On 11/12/2020 17:24, Stefano Garzarella wrote:

Hi Andra,

On Fri, Dec 11, 2020 at 12:32:37PM +0200, Andra Paraschiv wrote:

quoted

vsock enables communication between virtual machines and the host 
they are
running on. Nested VMs can be setup to use vsock channels, as the multi
transport support has been available in the mainline since the v5.5 
Linux kernel
has been released.

Implicitly, if no host->guest vsock transport is loaded, all the 
vsock packets
are forwarded to the host. This behavior can be used to setup 
communication
channels between sibling VMs that are running on the same host. One 
example can
be the vsock channels that can be established within AWS Nitro Enclaves
(see Documentation/virt/ne_overview.rst).

To be able to explicitly mark a connection as being used for a 
certain use case,
add a flags field in the vsock address data structure. The value of 
the flags
field is taken into consideration when the vsock transport is 
assigned. This way
can distinguish between different use cases, such as nested VMs / local
communication and sibling VMs.

The flags field can be set in the user space application connect 
logic. On the
listen path, the field can be set in the kernel space logic.

I reviewed all the patches and they are in a good shape!

Hi Stefano,

Thanks for the overall review and for the reconfirmation of the Rb for 
the vsock address data structure changes.

Maybe the last thing to add is a flags check in the
vsock_addr_validate(), to avoid that flags that we don't know how to
handle are specified.

I can add this validation as a new patch in the series, next revision.

Thanks,
Andra

For example if in the future we add new flags that this version of the
kernel is not able to satisfy, we should return an error to the
application.

I mean something like this:

    diff --git a/net/vmw_vsock/vsock_addr.c b/net/vmw_vsock/vsock_addr.c
    index 909de26cb0e7..73bb1d2fa526 100644
    --- a/net/vmw_vsock/vsock_addr.c
    +++ b/net/vmw_vsock/vsock_addr.c
    @@ -22,6 +22,8 @@ EXPORT_SYMBOL_GPL(vsock_addr_init);

     int vsock_addr_validate(const struct sockaddr_vm *addr)
     {
    +       unsigned short svm_valid_flags = VMADDR_FLAG_TO_HOST;
    +
            if (!addr)
                    return -EFAULT;

    @@ -31,6 +33,9 @@ int vsock_addr_validate(const struct sockaddr_vm 
*addr)
            if (addr->svm_zero[0] != 0)
                    return -EINVAL;

    +       if (addr->svm_flags & ~svm_valid_flags)
    +               return -EINVAL;
    +
            return 0;
     }
     EXPORT_SYMBOL_GPL(vsock_addr_validate);


Thanks,
Stefano

quoted

Thank you.

Andra

---

Patch Series Changelog

The patch series is built on top of v5.10-rc7.

GitHub repo branch for the latest version of the patch series:

* https://github.com/andraprs/linux/tree/vsock-flag-sibling-comm-v3

v2 -> v3

* Rebase on top of v5.10-rc7.
* Add "svm_flags" as a new field, not reusing "svm_reserved1".
* Update comments to mention when the "VMADDR_FLAG_TO_HOST" flag is 
set in the
 connect and listen paths.
* Update bitwise check logic to not compare result to the flag value.
* v2: 
https://lore.kernel.org/lkml/20201204170235.84387-1-andraprs@amazon.com/ (local)

v1 -> v2

* Update the vsock flag naming to "VMADDR_FLAG_TO_HOST".
* Use bitwise operators to setup and check the vsock flag.
* Set the vsock flag on the receive path in the vsock transport 
assignment
 logic.
* Merge the checks for the g2h transport assignment in one "if" block.
* v1: 
https://lore.kernel.org/lkml/20201201152505.19445-1-andraprs@amazon.com/ (local)

---

Andra Paraschiv (4):
 vm_sockets: Add flags field in the vsock address data structure
 vm_sockets: Add VMADDR_FLAG_TO_HOST vsock flag
 af_vsock: Set VMADDR_FLAG_TO_HOST flag on the receive path
 af_vsock: Assign the vsock transport considering the vsock address
   flags

include/uapi/linux/vm_sockets.h | 25 ++++++++++++++++++++++++-
net/vmw_vsock/af_vsock.c        | 21 +++++++++++++++++++--
2 files changed, 43 insertions(+), 3 deletions(-)

-- 
2.20.1 (Apple Git-117)




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Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.