zaprus/src/Client.zig

var rand: ?Random = null;

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();
    try network.init();
}

pub fn deinit() void {
    network.deinit();
}

fn broadcastSaprusMessage(msg: SaprusMessage, udp_port: u16, allocator: Allocator) !void {
    const msg_bytes = try msg.toBytes(allocator);
    defer allocator.free(msg_bytes);

    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);

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

pub fn sendRelay(payload: []const u8, dest: [4]u8, allocator: Allocator) !void {
    const msg = SaprusMessage{
        .relay = .{
            .header = .{ .dest = dest },
            .payload = payload,
        },
    };

    try broadcastSaprusMessage(msg, 8888, allocator);
}

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, initial_port: u16, allocator: Allocator) !SaprusMessage {
    const dest_port = randomPort();
    const msg = SaprusMessage{
        .connection = .{
            .header = .{
                .src_port = initial_port,
                .dest_port = dest_port,
            },
            .payload = payload,
        },
    };

    try broadcastSaprusMessage(msg, 8888, allocator);

    return msg;
}

pub fn connect(payload: []const u8, allocator: Allocator) !SaprusMessage {
    var initial_port: u16 = 0;
    if (rand) |r| {
        initial_port = r.intRangeAtMost(u16, 1024, 65000);
    } else unreachable;

    var initial_conn_res: ?SaprusMessage = null;
    errdefer if (initial_conn_res) |c| c.deinit(allocator);

    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);

    const msg = try sendInitialConnection(payload, initial_port, allocator);

    var response_buf: [4096]u8 = undefined;
    _ = try sock.receive(&response_buf); // Ignore message that I sent.
    const len = try sock.receive(&response_buf);

    initial_conn_res = try SaprusMessage.fromBytes(response_buf[0..len], allocator);

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

    return initial_conn_res.?;
}

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

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

const network = @import("network");

const Allocator = mem.Allocator;