zaprus/src/Client.zig

const base64Enc = std.base64.Base64Encoder.init(std.base64.standard_alphabet_chars, '=');
const base64Dec = std.base64.Base64Decoder.init(std.base64.standard_alphabet_chars, '=');

var rand: ?Random = null;
var socket: ?gcat.nic.RawSocket = null;

const max_message_size = 2048;

pub fn init() !void {
    var prng = Random.DefaultPrng.init(blk: {
        var seed: u64 = undefined;
        try posix.getrandom(mem.asBytes(&seed));
        break :blk seed;
    });
    rand = prng.random();

    socket = try .init("enp7s0");
}

pub fn deinit() void {
    socket.?.deinit();
}

/// Used for relay messages and connection handshake.
/// Assumes Client .init has been called.
fn broadcastInitialInterestMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8) !void {
    var packet_bytes: [max_message_size]u8 = comptime blk: {
        var b: [max_message_size]u8 = @splat(0);

        // Destination MAC addr to FF:FF:FF:FF:FF:FF
        for (0..6) |i| {
            b[i] = 0xff;
        }

        // Set Ethernet type to IPv4
        b[0x0c] = 0x08;
        b[0x0d] = 0x00;

        // Set IPv4 version to 4
        b[0x0e] = 0x45;

        // Destination broadcast
        for (0x1e..0x22) |i| {
            b[i] = 0xff;
        }

        // Set TTL
        b[0x16] = 0x40;

        // Set IPv4 protocol to UDP
        b[0x17] = 0x11;

        // Set interest filter value to 8888.
        b[0x24] = 0x22;
        b[0x25] = 0xb8;
        break :blk b;
    };
    var msg: *SaprusMessage = try .bytesAsValue(msg_bytes);
    try msg.networkFromNativeEndian();
    defer msg.nativeFromNetworkEndian() catch unreachable;

    // The byte position within the packet that the saprus message starts at.
    const saprus_start_byte = 42;
    @memcpy(packet_bytes[saprus_start_byte .. saprus_start_byte + msg_bytes.len], msg_bytes);

    try socket.?.linkLayer().send(packet_bytes[0 .. saprus_start_byte + msg_bytes.len]);
}

// fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8) !void {}

fn broadcastSaprusMessage(msg_bytes: []align(@alignOf(SaprusMessage)) u8, udp_port: u16) !void {
    if (false) {
        var foo: gcat.nic.RawSocket = try .init("enp7s0"); // /proc/net/dev
        defer foo.deinit();
    }
    const msg: *SaprusMessage = try .bytesAsValue(msg_bytes);
    try msg.networkFromNativeEndian();
    defer msg.nativeFromNetworkEndian() catch unreachable;

    var sock = try network.Socket.create(.ipv4, .udp);
    defer sock.close();

    try sock.setBroadcast(true);

    // Bind to 0.0.0.0:0
    const bind_addr = network.EndPoint{
        .address = network.Address{ .ipv4 = network.Address.IPv4.any },
        .port = 0,
    };

    const dest_addr = network.EndPoint{
        .address = network.Address{ .ipv4 = network.Address.IPv4.broadcast },
        .port = udp_port,
    };

    try sock.bind(bind_addr);

    std.debug.print("{x}\n", .{msg_bytes});

    _ = try sock.sendTo(dest_addr, msg_bytes);
}

pub fn sendRelay(payload: []const u8, dest: [4]u8) !void {
    var buf: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
    const msg_bytes = buf[0..try SaprusMessage.calcSize(
        .relay,
        base64Enc.calcSize(payload.len),
    )];
    const msg: *SaprusMessage = .init(.relay, msg_bytes);

    const relay = (try msg.getSaprusTypePayload()).relay;
    relay.dest = dest;
    _ = base64Enc.encode(relay.getPayload(), payload);

    try broadcastInitialInterestMessage(msg_bytes);
}

fn randomPort() u16 {
    var p: u16 = 0;
    if (rand) |r| {
        p = r.intRangeAtMost(u16, 1024, 65000);
    } else unreachable;

    return p;
}

pub fn sendInitialConnection(
    payload: []const u8,
    output_bytes: []align(@alignOf(SaprusMessage)) u8,
    initial_port: u16,
) !*SaprusMessage {
    const dest_port = randomPort();
    const msg_bytes = output_bytes[0..try SaprusMessage.calcSize(
        .connection,
        base64Enc.calcSize(payload.len),
    )];
    const msg: *SaprusMessage = .init(.connection, msg_bytes);

    const connection = (try msg.getSaprusTypePayload()).connection;
    connection.src_port = initial_port;
    connection.dest_port = dest_port;
    _ = base64Enc.encode(connection.getPayload(), payload);

    try broadcastSaprusMessage(msg_bytes, 8888);

    return msg;
}

pub fn connect(payload: []const u8) !?SaprusConnection {
    const initial_port = randomPort();

    var initial_conn_res: ?*SaprusMessage = null;

    var sock = try network.Socket.create(.ipv4, .udp);
    defer sock.close();

    // Bind to 255.255.255.255:8888
    const bind_addr = network.EndPoint{
        .address = network.Address{ .ipv4 = network.Address.IPv4.broadcast },
        .port = 8888,
    };

    // timeout 1s
    try sock.setReadTimeout(1 * std.time.us_per_s);
    try sock.bind(bind_addr);

    var sent_msg_bytes: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
    const msg = try sendInitialConnection(payload, &sent_msg_bytes, initial_port);

    var response_buf: [max_message_size]u8 align(@alignOf(SaprusMessage)) = undefined;
    _ = try sock.receive(&response_buf); // Ignore message that I sent.
    const len = try sock.receive(&response_buf);

    initial_conn_res = try .networkBytesAsValue(response_buf[0..len]);

    // Complete handshake after awaiting response
    try broadcastSaprusMessage(msg.asBytes(), randomPort());

    if (false) {
        return initial_conn_res.?;
    }
    return null;
}

const SaprusMessage = @import("message.zig").Message;
const SaprusConnection = @import("Connection.zig");

const std = @import("std");
const Random = std.Random;
const posix = std.posix;
const mem = std.mem;

const network = @import("network");
const gcat = @import("gatorcat");