Fix checksum issue

src/Connection.zig

@@ -14,12 +14,16 @@ pub fn init(socket: RawSocket, headers: EthIpUdp, connection: SaprusMessage) Con
 
 pub fn next(self: Connection, io: Io, buf: []u8) ![]const u8 {
     _ = io;
+    log.debug("Awaiting connection message", .{});
     const res = try self.socket.receive(buf);
+    log.debug("Received {} byte connection message", .{res.len});
     const connection_res = blk: {
         const msg: SaprusMessage = try .parse(res[42..]);
         break :blk msg.connection;
     };
 
+    log.debug("Payload was {s}", .{connection_res.payload});
+
     return connection_res.payload;
 }
 
@@ -29,14 +33,16 @@ pub fn send(self: *Connection, io: Io, buf: []const u8) !void {
         break :blk io_source.interface();
     };
 
+    log.debug("Sending connection message", .{});
+
     self.connection.connection.payload = buf;
     const connection_bytes = blk: {
         var connection_bytes: [2048]u8 = undefined;
         break :blk self.connection.toBytes(&connection_bytes);
     };
 
-    self.headers.setPayloadLen(connection_bytes.len);
     self.headers.ip.id = rand.int(u16);
+    self.headers.setPayloadLen(connection_bytes.len);
 
     const full_msg = blk: {
         var msg_buf: [2048]u8 = undefined;
@@ -47,12 +53,16 @@ pub fn send(self: *Connection, io: Io, buf: []const u8) !void {
     };
 
     try self.socket.send(full_msg);
+
+    log.debug("Sent {} byte connection message", .{full_msg.len});
 }
 
 const std = @import("std");
 const Io = std.Io;
 const Writer = std.Io.Writer;
 
+const log = std.log;
+
 const SaprusMessage = @import("./message.zig").Message;
 
 const EthIpUdp = @import("./EthIpUdp.zig").EthIpUdp;