control: TcpControl::None, .. }) => (),
_ => {
net_trace!("tcp:{}:{}: unexpected packet {}",
self.local_endpoint, self.remote_endpoint, repr);
return Err(Error::Malformed)
}
}
// Dequeue acknowledged octets.
if let Some(ack_number) = repr.ack_number {
let control_len =
if old_state == State::SynReceived { 1 } else { 0 };
if control_len > 0 {
net_trace!("tcp:{}:{}: ACK for a control flag",
self.local_endpoint, self.remote_endpoint);
}
if ack_number - self.local_seq_no - control_len > 0 {
net_trace!("tcp:{}:{}: ACK for {} octets",
self.local_endpoint, self.remote_endpoint,
ack_number - self.local_seq_no - control_len);
}
self.tx_buffer.advance((ack_number - self.local_seq_no - control_len) as usize);
self.local_seq_no = ack_number;
}
// Enqueue payload octets, which is guaranteed to be in order, unless we already did.
if repr.payload.len() > 0 {
net_trace!("tcp:{}:{}: receiving {} octets",
self.local_endpoint, self.remote_endpoint, repr.payload.len());
self.rx_buffer.enqueue_slice(repr.payload)
}
// Update window length.
self.remote_win_len = repr.window_len as usize;
Ok(())
}
/// See [Socket::dispatch](enum.Socket.html#method.dispatch).
@ -374,14 +437,22 @@ mod test {
buffer.enqueue(8).copy_from_slice(b"gefug"); // ...gefug
}
#[test]
fn test_buffer_wraparound() {
let mut buffer = SocketBuffer::new(vec![0; 8]); // ........
buffer.enqueue_slice(&b"foobar"[..]); // foobar..
assert_eq!(buffer.dequeue(3), b"foo"); // ...bar..
buffer.enqueue_slice(&b"bazhoge"[..]); // zhobarba
}
const LOCAL_IP: IpAddress = IpAddress::v4(10, 0, 0, 1);
const REMOTE_IP: IpAddress = IpAddress::v4(10, 0, 0, 2);
const LOCAL_PORT: u16 = 80;
const REMOTE_PORT: u16 = 49500;
const LOCAL_END: IpEndpoint = IpEndpoint::new(LOCAL_IP, LOCAL_PORT);
const REMOTE_END: IpEndpoint = IpEndpoint::new(REMOTE_IP, REMOTE_PORT);
const LOCAL_SEQ: i32 = 100;
const REMOTE_SEQ: i32 = -100;
const LOCAL_SEQ: i32 = 10000;
const REMOTE_SEQ: i32 = -10000;
const SEND_TEMPL: TcpRepr<'static> = TcpRepr {
src_port: REMOTE_PORT, dst_port: LOCAL_PORT,
@ -473,7 +544,8 @@ mod test {
send!(s, TcpRepr {
control: TcpControl::Syn,
seq_number: REMOTE_SEQ, ack_number: None,
seq_number: REMOTE_SEQ,
ack_number: None,
..SEND_TEMPL
});
assert_eq!(s.state(), State::SynReceived);
@ -481,16 +553,41 @@ mod test {
assert_eq!(s.remote_endpoint(), REMOTE_END);
recv!(s, TcpRepr {
control: TcpControl::Syn,
seq_number: LOCAL_SEQ, ack_number: Some(REMOTE_SEQ + 1),
seq_number: LOCAL_SEQ,
ack_number: Some(REMOTE_SEQ + 1),
..RECV_TEMPL
});
send!(s, TcpRepr {
control: TcpControl::None,
seq_number: REMOTE_SEQ + 1, ack_number: Some(LOCAL_SEQ + 1),
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
..SEND_TEMPL
});
assert_eq!(s.state(), State::Established);
assert_eq!(s.local_seq_no, LOCAL_SEQ + 1);
assert_eq!(s.remote_seq_no, REMOTE_SEQ + 1);
}
#[test]
fn test_recv_data() {
let mut s = socket();
s.state = State::Established;
s.local_endpoint = LOCAL_END;
s.remote_endpoint = REMOTE_END;
s.local_seq_no = LOCAL_SEQ + 1;
s.remote_seq_no = REMOTE_SEQ + 1;
send!(s, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1),
payload: &b"abcdef"[..],
..SEND_TEMPL
});
send!(s, TcpRepr {
seq_number: REMOTE_SEQ + 1 + 6,
ack_number: Some(LOCAL_SEQ + 1),
payload: &b"foo"[..],
..SEND_TEMPL
});
assert_eq!(s.rx_buffer.dequeue(9), &b"abcdeffoo"[..]);
}
}

44
src/wire/tcp.rs
View File

@ -187,8 +187,8 @@ impl<T: AsRef<[u8]>> Packet<T> {
pub fn segment_len(&self) -> i32 {
let data = self.buffer.as_ref();
let mut length = data.len() - self.header_len() as usize;
if self.syn() { length += 1}
if self.fin() { length += 1}
if self.syn() { length += 1 }
if self.fin() { length += 1 }
length as i32
}
@ -395,6 +395,27 @@ impl<'a, T: AsRef<[u8]> + AsMut<[u8]> + ?Sized> Packet<&'a mut T> {
}
}
/// The control flags of a Transmission Control Protocol packet.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum Control {
None,
Syn,
Fin,
Rst
}
impl Control {
/// Return the length of the control flag, in terms of sequence space.
pub fn len(self) -> i32 {
match self {
Control::None => 0,
Control::Syn => 1,
Control::Fin => 1,
Control::Rst => 0
}
}
}
/// A high-level representation of a Transmission Control Protocol packet.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub struct Repr<'a> {
@ -407,15 +428,6 @@ pub struct Repr<'a> {
pub payload: &'a [u8]
}
/// The control flags of a Transmission Control Protocol packet.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum Control {
None,
Syn,
Fin,
Rst
}
impl<'a> Repr<'a> {
/// Parse a Transmission Control Protocol packet and return a high-level representation.
pub fn parse<T: ?Sized>(packet: &Packet<&'a T>,
@ -498,9 +510,9 @@ impl<'a, T: AsRef<[u8]> + ?Sized> fmt::Display for Packet<&'a T> {
if self.ece() { try!(write!(f, " ece")) }
if self.cwr() { try!(write!(f, " cwr")) }
if self.ns() { try!(write!(f, " ns" )) }
try!(write!(f, " seq={}", self.seq_number() as u32));
try!(write!(f, " seq={}", self.seq_number()));
if self.ack() {
try!(write!(f, " ack={}", self.ack_number() as u32));
try!(write!(f, " ack={}", self.ack_number()));
}
try!(write!(f, " win={}", self.window_len()));
if self.urg() {
@ -513,7 +525,7 @@ impl<'a, T: AsRef<[u8]> + ?Sized> fmt::Display for Packet<&'a T> {
impl<'a> fmt::Display for Repr<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
try!(write!(f, "TCP src={} dst={} ",
try!(write!(f, "TCP src={} dst={}",
self.src_port, self.dst_port));
match self.control {
Control::Syn => try!(write!(f, " syn")),
@ -521,9 +533,9 @@ impl<'a> fmt::Display for Repr<'a> {
Control::Rst => try!(write!(f, " rst")),
Control::None => ()
}
try!(write!(f, " seq={}", self.seq_number as u32));
try!(write!(f, " seq={}", self.seq_number));
if let Some(ack_number) = self.ack_number {
try!(write!(f, " ack={}", ack_number as u32));
try!(write!(f, " ack={}", ack_number));
}
try!(write!(f, " win={}", self.window_len));
try!(write!(f, " len={}", self.payload.len()));