Re: [PATCH net-next v3 1/4] vm_sockets: Add flags field in the vsock address data structure

[Stefano Garzarella]

On Fri, Dec 11, 2020 at 12:32:38PM +0200, Andra Paraschiv wrote:
> vsock enables communication between virtual machines and the host they
> are running on. With the multi transport support (guest->host and
> host->guest), nested VMs can also use vsock channels for communication.
>
> In addition to this, by default, all the vsock packets are forwarded to
> the host, if no host->guest transport is loaded. This behavior can be
> implicitly used for enabling vsock communication between sibling VMs.
>
> Add a flags field in the vsock address data structure that can be used
> to explicitly mark the vsock connection as being targeted for a certain
> type of communication. This way, can distinguish between different use
> cases such as nested VMs and sibling VMs.
>
> This field can be set when initializing the vsock address variable used
> for the connect() call.
>
> Changelog
>
> v2 -> v3
>
> * Add "svm_flags" as a new field, not reusing "svm_reserved1".

Using the previous 'svn_zero[0]' for the new 'svn_flags' field make sure 
that if an application sets a flag and runs on an older kernel, it will 
receive an error and I think it's perfect, since that kernel is not able 
to handle the flag.

So I think is okay and I confirm my R-b tag ;-)

> v1 -> v2
>
> * Update the field name to "svm_flags".
> * Split the current patch in 2 patches.
>
> Signed-off-by: Andra Paraschiv <andraprs@xxxxxxxxxx>
> Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
> include/uapi/linux/vm_sockets.h | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/vm_sockets.h b/include/uapi/linux/vm_sockets.h
> index fd0ed7221645d..619f8e9d55ca4 100644
> --- a/include/uapi/linux/vm_sockets.h
> +++ b/include/uapi/linux/vm_sockets.h
> @@ -148,10 +148,13 @@ struct sockaddr_vm {
> 	unsigned short svm_reserved1;
> 	unsigned int svm_port;
> 	unsigned int svm_cid;
> +	unsigned short svm_flags;
> 	unsigned char svm_zero[sizeof(struct sockaddr) -
> 			       sizeof(sa_family_t) -
> 			       sizeof(unsigned short) -
> -			       sizeof(unsigned int) - sizeof(unsigned int)];
> +			       sizeof(unsigned int) -
> +			       sizeof(unsigned int) -
> +			       sizeof(unsigned short)];
> };
>
> #define IOCTL_VM_SOCKETS_GET_LOCAL_CID		_IO(7, 0xb9)
> --
> 2.20.1 (Apple Git-117)
>
>
>
>
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