vsock: switch to krun_add_vsock_port2 for listen mode support

[vyasgun]

Use krun_add_vsock_port2() which accepts a listen parameter, enabling host-initiated vsock connections when listen=true.

Add support for 'listen' mode as default

Related issue: #79

[jakecorrenti]

LGTM, thanks @vyasgun !

[vyasgun]

@jakecorrenti thanks for the review! I realised this PR inadvertently makes listen mode the default (due to missing the Connect action). I've added a follow-up commit that restores connect as the default behaviour when neither flag is specified.

[jakecorrenti]

@jakecorrenti thanks for the review! I realised this PR inadvertently makes listen mode the default (due to missing the Connect action). I've added a follow-up commit that restores connect as the default behaviour when neither flag is specified.

Thanks for the follow up. I'll get around to re-reviewing and testing it tomorrow

[tylerfanelli]

LGTM, thanks!

[jakecorrenti]

I'm having a little difficulty grokking this. Is the notion of what listen = true means different between libkrun and vfkit? In other words, listen = true for libkrun means the guest socket is listening for a connection from the host, but for vfkit listen = true means the host is listening for a socket connection from the guest? So this means that by passing the connect action to krunkit, we're doing the equivalent of the listen action in vfkit?

[vyasgun]

Yes, you are correct. The listen=true in libkrun means initiating host to guest connections while listen mode in vfkit is guest to host connections. Updated the code to reflect this. (listen=false by default (listen mode)).

• listen=true for host to guest direction (connect mode)
• listen=false for guest to host direction (listen mode)

This handles the inverted flag meaning between vfkit and libkrun.

[jakecorrenti]

Code seems fine but I'd like it if @slp took a look at this as well.

[slp]

Code LGTM, but I think docs/usage.md should be updated to reflect the new parameters for virtio-vsock.

[vyasgun]

@slp thanks for the review - I updated the docs to include the new parameters.

[slp]

LGTM, thanks!