virtio-vsock implementation for use with Firecracker

[jeromegn]

Firecracker supports vsocks, I don't know if the implementation is different from qemu's, but I thought I'd specify nonetheless.

I'm researching using nanos for very specific use cases and I noticed vsocks where not implemented yet. I assume that's not a widely used feature in VMs in general, but we use it for exporting logs from a VM. Assigning the serial console for stdout and stderr was far too slow for our own use case and instead we're passing them via a vsock.

Is a vsock implementation on a roadmap? I couldn't find much information about it.

[eyberg]

serial is indeed not really a prod choice; many choose a syslog destination for logs here;

yes we're planning on adding support in the somewhat near future but if you're looking to get it sooner can reach out via company's drift

[francescolavra]

1887 adds vsock support to Nanos. Example program using vsock to send a string to the host:

#include <sys/socket.h>
#include <unistd.h>

#include <linux/vm_sockets.h>

int main(int argc, char **argv)
{
    int vs;
    struct sockaddr_vm addr;
    const char hello[] = "Hello from Nanos!\n";

    vs = socket(AF_VSOCK, SOCK_STREAM, 0);
    addr.svm_family = AF_VSOCK;
    addr.svm_reserved1 = 0;
    addr.svm_cid = VMADDR_CID_HOST;
    addr.svm_port = 123;
    connect(vs, (struct sockaddr *)&addr, sizeof(addr));
    write(vs, hello, sizeof(hello) - 1);
    close(vs);
    return 0;
}

Snippet of Firecracker configuration file to specify a vsock device:

  "vsock": {
    "guest_cid": 3,
    "uds_path": "/tmp/vsock.sock"
  }

• to run a server on the host: $ nc -l -U /tmp/vsock.sock_123
• then, when running the above example program as a unikernel on Firecracker, the string "Hello from Nanos!" will be displayed by the server running on the host