I have a snippet below which is a part of a code to create and send raw packet, which works by the way.

However, the code sets the tcph-> window to htonl(65535). My issue is, the window is only 16 bits and actually gets assigned 0x0000 so I don’t get why not just set 0 directly.

Also, what is the significance of setting the Window to 0 ?

void setup_tcp_header(struct tcphdr *tcph)
{
    tcph->source = htons(src_port);                 // SOURCE PORT
    tcph->dest = htons(dst_port);                   // TARGET PORT

    tcph->seq = random();
    tcph->ack_seq = 0;
    tcph->res2 = 0;
    tcph->doff = 5;
    tcph->syn = 1;



    tcph->window = htonl(65535);  // 0x FFFF 0000 but window is uint16_t so only gets the 00 00 
                                  // LSBs


    tcph->check = 0;
    tcph->urg_ptr = 0;
}



Verified with WS and indeed Window is set to 0: