Support v2 and v3 options from libslirp

[5eraph]

Hi,

This is first draft of changes providing support for configuration v2 and v3 of libslirp.

Fixes #173

@AkihiroSuda please let me know your thoughts on this. I am not sure about organization of some parts.
E.g.:

• is it ok to parse outbound addresses in slirp4netns_config_from_options
  - if we want to print configured outbound address on slirp setup, is it ok to pass original char * outbound_addr/6 to parent function or is there better way ? (this is not implemented yet)

[AkihiroSuda]

Thanks!

• Please sign the commits with your full name (git commit -a -s)
• Please add tests

[5eraph]

Thanks!

• Please sign the commits with your full name (git commit -a -s)
• Please add tests

Alright will do. Thanks for prompt feedback. I will go through that tomorrow.

[5eraph]

I don't know why are the test failing yet. I ran Dockerfile.tests in my environment with same parameters and same code base without issues. 🤔

Any suggestions ?
Another run for same commit was successful.

[5eraph]

To me it looks like the final cleanup trap fails and returns error exit code and causes failure of entire test even though the test might be successful.

Can we outsource cleanup routine to avoid these errors? Like this:

function cleanup {
    kill -9 $nc_pid $child $slirp_pid &
}

Also regarding outbound address. Do you have any suggestions how to test it with automated tests?
I think to test it properly we need two endpoints - either servers or containers. Then grep non local host ip address which connects these two and verify whether the server is receiving connections from correct IPv4/6. And I am not sure whether this is achievable in reasonable/straightforward way.

[AkihiroSuda]

I think to test it properly we need two endpoints

I guess we can just test lo and eth0 and call it a day

[AkihiroSuda]

cc @giuseppe @elmarco PTAL

[5eraph]

I think to test it properly we need two endpoints

I guess we can just test lo and eth0 and call it a day

Ok, I am going to check out what we can do with it using nc -v -n .

[5eraph]

@AkihiroSuda can you please take a look at outbound-addr test? It should be sufficient for now.

I wasn't able to test ipv6. All ipv6 requests failed with network unreachable error. I tried both fe80::2 and fd00::2. Also there is no ipv6 test I could use as reference.

[AkihiroSuda]

Almost looks good except a couple of nits. The IPv6 tests can be added later.
Also, please squash and sigh the commits.

[AkihiroSuda]

LGTM except a typo, thanks

[AkihiroSuda]

@giuseppe @rhatdan PTAL

[giuseppe]

LGTM