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Fake Networking TCP Improvements #1247

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Feb 19, 2025
Merged

Fake Networking TCP Improvements #1247

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63 changes: 38 additions & 25 deletions src/browser/fake_network.js
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ const V86_ASCII = [118, 56, 54];
const TCP_STATE_CLOSED = "closed";
const TCP_STATE_SYN_RECEIVED = "syn-received";
const TCP_STATE_SYN_SENT = "syn-sent";
const TCP_STATE_SYN_PROBE = "syn-probe";
//const TCP_STATE_LISTEN = "listen";
const TCP_STATE_ESTABLISHED = "established";
const TCP_STATE_FIN_WAIT_1 = "fin-wait-1";
Expand Down Expand Up @@ -986,16 +987,8 @@ function fake_tcp_connect(dport, adapter)
if(adapter.tcp_conn[tuple]) {
throw new Error("pool of dynamic TCP port numbers exhausted, connection aborted");
}
let on_data;
let on_connect;
let on_close;
let on_shutdown;

let conn = new TCPConnection();
conn.net = adapter;
conn.on_data = function(data) { if(on_data) on_data.call(handle, data); };
conn.on_connect = function() { if(on_connect) on_connect.call(handle); };
conn.on_close = function() { if(on_close) on_close.call(handle); };
conn.on_shutdown = function() { if(on_shutdown) on_shutdown.call(handle); };

conn.tuple = tuple;
conn.hsrc = adapter.router_mac;
Expand All @@ -1004,20 +997,18 @@ function fake_tcp_connect(dport, adapter)
conn.hdest = adapter.vm_mac;
conn.dport = dport;
conn.pdest = adapter.vm_ip;
conn.net = adapter;
adapter.tcp_conn[tuple] = conn;
conn.connect();
// TODO: Real event source
let handle = {
write: function(data) { conn.write(data); },
on: function(event, cb) {
if(event === "data") on_data = cb;
if(event === "connect") on_connect = cb;
if(event === "close") on_close = cb;
if(event === "shutdown") on_shutdown = cb;
},
close: function() { conn.close(); }
};
return handle;
return conn;
}

function fake_tcp_probe(dport, adapter) {
return new Promise((res, rej) => {
let handle = fake_tcp_connect(dport, adapter);
handle.state = TCP_STATE_SYN_PROBE;
handle.on("probe", res);
});
}

/**
Expand All @@ -1032,8 +1023,19 @@ function TCPConnection()
this.in_active_close = false;
this.delayed_send_fin = false;
this.delayed_state = undefined;
this.events_handlers = {};
}

TCPConnection.prototype.on = function(event, handler) {
this.events_handlers[event] = handler;
};

TCPConnection.prototype.emit = function(event, ...args) {
if(!this.events_handlers[event]) return;
this.events_handlers[event].apply(this, args);
};


TCPConnection.prototype.ipv4_reply = function() {
let reply = {};
reply.eth = { ethertype: ETHERTYPE_IPV4, src: this.hsrc, dest: this.hdest };
Expand Down Expand Up @@ -1129,6 +1131,11 @@ TCPConnection.prototype.process = function(packet) {
return;
}
else if(packet.tcp.rst) {
if(this.state === TCP_STATE_SYN_PROBE) {
this.emit("probe", false);
this.release();
return;
}
// dbg_log(`TCP[${this.tuple}]: received RST in state "${this.state}"`, LOG_FETCH);
this.on_close();
this.release();
Expand All @@ -1144,9 +1151,13 @@ TCPConnection.prototype.process = function(packet) {
this.net.receive(make_packet(this.net.eth_encoder_buf, reply));
// dbg_log(`TCP[${this.tuple}]: received SYN+ACK in state "${this.state}", next "${TCP_STATE_ESTABLISHED}"`, LOG_FETCH);
this.state = TCP_STATE_ESTABLISHED;
if(this.on_connect) {
this.on_connect.call(this);
}
this.emit("connect");
}
else if(this.state === TCP_STATE_SYN_PROBE && packet.tcp.ack) {
this.emit("probe", true);
const reply = this.packet_reply(packet, {rst: true});
this.net.receive(make_packet(this.net.eth_encoder_buf, reply));
this.release();
}
else {
dbg_log(`TCP[${this.tuple}]: WARNING: unexpected SYN packet dropped`, LOG_FETCH);
Expand Down Expand Up @@ -1262,7 +1273,7 @@ TCPConnection.prototype.process = function(packet) {
this.ack += packet.tcp_data.length;
const reply = this.ipv4_reply();
this.net.receive(make_packet(this.net.eth_encoder_buf, reply));
this.on_data(packet.tcp_data);
this.emit("data", packet.tcp_data);
}

this.pump();
Expand Down Expand Up @@ -1325,10 +1336,12 @@ TCPConnection.prototype.close = function() {
};

TCPConnection.prototype.on_shutdown = function() {
this.emit("shutdown");
// forward FIN event from guest device to network adapter
};

TCPConnection.prototype.on_close = function() {
this.emit("close");
// forward RST event from guest device to network adapter
};

Expand Down
7 changes: 6 additions & 1 deletion src/browser/fetch_network.js
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ FetchNetworkAdapter.prototype.on_tcp_connection = function(packet, tuple)
let conn = new TCPConnection();
conn.state = TCP_STATE_SYN_RECEIVED;
conn.net = this;
conn.on_data = on_data_http;
conn.on("data", on_data_http);
conn.tuple = tuple;
conn.accept(packet);
this.tcp_conn[tuple] = conn;
Expand All @@ -61,6 +61,11 @@ FetchNetworkAdapter.prototype.connect = function(port)
return fake_tcp_connect(port, this);
};

FetchNetworkAdapter.prototype.tcp_probe = function(port)
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Out of curiosity, what do you use this for?

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@basicer basicer Feb 19, 2025 •
edited
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Great question! In alpine.sh I have some tech worked out so that the service worker can receive web requests, and then route them from the browser into an httpd server running in the VM. I like the classic look of it just being a terminal, so it uses this to probe common ports in the background. When it finds one open it adds a split pane with an iframe. You don't want to actually initiate the connections, as that can often confuse servers, so similar to nmap, we dont send SYN ACK so the user-space program never sees the probing connections.

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Cool stuff, looking forward to playing around with that.

{
return fake_tcp_probe(port, this);
};

/**
* @this {TCPConnection}
* @param {!ArrayBuffer} data
Expand Down
4 changes: 2 additions & 2 deletions src/browser/wisp_network.js
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Original file line number Diff line number Diff line change
Expand Up @@ -186,15 +186,15 @@ WispNetworkAdapter.prototype.on_tcp_connection = function(packet, tuple)
conn.stream_id = this.last_stream++;
this.tcp_conn[tuple] = conn;

conn.on_data = (data) => {
conn.on("data", data => {
if(data.length !== 0) {
this.send_wisp_frame({
type: "DATA",
stream_id: conn.stream_id,
data: data
});
}
};
});

conn.on_close = () => {
this.send_wisp_frame({
Expand Down
5 changes: 5 additions & 0 deletions tests/devices/fetch_network.js
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Original file line number Diff line number Diff line change
Expand Up @@ -107,8 +107,13 @@ const tests =
allow_failure: true,
start: async () =>
{
let open = await emulator.network_adapter.tcp_probe(80);
assert(!open, "Probe shows port not open");
emulator.serial0_send("echo -n hello | socat TCP4-LISTEN:80 - && echo -e done\\\\tlisten\n");
await wait(1000);
open = await emulator.network_adapter.tcp_probe(80);
assert(open, "Probe shows port open, but does not show as a connection");
await wait(1000);
let h = emulator.network_adapter.connect(80);
h.on("connect", () => {
h.write(new TextEncoder().encode("From VM: "));
Expand Down