[Feature request] IPv6 support.

[przemyslaw0]

I would like to use BindToInterface with IPv6

@JsBergbau
Could you please implement this feature?

[przemyslaw0]

@JsBergbau

I've modified the code for working with IPv6: https://paste.ee/p/L6FNt

export LD_PRELOAD=./bindToInterface.so
export BIND_INTERFACE=eth0
export BIND_SOURCE_IPV4=192.168.1.10
export BIND_SOURCE_IPV6=fe80::1
export DNS_OVERRIDE_IP=8.8.8.8
export DNS_OVERRIDE_PORT=53
export BIND_EXCLUDE=192.168.1.1,fe80::2
w3m -4 ipleak.net
w3m -6 ipleak.net

But there is a problem, perhaps with my system, both the original and my modified bindToInterface.c are not working with DNS when DNS_OVERRIDE_IP is set, the DNS uses the system DNS.

[JsBergbau]

Thanks for modifying the code.
Can you try using an IPv6 DNS-Server? I know it should also work with IPv4-DNS-Server, but who knows...

I don't have IPv6 access to assist with debugging, so I can't debug any further :(

[przemyslaw0]

I tried with $ host g.co

export LD_PRELOAD=./bindToInterface.so
export BIND_INTERFACE=vpngw
export BIND_SOURCE_IPV4=10.96.0.26
export BIND_SOURCE_IPV6=fd54:20a4:d33b:b10c:a70:0:60:1a
export DNS_OVERRIDE_IP=2620:fe::9
export DNS_OVERRIDE_PORT=53
export BIND_EXCLUDE=127.0.0.1,2620:fe::9

I tested also with DNS IPv4:

export LD_PRELOAD=./bindToInterface.so
export BIND_INTERFACE=vpngw
export BIND_SOURCE_IPV4=10.96.0.26
export BIND_SOURCE_IPV6=fd54:20a4:d33b:b10c:a70:0:60:1a
export DNS_OVERRIDE_IP=1.1.1.1
export DNS_OVERRIDE_PORT=53
export BIND_EXCLUDE=127.0.0.1,1.1.1.1

I noticed that not all programs use the DNS specified in bindToInterface.so, some examples are w3m and curl.

And I realized that SO_BINDTODEVICE is unstable and sometimes buggy across many kernel versions, even more with IPv6, setting up a policy based routing with a fwmark pointing to a separate table is more suitable.

[xeverse]

That GitHub repo was written for IPv4 and may not fully hook into IPv6 syscalls
(some distros changed from bind() to bind6(), setsockopt(IPV6_BOUND_IF), etc.).
That explains why it says Bound to: .