A new way to set up transparent proxying

[yrutschle]

@ftasnetamot came up with a new way to set up transparent proxying, which is much easier and clearer than the previous one.

Try it out, here are all his explanations:
https://github.com/yrutschle/sslh/blob/master/doc/simple_transparent_proxy.md
https://github.com/yrutschle/sslh/blob/master/doc/scenarios-for-simple-transparent-proxy.md

[hanjo]

Hi,
this new way sounds wonderful, and after some try+error I finally got it to work (even using the docker container). I extended this to also be able to use IPv6 by adding the following to interfaces:

/etc/network/interfaces.d $ cat 10-sslh.conf
auto dummy0
iface dummy0 inet static
        address 192.168.255.254/32
        #pre-up modprobe dummy
        ## Attention! with kernels, not automatically creating a dummy0
        ## interface after module loading the following line should be:
        pre-up modprobe dummy; if [ ! -e /sys/class/net/dummy0 ]; then ip link add dummy0 type dummy ; fi
        post-up ip rule add from 192.168.255.254 table sslh
        post-up ip route add local 0.0.0.0/0 dev dummy0 table sslh
        pre-down ip route del local 0.0.0.0/0 dev dummy0 table sslh
        pre-down ip rule del from 192.168.255.254 table sslh

iface dummy0 inet6 static
        address fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff/128
        pre-up modprobe dummy; if [ ! -e /sys/class/net/dummy0 ]; then ip link add dummy0 type dummy ; fi
        post-up ip -6 rule add from fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff table sslh
        post-up ip -6 route add local ::/0 dev dummy0 table sslh
        pre-down ip -6 route del local ::/0 dev dummy0 table sslh
        pre-down ip -6 rule del from fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff table sslh

However, when I cycle dummy0 I keep getting this message:

$ sudo ifdown dummy0 && sudo ifup dummy0
RTNETLINK answers: No such process
Error: ipv6: address not found.
Waiting for DAD... Done

I don't understand why I'm getting this, as the interface looks perfectly fine:

$ ip a s dummy0
5: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
    link/ether da:48:00:fb:14:a8 brd ff:ff:ff:ff:ff:ff
    inet 192.168.255.254/32 brd 192.168.255.254 scope global dummy0
       valid_lft forever preferred_lft forever
    inet6 fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff/128 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::d848:ff:fefb:14a8/64 scope link
       valid_lft forever preferred_lft forever

Any suggestions?
Thanks!