[FS#1083] ar71xx Kernel 4.9 PPTP Passthrough not working

[LEDE Bugs]

The following task has a new comment added:

FS#1083 - ar71xx Kernel 4.9  PPTP Passthrough not working
User who did this - Arjen de Korte (arjendekorte)

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This is not surprising. The default for automatic loading of connection tracking helpers was changed in kernel-4.7. So with kernel-4.4, the pptp helper will be loaded automatically when PPTP traffic is seen, but for kernel-4.9 you'll have to do that explicitly.

Adding something along the lines

    iptables -t raw -A OUTPUT -p tcp -m tcp --dport 1723 -j CT --helper pptp

should load the connection tracker helper in your firewall. You could append this line to your /etc/firewall.user for instance to load it automatically.
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1083#comment3936