Subject: [PATCH net-next v4 4/5] af_vsock: Set VMADDR_FLAG_TO_HOST flag on the receive path

From: Andra Paraschiv <[email-masked]>
Date: Mon, 14 Dec 2020 18:11:21 +0200

The vsock flags can be set during the connect() setup logic, when
initializing the vsock address data structure variable. Then the vsock
transport is assigned, also considering this flags field.

The vsock transport is also assigned on the (listen) receive path. The
flags field needs to be set considering the use case.

Set the value of the vsock flags of the remote address to the one
targeted for packets forwarding to the host, if the following conditions
are met:

* The source CID of the packet is higher than VMADDR_CID_HOST.
* The destination CID of the packet is higher than VMADDR_CID_HOST.

Changelog

v3 -> v4

* No changes.

v2 -> v3

* No changes.

v1 -> v2

* Set the vsock flag on the receive path in the vsock transport
  assignment logic.
* Use bitwise operator for the vsock flag setup.
* Use the updated "VMADDR_FLAG_TO_HOST" flag naming.

Signed-off-by: Andra Paraschiv <[email-masked]>
Reviewed-by: Stefano Garzarella <[email-masked]>
---
 net/vmw_vsock/af_vsock.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index d10916ab45267..83d035eab0b05 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -431,6 +431,18 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
 	unsigned int remote_cid = vsk->remote_addr.svm_cid;
 	int ret;
 
+	/* If the packet is coming with the source and destination CIDs higher
+	 * than VMADDR_CID_HOST, then a vsock channel where all the packets are
+	 * forwarded to the host should be established. Then the host will
+	 * need to forward the packets to the guest.
+	 *
+	 * The flag is set on the (listen) receive path (psk is not NULL). On
+	 * the connect path the flag can be set by the user space application.
+	 */
+	if (psk && vsk->local_addr.svm_cid > VMADDR_CID_HOST &&
+	    vsk->remote_addr.svm_cid > VMADDR_CID_HOST)
+		vsk->remote_addr.svm_flags |= VMADDR_FLAG_TO_HOST;
+
 	switch (sk->sk_type) {
 	case SOCK_DGRAM:
 		new_transport = transport_dgram;
-- 
2.20.1 (Apple Git-117)

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