Add support for AF_VSOCK

[emielvanseveren]

Proposal

Add support for AF_VSOCK which facilitates communication between virtual machines and the host they are running on. see vsock(7). The implementation should be very similar to AF_NETLINK.

More information on vsock programming can be found at: pubs.vmware.com/vsphere-60/topic/com.vmware.ICbase/PDF/ws9_esx60_vmci_sockets.pdf

Problem statement

There is no implementation available in std.

Motivation, use-cases

• Implement network‐based communication for off‐the‐network virtual machines
• Improve the privacy of data transmission on hosted virtual machines
• Increase host‐guest performance of socket‐modified applications and databases
• Practical example: firecracker, where vsock is used for communication between microvms and host.
• More examples can be found in the vsock programming guide listed above

Solution sketches

• Should include socketAddr (more information in vsock(7)
• a few special addresses:
  • VMADDR_CID_ANY
  • VMADDR_CID_HOST
  • VMADDR_CID_LOCAL
  • VMADDR_CID_LOCAL
  • VMADDR_CID_HYPERVISOR
• get_local_cid() which is supported through a ioctl on /dev/vsock.

Links and related work

• Implementation in Python
• some defines in libc
• VsockAddr in nix

[the8472]

There is no implementation available in std.

Well, does it have to be in std? It seems kind of niche, so wouldn't having it in a crate be enough?

[emielvanseveren]

There is no implementation available in std.

Well, does it have to be in std? It seems kind of niche, so wouldn't having it in a crate be enough?

I'm not sure if would consider it niche. Every application running inside a vm that wants to communicate with its host can do this over vsock. This could be very similar to everything that takes tcp sockets. E.g. a http server inside the guest that takes connections over vsock.

[the8472]

Every application running inside a vm that wants to communicate with its host

Which in my experience isn't all that common? At work we have a ton of services running in VMs, very few of them need to talk with the host. The only things that come to mind are wsl2, docker on windows and some vmware guest tools.

Running software in microvms and only there, to the extent that they need specialized communication channels, is not exactly mainstream software, is it?

This could be very similar to everything that takes tcp sockets. E.g. a http server inside the guest that takes connections over vsock.

Alas, sockets in the standard library are not a general BSD socket type. Instead everything is distinct struct type for each socket family + type. Hell, TCP sockets are even split into TcpListener and TcpStream.

This might be more appropriate for the socket2 crate, and even that focuses more on tcp/udp/unix sockets than other ones. E.g. netlink, icmp or raw sockets don't have any explicit support there and must be constructed manually.

[emielvanseveren]

You're right, I'm closing this for now.