Tap update for modern linux versions

[hfmanson]

This pull request re-enables the tap interface for modern linux versions

• when tuntap is detected in the configure script ethertap is no longer used and the user can enter tapN as ether device
• tunconfig (which should be renamed tapconfig IMO) is updated to use ip instead of ifconfig and now creates a tap device which has the current user as owner
• This pull request contains the temporarily disabled fork

http://backreference.org/2010/03/26/tuntap-interface-tutorial/ has been extremely useful

[karelbilek]

oh, it seems like I am not the only one who did the script fixes. :) well, someone should probably merge this.

[asvitkine]

This seems unrelated to the TAP fixes and I don't think should be in this commit.

[asvitkine]

I left some comments on the change.

[asvitkine]

I left some comments on the pull request.

On Fri, May 27, 2016 at 8:30 PM, Karel Bílek notifications@github.com
wrote:

oh, it seems like I am not the only one who did the script fixes. :) well,
someone should probably merge this.

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[dcoshea]

I think this is still quite relevant. I finally understand what this is about after reading it a few times (after seeing how Bochs does it) and I want this patch now, as it means that instead of BasiliskII creating the tap-type interface for me, it will use a pre-created tapN interface. The benefits of this are:

1. I can create that interface by running e.g. sudo ip tuntap add tap7 mode tap, then run sudo ip ... to configure it, possibly in my startup scripts. My old version of NetworkManager doesn't seem to have a way to create these interfaces, but perhaps newer versions do. Currently, for BasiliskII to create the interface, it either needs to be run as root, or you need to give the binary the cap_net_admin capability (e.g. sudo setcap cap_net_admin+eip PATH-TO-BasiliskII), which is a bit like setuid root but more restrictive. Having the interfaces created outside of BasiliskII is more secure, especially since the suggested solution currently (in the tunconfig script) is to have passwordless sudo access set up for your account.

2. At a more basic level, BasiliskII currently creates the tap-type interface with a name like tun0 which I found very confusing until I'd read this code and understood the kernel feature and realised that it's really a tap-type interface with the wrong name (note that tap and tun mean two different things).

I will respond to some of the review comments in more detail and perhaps raise some additional concerns. I suppose that after we've discussed the changes, unless @hfmanson appears, I'll need to submit my own PR to replace this one?

[phrxmd]

@dcoshea please do, it looks like @hfmanson is not active here anymore