[PATCH net-next v2 2/4] vm_sockets: Add VMADDR_FLAG_TO_HOST vsock flag

[Andra Paraschiv <andraprs@amazon.com>]

Add VMADDR_FLAG_TO_HOST vsock flag that is used to setup a vsock
connection where all the packets are forwarded to the host.

Then, using this type of vsock channel, vsock communication between
sibling VMs can be built on top of it.

Changelog

v1 -> v2

* New patch in v2, it was split from the first patch in the series.
* Remove the default value for the vsock flags field.
* Update the naming for the vsock flag to "VMADDR_FLAG_TO_HOST".

Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
---
 include/uapi/linux/vm_sockets.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/uapi/linux/vm_sockets.h b/include/uapi/linux/vm_sockets.h
index 46735376a57a8..72e1a3d05682d 100644
--- a/include/uapi/linux/vm_sockets.h
+++ b/include/uapi/linux/vm_sockets.h
@@ -114,6 +114,21 @@
 
 #define VMADDR_CID_HOST 2
 
+/* The current default use case for the vsock channel is the following:
+ * local vsock communication between guest and host and nested VMs setup.
+ * In addition to this, implicitly, the vsock packets are forwarded to the host
+ * if no host->guest vsock transport is set.
+ *
+ * Set this flag value in the sockaddr_vm corresponding field if the vsock
+ * packets need to be always forwarded to the host. Using this behavior,
+ * vsock communication between sibling VMs can be setup.
+ *
+ * This way can explicitly distinguish between vsock channels created for
+ * different use cases, such as nested VMs (or local communication between
+ * guest and host) and sibling VMs.
+ */
+#define VMADDR_FLAG_TO_HOST 0x0001
+
 /* Invalid vSockets version. */
 
 #define VM_SOCKETS_INVALID_VERSION -1U
-- 
2.20.1 (Apple Git-117)




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