Scapy set tcp flow window bigger then 65535

Question

When using scapy, how can I set a tcp packet with flow control window bigger than 65535? I know that writing in scapy:

packet1[TCP].window=65535

will set the window to 65535; But if there is a need to set windows size bigger then 65535, it should be set in a different way because at the tcp header the window field is just two bytes so it can't be greather than 65535 so it should be done in another way. I know it should be possible.

Thanks.

Answer 1

Sort answer is: you cannot set the field TCP.window to a bigger value than 65535, since it is coded on two bytes:

>>> ls(TCP)
[...]
window     : ShortField                          = (8192)
[...]

But TCP window can be higher than 65535, using the "Window Scale" option. The window value is the value of the window field multiplied by 2 raised to the power of the window scale value.

In Scapy:

>>> IP()/TCP(window=65535, options=[('WScale', 10)])

The value is 65535 * 2 ** 10, 67107840.