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Vi.
Asked: 2013-08-02 10:36:30 +0800 CST

How to edit TCP window size from iptables?

  • 772

There is TCPMSS target to edit MSS value of connections (including forwarded).

How to edit window size (for example, cap to some maximum value) by iptables rule?

Expecting something like

iptables -t mangle -A OUTPUT -p tcp --dport 1234 -j TCPWINDOW --tcpwindow-set 'min(val,100000)'
linux

2 Answers

  1. Best Answer

    To change TCP window from iptables you need to:

    iptables -t mangle -I OUTPUT -p tcp --sport 80 --tcp-flags SYN,ACK SYN,ACK -j TCPWIN --tcpwin-set 1000

    • 3

  2. Yes, you can use the option --set-mss to achieve this.

    Example: 

    iptables -I FORWARD -o ppp0 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1492

    Documentation: http://www.linuxtopia.org/Linux_Firewall_iptables/x4700.html

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